Antarctic meltwater induces competing climate feedbacks in an Earth system model coupled to an Antarctic ice melt emulator

Abstract. Antarctic ice-sheet mass loss is expected to accelerate under future warming, yet its climatic impacts remain poorly represented in Earth system models. Here, we present simulations with the EC-Earth3 Earth system model that incorporate the Antarctic Ice Melt Emulator (AIME), interactively coupled to the ocean component. AIME simulates regionally and temporally varying freshwater fluxes driven by subsurface ocean temperatures over the Antarctic continental shelf, accounts for the delayed dynamic response of the ice sheet, and enables two-way interactions between the climate system and Antarctic ice loss.

Under an abrupt quadrupling of atmospheric CO₂, the interactive freshwater forcing gives rise to two distinct feedback regimes. During the transient adjustment phase, enhanced freshwater input strengthens Southern Ocean stratification, suppresses vertical mixing, and modifies continental shelf circulation, leading to enhanced subsurface warming near the base of Antarctic ice shelves. During the subsequent quasi-equilibrium phase, the dominant climatic response shifts: reduced surface warming, increased sea-ice persistence, and decreased global ocean heat uptake weaken the atmospheric warming, ultimately reducing subsurface warming over the Antarctic continental shelf despite continued freshwater input.

Compared with a simulation without interactive Antarctic freshwater forcing, the coupled simulation exhibits lower equilibrium climate sensitivity and reduced global ocean heat storage under identical greenhouse-gas forcing. These results demonstrate that Antarctic freshwater feedbacks evolve over time, with an initial ocean-driven amplification followed by a longer-term atmosphere-mediated damping response. Our findings highlight the importance of representing interactive Antarctic freshwater fluxes in Earth system models to capture coupled ice-sheet-ocean-atmosphere feedbacks and improve projections of future climate change.