Abstract
Of all the components of the global sea-level budget, the future contribution of the Antarctic Ice Sheet is the most uncertain in sea-level rise projections. Dynamic ice sheet model simulations show considerable overlap in the projected Antarctic Ice Sheet sea-level contribution under various greenhouse gas emissions scenarios and the timescale at which scenario dependence will emerge is unclear. With historically constrained ice sheet simulations and a statistical emulator, we demonstrate that a high-emissions signature of the Antarctic Ice Sheet sea-level contribution will not unambiguously emerge from the wide potential range of low-emission sea-level projections for over 100 years due to current limitations in our understanding in ice flow and sliding. However, the results also indicate that the total global warming that occurs over the 21st century controls the resulting long-term Antarctic Ice Sheet sea-level commitment, with multi-meter differences between the highest and lowest emissions scenarios in subsequent centuries.
Highlights
Of all the components of the global sea-level budget, the future contribution of the Antarctic Ice Sheet is the most uncertain in sea-level rise projections
We investigate a fullfactorial parameter sampling of 4 unconstrained model parameters related to ice flow, rheology, and basal shear stress (Supplementary Table S1)
Our process-based ice sheet model simulations suggest that widespread thinning and partial collapse of the Ross and Ronne–Filchner ice shelves arising from decades of accumulated oceanic warming will be the earliest warning sign of the multimeter contributions of Antarctic Ice Sheet (AIS) that occur under high-emissions scenarios
Summary
Of all the components of the global sea-level budget, the future contribution of the Antarctic Ice Sheet is the most uncertain in sea-level rise projections. Of all the components of the global sea-level budget, the contribution of the Antarctic Ice Sheet (AIS) is the most uncertain[4,5,6] This uncertainty is clear in the recent community effort of the Ice Sheet Model Intercomparison Project 6 (ISMIP6), in which AIS contributions projected over the century ranged from −0.08 to +0.30 m of sea-level equivalent under an RCP8.5 scenario[7]. While some of this range is related to uncertainties in the climate response to a given emissions scenario and differences in model initialization[8], ice sheet model projections are subject to uncertainties in the parameterization of physical processes[9,10,11]. We relate our findings to global warming levels (GWLs), defined as 20-year moving windows with respect to the preindustrial 1850–1900 value, to provide AIS sea-level projections per degree of warming to 2300
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