From short-term uncertainties to long-term certainties in the future evolution of the Antarctic Ice Sheet

The future evolution of the Antarctic Ice Sheet with progressing warming constitutes one of the, if not the main uncertainty in projections of future sea-level change. As the largest potential source of sea-level rise and one of the key tipping elements in the climate system, robust projections are needed to inform coastal adaptation planning worldwide.

Using historically-calibrated perturbed-parameter ensembles of projections with two ice-sheet models, we assess the response of the Antarctic Ice Sheet and associated uncertainties to a wide range of climate futures extending to the year 2300 and beyond.

We show that the near-term projections of the Antarctic Ice Sheet are strongly influenced by ice-sheet model sensitivities, especially under limited warming, until strong changes in Antarctic climate beyond the end of the century, as projected under unmitigated emissions, clearly dominate the ice-sheet evolution. Irrespective of the wide range of uncertainties explored in our ensembles, large-scale ice loss is triggered in both West and East Antarctica under higher warming scenarios, but can be avoided by reaching net-zero emissions well before 2100. This leads to a multi-meter difference in the committed Antarctic sea-level contribution projected under low and very high emission pathways by the end of the millennium. Our results suggest that the next years and decades are decisive for the multi-centennial fate of the Antarctic Ice Sheet.