Rapid basal melting and destabilization of the Dotson Ice Shelf, Antarctica

Abstract:

The Amundsen Sea has been the setting of drastic grounding-line retreat, unprecedented ice-shelf thinning and associated glacier speed-up since the beginning of the satellite measurement era. While both the Thwaites and Crosson Ice Shelves have been severely impacted by this negative trend, leading toward partial collapse, the neighboring Dotson Ice Shelf has resisted acceleration despite high and increasing basal melt rates. Because of this lack of acceleration, previous publications have assumed that the Dotson Ice Shelf will remain stable for decades to centuries. This assumption has remained unchallenged due to the Dotson’s remote location and consequent lack of field data. Here we show field measurements collected during the 2019/20 Antarctic field season as part of the International Thwaites Glacier Collaboration TARSAN project that reveal basal melt rates of up to 50 m/yr. If such high rates turn out to be spatially extensive, disintegration of the entire shelf would be possible within the next 10 to 50 years. We link this high melt rate to the formation of a large basal channel, which has deepened over the last decade and migrated along a broad shear zone with the adjacent and much faster Crosson Ice Shelf. The loss of a series of stabilizing pinning points due to thinning of the ice raises further concern that buttressing of the tributary Smith Glacier is on the decline, leading to a reconfiguration of regional ice flow patterns.