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Abstract

It is virtually certain that Antarctica’s contribution to sea-level rise will increase with future warming, although
competing mass balance processes hamper accurate quantification of the exact magnitudes. Today, ocean-induced melting un-
derneath the floating ice shelves dominates mass losses, but melting at the surface will gain importance as global warming
continues. Meltwater at the ice surface has crucial implications for the ice sheet’s stability, as it increases the risk of hydrofrac-
turing and ice-shelf collapse that could cause enhanced glacier outflow into the ocean. Simultaneously, positive feedbacks5
between ice and atmosphere can accelerate mass losses and increase the ice sheet’s sensitivity to warming. However, due to
long response times it may take hundreds to thousands of years until the ice sheet fully adjusts to the environmental changes.
Therefore, ice sheet model simulations must be computationally fast and capture the relevant feedbacks, including the ones at
the ice–atmosphere interface.
Here we use the novel surface melt module dEBM-simple, coupled to the Parallel Ice Sheet Model (PISM), to estimate the
impact of 21st-century atmospheric warming on Antarctic surface melt and ice dynamics. As an enhancement compared to
the widely adopted positive degree-day (PDD) scheme, dEBM-simple includes an implicit diurnal cycle and computes melt
not only from the temperature, but also from the influence of solar radiation and changes in ice albedo, thus accounting for
the melt–albedo feedback. We calibrate PISM-dEBM-simple to reproduce historical and present-day Antarctic surface melt
rates given by the regional climate model RACMO2.3p2 and use the calibrated model to assess the range of possible future
surface melt trajectories under SSP5-8.5 warming projections until the year 2100. To investigate the committed impacts of the
enhanced surface melting on the ice-sheet dynamics, we extend the simulations under fixed climatological conditions until the
ice sheet has reached a state close to equilibrium with its environment. Our findings reveal a substantial surface melt-induced
speed-up in ice flow associated with large-scale elevation reductions in sensitive ice-sheet regions, underscoring the critical
role of self-reinforcing ice-sheet–atmosphere feedbacks on future mass losses and sea-level contribution from the Antarctic Ice
Sheet on centennial to millennial timescales.