Warm Water Slowed Formation of the West Antarctic Ice Sheet

Communications Earth & Environment, 21 February 2022

New evidence suggests the presence of warm, deep water delayed the expansion of the West Antarctic Ice Sheet as it formed 35 million years ago; and similar conditions today may cause its destabilization. The Pine Island Trough is a deep channel in the Amundsen Sea, sending ocean water directly towards the western coast of Antarctica. The accumulation of sediment along the trough’s eastern side, but not its western one could only have been produced by a deep water ocean current flowing from north to south along the contours of the trough. This deep current was produced by a combination of weakening easterly winds, southward migration of westerly winds, and a moderately strong circumpolar ocean current surrounding Antarctica. Together, these factors increased the upwelling of warm seawater through the Pine Island Trough and onto the Amundsen Sea self, which eroded the base of the ice sheet as it formed, delaying its spread. These ocean and wind current conditions are similar to the ones that surround Antarctica today; warm circumpolar water flows through seafloor troughs towards the coast, entering cavities and melting the base of ice shelves. These findings emphasize the importance of ocean currents and warming waters on the stability of the West Antarctic Ice Sheet, as well as the degree to which current warming from carbon emissions is pressing the Antarctic system towards unstable states that have not existed for many millions of years, risking long-term and essentially irreversible sea-level rise.