Impact of tropical oceans on dipole-like surface mass balance trends in West Antarctica

Abstract. The surface mass balance (SMB) of the Antarctic Ice Sheet is a critical factor in influencing global mean sea level rise and has substantial implications for future projections of sea level rise. In recent decades, the Antarctic Ice Sheet SMB trends show pronounced regional disparities, marked by an increase over the western part but a decrease over the eastern part of West Antarctica. Through a synthesis of ice core records and five reanalysis datasets, as well as atmospheric dynamics analysis and numerical model simulations, we demonstrate that the multi-decadal trends in tropical sea surface temperature are key drivers of the dipole-like SMB trends in West Antarctica. Specifically, the eastern tropical Pacific cooling associated with the phase changes of the Interdecadal Pacific Oscillation (IPO) and the tropical Atlantic warming associated with the Atlantic Multi-decadal Oscillation (AMO) stimulate Rossby wave trains propagating to the West Antarctic, resulting in the contrasting moisture divergence and precipitation changes between the western and eastern parts of West Antarctica. In particular, the statistical analysis and model simulation clarify the seasonality of these teleconnections. Both the Pacific and Atlantic contribute to the dipole-like SMB pattern during austral spring and autumn, while the Pacific is the major contributor during austral summer. Our findings have broad implications for understanding the recent observed SMB trends as well as the projecting future changes in the Antarctic SMB and consequent global sea level rise.