PNNL

Abstract

Arctic extreme precipitation (EP) broadly impacts permafrost degradation, glaciers and snow cover changes and ice sheet mass balance as well as ecosystems. However, investigation of EP spatiotemporal variations over Arctic remains challenging, and their primary drivers are still poorly understood. Performance estimation of three state-of-the-art reanalysis products (CFSR, ERA5 and MERRA-2) against gauge-based precipitation observations reveals that MERRA-2 outperforms other reanalysis for Arctic EP changes. Based on MERRA-2 data, both annual EP amount and occurrence days averaged over the Arctic show statistically significant positive trends during 1980-2022 (3.37±1.03 mm decade-1 and 0.42±0.17 days decade-1, respectively), with the most pronounced increase in autumn. Spatial heterogeneity in annual and seasonal EP trends is found across the Arctic, with the largest positive annual trends of mm decade-1 23 over the Bering Sea and the Denmark Strait. The significant EP increase is closely associated with intensified atmospheric rivers (ARs) and widespread decline in sea ice concentration (SIC). Specially, SIC and ARs are responsible for 12% and 50% of Arctic EP inter-annual variance, respectively, while ARs directly contribute 28.3% of total annual EP amounts. These findings explain the mechanistic controls on Arctic EP, providing critical insights for projecting polar weather and climate extremes and their impacts on Arctic environment.