Occurrence of submesoscale eddy in Terra Nova Bay and its impact on basal melting of Nasen Ice Shelf, East Antarctica

As a key driver of basal melting of ice shelves, ocean heat transport plays a central role in controlling ice shelf stability through ice-ocean interaction. A recent observational study confirmed the existence of an approximately 10 km-wide subsurface eddy (referred to as a cyclonic “thinny”) in Terra Nova Bay (TNB) and speculated that the shoreward advection of this observed eddy might enhance summertime melting of the Nansen Ice Shelf (NIS). Here, we for the first time report on the simulation of a cyclonic thinny transporting warm Antarctic Surface Water (AASW) into the cavity beneath the NIS performed using a regional coupled sea-ice/ocean model that includes the ocean-ice shelf dynamics/thermodynamics. By including eddy-wind interaction, our model successfully reproduced the occurrence of submesoscale cyclonic eddies in TNB, with warm AASW downward due to convergence at the eddy center, and demonstrated that the submesoscale eddy-meditated heat transport enhances the NIS basal melting. We examine how the cyclonic thinny influences the ice shelf melt through by analyzing the behavior of cyclonic eddies and its heat transport into the NIS cavity. Ocean heat supplied to the NIS cavity is most active when the cyclonic eddy elevating vertical heat transfer from the warm surface collides with the ice shelf front, which strengthens local basal melting at the ice shelf shallower than 200 m near the NIS front compared to the case without eddy collision with the ice shelf. This study highlights the significant role of subsurface eddies in localized ice shelf melting, which has the potential to impact the frequency of massive calving events.