Hysteresis of the Antarctic Ice Sheet With a Coupled Climate-Ice-Sheet Model

The stability of the Antarctic ice sheet under different fixed CO2 levels and orbital configurations is explored using a coupled climate-ice sheet model, starting from either a pre-industrial ice sheet or an ice-free, isostatically rebounded geometry. Simulations reveal a strong hysteresis effect: equilibrium ice volumes differ significantly for equivalent CO2 levels, depending on the initial ice sheet geometry. Crucially, the albedo-melt feedback is accounted for in our coupled setting, resulting in a nonlinear response of the ice sheet to the CO2 forcing. Critical CO2 thresholds trigger either the complete Antarctic ice sheet loss or near-complete regrowth. The orbital configuration influences these CO2 thresholds. These findings highlight the importance of ice sheet-atmosphere interactions, notably the albedo-melt feedback, in projecting future long-term ice sheet behavior. Neglecting these feedbacks could lead to an overestimation of CO2 thresholds for ice sheet destabilization, with implications for future long-term sea level rise under high emission scenarios.