Basal terraces beneath Totten Glacier, East Antarctica

The Totten Glacier is the primary outlet of the Aurora Subglacial Basin (ASB), draining at least 3.5 m of eustatic sea-level potential into the Sabrina Coast alongside the Moscow University Ice Shelf. Recent work has shown that the ASB has drained and filled many times since large-scale glaciation began, including evidence that it collapsed during the Pliocene. Steady thinning rates near the grounding line of Totten Glacier are the largest in East Antarctica and the nature of the thinning suggests that it is driven by enhanced basal melting due to ocean processes. Warm modified circumpolar deep water (MCDW), which has been linked to glacier retreat in West Antarctica, has been observed in summer and winter on the Sabrina Coast continental shelf by multiple marine expeditions and recent work has shown that depressions in the seafloor likely make the ice shelf vulnerable to MCDW intrusions that could cause enhanced basal melting. Here we use post-processed, focused airborne radar observations of the Totten Glacier Ice Shelf to delineate multi-kilometer-wide basal channels and flat basal terraces that are associated with high basal reflectivity and specularity anomalies and correspondingly large ice surface depressions that indicate active basal melt processes. Sub-ice-shelf ocean circulation modeling and under ice robotic observations of Pine Island Glacier Ice Shelf in West Antarctica and the Petermann Glacier Ice Shelf in Greenland have shown that basal terraces associated with large basal channels are an indication of rapidly melting ice shelves. Therefore, these new results identify an East Antarctic example of rapid basal melting processes and demonstrate that airborne radar can be used to identify basal characteristics relevant to ice-shelf basal processes.