Warm water intrusion onto the East Antarctic Shelf

Circumpolar Deep Water (CDW) poses a major threat for the future stability of the Antarctic Ice Sheet. In the Southern Ocean, CDW encroaches onto the Antarctic continental shelf in East Antarctica. CDW is the warmest deep-water mass within the Southern Ocean, and thus, harbours large amounts of heat with the potential to drive large basal melting under the ice shelf cavities it reaches. The PS141 expedition focused on the Denman Glacier, one of the fastest retreating glaciers in the East Antarctic Aurora subglacial basin. It holds a sea level rise equivalent of up to 1.6 m. However, the processes behind the Denman retreat remain undocumented. During PS141, found warm modified CDW intrusions in the immediate vicinity of the Denman ice shelf. mCDW temperature reached up to -0.1 °C, more than 1.5 °C higher than ambient water masses. It was present as the deepest water mass below 330 m on the continental shelf along a cross-shelf-transect at 100° E. Its minimum thickness was 50 m at the ice shelf and reached up to 100 m thickness mid shelf, where the warmest temperatures were measured. Predictions into how future climate scenarios may affect how CDW interacts with the Antarctic Ice Sheet suggest an increasing presence of mCDW within the Antarctic continental shelf. This could be a major threat to the stability of the East Antarctic Ice Sheet, especially if it reaches vulnerable regions such as the Aurora subglacial basin and Denman glacier. By documenting the ocean state near this critical region, we can deliver better climate-related advice to policy makers working on mitigating and adapting to future sea level rise.