Identifying the Impacts of Sea Ice Variability on the Climate and Surface Mass Balance of West Antarctica

The Antarctic ice sheet (AIS) is the largest freshwater body on Earth and a major component of the sea level budget. Over the satellite era, the AIS has experienced ∼130 Gt/year of mass loss. Net losses are partially mitigated by snow accumulation that varies ∼100–130 Gt/yr, underscoring a need to understand the drivers of snowfall variability. Here, we evaluate impacts of decreased sea ice in the Amundsen Sea region of West Antarctica on the overlying atmosphere and surface mass balance of the adjacent AIS using composites, spatial correlations, and a causal effect network method. Importantly, our findings show sea ice declines in the Amundsen Sea lead to enhanced integrated water vapor that is subsequently transported to the AIS resulting in positive anomalies in West Antarctic ice sheet snowfall. Our results suggest future decreases in sea ice may likely enhance ice sheet snowfall, thus partially offsetting Antarctic sea level contributions. Plain Language Summary The Antarctic ice sheet (AIS) is the largest freshwater body on Earth and is a major component of the sea level budget. Since the start of the satellite record in 1980, the AIS has been losing mass at an increasing rate. These losses are attributed to increased flow of ice into the ocean and are partially balanced each year by the accumulation of snow across the ice sheet's surface. The degree to which it snows across Antarctica therefore controls how much the ice sheet contributes to sea level in any given year. Thus, it is crucial for us to understand the drivers of snowfall variability. Here, we evaluate the impacts of decreased sea ice in the Amundsen Sea region of West Antarctica on snowfall over the adjacent ice sheet. Importantly, our findings show that sea ice declines in this region lead to enhanced moisture in the atmosphere which is then transported over the West Antarctic ice sheet resulting in greater snowfall. Key Points Observations and reanalyzes reveal decreased sea ice leads to increased precipitation over the West Antarctic ice sheet Causal discovery links low sea ice to enhanced water vapor and precipitation‐bearing clouds over the ice sheet Past and future changes in sea ice hold implications for ice sheet surface mass balance