Ice‐Sheet–Ocean Interactions and the Reversibility of a Regime Shift Beneath Filchner‐Ronne Ice Shelf

Future atmospheric warming could cause an abrupt increase in ocean temperature beneath the Filchner–Ronne Ice Shelf, Antarctica, from −2.2°C to more than 0°C in a few decades. In simulations, such a transition leads to a twenty-fold increase in sub-shelf melt rates, driving a retreat of the ice sheet. Here we investigate the evolution and reversibility of the ocean and ice sheet states using coupled ice-sheet–ocean model simulations. We show that sub-shelf melt rates increase only half as much as in the uncoupled system, and we find that, after a period of climate cooling, the cavity is reversible from warm to cold conditions, independently of ice-ocean interactions related to regional changes in sub-shelf melting, cavity geometry, and ocean dynamics. In contrast to the abrupt warming transition, the recovery of a cold ocean state takes more than a century. Meanwhile the ice sheet continues to lose mass and contribute to sea level rise with a maximum rate of up to 0.9 mm/a.