Record-Breaking Warm Late-Winter Over Antarctica in 2024: The Role of Western Pacific Warm Pool and Pacific Decadal Oscillation

Abstract

Antarctic warm extremes in winter have been one of major concerns because they are sometimes associated with anomalous snowfall and thus increase surface mass balance. Station observations and ERA5 showed that East Antarctic Ice Sheet (EAIS) experienced an unprecedented warm late-winter (July-August) in 2024 since the late 1950s. Record-breaking positive Western Pacific Warm Pool (WP) and negative Pacific Decadal Oscillation in July-August 2024 induced more frequent strong blocking highs over EAIS. Meanwhile, the stratospheric polar vortex weakened and elongated, and a record-negative Southern Annular Mode was observed in August. They caused favorable circulation for atmospheric rivers (ARs) with warm moist air to frequently landfall on EAIS. Heat domes triggered by high-pressure and net longwave radiation anomalies caused by intense moisture transport were largely responsible for the warm late-winter. Our findings underscored the crucial role of tropic teleconnection in mechanism underlying warm extremes during Antarctic winter.