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

Abstract 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.