Climatic Controls on West Antarctic Ice Sheet Surface Mass Balance

The West Antarctic Ice Sheet (WAIS) is a primary focal point of sea-level rise concerns due to its ice volumetric equivalent of 4.3 m. Understanding the climate mechanisms that influence the WAIS surface mass balance (SMB) can help reduce uncertainties in sea-level rise projections. Previous work focuses on variations in temperature and the impacts of well-known climate phenomena in the Pacific Ocean. To understand the patterns and fluctuations of the WAIS SMB, this study targets the Southern Hemisphere Pacific Ocean and Indian Ocean regions, specifically the propagation of Rossby wave trains. Using SMB measurements from 39 WAIS ice cores from 1851-2010, we found oppositely-signed mean SMB trends in two sectors of the WAIS. We then detrended the data to examine interannual variability and found similar tropical convection patterns for both high SMB in the East and West WAIS, characterized by a dipole in outgoing longwave radiation and enhanced convection from the eastern Indian Ocean to western Australia. However, there were noticeable differences in Rossby wave patterns. High East SMB showed wave activity flux centered around 120°W and a southward-shifted jet with high zonal wind speeds. In contrast, high West SMB showed weaker, less organized wave activity and a dipole shifted further west. We present evidence that these contrasting Rossby wave patterns arise more from the intervening jet waveguide than the nature of the source region convection.