Direct Observations of Rapid Basal Melting and Bed Topography in the Grounding Zones of the Dotson and Crosson Ice Shelves, West Antarctica

Abstract:

Glaciological changes of the Dotson and Crosson ice shelves and their tributary glaciers of Smith, Pope and Kohler are among the most noticeable in the Amundsen Sea Embayment region of West Antarctica. Here, we present sounding radar and laser altimetry observations of two aspects that are indispensable for understanding those changes: basal melting and bedrock topography in the grounding zones. We find that Smith Glacier in particular thinned by a remarkably fast 300-490 m between the years 2002 and 2009. Its grounding line has retreated far enough to be now at 2000 m below sea level in a previously identified trench. All three glacier grounding lines have already retreated down steeper parts of their bedrocks to flatter terrains, plausibly contributing to the reported slowing down in the acceleration of their ice volume discharges. The wider implications of the work emphasize the unprecedented perspectives that direct observation can offer of diverse grounding zone structures and evolution scenarios.