Long-term sea-level commitment and reversibility of ice loss from Antarctica

Abstract

The evolution of the Antarctic Ice Sheet is of vital importance given the coastal and societal implications of ice loss, with a potential to raise sea level by up to 58 m if melted entirely. However, future ice-sheet trajectories remain highly uncertain. In fact, current estimates range from a slight mass gain to a mass loss of the Antarctic Ice Sheet by the end of this century. What is more, due to ice-sheet inertia and potentially self-sustained mass loss when exceeding critical thresholds or tipping points, the bulk of sea-level rise is expected to arise beyond the end of this century as sea-level commitment.

Here, we systematically assess this long-term committed sea-level contribution from the Antarctic Ice Sheet in response to warming projected over the next centuries under lower- and higher-emission pathways, as well as the reversibility of the committed large-scale ice-sheet changes when reducing warming to relatively colder climate conditions.

We find that already the lower-emission pathway poses a considerable risk of Antarctic ice loss, raising global mean sea level by multiple meters over the next millennia in our experiments. Beyond warming levels reached by the end of this century under the higher-emission climate trajectories, a collapse of the West Antarctic Ice Sheet is triggered in our entire ensemble of simulations. Additional East Antarctic ice loss may increase sea level by several tens of meters over the next millennia with enhanced warming, stressing the importance of including the committed Antarctic sea-level contribution in future projections. Given ice-sheet inertia, an early reversal of climate may allow for avoiding this self-sustained Antarctic ice loss that would otherwise be irreversible (for the same reduction in warming) due to multistability of the ice sheet. While we show that such ‘safe’ overshoots of critical thresholds in Antarctica may be possible, it is also clear that limiting global warming is the only viable option to evade the risk of widespread ice loss in the long term.

Speaker Bio

Ann Kristin Klose is a PhD student in Climate Physics at University of Potsdam and the Potsdam Institute of Climate Impact Research (PIK) where she is part of the Research Group ‘Ice Dynamics’ and the FutureLab ‘Earth Resilience in the Anthropocene’. Her PhD project embedded in the EU-H2020 project PROTECT aims at understanding possible future trajectories of the Antarctic Ice Sheet on multi-millennial timescales, based on ice-sheet modelling and complex systems theory. Her current research focuses on (1) the Antarctic sea-level commitment, compared to typical sea-level projections covering decadal to centennial timescales, (2) the reversibility of ice loss including so-called ‘safe’ overshoots and (3) the potential for critical transitions (tipping) of the Antarctic Ice Sheet. Ann Kristin studied Environmental Sciences and Modelling at University of Oldenburg (Germany) and at University of Bergen (Norway).