Unprecedented 2024 East Antarctic winter heatwave driven by polar vortex weakening and amplified by anthropogenic warming.

During July-August 2024, East Antarctica experienced the most intense winter heatwave in the 46-year satellite era, with regional mean surface air temperatures across Dronning Maud Land exceeding the climatological mean by more than 9°C for 17 consecutive days. To explore the physical drivers and quantify the anthropogenic contribution to this unprecedented event, we propose a multi-model, multi-method attribution framework integrating regional climate model-based storyline attribution, circulation analogues, and large-ensemble probabilistic attribution. The results show that a pronounced weakening of the stratospheric polar vortex initiated a quasi-barotropic high-pressure anomaly, which enhanced meridional heat and moisture transport and accounted for approximately 50% of the observed surface warming. Across different models and attribution methods, synthesis of the attribution results indicates that anthropogenic warming intensified the event by approximately 0.7°C and more than doubled the likelihood of such exceptional winter heatwaves in the current climate. Probabilistic attribution further indicates that, compared to a natural climate without human influence, the likelihood of such events increases from 2-3 times today to ~6 times under moderate emissions and up to 26 times under high emissions by 2100. These findings reveal how human-induced warming is transforming even the coldest regions, with implications for ice shelf stability and predictability of future Antarctic extremes.