Abstract

Mass loss from the West Antarctic Ice Sheet (WAIS) has been well documented during the era of satellite observations. That loss has been attributed to warming of seawater on the adjacent continental shelf, or continuing ice response to a past climate anomaly, but may result from some combination of related processes. Here we report ocean measurements over a 16-year period near the Dotson Ice Shelf and estimate changes in its basal melting, compared with the flux of its glaciers into the sea. Decadal variability dominates the ocean records, and melting responds by factors of 3-6 between cool and warm extremes via a non-linear relationship with ocean temperature. The most recent warm phase caused ice shelf thinning and grounding line retreat, while some re-advance occurred during the subsequent cool phase. We argue that coherent regional ocean variability causes the more sustained mass loss from this sector of the WAIS , with warm extremes initiating episodes of inland thinning that are often only slightly damped by cool periods. The particular vulnerability of the ice sheet in the Amundsen Sea embayment can therefore be explained by the combination of ocean thermal forcing that is sensitive to wind changes and highly variable regional atmospheric circulation.