Disappearance of the El Niño-driven surface mass gain in West Antarctica under future climate change

Abstract Strong El Niño events drive substantial snowfall in West Antarctica, including the Antarctic Peninsula, by weakening the Amundsen Sea Low (ASL) through atmospheric teleconnections, increasing surface mass balance, and mitigating ice mass loss’s contribution to sea-level rise. However, we find that CMIP6 projections show a diminishing El Niño-driven precipitation effect as global warming intensifies. The El Niño-associated precipitation anomaly is projected to weaken in SSP3-7.0 and SSP5-8.5, becoming indistinguishable from zero by the late 21st century in the latter. This transition is caused by a strengthened polar jet, linked to a positive Southern Annular Mode (SAM) trend in a warmer climate, which extends the wavelength of Rossby waves. As a result, the ASL anomaly eventually migrates eastward and equatorward, reducing water vapor transport into West Antarctica’s interior. These findings indicate that El Niño-driven precipitation disappears in a high-emission future, eliminating one of the buffering mechanisms that help counteract sea-level rise.