International Ocean Discovery Program
Expedition 400 Preliminary Report
NW Greenland Glaciated Margin1
Cenozoic evolution of the northern Greenland Ice Sheet exposed by transect drilling in northeast Baffin Bay
Paul C. Knutz, Anne Jennings, Laurel B. Childress, and the Expedition 400 Scientists
1 Knutz, P.C., Jennings, A., Childress, L.B., and the Expedition 400 Scientists, 2024. Expedition 400 Preliminary Report: NW Greenland Glaciated Margin. International Ocean Discovery Program. https://doi.org/10.14379/iodp.pr.400.2024
Abstract
Elucidating the geologic history of the Greenland Ice Sheet (GrIS) is essential for understanding glacial instability thresholds, identified as major climate system tipping points, and how the cryosphere will respond to anthropogenic greenhouse gas emissions. To address current knowledge gaps in the evolution and variability of the GrIS and its role in Earth's climate system, International Ocean Discovery Program (IODP) Expedition 400 obtained sedimentary records from Sites U1603–U1608 across the northwest Greenland margin into Baffin Bay where thick Cenozoic sedimentary successions can be directly linked to the evolution of the northern GrIS (NGrIS). The strategy of drilling along this transect was to retrieve a composite stratigraphic succession representing the late Cenozoic era from the Oligocene/early Miocene to Holocene.
The proposed sites targeted high–accumulation rate deposits associated with contourite drifts and potential interglacial deposits within a trough mouth fan system densely covered by seismic data. The principal objectives were to (1) test if the NGrIS underwent near-complete deglaciations in the Pleistocene and assess the ice sheet’s response to changes in orbital cyclicities through the mid-Pleistocene transition; (2) ascertain the timing of the NGrIS expansion and examine a hypothesized linkage between marine heat transport through Baffin Bay and high Arctic warmth during the Pliocene; and (3) provide new understandings of climate-ecosystem conditions in Greenland during the geologic periods with increased atmospheric CO2 compared to preindustrial values, encompassing the last 30 My. The deep time objective was attained by coring at Site U1607 on the inner shelf to 978 meters below seafloor, capturing a succession of mainly Miocene and Oligocene age. The six sites drilled during Expedition 400 resulted in 2299 m of recovered core material, and wireline downhole logging was completed at Sites U1603, U1604, U1607, and U1608. This unique archive will provide the basis for understanding the full range of forcings and feedbacks—oceanic, atmospheric, orbital, and tectonic—that influence the GrIS over a range of timescales, as well as conditions prevailing at the time of glacial inception and deglacial to interglacial periods. We anticipate that the shipboard data and further analytical work on Expedition 400 material can constrain predictive models addressing the GrIS response to global warming and its impending effects on global sea levels.
Plain language summary
Sea level consequences of anthropogenic climate forcing hinge on how the polar ice sheets respond to global warming. If fully melted, the Greenland Ice Sheet has the potential to raise sea level by >7 meters, yet we know very little about its long-term responses to past climate warming or its role in Earth’s climate system. Expedition 400 seeks to address current knowledge gaps in the evolution and variability of the northern Greenland Ice Sheet by recovering sedimentary archives of warm and cold periods going millions of years back in time. This includes periods when the greenhouse gas content of the atmosphere was higher than it is today. By drilling at six sites to 978 meters below seafloor along a transect crossing the northwest Greenland margin into Baffin Bay, we obtained a total of 2299 meters of sediment. This extensive and unique sediment archive will be valuable for understanding the geologic history of the Greenland Ice Sheet and its response to past warming going back 30 million years before present. The sediment cores record climate conditions before Greenland became glaciated and indicate when the Greenland Ice Sheet first began to expand into the marine environment. We also see glacial and interglacial cycles when the ice sheet grew to its maximum position at the shelf edge and retreated toward land, possibly melting farther back than what is known from previous records.