Poleward shift of Circumpolar Deep Water threatens the East Antarctic Ice Sheet

Ocean changes could affect the East Antarctic Ice Sheet and its contribution to sea level rise. Oceanographic observations off East Antarctica show substantial warming of mid-depth Circumpolar Deep Water, linked to poleward wind shifts, with implications for glacial melt and ice sheet stability. Future sea-level rise projections carry large uncertainties, mainly driven by the unknown response of the Antarctic Ice Sheet to climate change. During the past four decades, the contribution of the East Antarctic Ice Sheet to sea-level rise has increased. However, unlike for West Antarctica, the causes of East Antarctic ice-mass loss are largely unexplored. Here, using oceanographic observations off East Antarctica (80-160 degrees E) we show that mid-depth Circumpolar Deep Water has warmed by 0.8-2.0 degrees C along the continental slope between 1930-1990 and 2010-2018. Our results indicate that this warming may be implicated in East Antarctic ice-mass loss and coastal water-mass reorganization. Further, it is associated with an interdecadal, summer-focused poleward shift of the westerlies over the Southern Ocean. Since this shift is predicted to persist into the twenty-first century, the oceanic heat supply to East Antarctica may continue to intensify, threatening the ice sheet's future stability.

Automated summary

Ocean changes near East Antarctica could impact ice sheet stability and sea level rise. The warming of mid-depth Circumpolar Deep Water, linked to poleward wind shifts, may contribute to ice-mass loss and coastal water-mass reorganization. This change is predicted to persist into the twenty-first century, intensifying the oceanic heat supply to East Antarctica and posing a threat to the ice sheet's stability.