Responses of stable water isotopes to a collapse of the West Antarctic Ice Sheet in high-resolution simulations with the Weather Research and Forecasting Model

Abstract:

A large part of Earth’s fresh water is currently stored in the West Antarctic Ice Sheet (WAIS). However, since much of its bed is below sea level, the WAIS is unstable and at risk of collapse due to global warming. This could lead to a sea level rise of up to 3 meters, drowning many current coastal areas. How exactly the WAIS will respond to warmer temperatures is still uncertain, but a glimpse into the future can be gained from looking at the past, specifically at paleoclimate records going back all the way to the last interglacial period (Eemian, 132 to 115 kyr ago), when Earth was about 1°C warmer than today. Such a long record will be obtained from the planned ice core site at Hercules Dome, which lies at the saddle between Antarctica’s western and eastern ice sheets. If the WAIS collapsed during the Eemian, this would be reflected in the ratios of stable water isotopes in ice at Hercules Dome. To find out if and how such a signal could be detected, we performed high-resolution simulations with a newly developed isotope-enabled version of the Weather Research and Forecasting Model both for a preindustrial (control) and a WAIS collapse scenario. Our results show that in the WAIS collapse scenario, δ¹⁸O is lower and d-excess is higher at Hercules Dome than in the control scenario. The isotope signal is caused by a combination of changes in topography and changes in sea surface temperatures and sea ice. This means that an ice core from Hercules Dome will be able to show whether the WAIS collapsed during the Eemian.