TY - JOUR AB - Diatom abundance and assemblage composition have been determined for 169 surface sediment samples from the Portuguese margin, an area where seasonal upwelling occurs each year from April to October. Absolute diatom abundance distribution patterns reflect the more intense and/or persistent and more homogeneous upwelling north of the Nazare Canyon, the position of the “inner” upwelling front south of Lisbon, and the eastern continuation of the coastal upwelling jet along the Algarve coast. Distribution patterns of species and of ecologically defined groups, meroplanktonic, oceanic, freshwater and marine benthic, support the hypothesis that diatom species and assemblages are good indicators of the changing character of the upwelling system. Small species of the genus Thalassiosira occur in areas of persistent upwelling where availability of nutrients is more constant and/or higher. Paralia sulcata (Ehr.) Cleve is an abundant species whose mean cell diameter increases as nutrient availability decreases. Resting spores, mainly of Chaetoceros Ehrenberg, record the position of the zone where higher variability occurs, the “inner” upwelling front. AU - Abrantes, Fatima DA - 1988/12/01/ DO - https://doi.org/10.1016/0025-3227(88)90082-5 IS - 1 N1 - https://www.sciencedirect.com/science/article/pii/0025322788900825 PY - 1988 SN - 0025-3227 SP - 15–39 ST - Diatom assemblages as upwelling indicators in surface sediments off Portugal T2 - Marine Geology TI - Diatom assemblages as upwelling indicators in surface sediments off Portugal UR - https://doi.org/10.1016/0025-3227(88)90082-5 VL - 85 ID - 17518 ER - TY - JOUR AB - Quantitative studies have been carried out on opaline microfossils and diatom assemblage composition and preservation in two latest Quarternary (⋍ 100 ka to P.D.) cores from the continental slope of Portugal. The sites are located in an area of modern summer coastal upwelling created by northerly trade winds. The spatial patterns and intensity of this upwelling system are accurately recorded by the diatom abundances and taxonomic composition in the surface sediments. The diatom record in these sequences indicates that coastal upwelling intensity was similar to present day during late Holocene, interglacial Stage 3 and late Stage 5; higher during Stage 2; and lower in the early Holocene. Paleoproductivity estimates are consistent with the diatom accumulation rates from Stage 3 to the Recent. This indicates that both the diatom and the organic carbon content of the sediments mainly reflect the biological productivity in the euphotic zone. AU - Abrantes, Fatima DA - 1991/07/01/ DO - https://doi.org/10.1016/0377-8398(91)90017-Z IS - 3–4 N1 - https://www.sciencedirect.com/science/article/pii/037783989190017Z PY - 1991 SN - 0377-8398 SP - 285–310 ST - Increased upwelling off Portugal during the last glaciation: diatom evidence T2 - Marine Micropaleontology TI - Increased upwelling off Portugal during the last glaciation: diatom evidence UR - https://doi.org/10.1016/0377-8398(91)90017-Z VL - 17 ID - 17519 ER - TY - JOUR AB - Diatom and coccolithophorid abundance and diatom assemblage composition found in the water column along the Portuguese margin, during upwelling and non-upwelling conditions, are compared to the distribution patterns observed in the recent sediments from the same area. The water column results indicate a one order of magnitude increase in phytoplankton biomass during upwelling conditions (summer). with diatoms being the most important contributors. Coccolithophorids, on the contrary, dominate the phytoplankton in winter (non-upwelling). The comparison of the upwelling and non-upwelling spatial distribution of these phytoplankton groups to their sedimentary record reveals the sediment record as a reflection of the upwelling situation, preserving most of its original spatial variability. The comparison between living and fossil diatom assemblages indicates that from the two genera which dominate the summer biological assemblage, Pseudo-nitzschia and Chaetoceros, Pseudo-nitzschia is not represented in the sediments, while Chaetoceros is the dominant form of the sediment. Thalassiosira, which occurs in the same abundance in both seasons, responding to both river and upwelling nutrient input, can not be a reliable indicator of any single process. However. this genus distribution in the sediments can be used as an indicator of continuous nutrient availability. Such results are of great importance for paleoceanographic reconstructions, since they constitute a good indication that the sediment record, even though somewhat altered with respect to assemblage composition, does reflect the water column characteristics. AU - Abrantes, F., and Moita, T. PY - 1999 SP - 319–336 ST - Water column and recent sediment data on diatoms and coccolithophorids, off Portugal, confirm sediment record of upwelling events T2 - Oceanologica Acta TI - Water column and recent sediment data on diatoms and coccolithophorids, off Portugal, confirm sediment record of upwelling events UR - https://doi.org/10.1016/S0399-1784(99)90007-5 VL - 22 ID - 17521 ER - TY - JOUR AB - Time series of diatom accumulation rates (DAR) and assemblage composition for the last 200 000 yr from the Atlantic major coastal upwelling loci of the eastern boundary currents and eastern Equator are compared together with independent proxies of export production, to upper ocean productivity and to nutrient concentration and utilization. Fluctuations in DAR are concomitant at all sites and in good correspondence to the other independent productivity proxies indicating glacial periods as the most productive times of the past 200 000 yr in both hemispheres of the eastern Atlantic. Maximum productivity, about one order of magnitude higher than at present, occurred at the last glacial maximum (LGM). Despite the ‘Atlantic’ similarities in both coastal and equatorial upwelling types, important regional and site specific variations emerge. In the southern Hemisphere site, a contradiction of proxies, diatoms and Corg, is noted at the base of stage 6 (185 000 yr). The good correlation found between the Corg and the benthic foraminifera fluxes is interpreted as a reflection of a shift in the phytoplankton community structure related to either a change in the N:P:Si ratio, or similar nutrient conditions associated with increased water column stratification. AU - Abrantes, Fatima DA - 2000/02/28/ DO - https://doi.org/10.1016/S0012-821X(99)00312-X IS - 1 KW - diatoms last glacial maximum productivity upwelling N1 - https://www.sciencedirect.com/science/article/pii/S0012821X9900312X PY - 2000 SN - 0012-821X SP - 7–16 ST - 200,000 yr diatom records from Atlantic upwelling sites reveal maximum productivity during LGM and a shift in phytoplankton community structure at 185 000 yr T2 - Earth and Planetary Science Letters TI - 200,000 yr diatom records from Atlantic upwelling sites reveal maximum productivity during LGM and a shift in phytoplankton community structure at 185 000 yr UR - https://doi.org/10.1016/S0012-821X(99)00312-X VL - 176 ID - 17520 ER - TY - JOUR AB - To investigate primary productivity conditions off SW Iberia and their relation to global climate variability between 1400 and 250 ka, a multi-proxy analysis, including primary production and terrestrial input indicators, is performed in Sites U1385 and U1391 that constitute an E-W transect at ± 37º 34’ N latitude, in a region influenced at Present by two upwelling filaments. The data reveal a shift in timing and magnitude of the processe(s) leading to the production record, but no apparent change in its cyclicity. Within the 41ky world, both CaCO3 and TOC records are coeval up to ±1000 ka, time at which the two records reverse. Diatoms have maximum abundance at ±950 ka followed by a sporadic occurrence of diatoms and low TOC contents. The 100ky world shows larger amplitude of variation for all proxies, higher diatom abundance as well as an increase in the concentration of total alkenones, CaCO3 and TOC. Similarly, n-alkanes, scanning XRF Fe and C/N reveal higher values. Such results suggest an increase in both upwelling related primary production and hinterland precipitation and input of continental organic matter (stronger seasonality?). Furthermore Terminations IV and V and the transition MIS15.2 / MIS15.1 are marked by sharp productivity peaks. Its occurrence on Site U1391, backs a coastal upwelling related increase in primary production also suggested by the Si/Al record of NW African ODP Site 658. A preservation effect cannot be discarded, implying the presence of southern source waters. AU - Abrantes, F., Rodrigues, T., Ventura, C., Santos, C., Roell, U., Voelker, A., and Hodell, D. PY - 2017 SP - EGU2017-9743 ST - Past productivity conditions off SW Iberia at the transition from the 41 ky to the 100 ky world: the record of IODP Sites U1385 and U1391 T2 - Geophysical Research Abstracts TI - Past productivity conditions off SW Iberia at the transition from the 41 ky to the 100 ky world: the record of IODP Sites U1385 and U1391 UR - https://meetingorganizer.copernicus.org/EGU2017/EGU2017-9743.pdf VL - 19 ID - 49342 ER - TY - JOUR AB - In an attempt to delineate past hydrographic conditions on the northeastern Atlantic Ocean Margin along a latitudinal transect (37°–63°N) and link the eastern North Atlantic Ocean with the Norwegian Sea, we have investigated planktonic and benthic stable oxygen isotopes, as well as abundances and fluxes of planktonic and benthic foraminifera, calcium carbonate, organic carbon, and detrital grains in six sediment cores studied by the ENAM project. In our joint approach, we focused on the major climatic events of the last 20 kyr, that is, the Last Glacial Maximum (LGM), the Heinrich event 1 (H1), the Younger Dryas (YD) and the Holocene Climatic Optimum (HCO). SIMMAX temperature estimates suggest glacial SSTs off Portugal, similar to Holocene values, contradicting the proposed polar front position of CLIMAP Project Members (1976). Besides, increased planktonic and benthic foraminiferal fluxes in the Norwegian Sea and the Faeroe Islands cores point to Nordic Seas partially ice-free with seasonally productive polynas. Multiple IRD spikes observed at the Faeroe Islands and Norwegian Sea sites, coeval with H1, suggest multiple pulses of the Fenno-Scandian ice sheet. At the same time the presence of IRD on the Portuguese Margin cores confirms the southward influence of icebergs. The increase in foraminiferal abundances and fluxes that parallel IRD spikes at all sites suggests that times of increased productivity either succeed or occur simultaneously with the iceberg surges in the open North Atlantic. Productivity conditions similar to those observed during H1 are also registered during the YD even though planktonic foraminiferal assemblages suggest less cold conditions. AU - Abrantes, F. AU - Baas, J. AU - Haflidason, H. AU - Rasmussen, T. AU - Klitgaard, D. AU - Loncaric, N. AU - Gaspar, L. DA - 1998/11/01/ DO - https://doi.org/10.1016/S0025-3227(98)00062-0 IS - 1–3 KW - eastern North Atlantic palaeocirculation sedimentary fluxes Heinrich event 1 productivity N1 - https://www.sciencedirect.com/science/article/pii/S0025322798000620 PY - 1998 SN - 0025-3227 SP - 7–23 ST - Sediment fluxes along the northeastern European margin: inferring hydrological changes between 20 and 8 kyr T2 - Marine Geology TI - Sediment fluxes along the northeastern European margin: inferring hydrological changes between 20 and 8 kyr UR - https://doi.org/10.1016/S0025-3227(98)00062-0 VL - 152 ID - 23009 ER - TY - JOUR AB - The glacial cycles of the Pleistocene involve changes in the circulation of the deep ocean in important ways. This review seeks to establish what were the robust patterns of deep-sea water mass changes and how they might have influenced important parts of the last glacial cycle. After a brief review of how tracers in the modern ocean can be used to understand the distribution of water masses, I examine the data for biogeochemical, circulation rate, and conservative tracers during glacial climates. Some of the robust results from the literature of the last 30 years include: a shoaled version of northern source deep water in the Atlantic, expanded southern source water in the abyss and deep ocean, salt (rather than heat) stratification of the last glacial maximum (LGM) deep-sea, and several lines of evidence for slower overturning circulation in the southern deep cell. We combine these observations into a new idea for how the ocean-atmosphere system moves from interglacial to glacial periods across a single cycle. By virtue of its influence on the melting of land-based ice around Antarctica, cooling North Atlantic Deep Water (NADW) leads to a cold and salty version of Antarctic Bottom Water (AABW). This previously underappreciated feedback can lead to a more stratified deep ocean that operates as a more effective carbon trap than the modern, helping to lower atmospheric CO2 and providing a mechanism for the deep ocean to synchronize the hemispheres in a positive feedback that drives the system to further cooling. AU - Adkins, Jess F. DO - https://doi.org/10.1002/palo.20046 IS - 3 PY - 2013 SN - 0883-8305 SP - 539–561 ST - The role of deep ocean circulation in setting glacial climates T2 - Paleoceanography and Paleoclimatology TI - The role of deep ocean circulation in setting glacial climates UR - https://doi.org/10.1002/palo.20046 VL - 28 ID - 7436 ER - TY - JOUR AU - Alley, Richard B. DO - https://doi.org/10.1029/2003PA000942 IS - 4 N1 - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2003PA000942 PY - 2003 SN - 0883-8305 SP - 1085 ST - Raising paleoceanography T2 - Paleoceanography and Paleoclimatology TI - Raising paleoceanography UR - https://doi.org/10.1029/2003PA000942 VL - 18 ID - 17522 ER - TY - JOUR AB - AbstractLinked, abrupt changes of North Atlantic deep water formation, North Atlantic sea ice extent, and widespread climate occurred repeatedly during the last ice age cycle and beyond in response to changing freshwater fluxes and perhaps other causes. This paradigm, developed and championed especially by W.S. Broecker, has repeatedly proven to be successfully predictive as well as explanatory with high confidence. Much work remains to fully understand what happened and to assess possible implications for the future, but the foundations for this work are remarkably solid. AU - Alley, Richard B. DO - 10.1146/annurev.earth.35.081006.131524 IS - 1 KW - paleoclimatology,ocean circulation,sea ice,Younger Dryas,meridional overturning circulation N1 - https://www.annualreviews.org/doi/abs/10.1146/annurev.earth.35.081006.131524 PY - 2007 SP - 241–272 ST - Wally was right: predictive ability of the North Atlantic “conveyor belt” hypothesis for abrupt climate change T2 - Annual Review of Earth and Planetary Sciences TI - Wally was right: predictive ability of the North Atlantic “conveyor belt” hypothesis for abrupt climate change UR - https://doi.org/10.1146/annurev.earth.35.081006.131524 VL - 35 ID - 17523 ER - TY - JOUR AB - Surface water conditions at the Integrated Ocean Drilling Program (IODP) Site U1314 (Southern Gardar Drift, 56° 21.8' N, 27°53.3' W, 2820 m depth) were inferred using planktic foraminifer assemblages between Marine Isotope Stage (MIS) 19 and 11 (ca. 800-400 ka). Factor analysis of the planktic foraminifer assemblages suggests that the assemblage was controlled by three factors. The first factor (which explained 49% of the variance) is dominated by transitional and subpolar species and points to warm and salty surface water conditions (Atlantic water). The second factor (37%) is dominated by Neogloboquadrina pachyderma sin and has been associated with the presence of cold and low saline surface waters (Arctic water). Finally, the third factor (9%), linked to a significant presence of Turborotalita quinqueloba, reflects the closeness of the Arctic front (the boundary between Atlantic and Arctic water). The position of the Arctic and Polar fronts has been estimated across the glacial-interglacial cycles studied according to planktic foraminifer abundances from Site U1314 (and their factor analysis) combined with a synthesis of planktic foraminifer and diatom data from other North Atlantic sites. Regarding at the migrations of the Arctic front and the surface water masses distribution across each climatic cycle we determined five phases of development. Furthermore, deep ocean circulation changes observed in glacial-interglacial cycles have been associated with each phase. The high abundance of transitional-subpolar foraminifers (above 65% at Site U1314) during the early interglacial phase indicated that the Arctic front position and surface water masses distribution were similar to present conditions. During the late interglacial phase, N. pachyderma sin and T. quinqueloba slightly increased indicating that winter sea ice slightly expanded southwestwards whereas the ice volume remained stable or was still decreasing. N. pachyderma sin increased rapidly (above 65% at Site U1314) at the first phase of glacial periods indicating the expansion of the Arctic waters in the western subpolar North Atlantic. During the second phase of glacial periods the transitional-subpolar assemblage throve again in the central subpolar North Atlantic associated with strong warming events that followed ice-rafting events. The third phase of glacial periods corresponds to full glacial conditions in which N. pachyderma sin dominated the assemblage for the whole subpolar North Atlantic. This division in phases may be applied to the last four climatic cycles. Abstract Copyright (2011) Elsevier, B.V. AU - Alonso-Garcia, Montserrat AU - Sierro, Francisco J. AU - Flores, José A. IS - 3 J2 - Affiliation (analytic): University of Salamanca, Department of Geology (Paleontology), Salamanca Affiliation (monographic): University of Salamanca, Department of Geology (Paleontology), Salamanca, Spain Coordinates: N562200 N562200 W0275300 W0275300 illus., incl. 1 table, sketch maps Contains 96 references Research Program: IODP Integrated Ocean Drilling Program Document Type: Journal Article Bibliographic Level: Analytic Source Note: Palaeogeography, Palaeoclimatology, Palaeoecology, 311(3-4), p.268-280. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0031-0182 Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands GeoRef ID: 2012016250 DOI: 10.1016/j.palaeo.2011.09.004 KW - Algae Arctic front Atlantic Ocean Atmospheric circulation C-13/C-12 Carbon Cenozoic Climate change Cycles Expedition 306 Expeditions 303/306 Factor analysis Foraminifera Gardar Drift Glacial environment Glaciomarine environment Globigerinacea IODP Site U1314 Ice Ice rafting Integrated Ocean Drilling Program Interglacial environment Invertebrata Isotope ratios Isotopes Marine environment Marine sediments Microfossils Middle Pleistocene Nannofossils Neogloboquadrina Neogloboquadrina pachyderma North Atlantic Northeast Atlantic O-18/O-16 Ocean circulation Oxygen Paleo-oceanography Paleoecology Planktonic taxa Plantae Pleistocene Polar regions Protista Quaternary Rotaliina Sea ice Sediments Stable isotopes Statistical analysis Subpolar regions Turborotalia quinqueloba 24 Surficial Geology, Quaternary Geology LA - English PY - 2011 SN - 0031-0182 SP - 268–280 ST - Arctic front shifts in the subpolar North Atlantic during the mid-Pleistocene (800–400 ka) and their implications for ocean circulation T2 - Palaeogeography, Palaeoclimatology, Palaeoecology TI - Arctic front shifts in the subpolar North Atlantic during the mid-Pleistocene (800–400 ka) and their implications for ocean circulation UR - https://doi.org/10.1016/j.palaeo.2011.09.004 VL - 311 ID - 3304 ER - TY - JOUR AB - An analysis of the field of mass produced a reasonably coherent pattern of circulation for the Mediterranean water outflow and estimates of the velocity of the undercurrent both before and after its subdivision into separate upper and lower cores were in good agreement with several previous direct current meter measurements. Meanders induced in the flow by the influence of the bottom topography are regarded as the main cause of the variability in the thermohaline and dynamic properties of the current system. A downstream increase in the volume of transport is interpreted in terms of an entrainment parameter that compares favourably with a recent streamtube model for bottom boundary currents. The analysis also indicates the presence of a deep countercurrent at about 1500 m beneath the main outflow in a region between 9°30′W and 8°30′W south of Cape St Vincent. AU - Ambar, I. AU - Howe, M. R. DA - 1979/05/01/ DO - https://doi.org/10.1016/0198-0149(79)90096-7 IS - 5 N1 - https://www.sciencedirect.com/science/article/pii/0198014979900967 PY - 1979 SN - 0198-0149 SP - 555–568 ST - Observations of the Mediterranean outflow—II. The deep circulation in the vicinity of the Gulf of Cadiz T2 - Deep Sea Research, Part A: Oceanographic Research Papers TI - Observations of the Mediterranean outflow—II. The deep circulation in the vicinity of the Gulf of Cadiz UR - https://doi.org/10.1016/0198-0149(79)90096-7 VL - 26 ID - 17524 ER - TY - JOUR AB - A multidisciplinary study of the Mediterranean outflow in the region west of the Strait of Gibraltar and off the southern and southwestern coasts of the Iberian Peninsula was developed in the frame of the Canary Islands Azores Gibraltar Observations Project. Two high-resolution CTD surveys, which included water sampling for chemical (nutrients and dissolved oxygen) and sedimentological analyses, took place in September 1997 (summer cruise) and January 1998 (winter cruise) in the study region. The correspondence between the high-salinity Mediterranean Water (MW) layer and the low-nutrient content and relatively high abundance of particles was a general result. Further details of the thermohaline analysis and of the geostrophic computations, especially for the layer of MW, are compared with the results obtained for the chemical properties and the sedimentological characteristics. AU - Ambar, I. AU - Serra, N. AU - Brogueira, M. J. AU - Cabeçadas, G. AU - Abrantes, F. AU - Freitas, P. AU - Gonçalves, C. AU - Gonzalez, N. DA - 2002/01/01/ DO - https://doi.org/10.1016/S0967-0645(02)00148-0 IS - 19 N1 - https://www.sciencedirect.com/science/article/pii/S0967064502001480 PY - 2002 SN - 0967-0645 SP - 4163–4177 ST - Physical, chemical and sedimentological aspects of the Mediterranean outflow off Iberia T2 - Deep Sea Research, Part II: Topical Studies in Oceanography TI - Physical, chemical and sedimentological aspects of the Mediterranean outflow off Iberia UR - https://doi.org/10.1016/S0967-0645(02)00148-0 VL - 49 ID - 49339 ER - TY - CHAP A2 - Clark, P.U., Webb, R.S., and Keigwin, L.D. (Eds.) AB - A crucial question to understand the climate system at millennial time-scales is whether we can detect leads and lags. We examine errors on downcore age data sets resulting from the application of two depth/radiocarbon age models: 1) interpolation between dates, versus 2) ordinary least squares (OLS) regression. In areas affected by changes in sediment accumulation rates, interpolation between dates on facies boundaries would seem most appropriate, whereas in areas of constant sedimentation OLS regression would seem appropriate. We estimated the ages of 50 and 21 data points respectively, from cores HU87033-009 and HU93030-007 (both with rates of sediment accumulation ca. 30–40 cm/ky) using the two age models. Both cores show intervals of increased sediment accumulation associated with iceberg rafting events possibly coeval with H-1, -2 and -3(?). The two age models produced average age differences of 0.88 ky in HU87033-009 and 0.48 ky in HU93030-007. Monte Carlo simulation experiments indicated that the interpolation method consistently resulted in the larger errors. We then examine the age distribution for the basal ages of two detrital carbonate (DC) “events” in Baffin Bay and the NW Labrador Sea, including H-1, and show that errors on dating the onset of these events are considerable (∼± 300 yrs). We conclude that, when dealing with the generation of millennial time-series and correlation of abrupt events, more attention needs to be given to appropriate age/depth models and attendant errors. This analysis does not take into account the calibration of the radiocarbon time-scale nor bioturbation, both of which can introduce additional errors. AU - Andrews, John AU - Barber, Donald AU - Jennings, Anne DO - 10.1029/GM112p0023 J2 - Geophysical Monograph Series N1 - DOI does not resolve (11/29/21) PY - 1999 SN - 0-87590-095-X SP - 23–33 ST - Errors in generating time-series and in dating events at Late Quaternary millenial (radiocarbon) time-scales: examples from Baffin Bay, NW Labrador Sea, and east Greenland SV - Geophysical Monograph T2 - Mechanisms of Global Climate Change at Millennial Time Scales TI - Errors in generating time-series and in dating events at Late Quaternary millenial (radiocarbon) time-scales: examples from Baffin Bay, NW Labrador Sea, and east Greenland UR - https://agupubs.onlinelibrary.wiley.com/doi/10.1029/GM112p0023 VL - 112 ID - 17525 ER - TY - JOUR AB - The late Quaternary sedimentary history of the continental margin off Portugal was reconstructed from sediment gravity cores. Hemipelagic sedimentation (lithofacies A) was dominant during glacial times. It was interrupted periodically by deposition of shelf- and upper-slope-derived silty and sandy terrigenous material by dilute turbidity currents (lithofacies B and C), ice-rafted debris during distinct periods of breakdown of North Atlantic ice sheets (Heinrich events, lithofacies D) and large amounts of pteropods (lithofacies F). Settling of biogenic particulate material (lithofacies E) prevailed during the Holocene, when sea level and sea surface temperatures were high and terrigenous shelf-input was low. Downslope transport was dominant on the northern part of the Portuguese margin, culminating in frequent turbidity current transport between 35 and 70 ka. This may be due to a humid climate and a high fluvial input. Pteropod muds are confined to cores south of 41°N. Prominent peaks in pteropod concentration were radiocarbon dated at 17.8 and 24.6 ka. Layers rich in ice-rafted debris (IRD) were found along the entire margin. The base of these layers have been dated at 13.6–15.9 14C ka, 21.0–22.0 14C ka, 33.8 14C ka and ±64.5 ka, which correspond well with the ages of Heinrich events 1, 2, 4 and 6 in the central North Atlantic. Heinrich events 0 (10.5 ka), 3 (27 ka) and 5 (50 ka) rarely influenced sedimentation on the Portuguese slope. A mineralogical study of the IRD within Heinrich layers suggests that most icebergs were derived from the Laurentide Ice Sheet in the Hudson Strait and Hudson Bay area through the Labrador Current and the Canary Current and flowed in a southward direction along the margin. IRD from European ice sheets may have been mixed in during Heinrich event 6. On their way along the margin the icebergs lost much of their sediment load due to melting of the ice in a progressively warmer climate. The southernmost latitude studied (37°N) may be close to the southeastern extension of iceberg transport during Heinrich events. AU - Baas, J. H. AU - Mienert, J. AU - Abrantes, F. AU - Prins, M. A. DA - 1997/05/01/ DO - https://doi.org/10.1016/S0031-0182(96)00135-6 IS - 1–4 KW - Portugal Continental margin Palaeoclimate Palaeoceanography Heinrich event Bottom current N1 - https://www.sciencedirect.com/science/article/pii/S0031018296001356 PY - 1997 SN - 0031-0182 SP - 1–23 ST - Late Quaternary sedimentation on the Portuguese continental margin: climate-related processes and products T2 - Palaeogeography, Palaeoclimatology, Palaeoecology TI - Late Quaternary sedimentation on the Portuguese continental margin: climate-related processes and products UR - https://doi.org/10.1016/S0031-0182(96)00135-6 VL - 130 ID - 17526 ER - TY - JOUR AB - Understanding more exactly how the timing of deglaciations depends on changes in insolation, or the energy received by Earth from the Sun, requires precise and independent records of both environmental change and solar energy input. Bajo et al. strengthened the weak link of that two-member chain, the environmental record, by developing a precise, radiometrically dated chronology of the 11 deglaciations of the past million years derived from speleothems. This allowed them to show more clearly how the initiation and duration of glacial terminations over that period depended on solar obliquity and precession.Science, this issue p. 1235Radiometric dating of glacial terminations over the past 640,000 years suggests pacing by Earth’s climatic precession, with each glacial-interglacial period spanning four or five cycles of ~20,000 years. However, the lack of firm age estimates for older Pleistocene terminations confounds attempts to test the persistence of precession forcing. We combine an Italian speleothem record anchored by a uranium-lead chronology with North Atlantic ocean data to show that the first two deglaciations of the so-called 100,000-year world are separated by two obliquity cycles, with each termination starting at the same high phase of obliquity, but at opposing phases of precession. An assessment of 11 radiometrically dated terminations spanning the past million years suggests that obliquity exerted a persistent influence on not only their initiation but also their duration. AU - Bajo, Petra AU - Drysdale, Russell N. AU - Woodhead, Jon D. AU - Hellstrom, John C. AU - Hodell, David AU - Ferretti, Patrizia AU - Voelker, Antje H. L. AU - Zanchetta, Giovanni AU - Rodrigues, Teresa AU - Wolff, Eric AU - Tyler, Jonathan AU - Frisia, Silvia AU - Spötl, Christoph AU - Fallick, Anthony E. DO - 10.1126/science.aaw1114 IS - 6483 N1 - https://science.sciencemag.org/content/sci/367/6483/1235.full.pdf PY - 2020 SP - 1235–1239 ST - Persistent influence of obliquity on ice age terminations since the middle Pleistocene transition T2 - Science TI - Persistent influence of obliquity on ice age terminations since the middle Pleistocene transition UR - https://doi.org/10.1126/science.aaw1114 VL - 367 ID - 10488 ER - TY - JOUR AB - A delay between surface cooling and the arrival of ice-rafted debris at a site southwest of Iceland over the past four glacial cycles implies that icebergs typically arrived too late to have triggered cooling, although the freshwater derived from melting icebergs may provide a positive feedback for cold stadial conditions. AU - Barker, Stephen AU - Chen, James AU - Gong, Xun AU - Jonkers, Lukas AU - Knorr, Gregor AU - Thornalley, David DA - 2015/04/01 DO - 10.1038/nature14330 IS - 7547 PY - 2015 SN - 1476-4687 SP - 333–336 ST - Icebergs not the trigger for North Atlantic cold events T2 - Nature TI - Icebergs not the trigger for North Atlantic cold events UR - https://doi.org/10.1038/nature14330 VL - 520 ID - 17527 ER - TY - JOUR AB - Within the Late Pleistocene, terminations describe the major transitions marking the end of glacial cycles. While it is established that abrupt shifts in the ocean/atmosphere system are a ubiquitous component of deglaciation, significant uncertainties remain concerning their specific role and the likelihood that terminations may be interrupted by large-amplitude abrupt oscillations. In this perspective we address these uncertainties in the light of recent developments in the understanding of glacial terminations as the ultimate interaction between millennial and orbital timescale variability. Innovations in numerical climate simulation and new geologic records allow us to highlight new avenues of research and identify key remaining uncertainties such as sea-level variability. AU - Barker, Stephen AU - Knorr, Gregor DA - 2021/04/15 DO - 10.1038/s41467-021-22388-6 IS - 1 PY - 2021 SN - 2041-1723 SP - 2273 ST - Millennial scale feedbacks determine the shape and rapidity of glacial termination T2 - Nature Communications TI - Millennial scale feedbacks determine the shape and rapidity of glacial termination UR - https://doi.org/10.1038/s41467-021-22388-6 VL - 12 ID - 23078 ER - TY - JOUR AB - We constructed an 800,000-year synthetic record of Greenland climate variability based on the thermal bipolar seesaw model. Our Greenland analog reproduces much of the variability seen in the Greenland ice cores over the past 100,000 years. The synthetic record shows strong similarity with the absolutely dated speleothem record from China, allowing us to place ice core records within an absolute timeframe for the past 400,000 years. Hence, it provides both a stratigraphic reference and a conceptual basis for assessing the long-term evolution of millennial-scale variability and its potential role in climate change at longer time scales. Indeed, we provide evidence for a ubiquitous association between bipolar seesaw oscillations and glacial terminations throughout the Middle to Late Pleistocene. AU - Barker, Stephen AU - Knorr, Gregor AU - Edwards, R. Lawrence AU - Parrenin, Frederic AU - Putnam, Aaron E. AU - Skinner, Luke C. AU - Wolff, Eric AU - Ziegler, Martin DO - 10.1126/science.1203580 IS - 6054 N1 - https://science.sciencemag.org/content/sci/334/6054/347.full.pdf PY - 2011 SP - 347–351 ST - 800,000 years of abrupt climate variability T2 - Science TI - 800,000 years of abrupt climate variability UR - https://doi.org/10.1126/science.1203580 VL - 334 ID - 7623 ER - TY - JOUR AB - Abstract The development of larger and longer lasting northern hemisphere ice sheets during the mid-Pleistocene Transition (MPT) coincided with global cooling. Here, we show that surface waters of the north-eastern Atlantic actually warmed across this interval (∼1.2–0.8 Ma), which we argue reflects an increase in the north-eastward transport of heat and moisture via the North Atlantic Current (NAC) into the Nordic Seas (the Atlantic Inflow). We suggest that simultaneous cooling and warming along the north-western and south-eastern margins (respectively) of the NAC during Marine Isotope Stage 28 (∼995 ka) reflected the increasing persistence of northern ice sheets as Atlantic Inflow increased. This resulted in a diachronous shift from ∼40 to ∼100 kyr cyclicity across the North East (NE) Atlantic as the growing influence of northern ice sheets spread southwards; to the north-west of the NAC the first “100 kyr” cycle preceded Termination 12 (∼960 ka), while on the south-eastern margin of the NAC the transition occurred ∼100 kyr later. Exploratory climate model simulations suggest that increasing Atlantic Inflow at this time could have accelerated ice sheet growth because pre-existing moderately sized ice sheets allowed the positive effect of increasing precipitation to outpace melting. In addition, we propose that the dependence of post-MPT ice sheets on moisture transport via the Atlantic Inflow may ultimately contribute to their apparent vulnerability to insolation forcing once a critical size threshold is crossed and high latitude ice sheets become starved of a vital moisture source. AU - Barker, Stephen AU - Zhang, Xu AU - Jonkers, Lukas AU - Lordsmith, Sian AU - Conn, Stephen AU - Knorr, Gregor DO - https://doi.org/10.1029/2020PA004200 IS - 4 N1 - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020PA004200 PY - 2021 SN - 2572-4517 SP - e2020PA004200 ST - Strengthening Atlantic inflow across the mid-Pleistocene transition T2 - Paleoceanography and Paleoclimatology TI - Strengthening Atlantic inflow across the mid-Pleistocene transition UR - https://doi.org/10.1029/2020PA004200 VL - 36 ID - 17528 ER - TY - JOUR AU - Bereiter, B. AU - Fischer, H. AU - Schwander, J. AU - Stocker, T. F. DO - 10.5194/tc-8-245-2014 IS - 1 N1 - https://tc.copernicus.org/articles/8/245/2014/ PY - 2014 SN - 1994-0424 SP - 245–256 ST - Diffusive equilibration of N2, O2 and CO2 mixing ratios in a 1.5-million-years-old ice core T2 - The Cryosphere TI - Diffusive equilibration of N2, O2 and CO2 mixing ratios in a 1.5-million-years-old ice core UR - https://doi.org/10.5194/tc-8-245-2014 VL - 8 ID - 23079 ER - TY - JOUR AB - Abstract We present a high-resolution planktonic foraminiferal stable isotope record (Globigerinoides ruber) spanning marine oxygen isotope stages (MISs) 6 through 8 in the northwestern subtropical Atlantic Ocean (Ocean Drilling Program Leg 172 Site 1059). The record fills a gap to produce an about 1.3 Myr long continuous time series of high-frequency (> ~1/12 kyr) surface ocean hydrography, the first of this kind. We test the hypothesis that the suborbital climate signals (i.e., half and quarter precession cycles) are linked to precession forcing in tropical latitudes. Semiprecession cycles present between 0 and 320 ka are of the right periodicity to relate to the dominant precession forcing (23 kyr). These cycles are evident as double peaks within the given precession framework, and there is good match in the amplitude modulation of the filter output and the δ18O time series. Quarter precession cycles dominate the suborbital spectra between 320 ka and 1.3 Ma. Periodicities are close to those expected from the harmonics of the dominant precession peaks in the δ18O record, but present in the time series only intermittently, and their amplitude modulation does not match that of the primary precession period. Thus, only the half precession cycles evidence a response to low-latitude insolation such as that introduced by insolation maxima at the equinoxes or solstices during the course of a precession cycle. Additionally, we find well-defined, rapid (~1.5–2 kyr) variations across the first of the interglacial maxima of MIS 7 adding to evidence of non–ice sheet-related forcing factors in driving climate instabilities. AU - Billups, Katharina AU - Scheinwald, Andre DO - https://doi.org/10.1002/2014PA002641 IS - 6 N1 - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2014PA002641 PY - 2014 SN - 0883-8305 SP - 612–627 ST - Origin of millennial-scale climate signals in the subtropical North Atlantic T2 - Paleoceanography and Paleoclimatology TI - Origin of millennial-scale climate signals in the subtropical North Atlantic UR - https://doi.org/10.1002/2014PA002641 VL - 29 ID - 17529 ER - TY - JOUR AB - Although millennial-scale climate variability (<10 ka) has been well studied during the last glacial cycles, little is known about this important aspect of climate in the early Pleistocene, prior to the middle Pleistocene Transition. Here we present an early Pleistocene climate record at centennial resolution for two representative glacials (marine isotope stages (MIS) 37-41 from approximately 1235 to 1320 ka) during the "41 ka world" at Integrated Ocean Drilling Program Site U1385 (the "Shackleton Site") on the southwest Iberian margin. Millennial-scale climate variability was suppressed during interglacial periods (MIS 37, MIS 39, and MIS 41) and activated during glacial inceptions when benthic δ18O exceeded 3.2 ppm. Millennial variability during glacials MIS 38 and MIS 40 closely resembled Dansgaard-Oeschger events from the last glacial (MIS 3) in amplitude, shape, and pacing. The phasing of oxygen and carbon isotope variability is consistent with an active oceanic thermal bipolar see-saw between the Northern and Southern Hemispheres during most of the prominent stadials. Surface cooling was associated with systematic decreases in benthic carbon isotopes, indicating concomitant changes in the meridional overturning circulation. A comparison to other North Atlantic records of ice rafting during the early Pleistocene suggests that freshwater forcing, as proposed for the late Pleistocene, was involved in triggering or amplifying perturbations of the North Atlantic circulation that elicited a bipolar see-saw response. Our findings support similarities in the operation of the climate system occurring on millennial time scales before and after the middle Pleistocene Transition despite the increases in global ice volume and duration of the glacial cycles. Abstract Copyright (2015), American Geophysical Union. All Rights Reserved. AU - Birner, B. AU - Hodell, D. A. AU - Tzedakis, P. C. AU - Skinner, L. C. IS - 1 J2 - Affiliation (analytic): University of Cambridge, Godwin Laboratory for Palaeoclimate Research, Cambridge Affiliation (monographic): University of Cambridge, Godwin Laboratory for Palaeoclimate Research, Cambridge, United Kingdom Coordinates: N373417 N373417 W0100719 W0100720 illus., incl. 1 table, sketch map Contains 77 references Research Program: IODP Integrated Ocean Drilling Program Document Type: Journal Article Bibliographic Level: Analytic Source Note: Paleoceanography, 31(1), p.203-217. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom GeoRef ID: 2017051934 DOI: 10.1002/2015PA002868 KW - Alkaline earth metals Anomalinidae Atlantic Ocean C-13/C-12 Calcium Carbon Cassidulinacea Cenozoic Cibicidoides Cibicidoides wuellerstorfi Expedition 339 Foraminifera Globigerina Globigerina bulloides Globigerinacea Globigerinidae IODP Site U1385 Integrated Ocean Drilling Program Invertebrata Isotope ratios Isotopes Lower Pleistocene MIS 3 MIS 37 MIS 38 MIS 39 MIS 40 MIS 41 Magnesium Marine environment Metals Mg/Ca Microfossils North Atlantic O-18/O-16 Oxygen Paleoclimatology Paleoenvironment Pleistocene Protista Quaternary Rotaliina Stable isotopes 02 Geochemistry 24 Surficial Geology, Quaternary Geology LA - English PY - 2016 SN - 0883-8305 SP - 203–217 ST - Similar millennial climate variability on the Iberian margin during two early Pleistocene glacials and MIS 3 T2 - Paleoceanography and Paleoclimatology TI - Similar millennial climate variability on the Iberian margin during two early Pleistocene glacials and MIS 3 UR - https://doi.org/10.1002/2015PA002868 VL - 31 ID - 4722 ER - TY - JOUR AB - Tuning is a widespread technique to combine, date and interpret multiple fossil proxy archives through aligning supposedly synchronous events between the archives. The approach will be reviewed by discussing a number of literature examples, ranging from peat and tephra layers to orbital tuning and δ18O series from marine and ice deposits. Potential problems will be highlighted such as the dangers of circular reasoning and unrecognised chronological uncertainties, and some solutions suggested. Fossil proxy research could become enhanced if tuning were approached in a more quantitative, reliable and objective way, and especially if individual proxy archives were non-tuned and kept on independent time-scales. AU - Blaauw, Maarten DA - 2012/03/12/ DO - https://doi.org/10.1016/j.quascirev.2010.11.012 N1 - https://www.sciencedirect.com/science/article/pii/S0277379110004087 PY - 2012 SN - 0277-3791 SP - 38–49 ST - Out of tune: the dangers of aligning proxy archives T2 - Quaternary Science Reviews TI - Out of tune: the dangers of aligning proxy archives UR - https://doi.org/10.1016/j.quascirev.2010.11.012 VL - 36 ID - 17530 ER - TY - JOUR AB - A precise relative chronology for Greenland and West Antarctic paleotemperature is extended to 90,000 years ago, based on correlation of atmospheric methane records from the Greenland Ice Sheet Project 2 and Byrd ice cores. Over this period, the onset of seven major millennial-scale warmings in Antarctica preceded the onset of Greenland warmings by 1500 to 3000 years. In general, Antarctic temperatures increased gradually while Greenland temperatures were decreasing or constant, and the termination of Antarctic warming was apparently coincident with the onset of rapid warming in Greenland. This pattern provides further evidence for the operation of a “bipolar see-saw” in air temperatures and an oceanic teleconnection between the hemispheres on millennial time scales. AU - Blunier, Thomas AU - Brook, Edward J. DO - doi:10.1126/science.291.5501.109 IS - 5501 N1 - https://www.science.org/doi/abs/10.1126/science.291.5501.109 PY - 2001 SP - 109–112 ST - Timing of millennial-scale climate change in Antarctica and Greenland during the last glacial period T2 - Science TI - Timing of millennial-scale climate change in Antarctica and Greenland during the last glacial period UR - https://doi.org/10.1126/science.291.5501.109 VL - 291 ID - 17531 ER - TY - JOUR AB - Subpolar Mode Waters (SPMW) in the eastern North Atlantic subpolar gyre are investigated with hydrographic and Lagrangian data (surface drifters and isopycnal floats). Historical hydrographic data show that SPMWs are surface water masses with nearly uniform properties, confined between the ocean surface and the permanent pycnocline. SPMWs represented by densities 27.3σθ, 27.4σθ, and 27.5σθ are present in the eastern subpolar gyre and are influenced by the topography and the regional circulation. Construction of an absolute surface stream function from surface drifters shows that SPMWs are found along the mean path of each of the several branches of the North Atlantic Current (NAC) and their density increases gradually downstream. The Rockall Trough branch of the NAC carries 27.3σθ, 27.4σθ, and 27.5σθ SPMW toward the Iceland-Faroe Front. In the Iceland Basin, the Subarctic Front along the western flank of the Rockall Plateau carries a similar sequence of SPMW. The western side of the Central Iceland Basin branch of the NAC, on the other hand, veers westward and joins the East Reykjanes Ridge Current, feeding the 27.5σθ SPMW on the Reykjanes Ridge. The separation among the various NAC branches most likely explains the different properties that characterize the 27.5σθ SPMW found on the Reykjanes Ridge and on the Iceland-Faroe Ridge. Since the branches of the NAC have a dominant northeastward direction, the newly observed distribution of SPMW combined with the new stream function calculation modify the original hypothesis of McCartney and Talley (1982) of a smooth cyclonic pathway for SPMW advection and density increase around the subpolar gyre. AU - Brambilla, Elena AU - Talley, Lynne D. DO - https://doi.org/10.1029/2006JC004062 IS - C4 N1 - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2006JC004062 PY - 2008 SN - 0148-0227 ST - Subpolar mode eater in the northeastern Atlantic: 1. Averaged properties and mean circulation T2 - Journal of Geophysical Research: Oceans TI - Subpolar mode eater in the northeastern Atlantic: 1. Averaged properties and mean circulation UR - https://doi.org/10.1029/2006JC004062 VL - 113 ID - 49488 ER - TY - JOUR AB - 230Th-dated oxygen isotope records of stalagmites from Sanbao Cave, China, characterize Asian Monsoon (AM) precipitation through the ends of the third- and fourthmost recent ice ages. As a result, AM records for the past four glacial terminations can now be precisely correlated with those from ice cores and marine sediments, establishing the timing and sequence of major events. In all four cases, observations are consistent with a classic Northern Hemisphere summer insolation intensity trigger for an initial retreat of northern ice sheets. Meltwater and icebergs entering the North Atlantic alter oceanic and atmospheric circulation and associated fluxes of heat and carbon, causing increases in atmospheric CO2 and Antarctic temperatures that drive the termination in the Southern Hemisphere. Increasing CO2 and summer insolation drive recession of northern ice sheets, with probable positive feedbacks between sea level and CO2. AU - Cheng, Hai AU - Edwards, R. Lawrence AU - Broecker, Wallace S. AU - Denton, George H. AU - Kong, Xinggong AU - Wang, Yongjin AU - Zhang, Rong AU - Wang, Xianfeng IS - 5950 J2 - Affiliation (analytic): University of Minnesota, Department of Geology and Geophysics, Minneapolis, MN Affiliation (monographic): University of Minnesota, Department of Geology and Geophysics, Minneapolis, MN, United States Coordinates: N314000 N314000 E1102600 E1102600 illus. Contains 63 references Document Type: Journal Article Bibliographic Level: Analytic Source Note: Science, 326(5950), p.248-252. Publisher: American Association for the Advancement of Science, Washington, DC, United States. ISSN: 0036-8075 Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. GeoRef ID: 2010030531 DOI: 10.1126/science.1177840 KW - Actinides Antarctica Asia Atlantic Ocean Carbon dioxide Cenozoic China Climate change Correlation Far East Hubei China Ice cores Isotope ratios Isotopes Metals North Atlantic O-18/O-16 Oxygen Paleoclimatology Paleotemperature Quaternary Radioactive isotopes Reconstruction Sanbao Cave Solution features Speleothems Stable isotopes Stalagmites Th-230 Thorium Upper Quaternary 24 Surficial Geology, Quaternary Geology LA - English PY - 2009 SN - 0036-8075 SP - 248–252 ST - Ice age terminations T2 - Science TI - Ice age terminations UR - https://doi.org/10.1126/science.1177840 VL - 326 ID - 6329 ER - TY - JOUR AB - High-resolution palaeoclimate records recovered from the Iberian margin in core MD95-2040 exhibit large fluctuations in oceanographic conditions over the last 190 ka. Large-scale cooling of the surface ocean is indicated by the presence of the polar planktonic foraminifer Neogloboquadrina pachyderma (sinistral), and in some instances the occurrence of ice-rafted debris (IRD). Ice-rafting episodes were prevalent in both of the last two glacials with greater intensity in Stages 2 through 4, than in Stage 6. The six youngest Heinrich events are well defined during the last glacial but detrital carbonate is absent from Heinrich layers HL6, HL5 and HL3. Dansgaard–Oeschger stadial-equivalent sub-millennial IRD deposition events have been detected, in particular during Stage 3, allowing a good match with the cooling displayed in the Greenland ice core (GISP2). Sea-surface temperature off Portugal in Stage 6 was in general warmer than during the last glacial, pointing towards a weaker southward influence of polar water masses. Ice rafting occurred mainly in mid-MIS (Marine Isotope Stage) 6 (between 173 and 153 kyr) as a group of poorly differentiated, short-duration quasi-continuous events, mainly marked by the high abundance of sinistral N. pachyderma. Differences exist in IRD composition relative to the last glacial, with a reduced Canadian-derived detrital carbonate component, combined with an important contribution of volcanic particles. The lower magnitude and higher frequency of these events suggest that the higher temperatures would have induced iceberg waning closer to the source areas. AU - de Abreu, Lúcia AU - Shackleton, Nicholas J. AU - Schönfeld, Joachim AU - Hall, Michael AU - Chapman, Mark DA - 2003/04/15/ DO - https://doi.org/10.1016/S0025-3227(03)00046-X IS - 1–2 KW - Iberian margin millennial-scale climate variability sea-surface temperature Stage 6 ice rafting planktonic foraminifera N1 - https://www.sciencedirect.com/science/article/pii/S002532270300046X PY - 2003 SN - 0025-3227 SP - 1–20 ST - Millennial-scale oceanic climate variability off the western Iberian margin during the last two glacial periods T2 - Marine Geology TI - Millennial-scale oceanic climate variability off the western Iberian margin during the last two glacial periods UR - https://doi.org/10.1016/S0025-3227(03)00046-X VL - 196 ID - 17533 ER - TY - JOUR AB - A major puzzle of paleoclimatology is why, after a long interval of cooling climate, each late Quaternary ice age ended with a relatively short warming leg called a termination. We here offer a comprehensive hypothesis of how Earth emerged from the last global ice age. A prerequisite was the growth of very large Northern Hemisphere ice sheets, whose subsequent collapse created stadial conditions that disrupted global patterns of ocean and atmospheric circulation. The Southern Hemisphere westerlies shifted poleward during each northern stadial, producing pulses of ocean upwelling and warming that together accounted for much of the termination in the Southern Ocean and Antarctica. Rising atmospheric CO2 during southern upwelling pulses augmented warming during the last termination in both polar hemispheres. AU - Denton, G. H. AU - Anderson, R. F. AU - Toggweiler, J. R. AU - Edwards, R. L. AU - Schaefer, J. M. AU - Putnam, A. E. DO - 10.1126/science.1184119 IS - 5986 N1 - https://science.sciencemag.org/content/sci/328/5986/1652.full.pdf PY - 2010 SP - 1652–1656 ST - The last glacial termination T2 - Science TI - The last glacial termination UR - https://doi.org/10.1126/science.1184119 VL - 328 ID - 8671 ER - TY - JOUR AB - Global cooling in intermediate glacial climate with northern ice sheets preconditions climatic instability with bipolar seesaw. Climatic variabilities on millennial and longer time scales with a bipolar seesaw pattern have been documented in paleoclimatic records, but their frequencies, relationships with mean climatic state, and mechanisms remain unclear. Understanding the processes and sensitivities that underlie these changes will underpin better understanding of the climate system and projections of its future change. We investigate the long-term characteristics of climatic variability using a new ice-core record from Dome Fuji, East Antarctica, combined with an existing long record from the Dome C ice core. Antarctic warming events over the past 720,000 years are most frequent when the Antarctic temperature is slightly below average on orbital time scales, equivalent to an intermediate climate during glacial periods, whereas interglacial and fully glaciated climates are unfavourable for a millennial-scale bipolar seesaw. Numerical experiments using a fully coupled atmosphere-ocean general circulation model with freshwater hosing in the northern North Atlantic showed that climate becomes most unstable in intermediate glacial conditions associated with large changes in sea ice and the Atlantic Meridional Overturning Circulation. Model sensitivity experiments suggest that the prerequisite for the most frequent climate instability with bipolar seesaw pattern during the late Pleistocene era is associated with reduced atmospheric CO2 concentration via global cooling and sea ice formation in the North Atlantic, in addition to extended Northern Hemisphere ice sheets. AU - Dome Fuji Ice Core Project Members DO - doi:10.1126/sciadv.1600446 IS - 2 N1 - Kenji Kawamura Ayako Abe-Ouchi Hideaki Motoyama Yutaka Ageta Shuji Aoki Nobuhiko Azuma Yoshiyuki Fujii Koji Fujita Shuji Fujita Kotaro Fukui Teruo Furukawa Atsushi Furusaki Kumiko Goto-Azuma Ralf Greve Motohiro Hirabayashi Takeo Hondoh Akira Hori Shinichiro Horikawa Kazuho Horiuchi Makoto Igarashi Yoshinori Iizuka Takao Kameda Hiroshi Kanda Mika Kohno Takayuki Kuramoto Yuki Matsushi Morihiro Miyahara Takayuki Miyake Atsushi Miyamoto Yasuo Nagashima Yoshiki Nakayama Takakiyo Nakazawa Fumio Nakazawa Fumihiko Nishio Ichio Obinata Rumi Ohgaito Akira Oka Jun’ichi Okuno Junichi Okuyama Ikumi Oyabu Frédéric Parrenin Frank Pattyn Fuyuki Saito Takashi Saito Takeshi Saito Toshimitsu Sakurai Kimikazu Sasa Hakime Seddik Yasuyuki Shibata Kunio Shinbori Keisuke Suzuki Toshitaka Suzuki Akiyoshi Takahashi Kunio Takahashi Shuhei Takahashi Morimasa Takata Yoichi Tanaka Ryu Uemura Genta Watanabe Okitsugu Watanabe Tetsuhide Yamasaki Kotaro Yokoyama Masakazu Yoshimori Takayasu Yoshimoto https://www.science.org/doi/abs/10.1126/sciadv.1600446 PY - 2017 SP - e1600446 ST - State dependence of climatic instability over the past 720,000 years from Antarctic ice cores and climate modeling T2 - Science Advances TI - State dependence of climatic instability over the past 720,000 years from Antarctic ice cores and climate modeling UR - https://doi.org/10.1126/sciadv.1600446 VL - 3 ID - 17545 ER - TY - CHAP A2 - Stow, D.A.V., Hernández-Molina, F.J., Alvarez Zarikian, C.A., and the Expedition 339 Scientists AB - During Integrated Ocean Drilling Program Expedition 339, five sites were drilled in the Gulf of Cadiz and two sites were drilled off the West Iberian margin from November 2011 to January 2012. Expedition 339 recovered 5447 m of core, with an average recovery of 86.4%. The Gulf of Cadiz was targeted for drilling as a key location for the investigation of Mediterranean Outflow Water (MOW) through the Strait of Gibraltar (Gibraltar Gateway) and its influence on global circulation and climate. The gulf is also a prime area for understanding the effects of tectonic activity on evolution of the Gibraltar Gateway and margin sedimentation. Drilling penetrated into the Miocene at two sites in the Gulf of Cadiz and showed a MOW signal in the sedimentary record following the opening of the Gibraltar Gateway. The Pliocene succession, penetrated at four sites, displays characteristics consistent with low bottom-current activity and weak MOW since near the beginning of the Pliocene at ∼4.5-4.2 Ma and a somewhat more pronounced contourite signal upward through the Pliocene. Significant widespread unconformities found at 3.0-3.2 Ma are interpreted as a signal of intensified MOW. The Quaternary succession was sampled at six sites and displays characteristics consistent with a much more pronounced phase of contourite drift development. There are three distinct periods of high MOW activity separated by two widespread unconformities at 2.2-2.4 Ma and ∼0.9 Ma related to even higher MOW. Following the ∼0.9 Ma unconformity, the final phase of drift evolution established the contourite depositional system architecture we see today. There is significant climatic and tectonic control on the evolution of MOW and bottom-current activity. Preliminary work has shown a remarkable record of orbital-scale variation in bulk sediment properties of contourites at several of the drift sites and good correlation between all sites. Climate control on contourite sedimentation is clearly significant at this scale; further work will determine the nature of controls at the millennial scale. However, from the closure of the Atlantic-Mediterranean gateways in Spain and Morocco around 6 Ma and the opening of the Gibraltar Gateway at 5.3 Ma to the present day, even stronger tectonic control has affected margin development, downslope sediment transport, and contourite drift evolution. Based on the timing of these events recorded in the sedimentary record, we propose that tectonic pulsing in the region, resulting from small movements of the Africa and Eurasia plates and associated deep-seated asthenosphere activity, has played an important role in controlling sedimentation on this margin. The Gulf of Cadiz is the world's premier contourite laboratory and thus presents an ideal testing ground for the contourite paradigm. Following recovery of more than 4.5 km of contourite cores from six of the sites under direct MOW influence, existing models for contourite deposition are found to be sound. Further study of these models will undoubtedly allow us to resolve outstanding issues of depositional processes, drift budgets, and recognition of fossil contourites in the ancient record onshore. The expedition also verified the presence of contourite sands that are clean and well sorted in a number of settings, including those created by local diapiric activity. These sands represent a completely new and important deepwater sand type that, where found deeper in the subsurface, could provide a significant exploration target for potential oil and gas reservoirs. At the deeper water site off southwest Portugal (the Shackleton site), we drilled five separate holes and recovered two complete splice sets of Quaternary hemipelagic sedimentation over the past 1.4 m.y. These will form the basis of detailed shore-based collaboration to establish a high-precision marine reference section of Quaternary climate change for comparison with other marine sections and with established ice-core and terrestrial records. AU - Expedition 339 Scientists CY - Tokyo J2 - Affiliation (analytic): Universidad de Vigo, Departmento Geociencias Marinas, Vigo Affiliation (monographic): Universidad de Vigo, Departmento Geociencias Marinas, Vigo, Spain Corporate Affiliation (monographic): Integrated Ocean Drilling Program, Expedition 399 Scientists, College Station, TX Coordinates: N361900 N373500 W0064700 W0100800 illus., incl. sects., 1 table, geol. sketch map Contains 129 references Research Program: IODP Integrated Ocean Drilling Program Document Type: Journal Article Bibliographic Level: Analytic Source Note: Proceedings of the Integrated Ocean Drilling Program; Mediterranean Outflow; Expedition 339 of the riserless drilling platform; Ponta Delgada, Azores (Portugal), to Lisbon, Portugal, Sites U1385-U1391, 16 November 2011-16 January 2012, Francisco J. Hernández-Molina, Dorrik A. V. Stow, Carlos Alvarez Zarikian, Johanna Lofi, Trevor Williams, Gary D. Acton, André Bahr, Barbara Balestra, Emmanuelle Ducassou, Roger D. Flood, José-Abel Flores, Satoshi Furota, Patrick Grunert, David A. Hodell, Francisco J. Jimenez-Espejo, Jin Kyoung Kim, Lawrence A. Krissek, Junichiro Kuroda, Li Baohua, Lucas Lourens, Madeline D. Miller, Futoshi Nanayama, Naohisa Nishida, Carl Richter, Maria F. Sanchez Goni, Francisco J. Sierro Sánchez, Arun D. Singh, Craig R. Sloss, Yasuhiro Takashimizu, Alexandrina Tzanova, Antje Voelker and Chuang Xuan; Integrated Ocean Drilling Program, Expedition 399 Scientists, College Station, TX. Proceedings of the Integrated Ocean Drilling Program (Online), Vol.339, 51p. Publisher: IODP Management International, Washington, DC, United States. ISSN: 1930-1014 Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. GeoRef ID: 2013057470 DOI: 10.2204/iodp.proc.339.101.2013 KW - Atlantic Ocean Boreholes Cenozoic Climate change Contourite Cores Expedition 339 Geophysical methods Geophysical profiles Geophysical surveys Gulf of Cadiz IODP Site U1385 IODP Site U1386 IODP Site U1387 IODP Site U1388 IODP Site U1390 IODP Site U1391 Integrated Ocean Drilling Program Lithostratigraphy Magnesium sulfates Magnetostratigraphy Marine sediments Mediterranean Outflow Neogene North Atlantic Northeast Atlantic Paleo-oceanography Paleoclimatology Paleoenvironment Paleogeography Quaternary Reconstruction Sea-level changes Sediments Seismic methods Seismic profiles Surveys Tertiary Vertical seismic profiles Well logs 12 Stratigraphy, Historical Geology and Paleoecology LA - English N1 - Francisco J. Hernández-Molina Dorrik A.V. Stow Carlos Alvarez Zarikian Johanna Lofi Trevor Williams Gary D. Acton André Bahr Barbara Balestra Emmanuelle Ducassou Roger D. Flood José-Abel Flores Satoshi Furota Patrick Grunert David A. Hodell Francisco J. Jimenez-Espejo Jin Kyoung Kim Lawrence A. Krissek Junichiro Kuroda Baohua Li Lucas Lourens Madeline D. Miller Futoshi Nanayama Naohisa Nishida Carl Richter Maria F. Sanchez Goni Francisco J. Sierro Sánchez Arun D. Singh Craig R. Sloss Yasuhiro Takashimizu Alexandrina Tzanova Antje Voelker Chuang Xuan PB - Integrated Ocean Drilling Program Management International, Inc. PY - 2013 SN - 1930-1014 ST - Expedition 339 summary T2 - Proceedings of the Integrated Ocean Drilling Program TI - Expedition 339 summary UR - https://doi.org/doi:10.2204/iodp.proc.339.101.2013 VL - 339 ID - 4678 ER - TY - CHAP A2 - Stow, D.A.V., Hernández-Molina, F.J., Alvarez Zarikian, C.A., and the Expedition 339 Scientists AU - Expedition 339 Scientists CY - Tokyo J2 - Affiliation (analytic): Universidad de Vigo, Departmento Geociencias Marinas, Vigo Affiliation (monographic): Universidad de Vigo, Departmento Geociencias Marinas, Vigo, Spain Corporate Affiliation (monographic): Integrated Ocean Drilling Program, Expedition 399 Scientists, College Station, TX Coordinates: N373400 N373400 W0100800 W0100800 illus., incl. 29 tables, sketch map Contains 67 references Research Program: IODP Integrated Ocean Drilling Program Document Type: Journal Article Bibliographic Level: Analytic Source Note: Proceedings of the Integrated Ocean Drilling Program; Mediterranean Outflow; Expedition 339 of the riserless drilling platform; Ponta Delgada, Azores (Portugal), to Lisbon, Portugal, Sites U1385-U1391, 16 November 2011-16 January 2012, Francisco J. Hernández-Molina, Dorrik A. V. Stow, Carlos Alvarez Zarikian, Johanna Lofi, Trevor Williams, Gary D. Acton, André Bahr, Barbara Balestra, Emmanuelle Ducassou, Roger D. Flood, José-Abel Flores, Satoshi Furota, Patrick Grunert, David A. Hodell, Francisco J. Jimenez-Espejo, Jin Kyoung Kim, Lawrence A. Krissek, Junichiro Kuroda, Li Baohua, Lucas Lourens, Madeline D. Miller, Futoshi Nanayama, Naohisa Nishida, Carl Richter, Maria F. Sanchez Goni, Francisco J. Sierro Sánchez, Arun D. Singh, Craig R. Sloss, Yasuhiro Takashimizu, Alexandrina Tzanova, Antje Voelker and Chuang Xuan; Integrated Ocean Drilling Program, Expedition 399 Scientists, College Station, TX. Proceedings of the Integrated Ocean Drilling Program (Online), Vol.339, 104p. Publisher: IODP Management International, Washington, DC, United States. ISSN: 1930-1014 Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. GeoRef ID: 2013057472 DOI: 10.2204/iodp.proc.339.103.2013 KW - Algae Arthropoda Atlantic Ocean Biostratigraphy Boreholes Cenozoic Chemostratigraphy Cores Correlation Crustacea Downhole methods Foraminifera Geochemistry Gulf of Cadiz Hydrochemistry IODP Site U1385 Invertebrata Lithofacies Lithostratigraphy Magnetostratigraphy Mandibulata Microfossils Miospores Nannofossils Neogene North Atlantic Ostracoda Paleomagnetism Palynomorphs Physical properties Plantae Pollen Pore water Protista Quaternary Tertiary Well logs 12 Stratigraphy, Historical Geology and Paleoecology LA - English N1 - Francisco J. Hernández-Molina Dorrik A.V. Stow Carlos Alvarez Zarikian Johanna Lofi Trevor Williams Gary D. Acton André Bahr Barbara Balestra Emmanuelle Ducassou Roger D. Flood José-Abel Flores Satoshi Furota Patrick Grunert David A. Hodell Francisco J. Jimenez-Espejo Jin Kyoung Kim Lawrence A. Krissek Junichiro Kuroda Baohua Li Lucas Lourens Madeline D. Miller Futoshi Nanayama Naohisa Nishida Carl Richter Maria F. Sanchez Goni Francisco J. Sierro Sánchez Arun D. Singh Craig R. Sloss Yasuhiro Takashimizu Alexandrina Tzanova Antje Voelker Chuang Xuan PB - Integrated Ocean Drilling Program Management International, Inc. PY - 2013 SN - 1930-1014 ST - Site U1385 T2 - Proceedings of the Integrated Ocean Drilling Program TI - Site U1385 UR - https://doi.org/doi:10.2204/iodp.proc.339.103.2013 VL - 339 ID - 4723 ER - TY - JOUR AB - The recovery of a 1.5 million yr long ice core from Antarctica represents a keystone of our understanding of Quaternary climate, the progression of glaciation over this time period and the role of greenhouse gas cycles in this progression. Here we tackle the question of where such ice may still be found in the Antarctic ice sheet. We can show that such old ice is most likely to exist in the plateau area of the East Antarctic ice sheet (EAIS) without stratigraphic disturbance and should be able to be recovered after careful pre-site selection studies. Based on a simple ice and heat flow model and glaciological observations, we conclude that positions in the vicinity of major domes and saddle position on the East Antarctic Plateau will most likely have such old ice in store and represent the best study areas for dedicated reconnaissance studies in the near future. In contrast to previous ice core drill site selections, however, we strongly suggest significantly reduced ice thickness to avoid bottom melting. For example for the geothermal heat flux and accumulation conditions at Dome C, an ice thickness lower than but close to about 2500 m would be required to find 1.5 Myr old ice (i.e., more than 700 m less than at the current EPICA Dome C drill site). Within this constraint, the resolution of an Oldest-Ice record and the distance of such old ice to the bedrock should be maximized to avoid ice flow disturbances, for example, by finding locations with minimum geothermal heat flux. As the geothermal heat flux is largely unknown for the EAIS, this parameter has to be carefully determined beforehand. In addition, detailed bedrock topography and ice flow history has to be reconstructed for candidates of an Oldest-Ice ice coring site. Finally, we argue strongly for rapid access drilling before any full, deep ice coring activity commences to bring datable samples to the surface and to allow an age check of the oldest ice. AU - Fischer, H. AU - Severinghaus, J. AU - Brook, E. AU - Wolff, E. AU - Albert, M. AU - Alemany, O. AU - Arthern, R. AU - Bentley, C. AU - Blankenship, D. AU - Chappellaz, J. AU - Creyts, T. AU - Dahl-Jensen, D. AU - Dinn, M. AU - Frezzotti, M. AU - Fujita, S. AU - Gallee, H. AU - Hindmarsh, R. AU - Hudspeth, D. AU - Jugie, G. AU - Kawamura, K. AU - Lipenkov, V. AU - Miller, H. AU - Mulvaney, R. AU - Parrenin, F. AU - Pattyn, F. AU - Ritz, C. AU - Schwander, J. AU - Steinhage, D. AU - van Ommen, T. AU - Wilhelms, F. DO - 10.5194/cp-9-2489-2013 IS - 6 N1 - https://cp.copernicus.org/articles/9/2489/2013/ PY - 2013 SN - 1814-9332 SP - 2489–2505 ST - Where to find 1.5 million yr old ice for the IPICS "oldest-ice" ice core T2 - Climate of the Past TI - Where to find 1.5 million yr old ice for the IPICS "oldest-ice" ice core UR - https://doi.org/10.5194/cp-9-2489-2013 VL - 9 ID - 17534 ER - TY - THES AU - Fiúza, A. CY - Portugal M3 - PhD dissertation PB - Universidade de Lisboa PY - 1984 ST - Hidrologia e Dinâmica das Águas Costeiras de Portugal TI - Hidrologia e Dinâmica das Águas Costeiras de Portugal ID - 17535 ER - TY - JOUR AB - The distribution of the water masses and their circulation in the eastern North Atlantic region off the northern half of the west coast of the Iberian Peninsula are analysed here based on CTD measurements made in May 1993 during the “MORENA 1” cruise. The upper layers of the ocean, down to about 100m, showed a typical spring, non-upwelling situation with a very shallow seasonal thermocline overlying thicker remnants of the mixed layer from the previous winter. Below, Central Water extended between a subsurface salinity maximum near depths of 100–140m and a salinity minimum at about 500m. Using quantitative water mass analysis and geostrophic calculations, a poleward surface current reaching down to depths of 250m and transporting relatively warm and saline Eastern North Atlantic Central Water (ENACW) of subtropical origin was characterised, centred at a few tens of km offshore the shelf break, therefore indicating that the northward current identified previously in this region during winter (the Portugal Coastal Countercurrent) continues to be present through the spring season. A large-scale transition zone, the Galicia Front, was found in the northwest area of the study region, reaching from the surface layers down to the depths of the Mediterranean Water. To the north of this front, relatively fresh Central Water of Western Atlantic origin replaced the subtropical branch of ENACW. At the deeper Central Water levels, ENACW from subpolar North Atlantic origin was present through the whole study region. The influence of the upper and lower cores of Mediterranean Water was present, centred at levels of 800 and 1100m, as indicated by their characteristic thermohaline maxima. The deduced flow of Mediterranean Water was towards the north in the whole study region, in clear relation with the Portugal Slope Undercurrent, and showed some tendency to branch towards the west through the gap between the Vigo Seamount and the Galicia Bank. The Mediterranean upper core occupied a relatively thin layer, O (100m), and underwent a strong dilution of about 45% from the south to the north of the study region; the lower core spread over a larger depth range, of about 400–500m, and decayed only by about 20% through the region. Below the Mediterranean Water, the influence of North Atlantic Deep Water spread through the study region, and an intermediate layer of Labrador Sea Water was also present, particularly offshore in the northwest zone. AU - Fiúza, Armando F. G. AU - Hamann, Meike AU - Ambar, Isabel AU - Dı́az del Rı́o, Guillermo AU - González, Nicolás AU - Cabanas, José M. DA - 1998/07/01/ DO - https://doi.org/10.1016/S0967-0637(98)00008-9 IS - 7 N1 - https://www.sciencedirect.com/science/article/pii/S0967063798000089 PY - 1998 SN - 0967-0637 SP - 1127–1160 ST - Water masses and their circulation off western Iberia during May 1993 T2 - Deep Sea Research, Part I: Oceanographic Research Papers TI - Water masses and their circulation off western Iberia during May 1993 UR - https://doi.org/10.1016/S0967-0637(98)00008-9 VL - 45 ID - 17536 ER - TY - JOUR AB - A first study from the subtropical western Atlantic, using 231Pa/ 230Th ratios as a kinematic proxy for deep water circulation, provided compelling evidence for a strong link between climate and the rate of Meridional Overturning Circulation (MOC) over the last deglaciation. However, these results warrant confirmation from additional locations and water depths because the interpretation of the sedimentary 231Pa/ 230Th ratio in terms of circulation vigor can be biased by variations in particle flux and composition. We have measured 231Pa/ 230Th in a core from the Iberian margin, in the Northeastern Atlantic basin, and have compared these new results to the data from the western Atlantic basin. We find that the reduction in the circulation during H1 and YD and the subsequent increases first recognized in the sediment deposited on Bermuda Rise are also evident in the eastern basin, in a totally different sedimentary regime, confirming that sedimentary 231Pa/ 230Th ratios record basin-wide changes in deep water circulation. However, some differences between the eastern and western records are also recognized, providing preliminary evidence to differentiate between renewal rates in the two North Atlantic basins and between shallower and deeper overturning. Our results suggest the possible existence of two sources of Glacial North Atlantic Intermediate Deep Water (GNAIW), one in the south Labrador Sea and another west of Rockall Plateau. Both sources contributed to the meridional overturning but the two had different sensitivity to meltwater from the Laurentide and the Fennoscandian ice sheets during the deglaciation. These results indicate that additional information on the geometry and strength of the ventilation of the deep Atlantic can be obtained by contrasting the evolution of sediment 231Pa/ 230Th in different sections of the Atlantic Ocean. AD - AA(Laboratoire des Sciences du Climat et de l'Environnement (Unité mixte CEA-CNRS), Domaine du CNRS, F-91198 Gif sur Yvette, France), AB(Laboratoire des Sciences du Climat et de l'Environnement (Unité mixte CEA-CNRS), Domaine du CNRS, F-91198 Gif sur Yvette, France; Institut Universitaire de France, Université Versailles St-Quentin, France), AC(Department of Geology and Geophysics, Woods Hole Oceanographic Institution, MA 02543, USA), AD(Department of Earth and Ocean Sciences, University of British Columbia, 6270 [1] University Blvd, Vancouver, BC, Canada V6T 1Z4), AE(Godwin Institute for quaternary Research, Department of Earth Sciences, University of Cambridge, new Museums Site, Pembroke Street, Cambridge, CB2 3SA, UK), AF(Laboratoire des Sciences du Climat et de l'Environnement (Unité mixte CEA-CNRS), Domaine du CNRS, F-91198 Gif sur Yvette, France) AU - Gherardi, J. -M. AU - Labeyrie, L. AU - McManus, J. F. AU - Francois, R. AU - Skinner, L. C. AU - Cortijo, E. DA - December 01, 2005 DO - 10.1016/j.epsl.2005.09.061 IS - 3–4 N1 - https://ui.adsabs.harvard.edu/abs/2005E&PSL.240..710G PY - 2005 SN - 0012-821X SP - 710–723 ST - Evidence from the northeastern Atlantic Basin for variability in the rate of the meridional overturning circulation through the last deglaciation T2 - Earth and Planetary Science Letters TI - Evidence from the northeastern Atlantic Basin for variability in the rate of the meridional overturning circulation through the last deglaciation UR - https://doi.org/10.1016/j.epsl.2005.09.061 VL - 240 ID - 17537 ER - TY - JOUR AB - The development, persistence, and variability of upwelling filaments off the Atlantic coast of the Iberian Peninsula are examined by means of advanced very high resolution radiometer infrared imagery observed between 1982 and 1990. These observations indicate that the regime is broadly similar to that observed in the California Current system and is closely related to the large scale wind climatology of the subtropical gyre. Upwelling generally starts in late May or early June and persists until late September or early October. In May or June, a narrow band of cold water of quite uniform width is observed along much of the west coast of the Iberian Peninsula. This band has a “fringed” appearance; that is it consists of many narrow “fingers” of cool water extending 20–30 km offshore. The major filament structures generally do not begin to form until late July or August. The filaments appear first as bulges in the upwelling front. These bulges grow offshore to form filaments that reach their maximum length (200–250 km) in September. The lengths of the filaments gradually decrease until the filaments become relatively rare in late October. Typically, five or six fully developed filaments are observed off the Iberian Peninsula late in the upwelling season. Most of these are associated with major topographic features of the region, in particular the large capes which are common to the north and south of the peninsula. It is therefore postulated that the dominant dynamical processes related to filament formation off Iberia is topographic forcing. The exceptions are two major filaments commonly observed along the more regular coastline of northern Portugal. It is hypothesized that these filaments are formed by flow instabilities resulting in meandering of the southward flowing jet. These instabilities may possibly be initiated by the large capes of northern Spain. AU - Haynes, R. AU - Barton, E. D. AU - Pilling, I. DO - https://doi.org/10.1029/93JC02016 IS - C12 N1 - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/93JC02016 PY - 1993 SN - 0148-0227 SP - 22681–22692 ST - Development, persistence, and variability of upwelling filaments off the Atlantic coast of the Iberian Peninsula T2 - Journal of Geophysical Research: Oceans TI - Development, persistence, and variability of upwelling filaments off the Atlantic coast of the Iberian Peninsula UR - https://doi.org/10.1029/93JC02016 VL - 98 ID - 49489 ER - TY - JOUR AB - Large decreases in Atlantic meridional overturning circulation accompanied every one of the cold Northern Hemispheric stadial events that occurred during the heart of the last glacial period. These events, lasting on average around 1000 years each, have long been thought to result from changes in deep ocean circulation. Henry et al. used a suite of geochemical proxies from marine sediments to show that reductions in the export of northern deep waters occurred before and during stadial periods (see the Perspective by Schmittner). This observation firmly establishes the role of ocean circulation as a cause of abrupt glacial climate change during that interval. Science, this issue p. 470; see also p. 445 Deep ocean circulation changes preceded and accompanied the millennial cold climate events of the past ice age. The most recent ice age was characterized by rapid and hemispherically asynchronous climate oscillations, whose origin remains unresolved. Variations in oceanic meridional heat transport may contribute to these repeated climate changes, which were most pronounced during marine isotope stage 3, the glacial interval 25 thousand to 60 thousand years ago. We examined climate and ocean circulation proxies throughout this interval at high resolution in a deep North Atlantic sediment core, combining the kinematic tracer protactinium/thorium (Pa/Th) with the deep water-mass tracer, epibenthic δ13C. These indicators suggest reduced Atlantic overturning circulation during every cool northern stadial, with the greatest reductions during episodic Hudson Strait iceberg discharges, while sharp northern warming followed reinvigorated overturning. These results provide direct evidence for the ocean’s persistent, central role in abrupt glacial climate change. AU - Henry, L. G. AU - McManus, J. F. AU - Curry, W. B. AU - Roberts, N. L. AU - Piotrowski, A. M. AU - Keigwin, L. D. DO - doi:10.1126/science.aaf5529 IS - 6298 N1 - https://www.science.org/doi/abs/10.1126/science.aaf5529 PY - 2016 SP - 470–474 ST - North Atlantic ocean circulation and abrupt climate change during the last glaciation T2 - Science TI - North Atlantic ocean circulation and abrupt climate change during the last glaciation UR - https://doi.org/10.1126/science.aaf5529 VL - 353 ID - 23080 ER - TY - JOUR AB - The trickle of water that began to flow from the Mediterranean Sea into the Atlantic Ocean after the opening of the Strait of Gibraltar turned into a veritable flood by the end of the Pliocene 2 to 3 million years ago. It then began to influence large-scale ocean circulation in earnest. Hernández-Molina et al. describe marine sediment cores collected by an ocean drilling expedition (see the Perspective by Filippelli). The results reveal a detailed history of the timing of Mediterranean outflow water activity and show how the addition of that warm saline water to the cooler less-salty waters of the Atlantic was related to climate changes, deep ocean circulation, and plate tectonics.Science, this issue p. 1244; see also p. 1228 Sediments cored along the southwestern Iberian margin during Integrated Ocean Drilling Program Expedition 339 provide constraints on Mediterranean Outflow Water (MOW) circulation patterns from the Pliocene epoch to the present day. After the Strait of Gibraltar opened (5.33 million years ago), a limited volume of MOW entered the Atlantic. Depositional hiatuses indicate erosion by bottom currents related to higher volumes of MOW circulating into the North Atlantic, beginning in the late Pliocene. The hiatuses coincide with regional tectonic events and changes in global thermohaline circulation (THC). This suggests that MOW influenced Atlantic Meridional Overturning Circulation (AMOC), THC, and climatic shifts by contributing a component of warm, saline water to northern latitudes while in turn being influenced by plate tectonics. AU - Hernández-Molina, F. Javier AU - Stow, Dorrik A. V. AU - Alvarez-Zarikian, Carlos A. AU - Acton, Gary AU - Bahr, André AU - Balestra, Barbara AU - Ducassou, Emmanuelle AU - Flood, Roger AU - Flores, José-Abel AU - Furota, Satoshi AU - Grunert, Patrick AU - Hodell, David AU - Jimenez-Espejo, Francisco AU - Kim, Jin Kyoung AU - Krissek, Lawrence AU - Kuroda, Junichiro AU - Li, Baohua AU - Llave, Estefania AU - Lofi, Johanna AU - Lourens, Lucas AU - Miller, Madeline AU - Nanayama, Futoshi AU - Nishida, Naohisa AU - Richter, Carl AU - Roque, Cristina AU - Pereira, Hélder AU - Sanchez Goñi, Maria Fernanda AU - Sierro, Francisco J. AU - Singh, Arun Deo AU - Sloss, Craig AU - Takashimizu, Yasuhiro AU - Tzanova, Alexandrina AU - Voelker, Antje AU - Williams, Trevor AU - Xuan, Chuang DO - 10.1126/science.1251306 IS - 6189 N1 - https://science.sciencemag.org/content/sci/344/6189/1244.full.pdf PY - 2014 SP - 1244–1250 ST - Onset of Mediterranean outflow into the North Atlantic T2 - Science TI - Onset of Mediterranean outflow into the North Atlantic UR - https://doi.org/10.1126/science.1251306 VL - 344 ID - 10609 ER - TY - JOUR AB - The late Pliocene-early Pleistocene sapropel-bearing sequences exposed in the Vrica, Semaforo, Singa and Punta Piccola sections of southern Italy and the Francocastello section on Crete have been calibrated to the new astronomical solutions for the precession of the equinox and the eccentricity of the Earth's orbit using inferred phase relationships between these orbital cycles and the sapropel cycles. A new Mediterranean Precession-Related Sapropel (MPRS) coding is introduced according to which sapropels are coded after the correlative peak of the precession index as numbered from the Recent. These sapropels can now be dated with an accuracy of 1 ka by taking a time lag of 4 ka between orbital forcing, and maximum climate response and sapropel formation into account. This tuning further results in ages for the Pliocene-Pleistocene boundary (1.81 Ma), the top of the Olduvai (1.79 or 1.84), the bottom of the Olduvai (1.95 ± 0.01), the Reunion (2.14–2.15), the Gauss/Matuyama (2.59/2.62) and the top of the Kaena (3.02 ± 0.01). These ages are remarkably similar to the astronomically calibrated ages obtained independently by Shackleton et al. based on ODP Site 677 ([1], Trans. R. Soc. Edinb., 81, 1990), but deviate considerably from those provided by Ruddiman et al. ([2], Paleoceanography, Vol. 4) and Raymo et al. based on DSDP Site 607 ([3], Paleoceanography, Vol. 4). The constant discrepancy of 130 ka with the time scale of Ruddiman et al. and Raymo et al. is explained by the new age of 0.78 instead of 0.73 Ma for the Brunhes/Matuyama, as recently proposed by Shackleton et al., and the fact that Ruddiman et al. missed two obliquity related cycles in the Brunhes/Matuyama to top Olduvai interval. Our astronomically calibrated ages do not confirm the conventional radiometric ages of the reversal boundaries, but, on the contrary, imply that K/Ar radiometric dating yields ages that are consistently too young by 5–7%. AU - Hilgen, F. J. DA - 1991/06/01/ DO - https://doi.org/10.1016/0012-821X(91)90206-W IS - 2–4 N1 - https://www.sciencedirect.com/science/article/pii/0012821X9190206W PY - 1991 SN - 0012-821X SP - 226–244 ST - Astronomical calibration of Gauss to Matuyama sapropels in the Mediterranean and implication for the Geomagnetic Polarity Time Scale T2 - Earth and Planetary Science Letters TI - Astronomical calibration of Gauss to Matuyama sapropels in the Mediterranean and implication for the Geomagnetic Polarity Time Scale UR - https://doi.org/10.1016/0012-821X(91)90206-W VL - 104 ID - 17538 ER - TY - JOUR AU - Hodell, D. AU - Crowhurst, S. AU - Lourens, L. AU - Margari, V. AU - Nicolson, J. AU - Rolfe, J. E. AU - Skinner, L. C. AU - Thomas, N. AU - Tzedakis, P. C. AU - Mleneck-Vautravers, M. J. AU - Wolff, E. W. DO - 10.5194/cp-2022-61 N1 - https://cp.copernicus.org/preprints/cp-2022-61/ PY - preprint SN - 1814-9359 ST - A 1.5-million-year record of orbital and millennial climate variability in the North Atlantic T2 - Climate of the Past TI - A 1.5-million-year record of orbital and millennial climate variability in the North Atlantic UR - https://doi.org/10.5194/cp-2022-61 VL - 2022 ID - 49338 ER - TY - JOUR AB - Here we report 420 kyr long records of sediment geochemical and color variations from the southwestern Iberian Margin. We synchronized the Iberian Margin sediment record to Antarctic ice cores and speleothem records on millennial time scales and investigated the phase responses relative to orbital forcing of multiple proxy records available from these cores. Iberian Margin sediments contain strong precession power. Sediment "redness" (a* and 570-560 nm) and the ratio of long-chain alcohols to n-alkanes (C26OH/(C26OH + C29)) are highly coherent and in-phase with precession. Redder layers and more oxidizing conditions (low alcohol ratio) occur near precession minima (summer insolation maxima). We suggest these proxies respond rapidly to low-latitude insolation forcing by wind-driven processes (e.g., dust transport, upwelling, precipitation). Most Iberian Margin sediment parameters lag obliquity maxima by 7-8 ka, indicating a consistent linear response to insolation forcing at obliquity frequencies driven mainly by high-latitude processes. Although the lengths of the time series are short (420 ka) for detecting 100 kyr eccentricity cycles, the phase relationships support those obtained by Shackleton []. Antarctic temperature and the Iberian Margin alcohol ratios (C26OH/(C26OH + C29)) lead eccentricity maxima by 6 kyr, with lower ratios (increased oxygenation) occurring at eccentricity maxima. CO2, CH4, and Iberian SST are nearly in phase with eccentricity, and minimum ice volume (as inferred from Pacific δ18Oseawater) lags eccentricity maxima by 10 kyr. The phase relationships derived in this study continue to support a potential role of the Earth's carbon cycle in contributing to the 100 kyr cycle. Abstract Copyright (2013), . American Geophysical Union. All Rights Reserved. AU - Hodell, David AU - Crowhurst, Simon AU - Skinner, Luke AU - Tzedakis, Polychronis C. AU - Margari, Vasiliki AU - Channell, James E. T. AU - Kamenov, George AU - Maclachlan, Suzanne AU - Rothwell, Guy IS - 1 J2 - Affiliation (analytic): University of Cambridge, Godwin Laboratory for Palaeoclimate Research, Cambridge Affiliation (monographic): University of Cambridge, Godwin Laboratory for Palaeoclimate Research, Cambridge, United Kingdom Coordinates: N373300 N375300 W0100500 W0101000 illus., incl. 1 table, sketch map Contains 82 references Research Program: IODP Integrated Ocean Drilling Program Document Type: Journal Article Bibliographic Level: Analytic Source Note: Paleoceanography, 28(1), p.185-199. Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from John Wiley & Sons, Chichester, United Kingdom GeoRef ID: 2014000264 DOI: 10.1002/palo.20017 KW - Alcohols Alkaline earth metals Atlantic Ocean Barium C-13/C-12 Ca/Ti Calcium Calcium carbonate Carbon Cenozoic Climate forcing Color Continental margin Cores Eccentricity Europe Expedition 339 Holocene IODP Site U1385 Iberian Peninsula Integrated Ocean Drilling Program Isotope ratios Isotopes Marine sediments Metals North Atlantic Northeast Atlantic O-18/O-16 Obliquity of the ecliptic Orbital forcing Organic compounds Oxygen Paleo-oceanography Paleoclimatology Paleomagnetism Pleistocene Portugal Precession Quaternary Reflectance Sediments Southern Europe Spectra Sr-87/Sr-86 Stable isotopes Statistical analysis Strontium Time series analysis Titanium Upper Pleistocene X-ray fluorescence spectra 02 Geochemistry 24 Surficial Geology, Quaternary Geology LA - English PY - 2013 SN - 0883-8305 SP - 185–199 ST - Response of Iberian margin sediments to orbital and suborbital forcing over the past 420 ka T2 - Paleoceanography and Paleoclimatology TI - Response of Iberian margin sediments to orbital and suborbital forcing over the past 420 ka UR - https://doi.org/10.1002/palo.20017 VL - 28 ID - 4714 ER - TY - JOUR AB - We produced a composite depth scale and chronology for Site U1385 on the SW Iberian Margin. Using log(Ca/Ti) measured by core scanning XRF at 1-cm resolution in all holes, a composite section was constructed to 166.5meter composite depth (mcd) that corrects for stretching and squeezing in each core. Oxygen isotopes of benthic foraminifera were correlated to a stacked δ18O reference signal (LR04) to produce an oxygen isotope stratigraphy and age model. Variations in sediment color contain very strong precession signals at Site U1385, and the amplitude modulation of these cycles provides a powerful tool for developing an orbitally-tuned age model. We tuned the U1385 record by correlating peaks in L* to the local summer insolation maxima at 37°N. The benthic δ18O record of Site U1385, when placed on the tuned age model, generally agrees with other time scales within their respective chronologic uncertainties. The age model is transferred to down-core data to produce a continuous time series of log(Ca/Ti) that reflect relative changes of biogenic carbonate and detrital sediment. Biogenic carbonate increases during interglacial and interstadial climate states and decreases during glacial and stadial periods. Much of the variance in the log(Ca/Ti) is explained by a linear combination of orbital frequencies (precession, tilt and eccentricity), whereas the residual signal reflects suborbital climate variability. The strong correlation between suborbital log(Ca/Ti) variability and Greenland temperature over the last glacial cycle at Site U1385 suggests that this signal can be used as a proxy for millennial-scale climate variability over the past 1.5Ma. Millennial climate variability, as expressed by log(Ca/Ti) at Site U1385, was a persistent feature of glacial climates over the past 1.5Ma, including glacial periods of the early Pleistocene (‘41-kyr world’) when boundary conditions differed significantly from those of the late Pleistocene (‘100-kyr world’). Suborbital variability was suppressed during interglacial stages and enhanced during glacial periods, especially when benthic δ18O surpassed ~3.3–3.5‰. Each glacial inception was marked by appearance of strong millennial variability and each deglaciation was preceded by a terminal stadial event. Suborbital variability may be a symptomatic feature of glacial climate or, alternatively, may play a more active role in the inception and/or termination of glacial cycles. AU - Hodell, D. AU - Lourens, L. AU - Crowhurst, S. AU - Konijnendijk, T. AU - Tjallingii, R. AU - Jiménez-Espejo, F. AU - Skinner, L. AU - Tzedakis, P.C. AU - the Shackleton Site Project Members DA - 2015/10/01/ DO - https://doi.org/10.1016/j.gloplacha.2015.07.002 KW - IODP Iberian Margin Stratigraphic correlation Millennial climate variability Oxygen isotopes Pleistocene Cyclostratigraphy N1 - Hodell, D. Lourens, L. Crowhurst, S. Konijnendijk, T. Tjallingii, R. Jiménez-Espejo, F. Skinner, L. Tzedakis, P. C. Abrantes, Fatima Acton, Gary D. Alvarez Zarikian, Carlos A. Bahr, André Balestra, Barbara Barranco, Estefanìa Llave Carrara, Gabriela Ducassou, Emmanuelle Flood, Roger D. Flores, José-Abel Furota, Satoshi Grimalt, Joan Grunert, Patrick Hernández-Molina, Javier Kim, Jin Kyoung Krissek, Lawrence A. Kuroda, Junichiro Li, Baohua Lofi, Johanna Margari, Vasiliki Martrat, Belen Miller, Madeline D. Nanayama, Futoshi Nishida, Naohisa Richter, Carl Rodrigues, Teresa Rodríguez-Tovar, Francisco J. Roque, Ana Cristina Freixo Sanchez Goñi, Maria F. Sierro Sánchez, Francisco J. Singh, Arun D. Sloss, Craig R. Stow, Dorrik A. V. Takashimizu, Yasuhiro Tzanova, Alexandrina Voelker, Antje Xuan, Chuang Williams, Trevor https://www.sciencedirect.com/science/article/pii/S0921818115001423 PY - 2015 SN - 0921-8181 SP - 49–64 ST - A reference time scale for Site U1385 (Shackleton Site) on the SW Iberian Margin T2 - Global and Planetary Change TI - A reference time scale for Site U1385 (Shackleton Site) on the SW Iberian Margin UR - https://doi.org/10.1016/j.gloplacha.2015.07.002 VL - 133 ID - 10626 ER - TY - JOUR AB - Nick Shackleton's research on piston cores from the Iberian margin highlighted the importance of this region for providing high-fidelity records of millennial-scale climate variability, and for correlating climate events from the marine environment to polar ice cores and European terrestrial sequences. During the Integrated Ocean Drilling Program (IODP) Expedition 339, we sought to extend the Iberian margin sediment record by drilling with the D/V JOIDES Resolution. Five holes were cored at Site U1385 using the advanced piston corer (APC) system to a maximum depth of ∼155.9 m below sea floor (m b.s.f.). Immediately after the expedition, cores from all holes were analyzed by core scanning X-ray fluorescence (XRF) at 1 cm spatial resolution. Ca/Ti data were used to accurately correlate from hole-to-hole and construct a composite spliced section, containing no gaps or disturbed intervals to 166.5 m composite depth (mcd). A low-resolution (20 cm sample spacing) oxygen isotope record confirms that Site U1385 contains a continuous record of hemipelagic sedimentation from the Holocene to 1.43 Ma (Marine Isotope Stage 46). The sediment profile at Site U1385 extends across the middle Pleistocene transition (MPT) with sedimentation rates averaging ∼10 cm kyr-1. Strong precession cycles in colour and elemental XRF signals provide a powerful tool for developing an orbitally tuned reference timescale. Site U1385 is likely to become an important type section for marine-ice-terrestrial core correlations and the study of orbital- and millennial-scale climate variability. AU - Hodell, D.A., Lourens, L., Stow, D.A.V., Hernández-Molina, F. Javier, and Alvarez-Zarikian, C.A. J2 - Affiliation (analytic): University of Cambridge, Department of Earth Sciences, @GBR Affiliation (monographic): University of Cambridge, Department of Earth Sciences, United Kingdom Corporate Affiliation (monographic): Integrated Ocean Drilling Program, Expedition 339, Shackleton Site Project Members, College Station, TX Coordinates: N373417 N373417 W0100734 W0100734 illus., incl. sketch map Contains 28 references Research Program: IODP Integrated Ocean Drilling Program Document Type: Journal Article Bibliographic Level: Analytic Source Note: Scientific Drilling, Vol.16, p.13-19. Publisher: Copernicus GmbH on behalf of the German Research Centre for Geosciences (GFZ), Gottingen, International. ISSN: 1816-8957 Copyright Information: GeoRef, Copyright 2020 American Geosciences Institute. Reference includes data from Copernicus Gesellschaft, Katlenburg-Lindau, Germany GeoRef ID: 2014034868 URL access: Open access DOI: 10.5194/sd-16-13-2013 KW - Atlantic Ocean Cenozoic Chemostratigraphy Climate change Climate forcing Continental margin Cores Correlation Europe Expedition 339 Gulf of Cadiz Holocene IODP Site U1385 Iberian Peninsula Ice cores Integrated Ocean Drilling Program Isotope ratios Isotopes Lithostratigraphy Marine sediments North Atlantic Northeast Atlantic O-18/O-16 Orbital forcing Oxygen Paleoclimatology Pleistocene Quaternary Sediments Southern Europe Southwestern Iberian Peninsula Stable isotopes 24 Surficial Geology, Quaternary Geology LA - English PY - 2013 SN - 1816-8957 SP - 13–19 ST - The "Shackleton Site" (IODP Site U1385) on the Iberian Margin T2 - Scientific Drilling TI - The "Shackleton Site" (IODP Site U1385) on the Iberian Margin UR - https://doi.org/10.5194/sd-16-13-2013 VL - 16 ID - 4721 ER - TY - BOOK AU - Hodell, D.A., Elderfield, H., Greaves, M., McCave, I.N., Skinner, L., Thomas, A., and White, N. CY - Liverpool, UK PB - British Oceanographic Data Centre PY - 2014 ST - The JC089 Cruise Report - IODP Site Survey of the Shackleton Sites, SW Iberian Margin TI - The JC089 Cruise Report - IODP Site Survey of the Shackleton Sites, SW Iberian Margin ID - 49490 ER - TY - JOUR AB - We present a 3.2 Myr record of stable isotopes and physical properties at IODP Site U1308 (reoccupation of DSDP Site 609) located within the ice-rafted detritus (IRD) belt of the North Atlantic. We compare the isotope and lithological proxies at Site U1308 with other North Atlantic records (e.g., sites 982, 607/U1313, and U1304) to reconstruct the history of orbital and millennial-scale climate variability during the Quaternary. The Site U1308 record documents a progressive increase in the intensity of Northern Hemisphere glacial-interglacial cycles during the late Pliocene and Quaternary, with mode transitions at ∼ 2.7, 1.5, 0.9, and 0.65 Ma. These transitions mark times of change in the growth and stability of Northern Hemisphere ice sheets. They also coincide with increases in vertical carbon isotope gradients between the intermediate and deep ocean, suggesting changes in deep carbon storage and atmospheric CO2. Orbital and millennial climate variability co-evolved during the Quaternary such that the trend towards larger and thicker ice sheets was accompanied by changes in the style, frequency, and intensity of millennial-scale variability. This co-evolution may be important for explaining the observed patterns of Quaternary climate change. AU - Hodell, David A. AU - Channell, James E. T. IS - 9 J2 - Affiliation (analytic): Godwin Laboratory for Palaeoclimate Research, Department of Earth Sciences, Cambridge Affiliation (monographic): Godwin Laboratory for Palaeoclimate Research, Department of Earth Sciences, Cambridge, United Kingdom Coordinates: N495300 N495300 W0241400 W0241400; N573100 N573100 W0155200 W0155200; N410000 N410000 W0325700 W0325700; N530300 N530300 W0333200 W0333200 illus., incl. sketch map Contains 124 references Research Program: DSDP Deep Sea Drilling Project; IODP Integrated Ocean Drilling Program; IPOD International Phase of Ocean Drilling; ODP Ocean Drilling Program Document Type: Journal Article Bibliographic Level: Analytic Source Note: Climate of the Past, 12(9), p.1805-1828. Publisher: Copernicus, Katlenburg-Lindau, International. ISSN: 1814-9324 Copyright Information: GeoRef, Copyright 2020 American Geosciences Institute. Reference includes data from Copernicus Gesellschaft, Katlenburg-Lindau, Germany GeoRef ID: 2017016944 URL access: Open access DOI: 10.5194/cp-12-1805-2016 KW - Atlantic Ocean C-13/C-12 Carbon Carbon dioxide Carbonates Cenozoic Chronology Climate change Climate forcing Cores Cyclic processes DSDP Site 607 DSDP Site 609 Deep Sea Drilling Project Deep-sea environment Density Detrital sedimentation Expedition 303 Expedition 306 Expeditions 303/306 Foraminifera Glacial environment Glacial extent Glacial geology Glaciation Global Grain size Heinrich events IODP Site U1302 IODP Site U1303 IODP Site U1304 IODP Site U1308 IODP Site U1313 IPOD Ice cores Ice rafting Ice sheets Integrated Ocean Drilling Program Intensity Interglacial environment Invertebrata Isotope ratios Isotopes Leg 162 Leg 94 Magnetic susceptibility Marine environment Marine sediments Microfossils Mid-Atlantic Ridge Natural gamma radiation North Atlantic Northeast Atlantic Northern Hemisphere Northwest Atlantic O-18/O-16 ODP Site 982 Ocean Drilling Program Ocean circulation Orbital forcing Oxygen Paleo-oceanography Paleoclimatology Periodicity Physical properties Pleistocene Protista Quaternary Rockall Bank Sea water Sedimentation Sediments Stable isotopes Statistical analysis Storage Temporal distribution Time series analysis Variations Ventilation 24 Surficial Geology, Quaternary Geology LA - English PY - 2016 SN - 1814-9324 SP - 1805–1828 ST - Mode transitions in Northern Hemisphere glaciation: co-evolution of millennial and orbital variability in Quaternary climate T2 - Climate of the Past TI - Mode transitions in Northern Hemisphere glaciation: co-evolution of millennial and orbital variability in Quaternary climate UR - https://doi.org/10.5194/cp-12-1805-2016 VL - 12 ID - 3379 ER - TY - JOUR AU - Hodell, David A. AU - Channell, James E. T. AU - Curtis, Jason H. AU - Romero, Oscar E. AU - Röhl, Ursula IS - 4 J2 - Affiliation (analytic): University of Florida, Department of Geological Sciences, Gainesville, FL Affiliation (monographic): University of Florida, Department of Geological Sciences, Gainesville, FL, United States Coordinates: N495300 N495300 W0241400 W0241400 illus., incl. 2 tables, sketch map Contains 81 references Research Program: IODP Integrated Ocean Drilling Program Document Type: Journal Article Bibliographic Level: Analytic Source Note: Paleoceanography, 23(4). Publisher: American Geophysical Union, Washington, DC, United States. ISSN: 0883-8305 Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. GeoRef ID: 2010051012 DOI: 10.1029/2008PA001591 KW - Atlantic Ocean C-13/C-12 Carbon Cenozoic Chemostratigraphy Expeditions 303/306 Glaciation Heinrich events Hudson Strait IODP Site U1308 Integrated Ocean Drilling Program Isotope ratios Isotopes Laurentide ice sheet Magnetic properties Magnetic susceptibility Marine environment Mid-Atlantic Ridge Middle Pleistocene North Atlantic Northeast Atlantic O-18/O-16 Oxygen Paleoclimatology Paleoenvironment Paleomagnetism Pleistocene Quaternary Spectra Stable isotopes X-ray fluorescence spectra 02 Geochemistry 24 Surficial Geology, Quaternary Geology LA - English PY - 2008 SN - 0883-8305 SP - PA4218 ST - Onset of "Hudson Strait" Heinrich events in the eastern North Atlantic at the end of the middle Pleistocene transition (∼640 ka)? T2 - Paleoceanography and Paleoclimatology TI - Onset of "Hudson Strait" Heinrich events in the eastern North Atlantic at the end of the middle Pleistocene transition (∼640 ka)? UR - https://doi.org/10.1029/2008PA001591 VL - 23 ID - 3387 ER - TY - JOUR AB - We report stable isotope, core scanning XRF, and ice-rafted detritus (IRD) data in glacial-aged sediments from piston Core KN166-14-JPC-13 (hereafter referred to as JPC-13) retrieved at 53.1°N 33.5°W on the southern Gardar Drift, North Atlantic. A chronology was established by correlating millennial-scale features in the benthic δ18O record to Portuguese Margin Core MD95-2042. Once the alignment of benthic δ18O of JPC-13 to MD95-2042 is fixed, the relative timing of proxy variables is used to determine the phasing of changes in IRD and surface-deep hydrography. Each peak in North Atlantic IRD coincided with a decrease in benthic δ18O that, in turn, has been linked to warming in Antarctica (Events A1–A7). The IRD pulses are followed shortly thereafter by abrupt decreases in planktonic δ18O, indicating warming and increased heat transport to the subpolar North Atlantic associated with Greenland interstadials (GIS) 8, 12,14, and 16–17. Grain-size and elemental (K/Ti) variations indicate that Iceland–Scotland Overflow Water (ISOW) was stronger during these long, warm interstadial periods of Marine Isotope Stage (MIS) 3. The results are consistent with interhemispheric phase relationships inferred from Iberian Margin sediment cores and with methane synchronization of Greenland and Antarctic ice cores. AU - Hodell, David A. AU - Evans, Helen F. AU - Channell, James E. T. AU - Curtis, Jason H. DA - 2010/12/01/ DO - https://doi.org/10.1016/j.quascirev.2010.09.006 IS - 27–28 N1 - https://www.sciencedirect.com/science/article/pii/S0277379110003288 PY - 2010 SN - 0277-3791 SP - 3875–3886 ST - Phase relationships of North Atlantic ice-rafted debris and surface-deep climate proxies during the last glacial period T2 - Quaternary Science Reviews TI - Phase relationships of North Atlantic ice-rafted debris and surface-deep climate proxies during the last glacial period UR - https://doi.org/10.1016/j.quascirev.2010.09.006 VL - 29 ID - 17540 ER - TY - JOUR AB - We present the distributions of hydrographic properties (potential temperature, salinity, dissolved oxygen, and micromolar level inorganic macronutrients) along two sections occupied in the subtropical North Atlantic as part of the first U.S. GEOTRACES (GA03) survey during 2010 and 2011. The purpose of this work is to place subsequent papers in this special issue in a general context and to provide a framework in which the observed distributions of Trace Elements and Isotopes can be interpreted. Using these hydrographic properties we use a modified Optimum Multiparameter water mass analysis method to diagnose the relative contributions of various water types along the sections and rationalize their distributions. The water mass compositions appear largely consistent with what is understood from previous studies about the large scale circulation and ventilation of the North Atlantic, with perhaps one exception. We found that the North Atlantic Deep water both east and west of the Mid Atlantic Ridge is more strongly influenced by Iceland Scotland Overflow Water relative to Denmark Straits Overflow Water (about 3:1) than inferred from other tracer studies (typically 2:1). It remains unclear whether this is an artifact of our calculation or a real change in deep water composition in the decades between the determinations. AU - Jenkins, W. J. AU - Smethie, W. M. AU - Boyle, E. A. AU - Cutter, G. A. DA - 2015/06/01/ DO - https://doi.org/10.1016/j.dsr2.2014.11.018 KW - North Atlantic Hydrography Water mass Ocean circulation N1 - https://www.sciencedirect.com/science/article/pii/S0967064514003257 PY - 2015 SN - 0967-0645 SP - 6–20 ST - Water mass analysis for the U.S. GEOTRACES (GA03) North Atlantic sections T2 - Deep Sea Research, Part II: Topical Studies in Oceanography TI - Water mass analysis for the U.S. GEOTRACES (GA03) North Atlantic sections UR - https://doi.org/10.1016/j.dsr2.2014.11.018 VL - 116 ID - 17542 ER - TY - JOUR AB - A high-resolution deuterium profile is now available along the entire European Project for Ice Coring in Antarctica Dome C ice core, extending this climate record back to marine isotope stage 20.2, ∼800,000 years ago. Experiments performed with an atmospheric general circulation model including water isotopes support its temperature interpretation. We assessed the general correspondence between Dansgaard-Oeschger events and their smoothed Antarctic counterparts for this Dome C record, which reveals the presence of such features with similar amplitudes during previous glacial periods. We suggest that the interplay between obliquity and precession accounts for the variable intensity of interglacial periods in ice core records. AU - Jouzel, J. AU - Masson-Delmotte, V. AU - Cattani, O. AU - Dreyfus, G. AU - Falourd, S. AU - Hoffmann, G. AU - Minster, B. AU - Nouet, J. AU - Barnola, J. M. AU - Chappellaz, J. AU - Fischer, H. AU - Gallet, J. C. AU - Johnsen, S. AU - Leuenberger, M. AU - Loulergue, L. AU - Luethi, D. AU - Oerter, H. AU - Parrenin, F. AU - Raisbeck, G. AU - Raynaud, D. AU - Schilt, A. AU - Schwander, J. AU - Selmo, E. AU - Souchez, R. AU - Spahni, R. AU - Stauffer, B. AU - Steffensen, J. P. AU - Stenni, B. AU - Stocker, T. F. AU - Tison, J. L. AU - Werner, M. AU - Wolff, E. W. DO - doi:10.1126/science.1141038 IS - 5839 N1 - https://www.science.org/doi/abs/10.1126/science.1141038 PY - 2007 SP - 793–796 ST - Orbital and millennial Antarctic climate variability over the past 800,000 years T2 - Science TI - Orbital and millennial Antarctic climate variability over the past 800,000 years UR - https://doi.org/10.1126/science.1141038 VL - 317 ID - 17543 ER - TY - JOUR AB - Stimulated by finding a novel cytheroid ostracod in a piece of sunken wood retrieved from the sea-bed in the Kuril–Kamchatka Trench, we have reviewed all previously published data on ostracods from similarly ephemeral deep-sea habitats (wood falls, hydrothermal vents and cold seeps). These data are placed in the context of all data on living, deep-sea ostracods from other environments. We confirm previous authors׳ conclusions that faunas from these ephemeral habitats are similar at the generic level, and include elements common to shallow and deep habitats. However, at the species level, endemism varies from zero at cold seeps, to 35% in wood falls and 60% at hydrothermal vents, which is an indication of the relative longevity of these habitats. Non-endemic species occur also in oligotrophic, deep-sea sediments but not in shallow environments. This is in contradiction to previous assumptions that these ephemeral faunas share more species and with shallow habitats than genera with the oligotrophic, deep-sea sediments. We agree with previous authors that the dispersal strategy of wood fall, vent and seep ostracods includes hitchhiking and we propose that it also includes the ability to survive ingestion by larger, more motile animals. The homogeneity of the faunas from ephemeral habitats collected off the American continent is in stark contrast to the highly endemic fauna found in Northwestern Pacific. This suggests that the ostracods may have biogeographical patterns similar to those previously proposed for other groups of benthos. However, any proposal for a global biogeographical scheme for ostracod distributions will have to await far more comprehensive coverage from presently unstudied regions. Finally, we describe and name a novel species of ostracod from the wood fall collected at a depth of 5229m in the abyss east to the Kuril–Kamchatka Trench, Northwestern Pacific; erecting a new family Keysercytheridae fam. nov. and a new genus, Keysercythere gen. nov., to accommodate it, and name it, Keysercythere enricoi sp. nov. We present a preliminary key to all Cytheroidea families for which living representatives have been described. AU - Karanovic, Ivana AU - Brandão, Simone Nunes DA - 2015/01/01/ DO - https://doi.org/10.1016/j.dsr2.2014.09.008 KW - Deep sea Ostracoda Biogeography Taxonomy Keysercytheridae Pacific N1 - https://www.sciencedirect.com/science/article/pii/S0967064514002616 PY - 2015 SN - 0967-0645 SP - 76–94 ST - Biogeography of deep-sea wood fall, cold seep and hydrothermal vent Ostracoda (Crustacea), with the description of a new family and a taxonomic key to living Cytheroidea T2 - Deep Sea Research, Part II: Topical Studies in Oceanography TI - Biogeography of deep-sea wood fall, cold seep and hydrothermal vent Ostracoda (Crustacea), with the description of a new family and a taxonomic key to living Cytheroidea UR - https://doi.org/10.1016/j.dsr2.2014.09.008 VL - 111 ID - 49491 ER - TY - JOUR AB - The Croll–Milankovitch theory of climate change proposes that glacial–interglacial cycles are driven by changes in the amount of solar radiation reaching the Earth's surface at high northern latitudes in summer, in turn caused by changes in orbital geometry. To test this hypothesis Kawamura et al. constructed a new chronology for Antarctic ice cores using a proxy — the ratio of oxygen to nitrogen molecules in air trapped in the ice — that reflects changes in local summer insolation. The results show that orbital-scale Antarctic climate change has lagged Northern Hemisphere insolation during the past 360,000 years, and that increases in Antarctic temperature at the last four glacial–interglacial transitions took place within phases of increasing Northern Hemisphere summer insolation. The findings therefore support the Croll–Milankovitch hypothesis. AU - Kawamura, Kenji AU - Parrenin, Frédéric AU - Lisiecki, Lorraine AU - Uemura, Ryu AU - Vimeux, Françoise AU - Severinghaus, Jeffrey P. AU - Hutterli, Manuel A. AU - Nakazawa, Takakiyo AU - Aoki, Shuji AU - Jouzel, Jean AU - Raymo, Maureen E. AU - Matsumoto, Koji AU - Nakata, Hisakazu AU - Motoyama, Hideaki AU - Fujita, Shuji AU - Goto-Azuma, Kumiko AU - Fujii, Yoshiyuki AU - Watanabe, Okitsugu DA - 2007/08/01 DO - 10.1038/nature06015 IS - 7156 PY - 2007 SN - 1476-4687 SP - 912–916 ST - Northern Hemisphere forcing of climatic cycles in Antarctica over the past 360,000 years T2 - Nature TI - Northern Hemisphere forcing of climatic cycles in Antarctica over the past 360,000 years UR - https://doi.org/10.1038/nature06015 VL - 448 ID - 17544 ER - TY - JOUR AB - The compilation of changes in the magnetic properties at various sites distributed along the path of the deepwater mass in North Atlantic shows large-amplitude short-term fluctuations reflecting changes in the strength of the North Atlantic Deep Water (NADW). These changes, which suggest a two-mode deep glacial circulation dynamic, are perfectly concurrent with air temperature changes over Greenland. They also share a similar pattern with those reported in the Nd isotope ratios from the deep Cape Basin during the same time period. Greenland interstadials were accompanied by increased flow speed of NADW and relatively more NADW reaching the Southern Ocean, while during Greenland stadials and Heinrich events, both the North Atlantic flow speed of NADW and its presence in the South Atlantic were reduced. It is demonstrated that both proxies are tracing the same water mass, and their reliability for monitoring changes in the deepwater circulation is therefore clearly established. After using the climatically independent geomagnetic assisted stratigraphy to put the Northern and Southern Hemisphere records on the same age scale, the South Atlantic record appears to lag changes in North Atlantic flow speeds by approximately 860 ± 220 years during the most prominent and best defined cycles (interstadials 12 and 8). Although future work is needed, this significant offset provides a first observation and tentative quantification of the time needed for glacial northern component water to mix downward and to flow from the North to the South Atlantic. AU - Kissel, Catherine AU - Laj, Carlo AU - Piotrowski, Alexander M. AU - Goldstein, Steven L. AU - Hemming, Sidney R. DO - https://doi.org/10.1029/2008PA001624 IS - 2 N1 - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2008PA001624 PY - 2008 SN - 0883-8305 SP - PA2102 ST - Millennial-scale propagation of Atlantic deep waters to the glacial Southern Ocean T2 - Paleoceanography and Paleoclimatology TI - Millennial-scale propagation of Atlantic deep waters to the glacial Southern Ocean UR - https://doi.org/10.1029/2008PA001624 VL - 23 ID - 17546 ER - TY - JOUR AB - Benthic oxygen isotope records of deep marine sedimentary archives have yielded a wealth of information regarding ice sheet dynamics and climate change during the Pleistocene. However, since they often lack independent age control, these records are generally bound by a fixed phase relationship between orbital forcing and the climate response, e.g. ice volume changes. We present the first long (∼1.2 Ma) benthic oxygen isotope record from the eastern Mediterranean, based on ODP Sites 967 and 968, which clearly reflects the behavior of global climate on a glacial–interglacial scale throughout the late Pleistocene time period. The age model for our record is based on tuning the elemental ratio of titanium versus aluminum (Ti/Al) against insolation. The Ti/Al record is dominated by the precession-related changes in northern African climate, i.e. monsoonal forcing, and hence largely independent of glacial–interglacial variability. We found the largest offset between our chronology and that of the widely applied, open ocean stacked record LR04 (Lisiecki and Raymo, 2005) for TVII (∼624 ka), which occurred ∼9 kyr earlier according to our estimates, though in agreement with the AICC2012 δDice chronology of EPICA Dome C (Bazin et al., 2013). Spectral cross-correlation analysis between our benthic δ18O record and 65°N summer insolation reveals significant amounts of power in the obliquity and precession range, with an average lag of 5.5 ± 0.8 kyr for obliquity, and 6.0 ± 1.0 kyr for precession. In addition, our results show that the obliquity-related time lag was smaller (3.0 ± 3.3 kyr) prior to ∼900 ka than after (5.7 ± 1.1 kyr), suggesting that on average the glacial response time to obliquity forcing increased during the mid-Pleistocene transition, much later than assumed by Lisiecki and Raymo (2005). Finally, we found that almost all glacial terminations have a consistent phase relationship of ∼45 ± 45° with respect to the precession and obliquity-driven increases in 65°N summer insolation, consistent with the general consensus that both obliquity and precession are important for deglaciation during the Late Pleistocene. Exceptions are glacial terminations TIIIb, T36 and potentially T32 (and TVII T24 and T34), which show this consistent phase relationship only with precession (only with obliquity). Our findings point towards an early (>1200 ka) onset of the Mid Pleistocene Transition. Vice versa, the timing of TVII, which can only be explained as a response to obliquity forcing, indicates that the transition lasted until at least after MIS 15. AU - Konijnendijk, T. Y. M. AU - Ziegler, M. AU - Lourens, L. J. DA - 2015/12/01/ DO - https://doi.org/10.1016/j.quascirev.2015.10.005 KW - Pleistocene Benthic isotopes Stratigraphy Mediterranean Astronomical tuning N1 - https://www.sciencedirect.com/science/article/pii/S0277379115301293 PY - 2015 SN - 0277-3791 SP - 308–320 ST - On the timing and forcing mechanisms of late Pleistocene glacial terminations: insights from a new high-resolution benthic stable oxygen isotope record of the eastern Mediterranean T2 - Quaternary Science Reviews TI - On the timing and forcing mechanisms of late Pleistocene glacial terminations: insights from a new high-resolution benthic stable oxygen isotope record of the eastern Mediterranean UR - https://doi.org/10.1016/j.quascirev.2015.10.005 VL - 129 ID - 23081 ER - TY - JOUR AB - The Horseshoe abyssal plain (HAP) is located on the Iberian margin at approximately 4800 m water depth, and is confined within topographic elevations with a relief of about 3000 m, with the exception of Gorringe Bank, which rises to only 20 m below sealevel. The plain is built up by an alternation of turbidites of the order of meter-thick beds, numbered H 2 , H 3 , H 8 , and H 13 , contrasting with sets of thinner beds of the order of decimeters thick (H (sub 4,5,6,7) and H (sub 9,10,11,12) ), and pelagites centimeters in thickness. An intensive study of eight piston cores, using visual observation (color and thickness), relative stratigraphic position of units, magnetic susceptibility logs, calcium carbonate content, and mineralogy of turbidite bases, concludes in a bed-by-bed correlation of all individual turbidites. The major source of terrigenous material feeding the HAP is the Sao Vicente canyon, which incises the Portuguese shelf, while minor sources are the surrounding seamounts. The elongate geometry of the abyssal plain with its single dominant source of sediments produced laterally continuous deposits from both large and small flows. These covered the entire 356 km length of the plain. Grain-size analysis of the four thickest turbidites (H 2 , H 3 , H 8 , and H 9 ) demonstrates only slight downcurrent fining and vertical grading, expressed best in the ratio of coarse silt to fine silt plus clay. A small amount of sand is carried the length of the plain. The thicker units all show the same pattern of thickness, with a maximum in the middle of the plain around a topographic constriction and bend. This is most plausibly explained as due to reduction in flow speed of an initially supercritical flow causing enhanced deposition. Some of the beds appear to have a double coarse layer in the base, which may indicate partial reflection of flows from the side of the basin. It is suggested by application of equations for flow behavior that both thick ( nearly equal 3 m) and thin ( nearly equal 0.3 m) beds are due to supercritical flows a few tens of meters high. However, the thick beds resulted from high-concentration flows ( C v nearly equal 4% by volume) whereas thinner beds require low concentration ( C v < 1%) to run out over the full length of the basin. The stratigraphy is tied into the dated oceanic pelagic record by analysis of foraminifera in the pelagic layers above the turbidites and through recognition of two Heinrich layers (H-1 and H-2, ages 14.3 and 21 ka). The resulting age framework shows higher turbidite frequency in the glacial (2.7/kyr) than interglacial (Holocene) (1.0/kyr). This also gives higher mass flux during the glacial. Emplacement of turbidites cannot be clearly related to sea-level changes but may well be due to seismic activity. However, one of the largest earthquakes in human experience (Lisbon in 1755) triggered only a thin turbidite, invalidating the term "seismite" for thick turbidites. AU - Lebreiro, Susana M. AU - McCave, I. Nicholas AU - Weaver, Philip P. E. DO - 10.1306/d4268658-2b26-11d7-8648000102c1865d IS - 5 PY - 1997 SN - 1527-1404 SP - 856–870 ST - Late Quaternary turbidite emplacement on the Horseshoe abyssal plain (Iberian margin) T2 - Journal of Sedimentary Research TI - Late Quaternary turbidite emplacement on the Horseshoe abyssal plain (Iberian margin) UR - https://doi.org/10.1306/D4268658-2B26-11D7-8648000102C1865D VL - 67 Y2 - 11/30/2021 ID - 17547 ER - TY - JOUR AB - It is well established that orbital scale sea-level changes generated larger transport of sediments into the deep-sea during the last glacial maximum than the Holocene. However, the response of sedimentary processes to abrupt millennial-scale climate variability is rather unknown. Frequency of distal turbidites and amounts of advected detrital carbonate are estimated off the Lisbon–Setúbal canyons (core MD03-2698, at 4602mwd), within a chronostratigraphy based on radiometric ages, oxygen isotopes and paleomagnetic key global anomalies. We found that: 1) higher frequency of turbidites concurred with Northern Hemisphere coldest temperatures (Greenland Stadials [GS], including Heinrich [H] events). But more than that, an escalating frequency of turbidites starts with the onset of global sea-level rising (and warming in Antarctica) and culminates during H events, at the time when rising is still in its early-mid stage, and the Atlantic Meridional Overturning Circulation (AMOC) is re-starting. This short time span coincides with maximum gradients of ocean surface and bottom temperatures between GS and Antarctic warmings (Antarctic Isotope Maximum; AIM 17, 14, 12, 8, 4, 2) and rapid sea-level rises. 2) Trigger of turbidity currents is not the only sedimentary process responding to millennial variability; land-detrital carbonate (with a very negative bulk δ18O signature) enters the deep-sea by density-driven slope lateral advection, accordingly during GS. 3) Possible mechanisms to create slope instability on the Portuguese continental margin are sea-level variations as small as 20m, and slope friction by rapid deep and intermediate re-accommodation of water masses circulation. 4) Common forcing mechanisms appear to drive slope instability at both millennial and orbital scales. AU - Lebreiro, S. M. AU - Voelker, A. H. L. AU - Vizcaino, A. AU - Abrantes, F. G. AU - Alt-Epping, U. AU - Jung, S. AU - Thouveny, N. AU - Gràcia, E. DA - 2009/12/01/ DO - https://doi.org/10.1016/j.quascirev.2009.08.007 IS - 27–28 N1 - https://www.sciencedirect.com/science/article/pii/S027737910900273X PY - 2009 SN - 0277-3791 SP - 3211–3223 ST - Sediment instability on the Portuguese continental margin under abrupt glacial climate changes (last 60 kyr) T2 - Quaternary Science Reviews TI - Sediment instability on the Portuguese continental margin under abrupt glacial climate changes (last 60 kyr) UR - https://doi.org/10.1016/j.quascirev.2009.08.007 VL - 28 ID - 17548 ER - TY - JOUR AB - We present a 5.3-Myr stack (the “LR04” stack) of benthic δ18O records from 57 globally distributed sites aligned by an automated graphic correlation algorithm. This is the first benthic δ18O stack composed of more than three records to extend beyond 850 ka, and we use its improved signal quality to identify 24 new marine isotope stages in the early Pliocene. We also present a new LR04 age model for the Pliocene-Pleistocene derived from tuning the δ18O stack to a simple ice model based on 21 June insolation at 65°N. Stacked sedimentation rates provide additional age model constraints to prevent overtuning. Despite a conservative tuning strategy, the LR04 benthic stack exhibits significant coherency with insolation in the obliquity band throughout the entire 5.3 Myr and in the precession band for more than half of the record. The LR04 stack contains significantly more variance in benthic δ18O than previously published stacks of the late Pleistocene as the result of higher-resolution records, a better alignment technique, and a greater percentage of records from the Atlantic. Finally, the relative phases of the stack's 41- and 23-kyr components suggest that the precession component of δ18O from 2.7–1.6 Ma is primarily a deep-water temperature signal and that the phase of δ18O precession response changed suddenly at 1.6 Ma. AU - Lisiecki, Lorraine E. AU - Raymo, Maureen E. DO - https://doi.org/10.1029/2004PA001071 IS - 1 N1 - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2004PA001071 PY - 2005 SN - 0883-8305 SP - PA1003 ST - A Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O records T2 - Paleoceanography TI - A Pliocene-Pleistocene stack of 57 globally distributed benthic δ18O records UR - https://doi.org/10.1029/2004PA001071 VL - 20 ID - 11206 ER - TY - JOUR AB - Ocean dynamics served an important role during past dramatic climate changes via impacts on deep-ocean carbon storage. Such changes are recorded in sedimentary proxies of hydrographic change on continental margins, which lie at the ocean–atmosphere–earth interface. However, interpretations of these records are challenging, given complex interplays among processes delivering particulate material to and from ocean margins. Here we report radiocarbon (14C) signatures measured for organic carbon in differing grain-size sediment fractions and foraminifera in a sediment core retrieved from the southwest Iberian margin, spanning the last ~25,000 yr. Variable differences of 0–5000 yr in radiocarbon age are apparent between organic carbon in differing grain-sizes and foraminifera of the same sediment layer. The magnitude of 14C differences co-varies with key paleoceanographic indices (e.g., proximal bottom-current density gradients), which we interpret as evidence of Atlantic–Mediterranean seawater exchange influencing grain-size specific carbon accumulation and translocation. These findings underscore an important link between regional hydrodynamics and interpretations of down-core sedimentary proxies. AU - Magill, Clayton R. AU - Ausín, Blanca AU - Wenk, Pascal AU - McIntyre, Cameron AU - Skinner, Luke AU - Martínez-García, Alfredo AU - Hodell, David A. AU - Haug, Gerald H. AU - Kenney, William AU - Eglinton, Timothy I. DA - 2018/11/08 DO - 10.1038/s41467-018-06973-w IS - 1 PY - 2018 SN - 2041-1723 SP - 4690 ST - Transient hydrodynamic effects influence organic carbon signatures in marine sediments T2 - Nature Communications TI - Transient hydrodynamic effects influence organic carbon signatures in marine sediments UR - https://doi.org/10.1038/s41467-018-06973-w VL - 9 ID - 16986 ER - TY - JOUR AB - Past glacials can be thought of as natural experiments in which variations in boundary conditions influenced the character of climate change. However, beyond the last glacial, an integrated view of orbital- and millennial-scale changes and their relation to the record of glaciation has been lacking. Here, we present a detailed record of variations in the land-ocean system from the Portuguese margin during the penultimate glacial and place it within the framework of ice-volume changes, with particular reference to European ice-sheet dynamics. The interaction of orbital- and millennial-scale variability divides the glacial into an early part with warmer and wetter overall conditions and prominent climate oscillations, a transitional mid-part, and a late part with more subdued changes as the system entered a maximum glacial state. The most extreme event occurred in the mid-part and was associated with melting of the extensive European ice sheet and maximum discharge from the Fleuve Manche river. This led to disruption of the meridional overturning circulation, but not a major activation of the bipolar seesaw. In addition to stadial duration, magnitude of freshwater forcing, and background climate, the evidence also points to the influence of the location of freshwater discharges on the extent of interhemispheric heat transport. AU - Margari, Vasiliki AU - Skinner, Luke C. AU - Hodell, David A. AU - Martrat, Belen AU - Toucanne, Samuel AU - Grimalt, Joan O. AU - Gibbard, Philip L. AU - Lunkka, J.P. AU - Tzedakis, P.C. DO - 10.1130/g35070.1 IS - 3 PY - 2014 SN - 0091-7613 SP - 183–186 ST - Land-ocean changes on orbital and millennial time scales and the penultimate glaciation T2 - Geology TI - Land-ocean changes on orbital and millennial time scales and the penultimate glaciation UR - https://doi.org/10.1130/G35070.1 VL - 42 Y2 - 11/30/2021 ID - 17550 ER - TY - JOUR AB - The abrupt nature of warming events recorded in Greenland ice-cores during the last glacial has generated much debate over their underlying mechanisms. Here, we present joint marine and terrestrial analyses from the Portuguese Margin, showing a succession of cold stadials and warm interstadials over the interval 35–57 ka. Heinrich stadials 4 and 5 contain considerable structure, with a short transitional phase leading to an interval of maximum cooling and aridity, followed by slowly increasing sea-surface temperatures and moisture availability. A climate model experiment reproduces the changes in western Iberia during the final part of Heinrich stadial 4 as a result of the gradual recovery of the Atlantic meridional overturning circulation. What emerges is that Greenland ice-core records do not provide a unique template for warming events, which involved the operation of both fast and slow components of the coupled atmosphere–ocean–sea-ice system, producing adjustments over a range of timescales. AU - Margari, Vasiliki AU - Skinner, Luke C. AU - Menviel, Laurie AU - Capron, Emilie AU - Rhodes, Rachael H. AU - Mleneck-Vautravers, Maryline J. AU - Ezat, Mohamed M. AU - Martrat, Belen AU - Grimalt, Joan O. AU - Hodell, David A. AU - Tzedakis, Polychronis C. DA - 2020/08/13 DO - 10.1038/s43247-020-0006-x IS - 1 PY - 2020 SN - 2662-4435 SP - 6 ST - Fast and slow components of interstadial warming in the North Atlantic during the last glacial T2 - Communications Earth & Environment TI - Fast and slow components of interstadial warming in the North Atlantic during the last glacial UR - https://doi.org/10.1038/s43247-020-0006-x VL - 1 ID - 23082 ER - TY - JOUR AB - Periodic iceberg discharges during the last glacial period led to a slowdown of the Atlantic meridional overturning circulation. Sediment records from the Portuguese margin show that similar events punctuated the penultimate glacial period as well, although their duration and broader climatic impacts were modified by different background climate conditions. AU - Margari, V. AU - Skinner, L. C. AU - Tzedakis, P. C. AU - Ganopolski, A. AU - Vautravers, M. AU - Shackleton, N. J. DA - 2010/02/01 DO - 10.1038/ngeo740 IS - 2 PY - 2010 SN - 1752-0908 SP - 127–131 ST - The nature of millennial-scale climate variability during the past two glacial periods T2 - Nature Geoscience TI - The nature of millennial-scale climate variability during the past two glacial periods UR - https://doi.org/10.1038/ngeo740 VL - 3 ID - 17549 ER - TY - JOUR AB - Centennial climate variability over the last ice age exhibits clear bipolar behavior. High-resolution analyses of marine sediment cores from the Iberian margin trace a number of associated changes simultaneously. Proxies of sea surface temperature and water mass distribution, as well as relative biomarker content, demonstrate that this typical north-south coupling was pervasive for the cold phases of climate during the past 420,000 years. Cold episodes after relatively warm and largely ice-free periods occurred when the predominance of deep water formation changed from northern to southern sources. These results reinforce the connection between rapid climate changes at Mediterranean latitudes and century-to-millennial variability in northern and southern polar regions. AU - Martrat, Belen AU - Grimalt, Joan O. AU - Shackleton, Nicholas J. AU - Abreu, Lucia de AU - Hutterli, Manuel A. AU - Stocker, Thomas F. DO - doi:10.1126/science.1139994 IS - 5837 N1 - https://www.science.org/doi/abs/10.1126/science.1139994 PY - 2007 SP - 502–507 ST - Four climate cycles of recurring deep and surface water destabilizations on the Iberian margin T2 - Science TI - Four climate cycles of recurring deep and surface water destabilizations on the Iberian margin UR - https://doi.org/10.1126/science.1139994 VL - 317 ID - 17551 ER - TY - JOUR AB - We generated 200-500 year resolution records of oceanic processes in the North Atlantic (Ocean Drilling Program Site 983, 60°24'N, 23°38'W, 1983 meters water depth) for intervals in the latest Pliocene (1.86-1.93 Ma) and the earliest Pleistocene (1.75-1.83 Ma) in order to examine the linkages between millennial-scale variations in the ocean and background glacial-interglacial climate change. Within glacial intervals we find evidence for variations similar to those observed in the late Pleistocene. We find discrete ice-rafted debris (IRD) events that reoccur every 2-5 kyr. These events are preceded by a short cooling and accompanied by a reorganization of glacial deep waters. The timing of IRD events in the late Pliocene and early Pleistocene intervals is similar to that of Dansgaard-Oeschger cycles, but we find no IRD events comparable in timing to late Pleistocene Heinrich events. Although interglacial intervals are much more stable, we do find evidence for low-amplitude variations in deep water properties that reoccur every ∼2 kyr within interglacial intervals. The similarity between our late Pliocene—early Pleistocene records and late Pleistocene records implies that the mechanism driving millennial-scale variations cannot be uniquely attributed to the strongly nonlinear linkage between climate and insolation and the large ice sheets of the late Pleistocene. AD - AA(Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, California, USA), AB(Ocean Sciences Department and Institute of Marine Sciences, University of California, Santa Cruz, California, USA), AC(Ocean Sciences Department and Institute of Marine Sciences, University of California, Santa Cruz, California, USA) AU - Mc Intyre, Katherine AU - Delaney, Margaret L. AU - Ravelo, A. Christina DA - October 01, 2001 DO - 10.1029/2000pa000526 KW - Meteorology and Atmospheric Dynamics: Paleoclimatology Oceanography: General: Paleoceanography Oceanography: Biological and Chemical: Stable isotopes Information Related to Geographic Region: Atlantic Ocean N1 - https://ui.adsabs.harvard.edu/abs/2001PalOc..16..535M PY - 2001 SN - 0883-8305 SP - 535–543 ST - Millennial-scale climate change and oceanic processes in the late Pliocene and early Pleistocene T2 - Paleoceanography and Paleoclimatology TI - Millennial-scale climate change and oceanic processes in the late Pliocene and early Pleistocene UR - https://doi.org/10.1029/2000PA000526 VL - 16 ID - 17552 ER - TY - CHAP AB - Long, continuous, marine sediment records from the subpolar North Atlantic document the glacial modulation of regional climate instability throughout the past 0.5 million years. Whenever ice sheet size surpasses a critical threshold indicated by the benthic oxygen isotope (δ18O) value of 3.5 per mil during each of the past five glaciation cycles, indicators of iceberg discharge and sea-surface temperature display dramatically larger amplitudes of millennial-scale variability than when ice sheets are small. Sea-surface temperature oscillations of 1° to 2°C increase in size to approximately 4° to 6°C, and catastrophic iceberg discharges begin alternating repeatedly with brief quiescent intervals. The glacial growth associated with this amplification threshold represents a relatively small departure from the modern ice sheet configuration and sea level. Instability characterizes nearly all observed climate states, with the exception of a limited range of baseline conditions that includes the current Holocene interglacial. AU - McManus, Jerry F. AU - Oppo, Delia W. AU - Cullen, James L. DO - 10.1126/science.283.5404.971 N1 - https://science.sciencemag.org/content/sci/283/5404/971.full.pdf PY - 1999 SP - 971–975 ST - A 0.5-million-year record of millennial-scale climate variability in the North Atlantic SV - 5404 T2 - Science TI - A 0.5-million-year record of millennial-scale climate variability in the North Atlantic UR - https://doi.org/10.1126/science.283.5404.971 VL - 283 ID - 12191 ER - TY - JOUR AB - Records of biogenic opal export in the North Atlantic Ocean show pronounced maxima during each glacial termination over the past 550,000 years, consistent with a strong deglacial reduction in the formation of silicate-poor glacial North Atlantic intermediate water and a consequent increase in upward silicate transport. AU - Meckler, A. N. AU - Sigman, D. M. AU - Gibson, K. A. AU - François, R. AU - Martínez-García, A. AU - Jaccard, S. L. AU - Röhl, U. AU - Peterson, L. C. AU - Tiedemann, R. AU - Haug, G. H. DA - 2013/03/01 DO - 10.1038/nature12006 IS - 7442 PY - 2013 SN - 1476-4687 SP - 495–498 ST - Deglacial pulses of deep-ocean silicate into the subtropical North Atlantic Ocean T2 - Nature TI - Deglacial pulses of deep-ocean silicate into the subtropical North Atlantic Ocean UR - https://doi.org/10.1038/nature12006 VL - 495 ID - 49492 ER - TY - JOUR AB - Paleoclimate reconstructions suggest that the complex variability within the Greenland stadial 1 (GS-1) over western Europe was governed by coupled ocean and atmospheric changes. However, few works from the North Atlantic mid-latitudes document both the GS-1 onset and its termination, which are often considered as single abrupt transition events. Here, we present a direct comparison between marine (alkenone-based sea surface temperatures) and terrestrial (pollen) data, at very high resolution (28 years mean), from the southwestern Iberian shelf record D13882. Our results reveal a rather complex climatic period with internally changing conditions. The GS-1 onset (GS-1a: 12890-12720 yr BP) is marked by a progressive cooling and drying; GS-1b (12720-12390 yr BP) is the coldest and driest phase; GS-1c (12390-12030 yr BP) is marked by a progressive warming and increase in moisture conditions; GS-1 termination (GS-1d: 12030-11770 yr BP) is marked by rapid switches between cool wet, cold dry and cool wet conditions. Although hydroclimate response was very unsteady throughout the GS-1 and in particular during its termination phase, the persistence of an open temperate and Mediterranean forest in southwestern Iberia during the entire episode suggests that at least some moisture was delivered via the Westerlies. We propose coupled ocean and atmospheric mechanisms to reproduce these scenaria. Changes in the strength of the Atlantic Meridional Overturning Circulation (AMOC) as well as variations in the North Atlantic sea-ice growth have favoured the displacement of the polar jet stream's latitudinal position and contributed to a complex spatial pattern and strength of the Westerlies across western Europe. AU - Naughton, F. AU - Costas, S. AU - Gomes, S. D. AU - Desprat, S. AU - Rodrigues, T. AU - Sanchez Goñi, M. F. AU - Renssen, H. AU - Trigo, R. AU - Bronk-Ramsey, C. AU - Oliveira, D. AU - Salgueiro, E. AU - Voelker, A. H. L. AU - Abrantes, F. DA - 2019/05/15/ DO - https://doi.org/10.1016/j.quascirev.2019.03.033 KW - Paleoclimate Greenland stadial 1 Younger Dryas Complex climate variability Moisture availability Jet stream Westerlies Iberian margin North atlantic N1 - https://www.sciencedirect.com/science/article/pii/S0277379118309302 PY - 2019 SN - 0277-3791 SP - 108–120 ST - Coupled ocean and atmospheric changes during Greenland stadial 1 in southwestern Europe T2 - Quaternary Science Reviews TI - Coupled ocean and atmospheric changes during Greenland stadial 1 in southwestern Europe UR - https://doi.org/10.1016/j.quascirev.2019.03.033 VL - 212 ID - 49340 ER - TY - JOUR AB - The comparison between modern terrestrial and marine pollen signals in and off western Iberia shows that marine pollen assemblages give an integrated image of the regional vegetation colonising the adjacent continent. Present-day Mediterranean and Atlantic forest communities of Iberia are well discriminated by south and north marine pollen spectra, respectively. Results from Total Pollen Concentration together with recognized conceptual models of fine particle dynamics in the Iberian margin have allowed us to establish the present-day pattern of pollen dispersion in this region. The 25000 year-long record of continental (pollen) and marine (δ18O of Globigerina bulloides, Ice-rafted detritus—IRD and Neogloboquadrina pachyderma s.) proxies, from the Galician margin composite core (MD99-2331 and MD03-2697), show that vegetation cover in north-western Iberia has responded contemporaneously to the climate variability of the North-Atlantic. The vegetation response to the well known North Atlantic Heinrich events 2 and 1 (H2 and H1) is however complex and characterised by two vegetation phases at low and mid-altitudes of north-western Iberia. The beginning of each Heinrich event is marked on land by an important pine forest reduction and the expansion of heathers which are synchronous with the heaviest planktic δ18O values and the maxima of N. pachyderma (s.) suggesting that these first phases were cold and wet. Pinus forest expansion characterising the second phase of each Heinrich event indicates a less cold episode associated, during H1, with an increase of dryness as suggested by the development of semi-desert associations. The comparison of our Galician margin multi-proxy record with several pollen sequences from in and off Iberia allows us to demonstrate that H1 event is the marine equivalent of the Oldest Dryas on the continent. The occurrence of temperate trees during the last glacial maximum (LGM) and the rapid expansion of deciduous Quercus during the Bölling-Allerød period in our Galician margin composite sequence show that not only the southern but also north-western Iberia was a refugium zone for deciduous trees during the last glacial period, especially at low and mid-altitude zones. Furthermore, the comparison between southern and northern marine and terrestrial sequences allows us to confirm that vegetation responded to the Bölling-Allerød warming, the Younger Dryas cold event and the Holocene more quickly in low and mid-altitudes of north-western Iberia and in the south than in the high altitude northern region most likely as the result of the higher density of refugia for temperate trees in these zones during the LGM. AU - Naughton, F. AU - Sanchez Goñi, M. F. AU - Desprat, S. AU - Turon, J. L. AU - Duprat, J. AU - Malaizé, B. AU - Joli, C. AU - Cortijo, E. AU - Drago, T. AU - Freitas, M. C. DA - 2007/02/01/ DO - https://doi.org/10.1016/j.marmicro.2006.07.006 IS - 2 KW - Marine palynology Pollen transport Iberian margin Heinrich events LGM Last glacial–interglacial transition N1 - https://www.sciencedirect.com/science/article/pii/S037783980600123X PY - 2007 SN - 0377-8398 SP - 91–114 ST - Present-day and past (last 25000 years) marine pollen signal off western Iberia T2 - Marine Micropaleontology TI - Present-day and past (last 25000 years) marine pollen signal off western Iberia UR - https://doi.org/10.1016/j.marmicro.2006.07.006 VL - 62 ID - 17553 ER - TY - JOUR AB - Bursts of carbon dioxide, released into the atmosphere and occurring on centennial time scales, were seen during the cold periods of the last glacial cycle but not in older or warmer conditions. Nehrbass-Ahles et al. present a record of atmospheric carbon dioxide concentrations retrieved from the European Project for Ice Coring in Antarctica Dome C ice core showing that these carbon dioxide jumps occurred during both cold and warm periods between 330,000 and 450,000 years ago. They relate these pulses to disruptions of the Atlantic meridional overturning circulation caused by freshwater discharge from ice sheets. Such rapid carbon dioxide increases could occur in the future if global warming also disrupts this ocean circulation pattern. Science, this issue p. 1000 Centennial-scale CO2 releases to the atmosphere have occurred during both cold and warm climate states in the past. Pulse-like carbon dioxide release to the atmosphere on centennial time scales has only been identified for the most recent glacial and deglacial periods and is thought to be absent during warmer climate conditions. Here, we present a high-resolution carbon dioxide record from 330,000 to 450,000 years before present, revealing pronounced carbon dioxide jumps (CDJ) under cold and warm climate conditions. CDJ come in two varieties that we attribute to invigoration or weakening of the Atlantic meridional overturning circulation (AMOC) and associated northward and southward shifts of the intertropical convergence zone, respectively. We find that CDJ are pervasive features of the carbon cycle that can occur during interglacial climate conditions if land ice masses are sufficiently extended to be able to disturb the AMOC by freshwater input. AU - Nehrbass-Ahles, C. AU - Shin, J. AU - Schmitt, J. AU - Bereiter, B. AU - Joos, F. AU - Schilt, A. AU - Schmidely, L. AU - Silva, L. AU - Teste, G. AU - Grilli, R. AU - Chappellaz, J. AU - Hodell, D. AU - Fischer, H. AU - Stocker, T. F. DO - doi:10.1126/science.aay8178 IS - 6506 N1 - https://www.science.org/doi/abs/10.1126/science.aay8178 PY - 2020 SP - 1000–1005 ST - Abrupt CO2 release to the atmosphere under glacial and early interglacial climate conditions T2 - Science TI - Abrupt CO2 release to the atmosphere under glacial and early interglacial climate conditions UR - https://doi.org/10.1126/science.aay8178 VL - 369 ID - 17554 ER - TY - JOUR AB - Climatic variability of Marine Isotope Stage (MIS) 11 is examined using a new high-resolution direct land-sea comparison from the SW Iberian margin Site U1385. This study, based on pollen and biomarker analyses, documents regional vegetation, terrestrial climate and sea surface temperature (SST) variability. Suborbital climate variability is revealed by a series of forest decline events suggesting repeated cooling and drying episodes in SW Iberia throughout MIS 11. Only the most severe events on land are coeval with SST decreases, under larger ice volume conditions. Our study shows that the diverse expression (magnitude, character and duration) of the millennial-scale cooling events in SW Europe relies on atmospheric and oceanic processes whose predominant role likely depends on baseline climate states. Repeated atmospheric shifts recalling the positive North Atlantic Oscillation mode, inducing dryness in SW Iberia without systematical SST changes, would prevail during low ice volume conditions. In contrast, disruption of the Atlantic meridional overturning circulation (AMOC), related to iceberg discharges, colder SST and increased hydrological regime, would be responsible for the coldest and driest episodes of prolonged duration in SW Europe. AU - Oliveira, Dulce AU - Desprat, Stéphanie AU - Rodrigues, Teresa AU - Naughton, Filipa AU - Hodell, David AU - Trigo, Ricardo AU - Rufino, Marta AU - Lopes, Cristina AU - Abrantes, Fatima AU - Sánchez Goñi, Maria Fernanda IS - 3 J2 - Affiliation (analytic): École Pratique des Hautes Études/PSL Research University, Laboratoire Paléoclimatologie et Paléoenvironnements Marins, Pessac Affiliation (monographic): École Pratique des Hautes Études/PSL Research University, Laboratoire Paléoclimatologie et Paléoenvironnements Marins, Pessac, France Coordinates: N373417 N373417 W0100719 W0100720 illus., incl. 2 tables, sketch map Contains 136 references Research Program: IODP Integrated Ocean Drilling Program Document Type: Journal Article Bibliographic Level: Analytic Source Note: Quaternary Research, 86(3), p.373-387. Publisher: Elsevier, New York, NY, United States. ISSN: 0033-5894 Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands GeoRef ID: 2017039463 DOI: 10.1016/j.yqres.2016.09.002 KW - Alkenones Atlantic Ocean Biostratigraphy Cenozoic Climate change Cores Europe Expedition 339 IODP Site U1385 Iberian Peninsula Integrated Ocean Drilling Program Ketones Lithostratigraphy MIS 11 Marine sediments Microfossils Miospores North Atlantic Northeast Atlantic Organic compounds Paleo-oceanography Paleoclimatology Paleotemperature Palynomorphs Pleistocene Pollen Quaternary Reconstruction Sea-surface temperature Sediments Southern Europe Upper Pleistocene Vegetation Western Europe 24 Surficial Geology, Quaternary Geology LA - English PY - 2016 SN - 0033-5894 SP - 373–387 ST - The complexity of millennial-scale variability in southwestern Europe during MIS 11 T2 - Quaternary Research TI - The complexity of millennial-scale variability in southwestern Europe during MIS 11 UR - https://doi.org/10.1016/j.yqres.2016.09.002 VL - 86 ID - 4667 ER - TY - JOUR AB - The suitability of MIS 11c and MIS 19c as analogues of our present interglacial and its natural evolution is still debated. Here we examine the regional expression of the Holocene and its orbital analogues over SW Iberia using a model–data comparison approach. Regional tree fraction and climate based on snapshot and transient experiments using the LOVECLIM model are evaluated against the terrestrial–marine profiles from Site U1385 documenting the regional vegetation and climatic changes. The pollen-based reconstructions show a larger forest optimum during the Holocene compared to MIS 11c and MIS 19c, putting into question their analogy in SW Europe. Pollen-based and model results indicate reduced MIS 11c forest cover compared to the Holocene primarily driven by lower winter precipitation, which is critical for Mediterranean forest development. Decreased precipitation was possibly induced by the amplified MIS 11c latitudinal insolation and temperature gradient that shifted the westerlies northwards. In contrast, the reconstructed lower forest optimum at MIS 19c is not reproduced by the simulations probably due to the lack of Eurasian ice sheets and its related feedbacks in the model. Transient experiments with time-varying insolation and CO2 reveal that the SW Iberian forest dynamics over the interglacials are mostly coupled to changes in winter precipitation mainly controlled by precession, CO2 playing a negligible role. Model simulations reproduce the observed persistent vegetation changes at millennial time scales in SW Iberia and the strong forest reductions marking the end of the interglacial “optimum”. AU - Oliveira, Dulce AU - Desprat, Stéphanie AU - Yin, Qiuzhen AU - Naughton, Filipa AU - Trigo, Ricardo AU - Rodrigues, Teresa AU - Abrantes, Fátima AU - Sánchez Goñi, Maria Fernanda DA - 2018/07/01 DO - 10.1007/s00382-017-3948-7 IS - 1 PY - 2018 SN - 1432-0894 SP - 667–686 ST - Unraveling the forcings controlling the vegetation and climate of the best orbital analogues for the present interglacial in SW Europe T2 - Climate Dynamics TI - Unraveling the forcings controlling the vegetation and climate of the best orbital analogues for the present interglacial in SW Europe UR - https://doi.org/10.1007/s00382-017-3948-7 VL - 51 ID - 49341 ER - TY - JOUR AB - Marine Isotope Stage (MIS) 13, ∼533–478 ka, has received particular attention due to the unexpected enhancement of monsoon systems under a cool climate characterized by lower atmospheric CO2 and larger ice volume than many other interglacials. Key questions remain about its regional expression (intensity, climate variability, length), and underlying forcing factors, in particular at the mid-latitudes. Here we examine the SW Iberian vegetation, terrestrial climate and sea surface temperature (SST) variability during MIS 13 by combining pollen and biomarker data from IODP Site U1385 with climate-model experiments. We show, for the first time, that despite strong precessional forcing, MIS 13 stands out for its large forest expansions with a reduced Mediterranean character alternating with muted forest contractions, indicating that this stage is marked by a cool-temperate climate regime with high levels of humidity. Results of our data-model comparison reveal that MIS 13 orbitally driven SW Iberian climate and vegetation changes are modulated by the relatively strong ice-sheet forcing. We find that the Northern Hemisphere ice-sheets prescribed at the MIS 13 climate optimum reinforce the insolation effect by increasing the tree fraction and both winter and summer precipitation. We propose that the interactions between ice-sheets and major atmospheric circulation systems may have resulted in the persistent influence of the mid-latitude cells over the SW Iberian region, which led to intensified moisture availability and reduced seasonality, and, in turn, to a pronounced expansion of the temperate forest. AU - Oliveira, Dulce AU - Desprat, Stéphanie AU - Yin, Qiuzhen AU - Rodrigues, Teresa AU - Naughton, Filipa AU - Trigo, Ricardo M. AU - Su, Qianqian AU - Grimalt, Joan O. AU - Alonso-Garcia, Montserrat AU - Voelker, Antje H. L. AU - Abrantes, Fátima AU - Sánchez Goñi, Maria Fernanda DA - 2020/11/01/ DO - https://doi.org/10.1016/j.quascirev.2020.106573 KW - Mid-Brunhes event Interglacial MIS 13 Mediterranean vegetation Model-data comparison Insolation Ice-sheets N1 - https://www.sciencedirect.com/science/article/pii/S0277379120305357 PY - 2020 SN - 0277-3791 SP - 106573 ST - Combination of insolation and ice-sheet forcing drive enhanced humidity in northern subtropical regions during MIS 13 T2 - Quaternary Science Reviews TI - Combination of insolation and ice-sheet forcing drive enhanced humidity in northern subtropical regions during MIS 13 UR - https://doi.org/10.1016/j.quascirev.2020.106573 VL - 247 ID - 10618 ER - TY - JOUR AB - Marine Isotope Stage 31 (MIS 31) is an important analog for ongoing and projected global warming, yet key questions remain about the regional signature of its extreme orbital forcing and intra-interglacial variability. Based on a new direct land-sea comparison in SW Iberian margin IODP Site U1385 we examine the climatic variability between 1100 and 1050 ka including the "super interglacial" MIS 31, a period dominated by the 41-ky obliquity periodicity. Pollen and biomarker analyses at centennial-scale-resolution provide new insights into the regional vegetation, precipitation regime and atmospheric and oceanic temperature variability on orbital and suborbital timescales. Our study reveals that atmospheric and SST warmth during MIS 31 was not exceptional in this region highly sensitive to precession. Unexpectedly, this warm stage stands out as a prolonged interval of a temperate and humid climate regime with reduced seasonality, despite the high insolation (precession minima values) forcing. We find that the dominant forcing on the long-term temperate forest development was obliquity, which may have induced a decrease in summer dryness and associated reduction in seasonal precipitation contrast. Moreover, this study provides the first evidence for persistent atmospheric millennial-scale variability during this interval with multiple forest decline events reflecting repeated cooling and drying episodes in SW Iberia. Our direct land-sea comparison shows that the expression of the suborbital cooling events on SW Iberian ecosystems is modulated by the predominance of high or low-latitude forcing depending on the glacial/interglacial baseline climate states. Severe dryness and air-sea cooling is detected under the larger ice volume during glacial MIS 32 and MIS 30. The extreme episodes, which in their climatic imprint are similar to the Heinrich events, are likely related to northern latitude ice-sheet instability and a disruption of the Atlantic Meridional Overturning Circulation (AMOC). In contrast, forest declines during MIS 31 are associated to neither SST cooling nor high-latitude freshwater forcing. Time-series analysis reveals a dominant cyclicity of about 6 ky in the temperate forest record, which points to a potential link with the fourth harmonic of precession and thus low-latitude insolation forcing. AU - Oliveira, Dulce AU - Sánchez Goñi, Maria Fernanda AU - Naughton, Filipa AU - Polanco-Martinez, J. M. AU - Jimenez-Espejo, Francisco J. AU - Grimalt, Joan O. AU - Martrat, Belen AU - Voelker, Antje H. L. AU - Trigo, Ricardo AU - Hodell, David AU - Abrantes, Fatima AU - Desprat, Stéphanie J2 - Affiliation (analytic): PSL Research University, École Pratique des Hautes E2.tudes, Pessac Affiliation (monographic): PSL Research University, École Pratique des Hautes E2.tudes, Pessac, France Coordinates: N373417 N373417 W0100719 W0100720 illus., incl. 1 table, sketch map Contains 144 references Research Program: IODP Integrated Ocean Drilling Program Document Type: Journal Article Bibliographic Level: Analytic Source Note: Quaternary Science Reviews, Vol.161, p.1-17. Publisher: Elsevier, International. ISSN: 0277-3791 Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands GeoRef ID: 2018044674 DOI: 10.1016/j.quascirev.2017.02.013 KW - Atlantic Ocean Biomarkers Biostratigraphy Cenozoic Chronostratigraphy Climate change Climate forcing Cores Expedition 339 IODP Site U1385 Integrated Ocean Drilling Program Interglacial environment Isotope ratios Isotopes Lower Pleistocene MIS 31 Marine sediments Mediterranean region Microfossils Miospores North Atlantic Northeast Atlantic O-18/O-16 Orbital forcing Oxygen Paleoclimatology Palynomorphs Pleistocene Pollen Pollen diagrams Quaternary Reconstruction Sediments Stable isotopes Statistical analysis Time series analysis Vegetation Western Mediterranean region 24 Surficial Geology, Quaternary Geology LA - English PY - 2017 SN - 0277-3791 SP - 1–17 ST - Unexpected weak seasonal climate in the western Mediterranean region during MIS 31, a high-insolation forced interglacial T2 - Quaternary Science Reviews TI - Unexpected weak seasonal climate in the western Mediterranean region during MIS 31, a high-insolation forced interglacial UR - https://doi.org/10.1016/j.quascirev.2017.02.013 VL - 161 ID - 4735 ER - TY - JOUR AB - Subpolar North Atlantic proxy records document millennial-scale climate variations 500,000 to 340,000 years ago. The cycles have an approximately constant pacing that is similar to that documented for the last glacial cycle. These findings suggest that such climate variations are inherent to the late Pleistocene, regardless of glacial state. Sea surface temperature during the warm peak of Marine Isotope Stage 11 (MIS 11) varied by 0.5° to 1°C, less than the 4° to 4.5°C estimated during times of ice growth and the 3°C estimated for glacial maxima. Coherent deep ocean circulation changes were associated with glacial oscillations in sea surface temperature. AU - Oppo, D. W. AU - McManus, J. F. AU - Cullen, J. L. DO - doi:10.1126/science.279.5355.1335 IS - 5355 N1 - https://www.science.org/doi/abs/10.1126/science.279.5355.1335 PY - 1998 SP - 1335–1338 ST - Abrupt climate events 500,000 to 340,000 years ago: evidence from subpolar North Atlantic sediments T2 - Science TI - Abrupt climate events 500,000 to 340,000 years ago: evidence from subpolar North Atlantic sediments UR - https://doi.org/10.1126/science.279.5355.1335 VL - 279 ID - 17555 ER - TY - JOUR AB - An overview of the winter circulation and upper ocean structure offshore of Western Iberia is presented. The focus is on winter slope currents, fronts and mesoscale eddies, as well as on the connection of these local features to the large-scale circulation of the region. Satellite sea surface temperature; sea surface elevation data from altimetry; cross-shore and meridional hydrological surveys and current meter observations, mainly obtained during winter periods, are used to illustrate features of the winter upper ocean structure and of the generation and evolution of the Iberia Poleward Current. A schematic/hypothetical model of winter upper ocean circulation on the scale of the Western Iberian Basin is given which attempts to systematize and resolve certain ambiguities in the existing circulation schemes and in the concepts and terminology used to describe observed features in the area. AU - Peliz, Álvaro AU - Dubert, Jesús AU - Santos, A. Miguel P. AU - Oliveira, Paulo B. AU - Le Cann, Bernard DA - 2005/04/01/ DO - https://doi.org/10.1016/j.dsr.2004.11.005 IS - 4 KW - Iberian Basin Iberian Poleward Current Western Iberia Winter Fronts Portugal Current Azores Current Swoddies N1 - https://www.sciencedirect.com/science/article/pii/S0967063704002316 PY - 2005 SN - 0967-0637 SP - 621–646 ST - Winter upper ocean circulation in the Western Iberian Basin—fronts, eddies and poleward flows: an overview T2 - Deep Sea Research, Part I: Oceanographic Research Papers TI - Winter upper ocean circulation in the Western Iberian Basin—fronts, eddies and poleward flows: an overview UR - https://doi.org/10.1016/j.dsr.2004.11.005 VL - 52 ID - 49493 ER - TY - CHAP A2 - Wefer, G., Berger, W.H., and Richter, C. (Eds.) AU - Pérez, Maria Elena AU - Lin, Hui-Ling AU - Lange, Carina Beatriz AU - Schneider, Ralph CY - College Station, TX J2 - Affiliation (analytic): Scripps Institution of Oceanography, La Jolla, CA Affiliation (monographic): Scripps Institution of Oceanography, La Jolla, CA, United States Corporate Affiliation (monographic): Ocean Drilling Program, Leg 175, Shipboard Scientific Party, College Station, TX Coordinates: S253049 S253049 E0130140 E0130140; S210539 S210539 E0114914 E0114914 illus., incl. 1 table, sketch map Contains 21 references Research Program: ODP Ocean Drilling Program Document Type: Journal Article Bibliographic Level: Analytic Source Note: Proceedings of the Ocean Drilling Program, scientific results, Benguela Current; covering Leg 175 of the cruises of the drilling vessel JOIDES Resolution; Las Palmas, Canary Islands, to Cape Town, South Africa; sites 1075-1087; 9 August-8 October 1997, Wolfgang H. Berger, Gerold Wefer, Carl Richter, Donald D. Adams, Linda Davis Anderson, Dyke J. Andreasen, Volker Brüchert, Hervé Cambray, Beth A. Christensen, Gina Marie Frost, Jacques Giraudeau, Thomas J. Gorgas, J. Otto R. Hermelin, J. H. Fred Jansen, Carina Beatriz Lange, Bernd Laser, Hui-Ling Lin, Mark A. Maslin, Philip A. Meyers, Isao Motoyama, Richard W. Murray, Maria Elena Perez, Peir Kenneth Pufahl, Volkhard Spiess, Laurence Vidal, Rochelle Wigley and Toshitsugu Yamazaki; Ocean Drilling Program, Leg 175, Shipboard Scientific Party, College Station, TX. Proceedings of the Ocean Drilling Program, Scientific Results (CD ROM), Vol.175, 16p. Publisher: Texas A&M University, Ocean Drilling Program, College Station, TX, United States. ISSN: 1096-2514 Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. GeoRef ID: 2002040461 DOI: 10.2973/odp.proc.sr.175.221.2001 KW - Africa Algae Atlantic Ocean Benguela Current Biostratigraphy Cenozoic Continental margin Currents Diatoms Framework silicates Leg 175 Matuyama Chron Microfossils Neogene ODP Site 1082 ODP Site 1084 Ocean Drilling Program Ocean currents Opal Paleocurrents Paleomagnetism Plantae Pleistocene Pliocene Quaternary Regression analysis Silica minerals Silicates South Atlantic Southeast Atlantic Statistical analysis Tertiary Upper Cenozoic 12 Stratigraphy, Historical Geology and Paleoecology LA - English N1 - Benguela Current; covering Leg 175 of the cruises of the drilling vessel JOIDES Resolution; Las Palmas, Canary Islands, to Cape Town, South Africa; sites 1075-1087; 9 August-8 October 1997 PB - Ocean Drilling Program PY - 2001 SN - 1096-2514 ST - Pliocene-Pleistocene opal records off Southwest Africa, Sites 1082 and 1084: a comparison of analytical techniques T2 - Proceedings of the Ocean Drilling Program, Scientific Results TI - Pliocene-Pleistocene opal records off Southwest Africa, Sites 1082 and 1084: a comparison of analytical techniques UR - https://doi.org/10.2973/odp.proc.sr.175.221.2001 VL - 175 ID - 21457 ER - TY - JOUR AB - While ocean circulation is driven by the formation of deep water in the North Atlantic and the Circum-Antarctic, the role of southern-sourced deep water formation in climate change is poorly understood. Here we address the balance of northern- and southern-sourced waters in the South Atlantic through the last glacial period using neodymium isotope ratios of authigenic ferromanganese oxides in thirteen deep sea cores from throughout the South Atlantic. The data indicate that northern-sourced water did not reach the Southern Ocean during the late glacial, and was replaced by southern-derived intermediate and deep waters. The high-resolution neodymium isotope record (~300 yr sample spacing) from two spliced deep Cape Basin sites indicates that over the last glacial period northern-sourced water mass export to the Southern Ocean was stronger during the major Greenland millennial warming intervals (and Southern Hemisphere cool periods), and particularly during the major interstadials 8, 12, and 14. Northern-sourced water mass export was weaker during Greenland stadials and reached minima during Heinrich Events. The benthic foraminiferal carbon isotopes in the same Cape Basin core reflect a partial control by Southern Hemisphere climate changes and indicate that deep water formation and ventilation occurred in the Southern Ocean during major Greenland cooling intervals (stadials). Together, neodymium isotopes and benthic carbon isotopes provide new information about water mass sourcing and circulation in deep Southern Ocean waters during rapid glacial climate changes. Combining carbon and neodymium isotopes can be used to monitor the relative proportion of northern- and southern-sourced waters in the Cape Basin to gain insight into the processes which control the carbon isotopic composition of deep waters. In this study we show that deep water formation and circulation was more important than biological productivity and nutrient regeneration changes for controlling the carbon isotope chemistry of Antarctic Bottom Water during millennial-scale glacial climate cycles. This observation also lends support to the hypothesis that ocean circulation is linked to interhemispheric climate changes on short timescales, and that ventilation in the glacial ocean rapidly switched between the northern and Southern Hemisphere on millennial timescales. AU - Piotrowski, Alexander M. AU - Goldstein, Steven L. AU - Hemming, Sidney R. AU - Fairbanks, Richard G. AU - Zylberberg, David R. DA - 2008/07/30/ DO - https://doi.org/10.1016/j.epsl.2008.05.011 IS - 1–2 KW - ocean circulation paleoclimate last glacial Heinrich Events interstadials southern ocean Antarctic Bottom Water N1 - https://www.sciencedirect.com/science/article/pii/S0012821X08003221 PY - 2008 SN - 0012-821X SP - 394–405 ST - Oscillating glacial northern and southern deep water formation from combined neodymium and carbon isotopes T2 - Earth and Planetary Science Letters TI - Oscillating glacial northern and southern deep water formation from combined neodymium and carbon isotopes UR - https://doi.org/10.1016/j.epsl.2008.05.011 VL - 272 ID - 11799 ER - TY - JOUR AB - Marine Isotope Stage 19 (MIS 19) is the oldest interglacial period archived in the EPICA Dome C ice core (~780ky BP) and the closest “orbital analogue” to the Holocene — albeit with a different obliquity amplitude and phase with precession. New detailed deuterium measurements have been conducted with a depth resolution of 11cm (corresponding time resolution of ~130years). They confirm our earlier low resolution profile (55cm), showing a relatively smooth shape over the MIS 20 to MIS 18 time period with a lack of sub-millennial climate variability, first thought to be due to this low resolution. The MIS 19 high resolution profile actually reveals a strong isotopic diffusion process leading to a diffusion length of at least ~40cm erasing sub-millennial climate variability. We suggest that this diffusion is caused by water-veins associated with large ice crystals at temperatures above −10°C, temperature conditions in which the MIS 19 ice has spent more than 200ky. This result has implications for the selection of the future “oldest ice” drilling site. AU - Pol, K. AU - Masson-Delmotte, V. AU - Johnsen, S. AU - Bigler, M. AU - Cattani, O. AU - Durand, G. AU - Falourd, S. AU - Jouzel, J. AU - Minster, B. AU - Parrenin, F. AU - Ritz, C. AU - Steen-Larsen, H. C. AU - Stenni, B. DA - 2010/09/15/ DO - https://doi.org/10.1016/j.epsl.2010.07.030 IS - 1 KW - water stable isotopes ice cores Antarctica isotopic diffusion N1 - https://www.sciencedirect.com/science/article/pii/S0012821X10004681 PY - 2010 SN - 0012-821X SP - 95–103 ST - New MIS 19 EPICA Dome C high resolution deuterium data: hints for a problematic preservation of climate variability at sub-millennial scale in the “oldest ice” T2 - Earth and Planetary Science Letters TI - New MIS 19 EPICA Dome C high resolution deuterium data: hints for a problematic preservation of climate variability at sub-millennial scale in the “oldest ice” UR - https://doi.org/10.1016/j.epsl.2010.07.030 VL - 298 ID - 23083 ER - TY - JOUR AB - Climate-proxy records of the past 100,000 years show that the Earth's climate has varied significantly and continuously on timescales as short as a few thousand years (1–7). Similar variability has also recently been observed for the interval 340–500 thousand years ago8. These dramatic climate shifts, expressed most strongly in the North Atlantic region, may be linked to — and possibly amplified by — alterations in the mode of ocean thermohaline circulation4,5,6,7,8,9. Here we use sediment records of past iceberg discharge and deep-water chemistry to show that such millennial-scale oscillations in climate occurred over one million years ago. This was a time of significantly different climate boundary conditions; not only was the early Pleistocene epoch generally warmer, but global climate variations were governed largely by changes in Earth's orbital obliguity. Our results suggest that such millennial-scale climate instability may be a pervasive and long-term characteristic of Earth's climate, rather than just a feature of the strong glacial–interglacial cycles of the past 800,000 years. AU - Raymo, M. E. AU - Ganley, K. AU - Carter, S. AU - Oppo, D. W. AU - McManus, J. DA - 1998/04/01 DO - 10.1038/33658 IS - 6677 PY - 1998 SN - 1476-4687 SP - 699–702 ST - Millennial-scale climate instability during the early Pleistocene epoch T2 - Nature TI - Millennial-scale climate instability during the early Pleistocene epoch UR - https://doi.org/10.1038/33658 VL - 392 ID - 17556 ER - TY - JOUR AB - Much progress has been made towards understanding what caused the waxing and the waning of the great ice sheets, but a complete theory of the ice ages is still elusive. AU - Raymo, Maureen E. AU - Huybers, Peter DA - 2008/01/01 DO - 10.1038/nature06589 IS - 7176 PY - 2008 SN - 1476-4687 SP - 284–285 ST - Unlocking the mysteries of the ice ages T2 - Nature TI - Unlocking the mysteries of the ice ages UR - https://doi.org/10.1038/nature06589 VL - 451 ID - 17557 ER - TY - JOUR AB - Analysis of sea surface temperature (SST) time series since 1960 from existing data bases shows a generalized warming trend in the northern Canary upwelling system. The field of the satellite-derived SST trends off Western Iberia was built at the pixel scale (4 × 4 km) for the period 1985–2008, revealing significant spatial differences in the warming rates. Weaker warming trends fit to the known upwelling pattern off the southern part of the Western Iberia, pointing out the intensification of this feature since 1985, particularly during the peak summer months. A more regular behavior is found further north suggesting significant decadal changes in the mesoscale patterns of the northern Canary upwelling system. AU - Relvas, P. AU - Luís, J. AU - Santos, A. M. P. DO - https://doi.org/10.1029/2009GL040504 IS - 22 N1 - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2009GL040504 PY - 2009 SN - 0094-8276 SP - L22601 ST - Importance of the mesoscale in the decadal changes observed in the northern Canary upwelling system T2 - Geophysical Research Letters TI - Importance of the mesoscale in the decadal changes observed in the northern Canary upwelling system UR - https://doi.org/10.1029/2009GL040504 VL - 36 ID - 49494 ER - TY - JOUR AB - During the “ANA” cruise in November 1988, Western North Atlantic Water (WNAW) was found linked to the Azores Current (AC) at 23°W, where according to various authors Eastern North Atlantic Water (ENAW) forms a boundary with WNAW east of the Mid-Atlantic Ridge (MAR). This boundary changes position during the year. The vein of Mediterranean Water (MW) moving towards the MAR seems to be connected with the AC, and restricts the penetration of ENAW of subpolar origin (ENAWP). A subsurface front has been found along 42°N, separating ENAW of subtropical origin (ENAWT) that moves northeastwards generating a cyclonic eddy that is confined between the lower limit of the surface layer and approximately the 27.06 isopycnal, and modified ENAWP that moves southwards forming various anticyclonic eddies. AU - Ríos, Aida F. AU - Pérez, Fiz F. AU - Fraga, F. DA - 1992/03/01/ DO - https://doi.org/10.1016/0198-0149(92)90093-9 IS - 3 N1 - https://www.sciencedirect.com/science/article/pii/0198014992900939 PY - 1992 SN - 0198-0149 SP - 645–658 ST - Water masses in the upper and middle North Atlantic Ocean east of the Azores T2 - Deep Sea Research, Part A. Oceanographic Research Papers TI - Water masses in the upper and middle North Atlantic Ocean east of the Azores UR - https://doi.org/10.1016/0198-0149(92)90093-9 VL - 39 ID - 49495 ER - TY - JOUR AB - The Iberian Margin is a sensitive area to track high and low latitude processes, and is a key location to understand major past climatic and oceanographic changes. Here we present new biomarker data from IODP Site U1385 ("Shackleton site") (1017-336 ka) that, when combined with existing data from Cores MD01-2443/4 (last 335 ka), allows us to assess the evolution of sea surface temperature (SST) and meltwater influx over the last 1 Ma at the Iberian Margin. Interglacial periods throughout the last 1 Ma show SST close to 20 °C, even during the so-called "luke-warm" interglacials that are marked by relatively low atmospheric CO2 concentrations. During glacial periods, extremely cold stadial events are recognized at the Iberian Margin, and are very likely related to meltwater discharges from the European and British-Irish ice sheets into the NE Atlantic, which were transported southwards by the Portugal Current. We subdivided the record into four intervals on the basis of the timing and the magnitude of these extremely cold stadials: 1) from 1017 to ∼900 ka, only minor sporadic freshwater input occurred during deglaciations; 2) from 900 to 675 ka extreme cold events occur as terminal stadial events at the beginning of the deglaciations, which results in abrupt deglacial SST shifts; 3) from 675 to 450 ka only a few, very short-lived events are recorded and seldom is there freshwater input at the Iberian Margin; 4) during the last 450 ka the extreme cold events occurred under full glacial conditions, with particularly severe events during MIS 6 and 8. We propose these mid-glacial events are associated with a strong discharges of European ice sheet (EIS). The fact that these extreme cold events do not coincide with deglaciations questions the role of European ice sheet discharges in triggering deglaciations. AU - Rodrigues, T. AU - Alonso-Garcia, M. AU - Hodell, D. A. AU - Rufino, M. AU - Naughton, F. AU - Grimalt, Joan O. AU - Voelker, A. H. L. AU - Abrantes, F. J2 - Affiliation (analytic): Instituto Portugues do Mar e da Atmosfera, Divisao de Geologia e Georecursos Marinhos, Lisbon Affiliation (monographic): Instituto Portugues do Mar e da Atmosfera, Divisao de Geologia e Georecursos Marinhos, Lisbon, Portugal Coordinates: N373417 N373417 W0100719 W0100720 illus., incl. 4 tables, sketch map Contains 90 references Research Program: IODP Integrated Ocean Drilling Program Document Type: Journal Article Bibliographic Level: Analytic Source Note: Quaternary Science Reviews, Vol.172, p.118-130. Publisher: Elsevier, International. ISSN: 0277-3791 Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands GeoRef ID: 2018050228 DOI: 10.1016/j.quascirev.2017.07.004 KW - Alkenones Atlantic Ocean Biomarkers Cenozoic Chemostratigraphy Cores Europe Expedition 339 Glacial environment IODP Site U1385 Iberian Peninsula Integrated Ocean Drilling Program Interglacial environment Isotope ratios Isotopes Ketones Lipids Lithostratigraphy Marine sediments North Atlantic Northeast Atlantic O-18/O-16 Organic compounds Oxygen Paleo-oceanography Paleoclimatology Paleotemperature Portugal Quaternary Sea-surface temperature Sediments Southern Europe Stable isotopes Upper Quaternary 24 Surficial Geology, Quaternary Geology LA - English PY - 2017 SN - 0277-3791 SP - 118–130 ST - A 1-Ma record of sea surface temperature and extreme cooling events in the North Atlantic: a perspective from the Iberian Margin T2 - Quaternary Science Reviews TI - A 1-Ma record of sea surface temperature and extreme cooling events in the North Atlantic: a perspective from the Iberian Margin UR - https://doi.org/10.1016/j.quascirev.2017.07.004 VL - 172 ID - 4657 ER - TY - JOUR AB - Past sea surface water conditions of the western Iberian Margin were reconstructed based on biomarker analyses of a marine deep sea core MD03-2699 from the Estremadura Spur north off Lisbon, providing new insights into orbital and suborbital-scale climate variability between marine isotope stage (MIS) 15 to MIS 9 (580 to 300 ka). We use biomarker-based proxy records such as the alkenone unsaturated index to estimate sea surface temperature (SST), the total alkenone concentration to reconstruct phytoplankton productivity, and terrestrial biomarkers to evaluate the continental input. The results extend the existing biomarker record, namely the SST for the Iberian Margin, back to the sixth climatic cycle (580 ka). A general trend of stable interglacials contrasts with glacial periods and glacial inceptions which are marked by high-frequency variability. Thus, several short-lived climatic coolings were identified by large SST decreases, the occurrence of ice-rafted detritus and high percentages of the tetraunsaturated alkenone C37:4. Some of these events were extremely cold and similar in their general trends to the well-known Heinrich events of the last glaciation. We identified eight Heinrich-type events between 580 and 300 ka. The general deglaciation pattern detected between MIS 15 and MIS 9 is similar in their general trends to that characterizing the more recent climatic cycles, i.e., marked by two coolings separated by a short warming episode which may reflect the southward, northward, and southward migration of the Polar Front. AU - Rodrigues, T. AU - Voelker, A. H. L. AU - Grimalt, J. O. AU - Abrantes, F. AU - Naughton, F. DO - https://doi.org/10.1029/2010PA001927 IS - 1 N1 - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2010PA001927 PY - 2011 SN - 0883-8305 SP - PA1204 ST - Iberian margin sea surface temperature during MIS 15 to 9 (580–300 ka): glacial suborbital variability versus interglacial stability T2 - Paleoceanography and Paleoclimatology TI - Iberian margin sea surface temperature during MIS 15 to 9 (580–300 ka): glacial suborbital variability versus interglacial stability UR - https://doi.org/10.1029/2010PA001927 VL - 26 ID - 17558 ER - TY - JOUR AB - A deep-sea sediment core from the western Portuguese margin has provided a continuous, high-resolution record of millennial-scale climatic oscillations during the interval 9000–65,000 yr B.P. Pollen analysis of the same sequence allows direct, in situ assessment of the phase relationship between the North Atlantic climate system and vegetation changes on the adjacent landmass. This demonstrates for the first time that variability in NW Iberian tree population size closely tracked millennial-scale climate variability. AU - Roucoux, Katherine H. AU - Shackleton, Nicholas J. AU - de Abreu, Lucia AU - Schönfeld, Joachim AU - Tzedakis, Polychronis C. DB - Cambridge Core DO - 10.1006/qres.2001.2218 DP - Cambridge University Press ET - 2017/01/20 IS - 1 KW - marine palynology marine isotope stage 3 Portuguese margin North Atlantic land–sea correlation N1 - https://www.cambridge.org/core/article/combined-marine-proxy-and-pollen-analyses-reveal-rapid-iberian-vegetation-response-to-north-atlantic-millennialscale-climate-oscillations/937C18C6C89525453F75A227969B406C PY - 2001 SN - 0033-5894 SP - 128–132 ST - Combined marine proxy and pollen analyses reveal rapid Iberian vegetation response to North Atlantic millennial-scale climate oscillations T2 - Quaternary Research TI - Combined marine proxy and pollen analyses reveal rapid Iberian vegetation response to North Atlantic millennial-scale climate oscillations UR - https://doi.org/10.1006/qres.2001.2218 VL - 56 ID - 17559 ER - TY - JOUR AB - Quantitative and qualitative analyses of planktonic foraminiferal assemblages from 134 core-top sediment samples collected along the western Iberian margin were used to assess the latitudinal and longitudinal changes in surface water conditions and to calibrate a Sea Surface Temperature (SST) transfer function for this seasonal coastal upwelling region. Q-mode factor analysis performed on relative abundances yielded three factors that explain 96% of the total variance: factor 1 (50%) is exclusively defined by Globigerina bulloides, the most abundant and widespread species, and reflects the modern seasonal (May to September) coastal upwelling areas; factor 2 (32%) is dominated by Neogloboquadrina pachyderma (dextral) and Globorotalia inflata and seems to be associated with the Portugal Current, the descending branch of the North Atlantic Drift; factor 3 (14%) is defined by the tropical–sub-tropical species Globigerinoides ruber (white), Globigerinoides trilobus trilobus, and G. inflata and mirrors the influence of the winter-time eastern branch of the Azores Current. In conjunction with satellite-derived SST for summer and winter seasons integrated over an 18 year period the regional foraminiferal data set is used to calibrate a SST transfer function using Imbrie & Kipp, MAT and SIMMAXndw techniques. Similar predicted errors (RMSEP), correlation coefficients, and residuals' deviation from SST estimated for both techniques were observed for both seasons. All techniques appear to underestimate SST off the southern Iberia margin, an area mainly occupied by warm waters where upwelling occurs only occasionally, and overestimate SST on the northern part of the west coast of the Iberia margin, where cold waters are present nearly all year round. The comparison of these regional calibrations with former Atlantic and North Atlantic calibrations for two cores, one of which is influenced by upwelling, reveals that the regional one attests more robust paleo-SSTs than for the other approaches. AU - Salgueiro, Emília AU - Voelker, Antje AU - Abrantes, Fátima AU - Meggers, Helge AU - Pflaumann, Uwe AU - Lončarić, Neven AU - González-Álvarez, Raquel AU - Oliveira, Paulo AU - Bartels-Jónsdóttir, Helga B. AU - Moreno, João AU - Wefer, Gerold DA - 2008/02/20/ DO - https://doi.org/10.1016/j.marmicro.2007.09.003 IS - 3–4 KW - planktonic foraminifera transfer functions Sea Surface Temperature upwelling Iberian margin N1 - https://www.sciencedirect.com/science/article/pii/S037783980700103X PY - 2008 SN - 0377-8398 SP - 135–164 ST - Planktonic foraminifera from modern sediments reflect upwelling patterns off Iberia: insights from a regional transfer function T2 - Marine Micropaleontology TI - Planktonic foraminifera from modern sediments reflect upwelling patterns off Iberia: insights from a regional transfer function UR - https://doi.org/10.1016/j.marmicro.2007.09.003 VL - 66 ID - 17561 ER - TY - JOUR AB - Present day hydrographic conditions along the western Iberian margin are characterized by seasonal upwelling with filaments that can penetrate more than 200 km into the open ocean and constitute areas of cold and highly productive waters. In order to investigate spatial and temporal gradients in temperature and productivity conditions during the last 150 ky, high-resolution proxy records were generated in 3 cores (SU92-03, MD95-2040, MD95-2042), located along the Iberian coast between 43°12′N and 37°48′N and forming a N–S profile. In all cores, planktonic foraminifera census counts are used to reconstruct summer sea surface temperature (SSTsu) and export productivity (Pexpsu) using the modern analog technique SIMMAX 28. SSTsu and Pexpsu values similar to the present are observed throughout the Holocene and MIS 5e periods for each site, respectively, indicating fairly stable conditions equivalent to the modern ones. On glacial/interglacial timescales, SSTsu increases by 2–3 °C from the northern to southernmost site. Pexpsu, on the other hand, shows a decrease of 30–40 gC/m2/yr from North to South at present time and during interglacial periods, and no significant variation (90–100 gC/m2/yr) during glacial periods. The northernmost core SU92-03 reveals the coldest conditions with records more similar to MD95-2040 than to MD95-2042, the later of which is, as at present, more affected by subtropical waters. Core SU92-03 shows higher interglacial productivity similar to open ocean mid- to high latitude sites, while the other two cores monitor higher glacial productivity conform with other upwelling sites off NW Africa. A boundary between differences in glacial/interglacial productivity appears to be present in our study between 43°12′N and 40°35′N. Especially north of 40°N, coldest SSTsu and lowest Pexpsu are found during Heinrich events (H)1–H8 and H10–H11. In contrast, lowest Pexpsu do not coincide with these events at site MD95-2042, but appear to be related to the presence of relatively warm and nutrient-poor subtropical Eastern North Atlantic Central Water advected with the Azores Current. AU - Salgueiro, E. AU - Voelker, A. H. L. AU - de Abreu, L. AU - Abrantes, F. AU - Meggers, H. AU - Wefer, G. DA - 2010/03/01/ DO - https://doi.org/10.1016/j.quascirev.2009.11.013 IS - 5–6 N1 - https://www.sciencedirect.com/science/article/pii/S0277379109003862 PY - 2010 SN - 0277-3791 SP - 680–695 ST - Temperature and productivity changes off the western Iberian margin during the last 150 ky T2 - Quaternary Science Reviews TI - Temperature and productivity changes off the western Iberian margin during the last 150 ky UR - https://doi.org/10.1016/j.quascirev.2009.11.013 VL - 29 ID - 17560 ER - TY - JOUR AB - We present high resolution pollen, dinocyst and isotopic data for the Last Interglacial complex from marine core MD952042 (southwestern margin of the Iberian Peninsula; 37°48′N; 10°10′W; 3148 m). Direct land-sea correlation from this core indicates that during this period, North Atlantic sea surface temperatures were in phase with Iberian climate. Our palynological analysis suggests a Younger Dryas-like event at the Marine Isotope Stage (MIS)-6/5 transition. The analysis also indicates that the Eemian spans from the lightest isotopic values of MIS-5e (ca. 126 ky BP) to the heavier isotopic values towards the MIS-5e/5d transition. Therefore, the Eemian is not entirely equivalent to MIS-5e. Pollen analysis identifies four climatic phases of low amplitude during the Eemian. A Mediterranean climate in southwestern Europe is gradually replaced by oceanic conditions. The middle of the Eemian is characterized by an increase in precipitation on the land and ocean, associated with a slight cooling. This seems to be the result of a displacement of the Polar Front as far south as southern Europe during this period. After the Eemian, three relatively short climatic phases on land (Mélisey I, St. Germain Ia and Montaigu cold event) occurred contemporaneously with three shifts of sea surface temperatures. The Montaigu event, first identified in terrestrial pollen sequences, is, therefore, also recorded in core MD952042 on the basis of pollen, dinocyst and planktonic isotopic data. Our results also show that the warm periods of MIS-5 are not characterized by similar climatic conditions on land. AU - Sánchez Goñi, M. F. AU - Eynaud, F. AU - Turon, J. L. AU - Shackleton, N. J. DA - 1999/08/15/ DO - https://doi.org/10.1016/S0012-821X(99)00141-7 IS - 1 KW - Eemian pollen dinoflagellates isotopes Southern Europe North Atlantic paleoclimatology N1 - https://www.sciencedirect.com/science/article/pii/S0012821X99001417 PY - 1999 SN - 0012-821X SP - 123–137 ST - High resolution palynological record off the Iberian margin: direct land-sea correlation for the Last Interglacial complex T2 - Earth and Planetary Science Letters TI - High resolution palynological record off the Iberian margin: direct land-sea correlation for the Last Interglacial complex UR - https://doi.org/10.1016/S0012-821X(99)00141-7 VL - 171 ID - 17562 ER - TY - JOUR AB - Grain size analysis and physical properties of Sites U1388, U1389 and U1390 collected in the Contourite Depositional System of the Gulf of Cadiz during the Integrated Ocean Drilling Program (IODP) Expedition 339 "Mediterranean Outflow" reveal relative changes in bottom current strength, a tracer of the dynamics of the Mediterranean Outflow Water (MOW), before and after the Middle Pleistocene Transition (MPT). The comparison of MOW behavior with climate changes identified by the pollen analysis and δ18O benthic foraminifera measurements of Site U1385, the Shackleton Site, collected in the south western Iberian margin shows that the interval MIS 31-MIS 30, ∼ 1.1-1.05 million years ago (Ma), before the MPT, was marked by wetter climate and weaker bottom current than the interval MIS 12-MIS 11 (0.47-0.39 Ma), after the MPT. Similarly, the increase in fine particles from these glacials to interglacials and in coarse fraction from interglacials to glacials was coeval with forest and semi-desert expansions, respectively, indicating the lowering/enhancement of MOW strength during periods of regional increase/decrease of moisture. While these findings may not necessarily apply to all glacial/interglacial cycles, they nonetheless serve as excellent supporting examples of the hypothesis that aridification can serve as a good tracer for MOW intensity. The strongest regional aridity during MIS 12 coincides with a remarkable increase of coarse grain size deposition and distribution that we interpret as a maximum in MOW strength. This MOW intensification may have pre-conditioned the North Atlantic by increasing salinity, thereby triggering the strong resumption of the Meridional Overturning Circulation that could contribute to the great warmth that characterizes the MIS 11c super-interglacial. Abstract Copyright (2016) Elsevier, B.V. AU - Sánchez Goñi, Maria Fernanda AU - Llave, E. AU - Oliveira, Dulce AU - Naughton, F. AU - Desprat, Stéphanie AU - Ducassou, E. AU - Hodell, D. A. AU - Hernández Molina, F. J. J2 - Affiliation (analytic): Université de Bordeaux, Ecole Pratique des Hautes Etudes, Pessac Affiliation (monographic): Université de Bordeaux, Ecole Pratique des Hautes Etudes, Pessac, France Coordinates: N361902 N361909 W0074304 W0092405; N353000 N370000 W0060000 W0090000 illus., incl. 1 table, sketch map Contains 70 references Research Program: IODP Integrated Ocean Drilling Program Document Type: Journal Article Bibliographic Level: Analytic Source Note: Global and Planetary Change, Vol.136, p.18-29. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0921-8181 Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands GeoRef ID: 2016089143 DOI: 10.1016/j.gloplacha.2015.11.006 KW - Assemblages Atlantic Ocean Cenozoic Climate change Cyclic processes Europe Expedition 339 Granulometry Gulf of Cadiz IODP Site U1388 IODP Site U1389 IODP Site U1390 Iberian Peninsula Integrated Ocean Drilling Program Isotope ratios Isotopes MIS 11 MIS 12 MIS 30 MIS 31 Marine sediments Mediterranean Outflow Mediterranean Sea Microfossils Miospores North Atlantic Northeast Atlantic O-18/O-16 Oxygen Paleo-oceanography Paleoclimatology Palynomorphs Plantae Pleistocene Pollen Quaternary Sedimentology Sediments Southern Europe Spectra Stable isotopes Strait of Gibraltar West Mediterranean X-ray fluorescence spectra 02 Geochemistry 24 Surficial Geology, Quaternary Geology LA - English PY - 2016 SN - 0921-8181 SP - 18–29 ST - Climate changes in south western Iberia and Mediterranean Outflow variations during two contrasting cycles of the last 1 myrs: MIS 31-MIS 30 and MIS 12-MIS 11 T2 - Global and Planetary Change TI - Climate changes in south western Iberia and Mediterranean Outflow variations during two contrasting cycles of the last 1 myrs: MIS 31-MIS 30 and MIS 12-MIS 11 UR - https://doi.org/10.1016/j.gloplacha.2015.11.006 VL - 136 ID - 4664 ER - TY - JOUR AB - Pollen, foraminifer, dinocyst, and coarse lithic high-resolution analyses and δ18O measurements have been carried out for the last-glacial section of marine core MD95-2042 located near the southwestern margin of the Iberian Peninsula. The pollen data indicate a high frequency of vegetational changes on the adjacent continent during this period, suggesting a climatic variability very similar to that of the Dansgaard-Oeschger cycles recorded by the Greenland ice cores. The detailed direct correlation of the terrestrial and marine proxy data from core MD95-2042 indicates a three-phase pattern of Heinrich events in land and ocean environments. The first and last phases of the H5 and H4 events are characterized by a mild and humid climate in southwestern Europe, probably associated with the European origin of the ice-rafted detritus. The middle phase exhibits a cold and dry climate in Iberia linked with the maximum input of ice-rafted detritus. This phase seems to correspond with the Laurentide ice-sheet surges. Between the Heinrich events, several cold and dry periods on land are correlated with stades of the Dansgaard-Oeschger cycles. The impact of the Dansgaard-Oeschger stades in southwestern Europe seems to be preferentially connected to the cold winter air masses reaching this mid-latitude region. AU - Sánchez Goñi, M.F. AU - Turon, Jean-Louis AU - Eynaud, Frédérique AU - Gendreau, Sandra DA - 2000/11/01/ DO - https://doi.org/10.1006/qres.2000.2176 IS - 3 KW - last glaciation Heinrich events Dansgaard-Oeschger cycles Iberian Peninsula pollen ice-rafted detritus dinocysts foraminifers N1 - https://www.sciencedirect.com/science/article/pii/S0033589400921768 PY - 2000 SN - 0033-5894 SP - 394–403 ST - European climatic response to millennial-scale changes in the atmosphere–ocean system during the last glacial period T2 - Quaternary Research TI - European climatic response to millennial-scale changes in the atmosphere–ocean system during the last glacial period UR - https://doi.org/10.1006/qres.2000.2176 VL - 54 ID - 17563 ER - TY - JOUR AB - A narrow gap (Discovery Gap) in the East Azores Fracture Zone at 37°N in the eastern Atlantic provides a channel for the exchange of bottom water between the Madeira and Iberian abyssal basins. A detailed survey defines its length (150 km), width (10–50 km), depth of sills (near 4800 m) and sediment thickness (0–500 m). Year-long measurements of deep flow are made from six moorings and ten current meters. Mean flows are about 5 cm s−1. These data are supplemented by 10 days of float tracking near 4700 m and numerous density profiles within and around the gap. A persistent southwest-northeast flow of dense water is found in Discovery Gap, and the flux of water colder than a potential temperature of 2.05°C is measured to be (0.21 ± .04) × 106 m3 s−1. This discharge spreads over an area of about 1011 m2 beyond the Gap exit, where it is warmed both by geothermal heating and by mixing with overlying water. An estimate of 1.5 to 4 cm2 s−1 is derived for the diapycnal diffusivity, similar to values determined from much larger channels in the western Atlantic, but the relative importance of boundary versus interior mixing cannot be established. The cold water arrives from the south along the deep eastern margin; its hydrographic signal is the “piling up” of isotherms against the lower continental rise. New 32°N, about 500 km south of Discovery Gap, the signal is small, and it is proposed that just south of this latitude the eastern boundary current ends. AU - Saunders, P. M. DA - 01 May. 1987 DO - 10.1175/1520-0485(1987)017<0631:Ftdg>2.0.Co;2 IS - 5 LA - English N1 - https://journals.ametsoc.org/view/journals/phoc/17/5/1520-0485_1987_017_0631_ftdg_2_0_co_2.xml PY - 1987 SN - 0022-3670 SP - 631–643 ST - Flow through Discovery Gap T2 - Journal of Physical Oceanography TI - Flow through Discovery Gap UR - https://doi.org/10.1175/1520-0485(1987)017%3C0631:FTDG%3E2.0.CO;2 VL - 17 ID - 17564 ER - TY - CHAP A2 - Pisias, N.G., Mayer, L.A., Janecek, T.R., Palmer-Julson, A., and van Andel, T.H. (Eds.) AU - Shackleton, N.J., Hall, M.A., and Pate, D. CY - College Station, TX PB - Ocean Drilling Program PY - 1995 SP - 337–355 ST - Pliocene stable isotope stratigraphy of Site 846 T2 - Proceedings of the Ocean Drilling Program, Scientific Results TI - Pliocene stable isotope stratigraphy of Site 846 UR - https://doi.org/10.2973/odp.proc.sr.138.117.1995 VL - 138 ID - 17565 ER - TY - JOUR AB - Since its identification nearly fifty years ago, Marine Isotope Stage 5 (MIS 5) has been placed onto absolute time scales on the basis of three independent approaches. Cesare Emiliani, who set up the isotope stages (Emiliani, 1955), depended on uranium-series dating of the sediments, a method that today is regarded as not generally capable of yielding useful precision or accuracy. Broecker and van Donk (1970) pioneered the approach of correlating to radiometrically dated marine coral terraces; this has been much aided in recent years by improvements in the precision and accuracy of these age determinations that have flowed from the development of thermal ionization mass spectrometry (TIMS) for uranium-series dating (Edwards et al., 1986). The third approach is to use the astronomical record as a guide to the time scale. Martinson et al. (1987) generated a detailed time scale for MIS 5 using this approach. These authors suggested that the overall average error was of the order ±5000 yr, although the error would be smaller during interglacial periods with high precession-related variability, such as MIS5. At that time, the suggested confidence limits were smaller than typical values quoted for the radiometric dating of corals (typically ±6000 yr). Today the accuracy of the time scale of Martinson et al. (1987) is challenged by high-precision TIMS dates with quoted uncertainties of the order ±1000 yr or better. From the point of view of achieving a better understanding of the last interglacial period, the more serious disadvantage of the Martinson et al. (1987) time scale is the underlying hypothesis that all the proxy palaeoclimate records represent smoothly varying responses to changes in insolation; hence, there is no basis for estimating the duration of an extended interval with northern ice sheet volumes static at a size no greater than at present. From this point of view, the model of Gallée et al. (1993) is more promising, but that model is not at present sufficiently realistic to provide a reliable independent time scale. We have therefore chosen to depict the oxygen isotope record of core MD95-2042 (37°48′N, 10°10′W, water depth of 3146 m) on a time scale (Shackleton et al., 2001) that is based only on making use of selected radiometric dates obtained from fossil corals to calibrate the isotope record. AU - Shackleton, Nicholas J. AU - Chapman, Mark AU - Sánchez-Goñi, Maria Fernanda AU - Pailler, Delphine AU - Lancelot, Yves DB - Cambridge Core DO - 10.1006/qres.2001.2312 DP - Cambridge University Press ET - 2017/01/20 IS - 1 N1 - https://www.cambridge.org/core/article/classic-marine-isotope-substage-5e/9FE497FD82DB392358302A7132D21AA4 PY - 2002 SN - 0033-5894 SP - 14–16 ST - The classic Marine Isotope Substage 5e T2 - Quaternary Research TI - The classic Marine Isotope Substage 5e UR - https://doi.org/10.1006/qres.2001.2312 VL - 58 ID - 17569 ER - TY - JOUR AB - We propose a new age scale for the two ice cores (GRIP and GISP2) that were drilled at Greenland summit, based on accelerator mass spectrometry 14C dating of foraminifera in core MD95-2042 (Paleoceanography 15 (2000) 565), calibrated by means of recently obtained paired 14C and 230Th measurements on pristine corals (Marine radiocarbon calibration curve spanning 10,500 to 50,000 years BP (thousand years before present) Based on paired 230Th/234U/238U and 14C dates on Pristine Corals Geological Society of America Bulletin, 2003, submitted for publication). The record of core MD95-2042 can be correlated very precisely to the Greenland ice cores. Between 30 and 40ka BP our scale is 1.4ka older than the GRIP SS09sea time scale (Journal of Quaternary Science 16 (2001) 299). At the older end of Marine Isotope Stage 3 we use published 230Th dates from speleothems to calibrate the record. Using this scale we show a Δ14C record that is broadly consistent with the modelled record (Earth Planet. Sci. Lett. 200 (2002) 177) and with the data of Hughen et al. (Science 303 (2004) 202), but not consistent with the high values obtained by Beck et al. (Science 292 (2001) 2453) or by Voelker et al. (Radiocarbon 40 (1998) 517). We show how a set of age scales for the Antarctic ice cores can be derived that are both fully consistent with the Greenland scale, and glaciologically reasonable. AU - Shackleton, N. J. AU - Fairbanks, R. G. AU - Chiu, Tzu-chien AU - Parrenin, F. DA - 2004/07/01/ DO - https://doi.org/10.1016/j.quascirev.2004.03.006 IS - 14–15 N1 - https://www.sciencedirect.com/science/article/pii/S0277379104000824 PY - 2004 SN - 0277-3791 SP - 1513–1522 ST - Absolute calibration of the Greenland time scale: implications for Antarctic time scales and for Δ14C T2 - Quaternary Science Reviews TI - Absolute calibration of the Greenland time scale: implications for Antarctic time scales and for Δ14C UR - https://doi.org/10.1016/j.quascirev.2004.03.006 VL - 23 ID - 17567 ER - TY - JOUR AB - A core recovered on the Iberian margin off southern Portugal can be correlated with Greenland ice cores using oxygen isotope variability in planktonic foraminifera which closely matches the ice core records of temperature over Greenland. Our age model identifies the base of every interstadial between 64,000 and 24,000 years ago and uses the Greenland Ice Core Project (GRIP) timescale. The oxygen isotope signal in benthic foraminifera (on this GRIP-based timescale) is quite different from the planktonic record and resembles the temperature record over Antarctica when this is synchronized with Greenland using the record of methane in the atmospheric air in the polar ice cores. We interpret the benthic record as indicating significant fluctuations in ice volume during millennial events, and we suggest that Antarctic temperature changed as a function of ice volume. AU - Shackleton, Nicholas J. AU - Hall, Michael A. AU - Vincent, Edith DO - https://doi.org/10.1029/2000PA000513 IS - 6 N1 - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2000PA000513 PY - 2000 SN - 0883-8305 SP - 565–569 ST - Phase relationships between millennial-scale events 64,000–24,000 years ago T2 - Paleoceanography and Paleoclimatology TI - Phase relationships between millennial-scale events 64,000–24,000 years ago UR - https://doi.org/10.1029/2000PA000513 VL - 15 ID - 17566 ER - TY - JOUR AB - The subdivision of Marine Isotope Stage 5 (MIS5) into five substages is robustly applicable to benthic oxygen isotope records from almost all areas of the ocean. The association of the Eemian Interglacial (in the sense that this concept is utilized by palynologists) with MIS 5e is widely agreed on the basis of a diversity of evidence. Here we present the first direct evidence regarding the relationships between the boundaries of these two stratigraphic entities. The base of the Eemian as recognized here is significantly younger than the base of MIS 5, and indeed falls within the isotopic “plateau” of MIS 5e during which global sea-level is thought to have been a few meters higher than at present. The termination of the Eemian Interglacial in Portugal as recognized in the palynological record in this core off southern Portugal is well within MIS 5d. AU - Shackleton, Nicholas J. AU - Sánchez-Goñi, Maria Fernanda AU - Pailler, Delphine AU - Lancelot, Yves DA - 2003/04/01/ DO - https://doi.org/10.1016/S0921-8181(02)00181-9 IS - 3 KW - Marine Isotope Stage 5 (MIS5) Eemian Interglacial oxygen isotope N1 - https://www.sciencedirect.com/science/article/pii/S0921818102001819 PY - 2003 SN - 0921-8181 SP - 151–155 ST - Marine Isotope Substage 5e and the Eemian interglacial T2 - Global and Planetary Change TI - Marine Isotope Substage 5e and the Eemian interglacial UR - https://doi.org/10.1016/S0921-8181(02)00181-9 VL - 36 ID - 17568 ER - TY - JOUR AB - Our understanding of past ocean-climate interactions has been hampered by a paucity of proxy reconstructions of physical ocean circulation parameters. Here we present the first detailed record of deepwater temperature variability that resolves Dansgaard-Oeschger climate fluctuations during the last glaciation. Results indicate a positive coupling between abrupt temperature changes over Greenland and in the deep North Atlantic that was mediated by perturbations to the Atlantic overturning circulation. The occurrence of sharp warming events at the center of the “Heinrich” stadials 4 and 5 further indicates that the response of the ocean interior was less static across these major climate events than has been previously apparent. AU - Skinner, L. C. AU - Elderfield, H. DO - https://doi.org/10.1029/2006PA001338 IS - 1 N1 - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2006PA001338 PY - 2007 SN - 0883-8305 SP - PA1205 ST - Rapid fluctuations in the deep North Atlantic heat budget during the last glacial period T2 - Paleoceanography and Paleoclimatology TI - Rapid fluctuations in the deep North Atlantic heat budget during the last glacial period UR - https://doi.org/10.1029/2006PA001338 VL - 22 ID - 17573 ER - TY - CHAP A2 - Schmittner, A., Chiang, J.C.H., and Hemming, S.R. (Eds.) AB - Summary This chapter contains sections titled: Introduction Materials and Methods Chronostratigraphy Deep-Water Temperature Change on the Iberian Margin Deep-Water δ18O Change on the Iberian Margin Constraining the Mechanisms of Interhemispheric Climate Change? Conclusions AU - Skinner, L. C. AU - Elderfield, H. AU - Hall, M. DO - https://doi.org/10.1029/173GM14 N1 - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/173GM14 PY - 2007 SP - 197–208 ST - Phasing of millennial climate events and northeast Atlantic deep-water temperature change since 50 Ka Bp SV - Geophysical Monograph T2 - Ocean Circulation: Mechanisms and Impacts—Past and Future Changes of Meridional Overturning TI - Phasing of millennial climate events and northeast Atlantic deep-water temperature change since 50 Ka Bp UR - https://doi.org/10.1029/173GM14 VL - 173 ID - 17574 ER - TY - JOUR AB - Abstract Changes in ocean ventilation, controlled by both overturning rates and air-sea gas exchange, are thought to have played a central role in atmospheric CO2 rise across the last deglaciation. Here, we constrain the nature of Atlantic Ocean ventilation changes over the last deglaciation using radiocarbon and stable carbon isotopes from two depth transects in the Atlantic basin. Our findings broadly cohere with the established pattern of deglacial Atlantic overturning change, and underline the existence of active northern sourced deep-water export at the Last Glacial Maximum (LGM). We find that the western Atlantic was less affected by incursions of southern-sourced deep water, as compared to the eastern Atlantic, despite both sides of the basin being strongly influenced by the air-sea equilibration of both northern and southern deep-water end-members. Ventilation at least as strong as modern is observed throughout the Atlantic during the Bølling-Allerød (BA), implying a “flushing” of the entire Atlantic water column that we attribute to the combined effects of Atlantic meridional overturning circulation (AMOC) reinvigoration and increased air-sea equilibration of southern sourced deep-water. This ventilation “overshoot” may have counteracted a natural atmospheric CO2 decline during interstadial conditions, helping to make the BA a “point of no return” in the deglacial process. While the collected data emphasize a predominantly indirect AMOC contribution to deglacial atmospheric CO2 rise, via far field impacts on convection in the Southern Ocean and/or North Pacific during Heinrich Stadial 1 and the Younger Dryas, the potential role of the AMOC in centennial CO2 pulses emerges as an important target for future work. AU - Skinner, L. C. AU - Freeman, E. AU - Hodell, D. AU - Waelbroeck, C. AU - Vazquez Riveiros, N. AU - Scrivner, A. E. DO - https://doi.org/10.1029/2020PA004074 IS - 2 N1 - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2020PA004074 PY - 2021 SN - 2572-4517 SP - e2020PA004074 ST - Atlantic Ocean ventilation changes across the last deglaciation and their carbon cycle implications T2 - Paleoceanography and Paleoclimatology TI - Atlantic Ocean ventilation changes across the last deglaciation and their carbon cycle implications UR - https://doi.org/10.1029/2020PA004074 VL - 36 ID - 23084 ER - TY - JOUR AB - A sequence of accelerator mass spectrometry (AMS) 14C dates performed on benthic and planktonic foraminifera from a northeast Atlantic deep-sea core (MD99-2334K; 37°48′N, 10°10′W; 3146 m) permit the reconstruction of deep water “14C ventilation ages” across the last deglaciation. The records from MD99-2334K have been placed on the GISP2 timescale via the synchrony of temperature changes recorded in the Greenland ice cores and in North Atlantic planktonic δ18Occ (calcite δ18O). On the basis of a range of estimates for past source water Δ14C, this permits the estimation of 14C projection ventilation ages for comparison with benthic-planktonic 14C age differences. Although the accurate estimation of past ventilation ages is precluded by unknown deep water Δ14C source signatures, and by uncertainty regarding the extent of deep water mixing, it is clear that deep water ventilation in the northeast Atlantic was significantly reduced during the last glaciation, increased abruptly coincident with the Bølling-Allerød warming, and rapidly became reduced again during the Younger Dryas cold reversal. The character of these changes is consistent with a varying dominance of North Atlantic Deep Water (NADW) versus Antarctic Bottom Water (AABW). Parallel benthic δ13C, deep water temperature (Tdw), and deep water δ18O (δ18Odw) estimates support this inference. The fact that deglacial changes in the deep water radiocarbon content of the northeast Atlantic run parallel to opposite changes in atmospheric radiocarbon content, and in parallel with Greenland temperature fluctuations, unequivocally implicates changes in ocean circulation in deglacial climate evolution and illustrates the capacity for the deep ocean to respond and contribute to abrupt climate change. AU - Skinner, L. C. AU - Shackleton, N. J. DO - https://doi.org/10.1029/2003PA000983 IS - 2 N1 - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2003PA000983 PY - 2004 SN - 0883-8305 SP - PA2005 ST - Rapid transient changes in northeast Atlantic deep water ventilation age across Termination I T2 - Paleoceanography and Paleoclimatology TI - Rapid transient changes in northeast Atlantic deep water ventilation age across Termination I UR - https://doi.org/10.1029/2003PA000983 VL - 19 ID - 17571 ER - TY - JOUR AB - Benthic and planktonic oxygen isotope (δ18Occ) and Mg/Ca analyses in two cores from the Northeast Atlantic have permitted the reconstruction of surface- and deep-water temperature (Tdw) and δ18O (δ18Ow) variations across the last two deglaciations. These records allow the timing of de-glacial melt-water pulses reaching the Northeast Atlantic to be compared with the evolution of local deep-water Tdw–δ18Ow conditions. Although each glacial termination is unique in detail, a similar pattern of hydrographic change is reconstructed for both deglaciations, with the first major decrease in deep-water δ18Ow (due to sea-level and/or purely local deep-water change) occurring in parallel with the onset of intensely cold glacial surface-water temperatures, and prior to a ‘terminal’ ice-rafting and melt-water event. The evolution of deep-water across both de-glaciations involved two transient incursions of cold, low-δ18O water into the deep Northeast Atlantic, the second of which was particularly pronounced each time. These pulses of cold deep-water are interpreted to reflect the incursion of water directly analogous to modern Antarctic Bottom Water (AABW), and containing a significant component of brine rejected during sea-ice formation. The results presented here show that the same type of transient changes in deep-water circulation that occurred across Termination I also occurred across Termination II, and that as a result of these deep-ocean changes, the timing of each benthic δ18O ‘termination’ cannot precisely reflect the timing of de-glacial sea-level change, as many palaeoceanographic interpretations (and some controversies) are prone to assume. Such ‘imprecision’ (in timing especially) may well extend to marine isotope stage (MIS) boundaries in general, as a principle of hydrographic variability and its expression in the geological record. AU - Skinner, L. C. AU - Shackleton, N. J. DA - 2006/12/01/ DO - https://doi.org/10.1016/j.quascirev.2006.07.005 IS - 23–24 N1 - https://www.sciencedirect.com/science/article/pii/S0277379106002307 PY - 2006 SN - 0277-3791 SP - 3312–3321 ST - Deconstructing Terminations I and II: revisiting the glacioeustatic paradigm based on deep-water temperature estimates T2 - Quaternary Science Reviews TI - Deconstructing Terminations I and II: revisiting the glacioeustatic paradigm based on deep-water temperature estimates UR - https://doi.org/10.1016/j.quascirev.2006.07.005 VL - 25 ID - 17572 ER - TY - JOUR AB - Paired measurements of Mg/Ca and δ18Occ (calcite δ18O) in benthic foraminifera from a deep-sea core recovered on the Iberian Margin (MD99-2334K; 37°48′N, 10°10′W; 3,146 m) have been performed in parallel with planktonic δ18Occ analyses and counts of ice-rafted debris (IRD). The synchrony of temperature changes recorded in the Greenland ice cores and in North Atlantic planktonic δ18Occ allows the proxy records from MD99-2334K to be placed confidently on the GISP2 time-scale. This correlation is further corroborated by AMS 14C-dates. Benthic Mg/Ca measurements in MD99-2334K permit the reconstruction of past deep-water temperature (Tdw) changes since ∼34 cal. ka BP (calendar kiloyears before present). Using these Tdw estimates and parallel benthic δ18Occ measurements, a record of deep-water δ18O (δ18Odw) has been calculated. Results indicate greatly reduced Tdw in the deep Northeast Atlantic during the last glaciation until ∼15 cal. ka BP, when Tdw warmed abruptly to near-modern values in parallel with the onset of the Bølling-Allerød interstadial. Subsequently, Tdw reverted to cold glacial values between ∼13.4 and ∼11.4 cal. ka BP, in parallel with the Younger Dryas cold reversal and the H0 ice-rafting event. Similar millennial-scale Tdw changes also occurred during the last glaciation. Indeed, throughout the last ∼34 cal. ka, millennial δ18Odw and Tdw changes have remained well coupled and are linked with IRD pulses coincident with Heinrich events 3, 2, 1, and the Younger Dryas, when transitions to lower Tdw and δ18Odw conditions occurred. In general, millennial Tdw and δ18Odw variations recorded in MD99-2334K describe an alternation between colder, low-δ18Odw and warmer, high δ18Odw conditions, which suggests the changing local dominance of northern-sourced North Atlantic Deep Water (NADW) versus southern-sourced Antarctic Bottom Water (AABW). The observed similarity of the Tdw and GISP2 δ18Oice records would therefore suggest a common component of variability resulting from the coupling of NADW formation and Greenland climate. A link between Greenland stadials and the incursion of cold, low-δ18Odw AABW in the deep Northeast Atlantic is thus implied, which contributes to the relationship between Greenland climate and the millennial benthic δ18Occ signal since ∼34 cal. ka BP. AU - Skinner, L. C. AU - Shackleton, N. J. AU - Elderfield, H. DO - https://doi.org/10.1029/2003GC000585 IS - 12 N1 - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2003GC000585 PY - 2003 SN - 1525-2027 SP - 1098 ST - Millennial-scale variability of deep-water temperature and δ18Odw indicating deep-water source variations in the northeast Atlantic, 0–34 cal. ka BP T2 - Geochemistry, Geophysics, Geosystems TI - Millennial-scale variability of deep-water temperature and δ18Odw indicating deep-water source variations in the northeast Atlantic, 0–34 cal. ka BP UR - https://doi.org/10.1029/2003GC000585 VL - 4 ID - 17570 ER - TY - JOUR AB - A series of 25 Nimbus 7 coastal zone color scanner images obtained from July 1981 to September 1983 in Portuguese coastal waters was analyzed in order to study the space-time distribution of phytoplankton pigment. In the images from winter and spring, the phytoplankton distributions showed no significant spatial patterns. During the upwelling season, from late June to October, several recurrent patterns were observed. Filaments of high pigment concentration extended zonally 200 km off the west coast of Portugal, north of Lisbon. Pigment-rich plumes were observed south of capes along the west coast, south of Lisbon, and parallel to the south coast of Portugal. The location of the filaments and plumes coincided with topographic features such as submarine ridges. South of Lisbon the location of plumes was also related to coastal morphology. The temporal variability of the pigment patterns was compared with the wind-induced offshore Ekman transport calculated from measurements made at two meteorological stations, located at Lisbon and Faro, on the south coast. A significant relationship was found: well-developed phytoplankton structures were generally related to moderate or intense offshore transport, whereas the absence of plumes corresponded to either weak offshore transport or coastal convergence. For each of the three coastal areas in this study, scatter plots showed linear relationships between digital counts of phytoplankton concentration and sea surface temperature. The spatial variation of the temperature range decreased in time after the onset of an upwelling event. One cause of this variation could be the north-south change in temperature of the upwelled Eastern North Atlantic Central Water along the Portuguese coast. AU - Sousa, Fátima M. AU - Bricaud, Annick DO - https://doi.org/10.1029/92JC00786 IS - C7 N1 - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/92JC00786 PY - 1992 SN - 0148-0227 SP - 11343–11356 ST - Satellite-derived phytoplankton pigment structures in the Portuguese upwelling area T2 - Journal of Geophysical Research: Oceans TI - Satellite-derived phytoplankton pigment structures in the Portuguese upwelling area UR - https://doi.org/10.1029/92JC00786 VL - 97 ID - 17575 ER - TY - CHAP A2 - Whatley, R.C., and Maybury, C. (Eds.) AU - Steineck, P.L., Maddocks, R.F., Coles, G.P., and Whatley, R.C. CY - London PB - Chapman and Hall PY - 1990 SP - 307–319 ST - Xylophile ostracoda in the deep sea T2 - Ostracoda and Global Events TI - Xylophile ostracoda in the deep sea ID - 49496 ER - TY - CHAP A2 - Head, M.J., and Gibbard, P.L. (Eds.) AB - This synthesis incorporates the 16 most important pollen records available across the North Mediterranean region sensu lato for the last 2.7 Ma. Their location is discussed with respect to the present-day bioclimatic Mediterranean realm. A special effort has been made to redraw, where necessary, the pollen records in terms of modern cyclostratigraphy. The complexity of the evolution of the Mediterranean flora and vegetation as forced by the climatic cycles is evident. The influence of the latitudinal thermic (and xeric) gradient is confirmed, and the superimposition of a longitudinal gradient, forced by the Asian monsoon, is considered. The Mediterranean flora and vegetation were not altered by any important event during the Early-Middle Pleistocene transition between 1.2 and 0.7 Ma. AU - Suc, Jean-Pierre AU - Popescu, Speranta-Maria DO - 10.1144/gsl.Sp.2005.247.01.08 N1 - https://sp.lyellcollection.org/content/specpubgsl/247/1/147.full.pdf PY - 2005 SP - 147–158 ST - Pollen records and climatic cycles in the North Mediterranean region since 2.7 Ma SV - Geological Society Special Publication T2 - Early-Middle Pleistocene Transitions: The Land-Ocean Evidence TI - Pollen records and climatic cycles in the North Mediterranean region since 2.7 Ma UR - https://doi.org/10.1144/GSL.SP.2005.247.01.08 VL - 247 ID - 17576 ER - TY - JOUR AB - Palynology provides information about Pliocene and early Pleistocene vegetation and climate evolution inthe north-west Mediterranean area in relation to high northern latitude climatic trends. An important change occurred approximately 3.2 Myr ago with the appearance of the Mediterranean climatic rhythm (summer drought) causing the individualization of the modern Mediterranean floral elements. Quaternary-type mediterranean climatic fluctuations started approximately 2.3 Myr ago (early Glacial) causing the Mediterranean-type of vegetational organization. AU - Suc, J. P. DA - 1984/02/01 DO - 10.1038/307429a0 IS - 5950 PY - 1984 SN - 1476-4687 SP - 429–432 ST - Origin and evolution of the Mediterranean vegetation and climate in Europe T2 - Nature TI - Origin and evolution of the Mediterranean vegetation and climate in Europe UR - https://doi.org/10.1038/307429a0 VL - 307 ID - 17578 ER - TY - JOUR AB - Abundant evidence from marine, ice-core and terrestrial records demonstrates that Earth’s climate has experienced co-evolution of orbital- and millennial-scale variability through the Pleistocene. The varying magnitude of millennial climate variability (MCV) was linked to orbitally paced glacial cycles over the past 800 kyr. Before this interval, global glaciations were less pronounced but more frequent, yet scarcity of a long-term integration of high-resolution continental and marine records hampers our understanding of the evolution and dynamics of MCV before the mid-Pleistocene transition. Here we present a synthesis of four centennial-resolved elemental time series, which we interpret as proxies for MCV, from North Atlantic, Iberian margin, Balkan Peninsula (Lake Ohrid) and Chinese Loess Plateau. The proxy records reveal that MCV was pervasive and persistent over the mid-latitude Northern Hemisphere during the past 1.5 Myr. Our results suggest that the magnitude of MCV is not only strongly modulated by glacial boundary conditions on Earth after the mid-Pleistocene transition, but also persistently influenced by variations in precession and obliquity through the Pleistocene. The combination of these four proxies into a new MCV stack offers a credible reference for further assessing the dynamical interactions between orbital and millennial climate variability. AU - Sun, Youbin AU - McManus, Jerry F. AU - Clemens, Steven C. AU - Zhang, Xu AU - Vogel, Hendrik AU - Hodell, David A. AU - Guo, Fei AU - Wang, Ting AU - Liu, Xingxing AU - An, Zhisheng DA - 2021/11/01 DO - 10.1038/s41561-021-00794-1 IS - 11 PY - 2021 SN - 1752-0908 SP - 812–818 ST - Persistent orbital influence on millennial climate variability through the Pleistocene T2 - Nature Geoscience TI - Persistent orbital influence on millennial climate variability through the Pleistocene UR - https://doi.org/10.1038/s41561-021-00794-1 VL - 14 ID - 17462 ER - TY - JOUR AB - This paper described Xylocythere sarrazinae sp. nov. (Ostracoda: Cytheroidea: Cytheruridae: Eucytherurinae), collected at 2196 m depth from the Grotto hydrothermal edifice (Main Endeavor Field, Juan de Fuca Ridge) in the northeastern Pacific Ocean. This new species was found living in association with Ridgeia piscesae tubeworm assemblages. It is the second representative of Xylocythere described from such vents. Xylocythere sarrazinae sp. nov. is easily distinguished from the seven described species of Xylocythere by the surface ornamentations of its carapace, with the most similar species to it being Xylocythere pointillissima Maddocks & Steineck, 1987. However, Xylocythere sarrazinae sp. nov can be distinguished from X. pointillissima based on the following characters: having a subsquare basal capsule outline, a spatulate upper ramus, a flattened distal lobe of the male copulatory organ, and having 15 maxillula branchial plate setae. We found that one specimen of this new species had multiple spherical objects associated with the internal openings of its pore clusters. These objects were quite similar in shape to that of chemoautotrophic bacteria, which were previously reported from the outer surfaces of pore clusters in other Xylocythere species. Finally, we provided a preliminary phylogenetic analysis of this new species based on 18S rRNA gene sequences to determine the phylogenetic position of the subfamily Eucytherurinae within the superfamily Cytheroidea. This analysis revealed that Xylocythere (Eucytherurinae) may be the most ancestral lineage among the Cytheruridae and identified paraphyletic relationships among the three subfamilies within Cytheruridae. This result supported certain previous studies’ conclusions based on morphology and fossil records. AU - Tanaka, Hayato AU - Lelièvre, Yann AU - Yasuhara, Moriaki DA - 2019/12/01 DO - 10.1007/s12526-019-00987-3 IS - 6 PY - 2019 SN - 1867-1624 SP - 2571–2586 ST - Xylocythere sarrazinae, a new cytherurid ostracod (Crustacea) from a hydrothermal vent field on the Juan de Fuca Ridge, northeast Pacific Ocean, and its phylogenetic position within Cytheroidea T2 - Marine Biodiversity TI - Xylocythere sarrazinae, a new cytherurid ostracod (Crustacea) from a hydrothermal vent field on the Juan de Fuca Ridge, northeast Pacific Ocean, and its phylogenetic position within Cytheroidea UR - https://doi.org/10.1007/s12526-019-00987-3 VL - 49 ID - 49497 ER - TY - JOUR AB - The oxygen concentrations of oceanic deep-water and atmospheric carbon dioxide (pCO2) are intrinsically linked through organic carbon remineralization and storage as dissolved inorganic carbon in the deep sea. We present a high-resolution reconstruction of relative changes in oxygen concentration in the deep North Atlantic for the past 1.5 million years using the carbon isotope gradient between epifaunal and infaunal benthic foraminifera species as a proxy for paleo-oxygen. We report a significant (>40 micromole per kilogram) reduction in glacial Atlantic deep-water oxygenation at ~960 thousand to 900 thousand years ago that coincided with increased continental ice volume and a major change in ocean thermohaline circulation. Paleo-oxygen results support a scenario of decreasing deep-water oxygen concentrations, increased respired carbon storage, and a reduction in glacial pCO2 across the Middle Pleistocene Transition. Between about 1.25 million and 800,000 years ago, the climate system went through a major change during a period called the Middle Pleistocene Transition. Was the inventory of dissolved oxygen in the ocean affected by this episode? Thomas et al. show that oxygen concentrations in glacial deep North Atlantic waters suffered a stepped reduction about 900,000 years ago, coincident with reductions in the concentration of glacial atmospheric carbon dioxide and global ice volume. —HJS Glacial deep-sea oxygen concentrations, fell along with ice volume and atmospheric pCO2, around 900 thousand years ago. AU - Thomas, Nicola C. AU - Bradbury, Harold J. AU - Hodell, David A. DO - doi:10.1126/science.abj7761 IS - 6606 N1 - https://www.science.org/doi/abs/10.1126/science.abj7761 PY - 2022 SP - 654–659 ST - Changes in North Atlantic deep-water oxygenation across the Middle Pleistocene Transition T2 - Science TI - Changes in North Atlantic deep-water oxygenation across the Middle Pleistocene Transition UR - https://doi.org/10.1126/science.abj7761 VL - 377 ID - 48910 ER - TY - JOUR AU - Thurow, J. AU - Peterson, L. C. AU - Harms, U. AU - Hodell, D. A. AU - Cheshire, H. AU - Brumsack, H. J. AU - Irino, T. AU - Schulz, M. AU - Masson-Delmotte, V. AU - Tada, R. DO - 10.2204/iodp.sd.8.08.2009 N1 - https://sd.copernicus.org/articles/8/46/2009/ PY - 2009 SN - 1816-3459 SP - 46–56 ST - Acquiring high to ultra-high resolution geological records of past climate change by scientific drilling T2 - Scientific Drilling TI - Acquiring high to ultra-high resolution geological records of past climate change by scientific drilling UR - https://doi.org/10.2204/iodp.sd.8.08.2009 VL - 8 ID - 17579 ER - TY - JOUR AB - At Site U1385, drilled during IODP Expedition 339 off the coast of Portugal on the continental slope, high-resolution sulfate concentration measurements in the pore fluids display non-steady-state behavior. At this site there is a zone of sulfate reduction in the uppermost seven meters of sediment, followed by a 38-meter interval where sulfate concentrations do not change, and finally sulfate concentrations are depleted to zero between 45 and 55 meters below seafloor. Below the sulfate minimum zone, there is abundant methane, suggesting that the lower sulfate consumption zone is coupled to anaerobic methane oxidation. We analyze pore water samples from IODP Site U1385 for sulfur and oxygen isotope ratios of dissolved sulfate, as well as the sulfur isotope composition of sedimentary pyrite. The sulfur isotopes in pore fluid sulfate display similar non-steady-state behavior similar to that of the sulfate concentrations, increasing over the uppermost zone of sulfate reduction and again over the lower zone of sulfate-driven anaerobic methane oxidation. The oxygen isotopes in sulfate increase to the 'apparent equilibrium' value in the uppermost zone of sulfate reduction and do not change further. Our calculations support the idea that sulfite to sulfide reduction is the limiting step in microbial sulfate reduction, and that the isotope fractionation expressed in the residual pore water sulfate pool is inversely proportional to the net sulfate reduction rate. The sulfur isotope composition of pyrite acquires one value in the uppermost sediments, which may be overprinted by a second value in the deeper sediments, possibly due to iron release during anaerobic methane oxidation or iron diffusion from a higher zone of bacterial iron reduction. Our results have implications for modeling the sulfur isotope composition of the pyrite burial flux in the global biogeochemical sulfur cycle. AU - Turchyn, Alexandra V. AU - Antler, Gilad AU - Byrne, David AU - Miller, Madeline AU - Hodell, David A. J2 - Affiliation (analytic): University of Cambridge, Department of Earth Sciences, Cambridge Affiliation (monographic): University of Cambridge, Department of Earth Sciences, Cambridge, United Kingdom Coordinates: N373417 N373417 W0100719 W0100720 illus. Contains 62 references Research Program: IODP Integrated Ocean Drilling Program Document Type: Journal Article Bibliographic Level: Analytic Source Note: Global and Planetary Change, Vol.141, p.82-90. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0921-8181 Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands GeoRef ID: 2016087028 DOI: 10.1016/j.gloplacha.2016.03.004 KW - Atlantic Ocean Chemical composition Chemical reactions Crystal chemistry Expedition 339 Fluid phase IODP Site U1385 Integrated Ocean Drilling Program Isotope ratios Isotopes Marine sediments Mathematical methods Metabolism Microorganisms North Atlantic O-18/O-16 Oxygen Pore water Pyrite S-34/S-32 Sediments Stable isotopes Sulfates Sulfides Sulfur 02 Geochemistry 07 Marine Geology and Oceanography LA - English PY - 2016 SN - 0921-8181 SP - 82–90 ST - Microbial sulfur metabolism evidenced from pore fluid isotope geochemistry at Site U1385 T2 - Global and Planetary Change TI - Microbial sulfur metabolism evidenced from pore fluid isotope geochemistry at Site U1385 UR - https://doi.org/10.1016/j.gloplacha.2016.03.004 VL - 141 ID - 4695 ER - TY - JOUR AB - A review of seven outstanding issues on Mediterranean palaeoenvironments is presented. These are related to the dominant orbital pacing of climate variability, the length of the interglacial vegetation succession, the influence of the African summer monsoon, the seasonality of precipitation during boreal insolation maxima, the moisture balance during glacial maxima and the appearance of the mediterranean-type climate rhythm and evolution of mediterranean sclerophyllous plants. What emerges is that (1) marine δ18Oplanktonic and SST records show that precession has been a fundamental tempo of Mediterranean climate change, representing both a low-latitude signal (runoff from North Africa) and the direct influence of insolation at Mediterranean latitudes, but high-latitude glacial effects (41-kyr and 100-kyr cycles) became superimposed after 2.8Ma. Sapropel and dust deposition patterns in marine cores reveal that obliquity also has an effect on Mediterranean climate through dry–wet oscillations, which are independent of glacial–interglacial variability. (2) The temperate part of interglacial vegetation succession has a duration of approximately half a precession cycle. This persisted during the interval of obliquity-dominated glacial cycles (∼2.8–1Ma), with distinct forest successions following the precessional cycles. However, these are not always separated by an open vegetation phase because of minimal ice growth, producing an impression of a prolonged interglacial forest interval. (3) The effect of an enhanced African monsoon during summer insolation maxima has been mainly indirect, in terms of Nile discharge and runoff along the North African coast, leading to increased freshwater input into the Mediterranean Sea, reduced deep-water ventilation and sapropel deposition. (4) The notion of an accentuated summer rain regime in the northern Mediterranean borderlands also contributing to a freshening of the Mediterranean Sea during boreal insolation maxima is not supported by the available evidence, which suggests increased summer aridity. (5) Recent improvements in chronological precision and data resolution point to an increase in aridity and decreased temperatures during the Last Glacial Maximum (21±2ka), but suggest an increase in effective moisture during the immediately preceding interval of 24–27ka. (6) The mediterranean-type climate is not exclusively a post-3.6Ma phenomenon, but may have appeared intermittently during the course of the Tertiary (or before). (7) If that is the case, then the paradigm that the sclerophyllous evergreen habit represents a pre-adaptation to summer drought may need re-evaluation. AU - Tzedakis, P. C. DA - 2007/09/01/ DO - https://doi.org/10.1016/j.quascirev.2007.03.014 IS - 17 N1 - https://www.sciencedirect.com/science/article/pii/S0277379107001308 PY - 2007 SN - 0277-3791 SP - 2042–2066 ST - Seven ambiguities in the Mediterranean palaeoenvironmental narrative T2 - Quaternary Science Reviews TI - Seven ambiguities in the Mediterranean palaeoenvironmental narrative UR - https://doi.org/10.1016/j.quascirev.2007.03.014 VL - 26 ID - 17580 ER - TY - JOUR AB - Considerable ambiguity remains over the extent and nature of millennial/centennial-scale climate instability during the Last Interglacial (LIG). Here we analyse marine and terrestrial proxies from a deep-sea sediment sequence on the Portuguese Margin and combine results with an intensively dated Italian speleothem record and climate-model experiments. The strongest expression of climate variability occurred during the transitions into and out of the LIG. Our records also document a series of multi-centennial intra-interglacial arid events in southern Europe, coherent with cold water-mass expansions in the North Atlantic. The spatial and temporal fingerprints of these changes indicate a reorganization of ocean surface circulation, consistent with low-intensity disruptions of the Atlantic meridional overturning circulation (AMOC). The amplitude of this LIG variability is greater than that observed in Holocene records. Episodic Greenland ice melt and runoff as a result of excess warmth may have contributed to AMOC weakening and increased climate instability throughout the LIG. AU - Tzedakis, P. C. AU - Drysdale, R. N. AU - Margari, V. AU - Skinner, L. C. AU - Menviel, L. AU - Rhodes, R. H. AU - Taschetto, A. S. AU - Hodell, D. A. AU - Crowhurst, S. J. AU - Hellstrom, J. C. AU - Fallick, A. E. AU - Grimalt, J. O. AU - McManus, J. F. AU - Martrat, B. AU - Mokeddem, Z. AU - Parrenin, F. AU - Regattieri, E. AU - Roe, K. AU - Zanchetta, G. DA - 2018/10/12 DO - 10.1038/s41467-018-06683-3 IS - 1 PY - 2018 SN - 2041-1723 SP - 4235 ST - Enhanced climate instability in the North Atlantic and southern Europe during the last interglacial T2 - Nature Communications TI - Enhanced climate instability in the North Atlantic and southern Europe during the last interglacial UR - https://doi.org/10.1038/s41467-018-06683-3 VL - 9 ID - 23085 ER - TY - JOUR AB - The regional expression of millennial-scale climate variability during the last glacial is examined with particular reference to the vegetation response in Greece. Inspection of three pollen records from contrasting bioclimatic areas suggests that differences in the magnitude of cold events as recognized in the North Atlantic and western Mediterranean are expressed in terms of tree population changes only in areas with a range of favorable habitats. By contrast, records from sites where populations approach their tolerance threshold do not appear to resolve differences in the amplitude of the climate oscillations. Understanding the importance of local factors in modulating the biological response to climate change is critical when attempting to establish the spatial pattern of millennial variability. AU - Tzedakis, P.C. AU - Frogley, M.R. AU - Lawson, I.T. AU - Preece, R.C. AU - Cacho, I. AU - de Abreu, L. DO - 10.1130/g20118.1 IS - 2 PY - 2004 SN - 0091-7613 SP - 109–112 ST - Ecological thresholds and patterns of millennial-scale climate variability: the response of vegetation in Greece during the last glacial period T2 - Geology TI - Ecological thresholds and patterns of millennial-scale climate variability: the response of vegetation in Greece during the last glacial period UR - https://doi.org/10.1130/G20118.1 VL - 32 Y2 - 11/30/2021 ID - 17583 ER - TY - JOUR AB - In addition to being of interest to ancient Greek and Roman historians, the site of Philippi, NE Greece, has long been noted in Quaternary circles for providing the longest continuous European pollen record, spanning the last one million years. Here the original age model is re-evaluated and a new marine-terrestrial correlation is proposed. An astronomical calibration procedure, based on a correspondence between changes in certain vegetation elements and March and June perihelion configurations, suggests that the base of the sequence extends back to 1.35 million years ago. The revised chronological framework for the Tenaghi Philippon sequence provides an opportunity to examine the long-term behaviour of individual taxa and vegetation trends within the context of global climate changes. Comparisons reveal a close correspondence between the terrestrial and marine records, in terms of orbital and suborbital variability. However, joint time-frequency analysis of the arboreal pollen record shows that the obliquity and eccentricity/precession signals persist into the ‘100-kyr’ and ‘41-kyr’ worlds, respectively, suggesting the operation of additional climate mechanisms that are independent of high-latitude glacial–interglacial effects. Unlike ice core and marine sequences, no change in the magnitude of interglacial tree population expansions is observed after the Mid-Brunhes Event. Instead, the Tenaghi Philippon record suggests a major shift in the vegetational composition of interglacials after MIS 16, with the establishment of forests of reduced diversity and a ‘modern’ appearance. AU - Tzedakis, P. C. AU - Hooghiemstra, H. AU - Pälike, H. DA - 2006/12/01/ DO - https://doi.org/10.1016/j.quascirev.2006.09.002 IS - 23–24 N1 - https://www.sciencedirect.com/science/article/pii/S0277379106002708 PY - 2006 SN - 0277-3791 SP - 3416–3430 ST - The last 1.35 million years at Tenaghi Philippon: revised chronostratigraphy and long-term vegetation trends T2 - Quaternary Science Reviews TI - The last 1.35 million years at Tenaghi Philippon: revised chronostratigraphy and long-term vegetation trends UR - https://doi.org/10.1016/j.quascirev.2006.09.002 VL - 25 ID - 17581 ER - TY - JOUR AB - While a growing body of evidence indicates that North Atlantic millennial-scale climate variability extends to the Early Pleistocene, its impact on terrestrial ecosystems has not been established. Here we present ultra-high resolution (70-140 year) joint foraminiferal isotopic and pollen analyses from IODP Site U1385 off Portugal, focusing on a short glacial section of Marine Isotope Stage 38, ∼ 1.26 million years ago. Our records reveal the presence of millennial-scale variability in the coupled ocean-atmosphere-land system in the North Atlantic and provide the first direct evidence for the response of western Iberian vegetation to abrupt climate changes in the Early Pleistocene. The magnitude and pacing of changes bear significant similarities to Dansgaard-Oeschger variability of the last two glacials. Abstract Copyright (2015) Elsevier, B.V. AU - Tzedakis, P. C. AU - Margari, V. AU - Hodell, David A. J2 - Affiliation (analytic): University College London, Department of Geography, London Affiliation (monographic): University College London, Department of Geography, London, United Kingdom Coordinates: N373417 N373417 W0100719 W0100720 illus., incl. sketch map Contains 49 references Research Program: IODP Integrated Ocean Drilling Program Document Type: Journal Article Bibliographic Level: Analytic Source Note: Global and Planetary Change, Vol.135, p.83-88. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0921-8181 Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands GeoRef ID: 2016042298 DOI: 10.1016/j.gloplacha.2015.10.008 KW - Atlantic Ocean Cenozoic Climate change Dansgaard-Oeschger cycles Expedition 339 Foraminifera Geochemistry IODP Site U1385 Integrated Ocean Drilling Program Invertebrata Isotope ratios Isotopes Lower Pleistocene Microfossils Miospores North Atlantic Northeast Atlantic O-18/O-16 Oxygen Paleo-oceanography Paleoclimatology Paleoecology Paleogeography Palynomorphs Plantae Pleistocene Pollen Protista Quaternary Stable isotopes 24 Surficial Geology, Quaternary Geology LA - English PY - 2015 SN - 0921-8181 SP - 83–88 ST - Coupled ocean-land millennial scale changes 1.26 million years ago, recorded at Site U1385 off Portugal T2 - Global and Planetary Change TI - Coupled ocean-land millennial scale changes 1.26 million years ago, recorded at Site U1385 off Portugal UR - https://doi.org/10.1016/j.gloplacha.2015.10.008 VL - 135 ID - 4669 ER - TY - JOUR AB - Pollen records from marine and terrestrial sequences in southern Europe reveal a strong coherence between changes in tree populations and atmospheric methane concentrations over the last 800 thousand years. Variations in the continental hydrological balance provide a link for the observed patterns, leading to concomitant changes in southern European vegetation, and low-latitude wetland extent and methane/volatile organic compound emissions, although additional contributions to the methane budget from extratropical sources are not excluded. Here we propose that the close coupling between low- and mid-latitude hydrological changes reflects shifts in the mean latitudinal position of the Intertropical Convergence Zone, which determines the extent to which southern Europe is dominated by subtropical or mid/high-latitude influences. This provides a conceptual framework within which to view vegetation variability in southern Europe on orbital and millennial timescales. AU - Tzedakis, P. C. AU - Pälike, H. AU - Roucoux, K. H. AU - de Abreu, L. DA - 2009/01/30/ DO - https://doi.org/10.1016/j.epsl.2008.10.027 IS - 3–4 KW - methane pollen vegetation Mediterranean ITCZ orbital millennial N1 - https://www.sciencedirect.com/science/article/pii/S0012821X08006900 PY - 2009 SN - 0012-821X SP - 307–317 ST - Atmospheric methane, southern European vegetation and low-mid latitude links on orbital and millennial timescales T2 - Earth and Planetary Science Letters TI - Atmospheric methane, southern European vegetation and low-mid latitude links on orbital and millennial timescales UR - https://doi.org/10.1016/j.epsl.2008.10.027 VL - 277 ID - 8591 ER - TY - JOUR AB - The intermediate water masses in the eastern Atlantic Ocean between 31°N and 53°N were studied by analysis of the distributions of potential temperature, salinity, dissolved nutrients and oxygen. Sub-surface salinity minima are encountered everywhere in the area. At the northern and southern boundary they are connected with the presence of Sub-Arctic Intermediate Water and Antarctic Intermediate Water, respectively, but towards the European ocean margin the sub-surface salinity minima shift to shallower density levels. The sub-surface salinity minima observed west of the Iberian Peninsula represent a water mass formed by winter convection in the Porcupine Sea Bight and the northern Bay of Biscay. These minima gain salt by diapycnal mixing with the underlying Mediterranean Sea Outflow water and with the overlying permanent thermocline. The core of Antarctic Intermediate Water appears to contribute to the formation of Mediterranean Sea Outflow Water since it becomes entrained into the overflow near Gibraltar. This entrainment gives rise to an enhanced concentration of the nutrients in the Mediterranean water in the North Atlantic. The deep salinity minimum, due to the presence of Labrador Sea Water, is restricted mainly to the Porcupine Abyssal Plain. In the Bay of Biscay this water type is strongly modified by enhanced diapycnal mixing near the continental slope. At all intermediate levels the continental slope in the Bay of Biscay seems to be a focal point for water mass modification by diapycnal mixing. Below the core of the Mediterranean Sea Outflow Water the Labrador Sea Water is also strongly modified. Its salinity is strongly enhanced by diapycnal mixing with the overlying core of Mediterranean Sea Outflow Water. An analysis of the oxygen and nutrient data indicates that the large spatial concentration differences at the level of the Labrador Sea Water are caused mainly by ageing of the water. The youngest water is observed at 52°N, and, especially in the Bay of Biscay and off south-west Portugal, the water at levels of about 1700dbar are strongly enriched in nutrients and depleted in oxygen. AU - van Aken, Hendrik M. DA - 2000/05/01/ DO - https://doi.org/10.1016/S0967-0637(99)00112-0 IS - 5 N1 - https://www.sciencedirect.com/science/article/pii/S0967063799001120 PY - 2000 SN - 0967-0637 SP - 789–824 ST - The hydrography of the mid-latitude Northeast Atlantic Ocean: II: the intermediate water masses T2 - Deep Sea Research, Part I: Oceanographic Research Papers TI - The hydrography of the mid-latitude Northeast Atlantic Ocean: II: the intermediate water masses UR - https://doi.org/10.1016/S0967-0637(99)00112-0 VL - 47 ID - 17584 ER - TY - JOUR AU - Vanney, J.R., and Mougenot, D. DA - 1982/03/01 DO - 10.1007/BF02462809 PY - 1981 SN - 1432-1157 SP - 109 ST - La plate-forme continentale du portugal et les provinces adjacentes: analyse géomorphologique T2 - Memórias dos Serviços Geológicos de Portugal TI - La plate-forme continentale du portugal et les provinces adjacentes: analyse géomorphologique VL - 28 ID - 49498 ER - TY - JOUR AB - Variations in Northern Hemisphere ice volume over the past 3 million years have been described in numerous studies and well documented. These studies depict the mid-Pleistocene transition from 40 kyr oscillations of global ice to predominantly 100 kyr oscillations around 1 million years ago. It is generally accepted to attribute the 40 kyr period to astronomical forcing and to attribute the transition to the 100 kyr mode to a phenomenon caused by a slow trend, which around the mid-Pleistocene enabled the manifestation of nonlinear processes. However, both the physical nature of this nonlinearity and its interpretation in terms of dynamical systems theory are debated. Here, we show that ice-sheet physics coupled with a linear climate temperature feedback conceal enough dynamics to satisfactorily explain the system response over the full Pleistocene. There is no need, a priori, to call for a nonlinear response of the carbon cycle. Without astronomical forcing, the obtained dynamical system evolves to equilibrium. When it is astronomically forced, depending on the values of the parameters involved, the system is capable of producing different modes of nonlinearity and consequently different periods of rhythmicity. The crucial factor that defines a specific mode of system response is the relative intensity of glaciation (negative) and climate temperature (positive) feedbacks. To measure this factor, we introduce a dimensionless variability number, V. When positive feedback is weak (V∼0), the system exhibits fluctuations with dominating periods of about 40 kyr which is in fact a combination of a doubled precession period and (to smaller extent) obliquity period. When positive feedback increases (V∼0.75), the system evolves with a roughly 100 kyr period due to a doubled obliquity period. If positive feedback increases further (V∼0.95), the system produces fluctuations of about 400 kyr. When the V number is gradually increased from its low early Pleistocene values to its late Pleistocene value of V∼0.75, the system reproduces the mid-Pleistocene transition from mostly 40 kyr fluctuations to a 100 kyr period rhythmicity. Since the V number is a combination of multiple parameters, it implies that multiple scenarios are possible to account for the mid-Pleistocene transition. Thus, our theory is capable of explaining all major features of the Pleistocene climate, such as the mostly 40 kyr fluctuations of the early Pleistocene, a transition from an early Pleistocene type of nonlinear regime to a late Pleistocene type of nonlinear regime, and the 100 kyr fluctuations of the late Pleistocene. When the dynamical climate system is expanded to include Antarctic glaciation, it becomes apparent that climate temperature positive feedback (or its absence) plays a crucial role in the Southern Hemisphere as well. While the Northern Hemisphere insolation impact is amplified by the outside-of-glacier climate and eventually affects Antarctic surface and basal temperatures, the Antarctic ice-sheet area of glaciation is limited by the area of the Antarctic continent, and therefore it cannot engage in strong positive climate feedback. This may serve as a plausible explanation for the synchronous response of the Northern and Southern Hemisphere to Northern Hemisphere insolation variations. Given that the V number is dimensionless, we consider that this model could be used as a framework to investigate other physics that may possibly be involved in producing ice ages. In such a case, the equation currently representing climate temperature would describe some other climate component of interest, and as long as this component is capable of producing an appropriate V number, it may perhaps be considered a feasible candidate. AU - Verbitsky, M. Y. AU - Crucifix, M. AU - Volobuev, D. M. DO - 10.5194/esd-9-1025-2018 IS - 3 N1 - https://esd.copernicus.org/articles/9/1025/2018/ PY - 2018 SN - 2190-4987 SP - 1025–1043 ST - A theory of Pleistocene glacial rhythmicity T2 - Earth System Dynamics TI - A theory of Pleistocene glacial rhythmicity UR - https://doi.org/10.5194/esd-9-1025-2018 VL - 9 ID - 49499 ER - TY - JOUR AB - A new ice core from West Antarctica shows that, during the last ice age, abrupt Northern Hemisphere climate variations were followed two centuries later by a response in Antarctica, suggesting an oceanic propagation of the climate signal to the Southern Hemisphere high latitudes. AU - WAIS Divide Project Members DA - 2015/04/01 DO - 10.1038/nature14401 IS - 7549 N1 - Buizert, Christo Adrian, Betty Ahn, Jinho Albert, Mary Alley, Richard B. Baggenstos, Daniel Bauska, Thomas K. Bay, Ryan C. Bencivengo, Brian B. Bentley, Charles R. Brook, Edward J. Chellman, Nathan J. Clow, Gary D. Cole-Dai, Jihong Conway, Howard Cravens, Eric Cuffey, Kurt M. Dunbar, Nelia W. Edwards, Jon S. Fegyveresi, John M. Ferris, Dave G. Fitzpatrick, Joan J. Fudge, T. J. Gibson, Chris J. Gkinis, Vasileios Goetz, Joshua J. Gregory, Stephanie Hargreaves, Geoffrey M. Iverson, Nels Johnson, Jay A. Jones, Tyler R. Kalk, Michael L. Kippenhan, Matthew J. Koffman, Bess G. Kreutz, Karl Kuhl, Tanner W. Lebar, Donald A. Lee, James E. Marcott, Shaun A. Markle, Bradley R. Maselli, Olivia J. McConnell, Joseph R. McGwire, Kenneth C. Mitchell, Logan E. Mortensen, Nicolai B. Neff, Peter D. Nishiizumi, Kunihiko Nunn, Richard M. Orsi, Anais J. Pasteris, Daniel R. Pedro, Joel B. Pettit, Erin C. Buford Price, P. Priscu, John C. Rhodes, Rachael H. Rosen, Julia L. Schauer, Andrew J. Schoenemann, Spruce W. Sendelbach, Paul J. Severinghaus, Jeffrey P. Shturmakov, Alexander J. Sigl, Michael Slawny, Kristina R. Souney, Joseph M. Sowers, Todd A. Spencer, Matthew K. Steig, Eric J. Taylor, Kendrick C. Twickler, Mark S. Vaughn, Bruce H. Voigt, Donald E. Waddington, Edwin D. Welten, Kees C. Wendricks, Anthony W. White, James W. C. Winstrup, Mai Wong, Gifford J. Woodruff, Thomas E. PY - 2015 SN - 1476-4687 SP - 661–665 ST - Precise interpolar phasing of abrupt climate change during the last ice age T2 - Nature TI - Precise interpolar phasing of abrupt climate change during the last ice age UR - https://doi.org/10.1038/nature14401 VL - 520 ID - 17532 ER - TY - JOUR AB - We use the oxygen isotopic composition of planktonic foraminifera Globigerinoides ruber (white) from Ocean Drilling Program Site 1058 in the subtropical northwestern Atlantic to construct a high-resolution (∼ 800 year) climate record spanning the mid-Pleistocene climate transition (∼410 ka to 1350 ka). We investigate whether or not millennial-scale instabilities in the proxy record are associated with the extent of continental glaciation. G. ruberδ18O values display high-frequency fluctuations throughout the record, but the amplitude about mean glacial and interglacial δ18O values increases at marine isotope stage (MIS) 22 (880 ka) and is highest during MIS 12. These observations support that millennial-scale climate instabilities are associated with ice sheet size. Time series analysis illustrates that these variations have significant concentration of spectral power centered on periods of ∼10–12 ka and ∼5 ka. The timing of these fluctuations agrees well, or coincides with, the periodicities of the second and fourth harmonics, respectively, of precessional forcing at the equator. An insolation-based origin of the millennial-scale instabilities would be independent of ice volume and explains the presence of these fluctuations before the mid-Pleistocene climate transition as well as during interglacial intervals (e.g., MIS 37 and 17). Because the amplitude of the millennial-scale variations increases during the mid-Pleistocene transition, feedback mechanisms associated with the growth of large, 100-ka-paced, polar ice sheets may be important amplifiers of regional surface water hydrographic changes. AU - Weirauch, D. AU - Billups, K. AU - Martin, P. DO - https://doi.org/10.1029/2007PA001584 IS - 3 N1 - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2007PA001584 PY - 2008 SN - 0883-8305 SP - PA3216 ST - Evolution of millennial-scale climate variability during the mid-Pleistocene T2 - Paleoceanography and Paleoclimatology TI - Evolution of millennial-scale climate variability during the mid-Pleistocene UR - https://doi.org/10.1029/2007PA001584 VL - 23 ID - 17585 ER - TY - JOUR AB - Benthic Cd/Ca and δ13C records from the midlatitude and northern North Atlantic are used to derive nutrient inventories and water mass distribution patterns for the past 50,000 years. Inferred Holocene water column Cd concentrations (CdW′) and δ13C values are 0.17–0.24 nmol kg−1 and 1.0–1.3‰ Peedee belemnite (PDB), which document the dominance of nutrient-depleted Mediterranean Outflow Water (MOW) and Upper North Atlantic Deep Water (UNADW). Glacial benthic Cd/Ca and δ13C indicate a continued contribution of UNADW to the northern North Atlantic and upper Portuguese margin (CdW′=0.08 nmol kg−1; δ13C=+1.86‰ PDB). At the upper Moroccan margin, glacial CdW′ (0.23 nmol kg−1) is higher, and δ13C (+1.44‰ PDB) is lower. During “Heinrich” events, benthic δ13C decreases by up to 1.3‰, and peak Cd/Ca increases by 0.1–0.14 µmol mol−1; water column phosphorus equivalents are 1.8–2.8 µmol kg−1. The combined Cd/Ca and δ13C pattern indicates that during mean glacial conditions Antarctic Intermediate Water, (AAIW) reached the midlatitude northeast Atlantic (30°N). During Heinrich events, AAIW contribution maximized so that Southern Hemisphere waters filled the North Atlantic basin from bottom water to middepth levels. AU - Willamowski, Claudia AU - Zahn, Rainer DO - https://doi.org/10.1029/1999PA000467 IS - 5 N1 - https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/1999PA000467 PY - 2000 SN - 0883-8305 SP - 515–527 ST - Upper ocean circulation in the glacial North Atlantic from benthic foraminiferal isotope and trace element fingerprinting T2 - Paleoceanography and Paleoclimatology TI - Upper ocean circulation in the glacial North Atlantic from benthic foraminiferal isotope and trace element fingerprinting UR - https://doi.org/10.1029/1999PA000467 VL - 15 ID - 17586 ER - TY - JOUR AB - The timing and mechanisms of the transition from a glacial to an interglacial state are controversial. An analysis of Antarctic ice-core records indicates that glacial terminations may begin as millennial-scale warmings in the southern hemisphere that, unlike previous events, are not reversed by abrupt warming in the northern hemisphere. AU - Wolff, E. W. AU - Fischer, H. AU - Röthlisberger, R. DA - 2009/03/01 DO - 10.1038/ngeo442 IS - 3 PY - 2009 SN - 1752-0908 SP - 206–209 ST - Glacial terminations as southern warmings without northern control T2 - Nature Geoscience TI - Glacial terminations as southern warmings without northern control UR - https://doi.org/10.1038/ngeo442 VL - 2 ID - 17587 ER - TY - JOUR AB - The international ice core community has a target to obtain continuous ice cores stretching back as far as 1.5 Myr. This would provide vital data (including a CO2 profile) allowing us to assess ideas about the cause of the Mid-Pleistocene Transition (MPT). The European Beyond EPICA project and the Australian Million Year Ice Core project each plan to drill such a core in the region known as Little Dome C. Dating the cores will be challenging, and one approach will be to match some of the records obtained with existing marine sediment datasets, informed by similarities in the existing 800 kyr period. Water isotopes in Antarctica have been shown to closely mirror deepwater temperature, estimated from ratios of benthic foraminifera, in a marine core on the Chatham Rise near to New Zealand. The dust record in ice cores resembles very closely a South Atlantic marine record of iron accumulation rate. By assuming these relationships continue beyond 800 ka, our ice core record could be synchronised to dated marine sediments. This could be supplemented, and allow synchronisation at higher resolution, by the identification of rapid millennial-scale events that are observed both in Antarctic methane records and in emerging records of planktic oxygen isotopes and alkenone sea surface temperature (SST) from the Portuguese Margin. Although published data remain quite sparse, it should also be possible to match 10Be from ice cores to records of geomagnetic palaeo-intensity and authigenic in marine sediments. However, there are a number of issues that have to be resolved before the ice core 10Be record can be used. The approach of matching records to a template will be most successful if the new core is in stratigraphic order but should also provide constraints on disordered records if used in combination with absolute radiogenic ages. AU - Wolff, E. W. AU - Fischer, H. AU - van Ommen, T. AU - Hodell, D. A. DO - 10.5194/cp-18-1563-2022 IS - 7 N1 - https://cp.copernicus.org/articles/18/1563/2022/ PY - 2022 SN - 1814-9332 SP - 1563–1577 ST - Stratigraphic templates for ice core records of the past 1.5 Myr T2 - Climate of the Past TI - Stratigraphic templates for ice core records of the past 1.5 Myr UR - https://doi.org/10.5194/cp-18-1563-2022 VL - 18 ID - 49500 ER - TY - JOUR AB - Hypotheses and inferences concerning the nature of abrupt climate change, exemplified by the Dansgaard–Oeschger (D–O) events, are reviewed. There is little concrete evidence that these events are more than a regional Greenland phenomenon. The partial coherence of ice core δ18O and CH4 is a possible exception. Claims, however, of D–O presence in most remote locations cannot be distinguished from the hypothesis that many regions are just exhibiting temporal variability in climate proxies with approximately similar frequency content. Further suggestions that D–O events in Greenland are generated by shifts in the North Atlantic ocean circulation seem highly implausible, given the weak contribution of the high latitude ocean to the meridional flux of heat. A more likely scenario is that changes in the ocean circulation are a consequence of wind shifts. The disappearance of D–O events in the Holocene coincides with the disappearance also of the Laurentide and Fennoscandian ice sheets. It is thus suggested that D–O events are a consequence of interactions of the windfield with the continental ice sheets and that better understanding of the wind field in the glacial periods is the highest priority. Wind fields are capable of great volatility and very rapid global-scale teleconnections, and they are efficient generators of oceanic circulation changes and (more speculatively) of multiple states relative to great ice sheets. Connection of D–O events to the possibility of modern abrupt climate change rests on a very weak chain of assumptions. AU - Wunsch, Carl DA - 2006/03/01/ DO - https://doi.org/10.1016/j.yqres.2005.10.006 IS - 2 KW - Abrupt climate change Dansgaard–Oeschger events Ocean circulation N1 - https://www.sciencedirect.com/science/article/pii/S0033589405001717 PY - 2006 SN - 0033-5894 SP - 191–203 ST - Abrupt climate change: an alternative view T2 - Quaternary Research TI - Abrupt climate change: an alternative view UR - https://doi.org/10.1016/j.yqres.2005.10.006 VL - 65 ID - 17588 ER - TY - JOUR AB - The missing link in the plate boundary between Eurasia and Africa in the central Atlantic is presented and discussed. A set of almost linear and sub parallel dextral strike–slip faults, the SWIM11SWIM is the acronym of the ESF EuroMargins project “Earthquake and Tsunami hazards of active faults at the South West Iberian Margin: deep structure, high-resolution imaging and paleoseismic signature”. Faults, that form a narrow band of deformation over a length of 600 km coincident with a small circle centred on the pole of rotation of Africa with respect to Eurasia, was mapped using a new swath bathymetry compilation available in the area offshore SW Portugal. These faults connect the Gloria Fault to the Rif–Tell Fault Zone, two segments of the plate boundary between Africa and Eurasia. The SWIM faults cut across the Gulf of Cadiz, in the Atlantic Ocean, where the 1755 Great Lisbon earthquake, M~8.5–8.7, and tsunami were generated, providing a new insight on its source location. AU - Zitellini, N. AU - Gràcia, E. AU - Matias, L. AU - Terrinha, P. AU - Abreu, M. A. AU - DeAlteriis, G. AU - Henriet, J. P. AU - Dañobeitia, J. J. AU - Masson, D. G. AU - Mulder, T. AU - Ramella, R. AU - Somoza, L. AU - Diez, S. DA - 2009/04/15/ DO - https://doi.org/10.1016/j.epsl.2008.12.005 IS - 1–4 KW - Africa–Eurasia plate boundary Nubia Iberia Great Lisbon Earthquake Gulf of Cadiz N1 - https://www.sciencedirect.com/science/article/pii/S0012821X0800753X PY - 2009 SN - 0012-821X SP - 13–50 ST - The quest for the Africa–Eurasia plate boundary west of the Strait of Gibraltar T2 - Earth and Planetary Science Letters TI - The quest for the Africa–Eurasia plate boundary west of the Strait of Gibraltar UR - https://doi.org/10.1016/j.epsl.2008.12.005 VL - 280 ID - 17589 ER -