Projected increases in Antarctic snow accumulation from CMIP6 to 2300

As the atmosphere warms in response to increasing greenhouse gas emissions, snow accumulation over the Antarctic Ice Sheet is projected to increase over the next century. Furthermore, short-term emissions scenarios are also expected to have long-term impacts on ice sheet mass balance for centuries to come. Here, we analysed the extended runs of the Coupled Model Intercomparison Project’s Sixth Phase (CMIP6) to investigate the consequences of emissions scenarios on Antarctic surface mass balance until 2300. Unlike the Arctic, which shows a regime shift from snow-dominated precipitation to rain-dominated precipitation, snow accumulation continues to outpace ablation over the Antarctic Ice Sheet through the year 2300, even under the high emissions Shared Socioeconomic Pathway 5-8.5 scenario. The positive relationship between precipitation and temperature increases through time at both high elevation in the continental interior as well as at the coastal margins of the ice sheet. Under high emissions, although rainfall is projected in some vulnerable regions, such as Thwaites Glacier, overall surface mass balance remains positive and increases through time. In corresponding ice sheet model experiments using the Parallel Ice Sheet Model, the sea level compensation of this increased surface mass balance is as high as 10 cm by 2100 and 1.8 m by 2300, though considerable intermodel spread exists. These model results suggest that mass loss of the ice sheet will continue to be dominated by ocean driven-melting rather than melting of the ice sheet surface for the next centuries.