Antarctica completely collapsed 9,000 years ago under similar climate conditions as Earth has today

Abstract

Circumpolar Deep Water inflow onto Antarctica’s continental shelves is a key driver of accelerated Antarctic Ice Sheet mass loss, both presently and during the last deglaciation. However, the mechanisms driving enhanced inflow and the resultant impact on large-scale ice-sheet retreat events are still not fully understood. Here we address this topic using marine sediment cores from Lützow–Holm Bay, East Antarctica, through analyses of sedimentary beryllium isotopes and complementary proxies. These records, when compared to inland mountain outcrop records, show that ice-shelf collapse and simultaneous inland ice-sheet thinning ~9,000 years ago were associated with enhanced Circumpolar Deep Water inflow and sea-level rise. A hierarchical modelling approach that combines climate and high-resolution ocean simulations suggests that freshwater discharge from adjacent Antarctic sectors into the Southern Ocean probably enhanced the regional inflow into submarine troughs in Lützow–Holm Bay between 10,000 and 9,000 years ago. We propose a feedback loop whereby meltwater from rapidly retreating Antarctic sectors since the Last Glacial Maximum enhanced stratification and Circumpolar Deep Water incursions onto adjacent shelves. Alongside relative sea-level rise, this meltwater feedback triggers further ice-shelf instability and enhances dynamic inland ice discharge, highlighting a mechanism relevant to future Antarctic Ice Sheet changes.