Antarctic ice sheet - climate feedbacks under high future carbon emissions

TL;DR

This study uses coupled climate and ice sheet models to show how Antarctic meltwater impacts global climate projections, highlighting the importance of including ice sheet feedbacks for accurate future climate predictions.

Contribution

It introduces multi-century climate simulations that incorporate dynamic Antarctic ice sheet meltwater discharge, revealing significant climate feedbacks under future emissions scenarios.

Findings

Meltwater raises subsurface ocean temperatures by 1°C at the ice margin.

Surface air and ocean temperatures in the Southern Ocean are 2-10°C cooler, delaying warming.

Loss of Arctic sea ice and Atlantic circulation weakening are delayed by decades.

Abstract

Freshwater forcing from a retreating Antarctic Ice Sheet could have a wide range of impacts on future global climate. Here, we report on multi-century (present-2250) climate simulations performed using a fully coupled numerical model integrated under future greenhouse gas emissions scenarios IPCC RCP4.5 and 8.5, with meltwater discharge provided by a dynamic-thermodynamic ice sheet model. Accounting for Antarctica's meltwater contribution raises sub-surface ocean temperatures by 1 C at the ice margin, beyond rates currently projected. In contrast, 2-10 C cooler surface air and ocean temperatures in the Southern Ocean cause sea ice to expand and delay the increase of projected global mean anthropogenic warming. In addition, the projected loss of Arctic winter sea ice and weakening of the Atlantic Meridional Overturning Circulation are delayed be several decades. Our results demonstrate a clear need to more accurately account for meltwater input from ice sheets if we are to make confident climate predictions.