Ice-Front Retreat Controls on Ocean Dynamics Under Larsen C Ice Shelf, Antarctica

Iceberg A-68 separated from the Larsen C Ice Shelf in July 2017 and the impact of this event on the local ocean circulation has yet to be assessed. Here, we conduct numerical simulations of ocean dynamics near and below the ice shelf pre- and post-calving. Results agree with in situ and remote observations of the area as they indicate that basal melt is primarily controlled by wintertime sea-ice formation, which in turn produces High Salinity Shelf Water (HSSW). After the calving event, we simulate a 50% increase in HSSW intrusion under the ice shelf, enhancing ocean heat delivery by 30%. This results in doubling of the melt rate under Gipps Ice Rise, suggesting a positive feedback for further retreat that could destabilize the Larsen C Ice Shelf. Assessing the impact of ice-front retreat on the heat delivery under the ice is crucial to better understand ice-shelf dynamics in a warming environment. In July 2017, the Larsen C Ice Shelf, Antarctica, calved one of the largest icebergs ever observed: A-68. The impact of this event on the ocean circulation near and below the ice remains unknown. Our simulations from an ocean model suggest that the iceberg separation may have led to increased ocean heat delivery under the ice, yielding more vigorous bottom melt. We present ocean simulations under Larsen C in good agreement with local ocean, basal melt and sea-ice observationsThe removal of iceberg A-68 yields heat intrusion to increase by 30% causing melt around Gipps Ice Rise to doubleOcean models need to consider ice-front retreat events and realistic ice-shelf geometry to accurately project sub-shelf ocean circulation