Mass loss of the Antarctic ice sheet until the year 3000 under a sustained late-21st-century climate

Fuyuki Saito,Christopher Chambers,Ayako Abe-Ouchi,Ralf Greve,Takashi Obase

doi:10.1017/jog.2021.124

Abstract

AbstractIce-sheet simulations of Antarctica extending to the year 3000 are analysed to investigate the long-term impacts of 21st-century warming. Climate projections are used as forcing until 2100 and afterwards no climate trend is applied. Fourteen experiments are for the ‘unabated warming’ pathway, and three are for the ‘reduced emissions’ pathway. For the unabated warming path simulations, West Antarctica suffers a much more severe ice loss than East Antarctica. In these cases, the mass loss amounts to an ensemble average of ~3.5 m sea-level equivalent (SLE) by the year 3000 and ~5.3 m for the most sensitive experiment. Four phases of mass loss occur during the collapse of the West Antarctic ice sheet. For the reduced emissions pathway, the mean mass loss is ~0.24 m SLE. By demonstrating that the consequences of the 21st century unabated warming path forcing are large and long term, the results present a different perspective to ISMIP6 (Ice Sheet Model Intercomparison Project for CMIP6). Extended ABUMIP (Antarctic BUttressing Model Intercomparison Project) simulations, assuming sudden and sustained ice-shelf collapse, with and without bedrock rebound, corroborate a negative feedback for ice loss found in previous studies, where bedrock rebound acts to slow the rate of ice loss.

Highlights

The Antarctic ice sheet (AIS) contains more than half of the Earth’s fresh water, enough to raise sea levels by 58 m (Fretwell and others, 2013)
In contrast to the East Antarctic Ice Sheet (EAIS), the West Antarctic Ice Sheet (WAIS) is grounded on a bed that is mostly well below the sea level (Fig. 1) making it primarily a marine ice sheet
This phase is the period of most rapid ice-sheet mass loss and there is a fair degree of variability between the simulations in both the timing of the transition from phase 2 to 3, and in the level of sea-level equivalent (SLE) contribution at which this phase begins

Summary

Introduction

The Antarctic ice sheet (AIS) contains more than half of the Earth’s fresh water, enough to raise sea levels by 58 m (Fretwell and others, 2013). An ice mass of 7.4 mm sea-level equivalent (SLE) was lost from the AIS between 1992 and 2017 (The IMBIE team, 2018), and there is evidence to suggest that parts of the West Antarctic Ice Sheet (WAIS) may already have begun an irreversible retreat (Joughin and others, 2014; Rignot and others, 2014). The possibility of WAIS retreat and collapse was first presented by Mercer (1968) and there is palaeoclimatic evidence that it collapsed during past warm periods (Pollard and DeConto, 2009; Alley and other, 2015; Dutton and others, 2015; Gasson and others, 2016; Turney and others, 2020). In contrast to the East Antarctic Ice Sheet (EAIS), the WAIS is grounded on a bed that is mostly well below the sea level (Fig. 1) making it primarily a marine ice sheet. The WAIS is bounded by the two largest iceshelf systems in the world, the Ross and the Ronne-Filchner, which currently act to buttress the grounded ice sheet (e.g. Joughin and Alley, 2011) and reduce ice flow across long, below-sea-level grounding lines

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Conclusion