Recent intensification of extreme precipitation over East Antarctica driven by increases in greenhouse gases and stratospheric ozone

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Abstract. Extreme precipitation is a major contributor to the total precipitation over Antarctica and its variability. However, it remains poorly understood whether Antarctic extreme precipitation has undergone recent changes and, if so, whether these changes are anthropogenically driven. Using ERA5 reanalysis for 1979–2023, we identify significant regional trends in total and extreme precipitation across Antarctic drainage basins, including significant increases over the Filchner-Ronne sector, Dronning Maud Land, and Enderby Land in East Antarctica. We then perform a regression-based detection and attribution analysis of these trends using precipitation outputs from CESM1 global climate model large ensembles based on “all-forcing” experiments and “single-forcing” experiments that isolate the effects of greenhouse gases, anthropogenic aerosols, and stratospheric ozone. For five of the six basins exhibiting positive trends in total precipitation (within the Filchner-Ronne sector, Dronning Maud Land, and Enderby Land) and three of the four basins exhibiting positive trends in extreme precipitation (within Dronning Maud Land and Enderby Land), the ERA5 signal was formally detected in the CESM1 all-forcing simulations, indicating that these trends are driven by a combination of anthropogenic and natural forcings. Our analysis further show that for one basin (within Enderby Land) the increases in total and extreme precipitation are robustly attributed to greenhouse gases and stratospheric ozone, while for another basin (within Dronning Maud Land) the increases in total precipitation are attributed to stratospheric ozone only. In contrast, none of the precipitation trends could be attributed to anthropogenic aerosols despite all-forcing and single-forcing simulations of anthropogenic aerosols exhibiting similar trend patterns. Applying the same analysis to CESM2 large ensembles confirmed that the ERA5 precipitation signal was detected in the all-forcing simulations but unlike CESM1 did not provide robust attribution of total or extreme precipitation to any individual forcing. These findings provide evidence that external drivers have already impacted East Antarctic total and extreme precipitation, while demonstrating that uncertainties in attributing individual forcings remain a key limitation in understanding future changes to the Antarctic surface mass balance.

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