The Amundsen Sea embayment is the least well-studied sector of the Pacific margin of West Antarctica. Even though more than 40% of the area of the West Antarctic Ice Sheet (WAIS) drains towards the SE Pacific Ocean, very little is known about the history of the major glacial systems on this flank of the ice sheet. The only part of the SE-Pacific margin of the WAIS for which a chronology of ice retreat has been proposed is Pine Island Bay, in the southeastern corner of the Amundsen Sea. However, this chronology is based on only a small number of radiocarbon dates with large uncertainties. The Amundsen Sea embayment lies offshore from Pine Island and Thwaites glaciers, which exhibit the most rapid ice thinning and grounding-line retreat in present-day Antarctica. It has been suggested that this area may be the most likely site for the initiation of collapse of the two million km2 WAIS, which is a marine ice sheet with large parts of its ice grounded below sea level. At present it is not clear to what extent current retreat of WAIS grounding lines is part of ongoing recession that started during the last deglaciation and to what extent it reflects more recent climatic changes. Preliminary results will be presented from recent RRS James Clark Ross Cruise JR141 and RV Polarstern Expedition ANT-XXIII/4, on which glacial history and sedimentary processes on the Amundsen Sea continental shelf and slope were investigated using multibeam bathymetry data, high-resolution seismic reflection profiles, sub-bottom acoustic profiles, and sediment cores. The data will be used to determine the maximum extent of the WAIS during the last glacial period, the extent of fast ice flow in the former ice sheet, controls on the location and onset position of fast ice flow, the retreat history of the WAIS, how changes on the shelf affected sedimentary processes on the slope, and whether the last ice sheet and its deglaciation are representative of events during earlier Quaternary glacial cycles. The marine record of late Quaternary deglaciations in the Amundsen Sea embayment, coupled with ice sheet models, will provide important clues to understanding the stability and climate sensitivity of the WAIS.
Helmholtz Research Programs > MARCOPOLI (2004-2008) > POL6-Earth climate variability since the Pliocene