Repeated loss of the West Antarctic Ice Sheet’s Amundsen Sea sector during late Pleistocene interglacials

Sea-level reconstructions and numerical models suggest that the vulnerable West Antarctic Ice Sheet underwent major mass losses during the late Pleistocene, raising global sea level by several metres. However, direct evidence from ice-sheet proximal records for such retreat has remained inconclusive. Here we investigate variations in clay mineral assemblages and past ocean temperatures archived in West Antarctic continental margin sediments during the last 800,000 years. Our results demonstrate that the supply of glacigenic detritus sourced from the main outlet glaciers in the Amundsen Sea sector of the West Antarctic Ice Sheet ceased almost entirely during all previous warm periods, documenting the loss of their drainage basins. Concomitant seawater warming, revealed by a microfossil proxy, is attributed to intensified deep-water advection towards Antarctica’s Pacific margin, which is corroborated by the clay mineralogical evidence. Our findings show that ocean forcing can drive major deglaciation of West Antarctica and related global sea-level rise.