Ocean–ice sheet interactions and West Antarctic Ice Sheet vulnerability: clues from the Neogene and Quaternary record of the outer Ross Sea continental margin1
Published September 2017
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Observations from the past several decades indicate that the Southern Ocean is warming significantly and that Southern Hemisphere westerly winds have migrated southward and strengthened due to increasing atmospheric CO2 concentrations and/or ozone depletion. These changes have been linked to thinning of Antarctic ice shelves and marine terminating glaciers. Results from geologic drilling on Antarctica’s continental margins show late Neogene marine-based ice sheet variability, and numerical models indicate a fundamental role for oceanic heat in controlling this variability over at least the past 20 My. Although evidence for past ice sheet variability has been observed in marginal settings, sedimentological sequences from the outer continental shelf are required to evaluate the extent of past ice sheet variability and the role of oceanic heat flux in controlling ice sheet mass balance.
International Ocean Discovery Program (IODP) Expedition 374 proposes a latitudinal and depth transect of six drill sites from the outer continental shelf and rise in the eastern Ross Sea to resolve the relationship between climatic/oceanic change and West Antarctic Ice Sheet (WAIS) evolution through the Neogene and Quaternary. This location was selected because numerical ice sheet models indicate that it is highly sensitive to changes in ocean heat flux and sea level. The proposed drilling is designed for optimal data-model integration, which will enable an improved understanding of the sensitivity of Antarctic Ice Sheet mass balance during warmer-than-present climates (e.g., the early Pliocene and middle Miocene). Additionally, the proposed transect links ice-proximal records from the inner Ross Sea continental shelf (e.g., ANDRILL sites) to deepwater Southwest Pacific drilling sites/targets to obtain an ice-proximal to far-field view of Neogene climate and Antarctic cryosphere evolution. The proposed scientific objectives directly address Ocean and Climate Challenges 1 and 2 of the 2013–2023 IODP Science Plan.
- Evaluate the contribution of West Antarctica to far-field ice volume and sea level estimates.
- Reconstruct ice-proximal atmospheric and oceanic temperatures to identify past polar amplification and assess its forcings/feedbacks.
- Assess the role of oceanic forcing (e.g., sea level and temperature) on Antarctic Ice Sheet stability/instability.
- Identify the sensitivity of the AIS to Earth’s orbital configuration under a variety of climate boundary conditions.
- Reconstruct eastern Ross Sea bathymetry to examine relationships between seafloor geometry, ice sheet stability/instability, and global climate.
To achieve these objectives, we will (1) use data and models to reconcile intervals of maximum Neogene and Quaternary Antarctic ice advance with far-field records of eustatic sea level change; (2) reconstruct past changes in oceanic and atmospheric temperatures using a multiproxy approach; (3) reconstruct Neogene and Quaternary ice margin fluctuations in datable marine continental slope and rise records and correlate these records to existing inner continental shelf records; (4) examine relationships among WAIS stability/instability, Earth’s orbital configuration, oceanic temperature and circulation, and atmospheric pCO2; and (5) constrain the timing of Ross Sea continental shelf overdeepening and assess its impact on Neogene and Quaternary ice dynamics.
1McKay, R.M., De Santis, L., and Kulhanek, D.K., 2017. Expedition 374 Scientific Prospectus: Ross Sea West Antarctic Ice Sheet History. International Ocean Discovery Program. https://doi.org/10.14379/iodp.sp.374.2017