Synchrony of Extreme Warm Events and Extreme Precipitation in Antarctica

Compound extremes pose major threats to socioeconomic and ecological systems. Heatwave and drought events have garnered substantial attention due to their impact on human mortality in densely populated regions. However, delving into extreme events within polar regions shifts our perspective to the simultaneous occurrence of warm anomalies and high precipitation. In this study, we examine the climatological prevalence of concurrent Extreme Warm Events (EWEs) and Extreme Precipitation Events (EPEs) in 1979-2021 utilizing the ECMWF ERA 5 reanalysis for global temperature and precipitation data. Across the globe, the synchrony of EWEs during EPEs is about 15%. Notably, the most striking distinctive synchrony occurs in the polar ice sheets, encompassing Antarctica and Greenland, the average synchrony is 49.9% and 28.7%, respectively. Moreover, on plateaus, this synchrony reaches even higher levels of 70% and 50%, respectively. Our analysis reveals a shift of compound extremes, transitioning from predominantly hot-dry conditions across most ex-polar lands to warm-wet conditions over polar ice sheets. In polar regions, local feedback processes are rather weak, extreme weather is mostly driven by intruding moist air from lower latitudes through long-range advective transport. The occurrence of such compound extreme events can imply profound impacts on polar regions, which could destabilize polar ice sheets and lead to variations in the global sea level.