Returning Climate to Present Day May not Reduce Antarctic Mass Loss

Abstract

Using the BISICLES ice sheet model, we explore the Antarctic Ice Sheet's response over the 22nd century under two climate scenarios. In the return scenario , climate forcing is returned to present‐day levels (2015) in either 2050 or 2100 and then held constant until 2200. In the stabilization scenario , climate forcing is held at 2050 or 2100 levels through to 2200. Results are highly climate model dependent, with larger differences between models than between return and stabilization scenarios, but show that returning the climate cannot prevent significant losses from Antarctica over the next two centuries due to committed changes and the possibility of ice sheet instabilities already being under way. The timing of returning the climate is important, with substantially different Antarctic responses between returning the climate in 2050 versus 2100. If the climate is returned in 2050, sea level contributions are generally lower than under stabilization scenarios. However, if returning is delayed until 2100, under high emissions, the return scenarios produce higher sea level contributions than stabilization scenarios, as increased surface mass balance in the warmer stabilization scenarios offsets some of the dynamic losses. Despite this, dynamic losses appear to accelerate and may eventually negate this initial offset, indicating that beyond 2200, returning in 2100 could eventually be more effective. Our results suggest that a large scale climate intervention may not be a complete solution to mitigating sea level contribution from the ice sheet nor reverse it on multi‐century timescales.