DIACHRONOUS RETREAT OF WEST ANTARCTIC ICE SHEET DURING AND FOLLOWING THE LAST GLACIAL MAXIMUM

Detailed marine geological surveys have been completed on the continental shelves offshore of all major drainage outlets of the West Antarctic Ice Sheet, with the exception of the southern Weddell Sea. These studies have focused on large glacial troughs where ice streams are believed to have been located during the last glacial maximum. Radiocarbon ages from sediment cores indicate a diachronous retreat history of different ice streams that drained the ice sheet.

Ice streams that flowed across the eastern Ross Sea shelf, one of the main discharge centers for the WAIS, was rapid and occurred between 22 Ka and 19 Ka. This was prior to, and faster than, the retreat of ice streams in the western Ross Sea and off Marie Byrd Land. It is suggested that over-extension of ice streams flowing across sedimentary basins resulted in draw down of the ice sheet, causing it to de-couple from the bed, even while global sea level was at a lowstand. Deep (up to 750 meters water depth) iceberg furrows record the break-up of the ice sheet. To date, we have not found an IRD record of ice sheet retreat from the shelf.