West Antarctic Ice Sheet advance since the early Pliocene

Abstract

Abstract Current understanding of past ice dynamics in the Amundsen Sea—the most vulnerable part of the West Antarctic ice sheet (WAIS)—remains incomplete, hampering future predictions. Here, sediments from International Ocean Discovery Program Site U1532 on the continental rise reveal that ice-sheet dynamics strongly influenced detrital magnetic minerals supply. Minimal magnetite concentration during ~4.1-3.8 Ma reflects the smallest WAIS extent in the Amundsen Sea sector since ~4.33 Ma. Since ~4.1 Ma, WAIS expansion was closely linked to long-term global cooling. After ~3.2 Ma, elevated fine-grained magnetite indicates a sustained increase in sediment contribution from the Thwaites Glacier catchment. The abrupt ice-sheet expansion at ~3.2 Ma may reflect the crossing of a climatic threshold that triggered qualitative transformations in ice-sheet development. Cessation of major WAIS growth after ~0.9 Ma aligns with stabilized long-term CO 2 levels and ocean temperatures. Collectively, these results underscore the high sensitivity of the Amundsen Sea sector to global climate forcing.