Arctic Atmospheric Rivers in a Changing Climate and the Impacts on Sea Ice

Abstract Atmospheric rivers (ARs) transport heat and moisture from lower latitudes to the Arctic, contributing to sea ice loss. As climate warming and sea ice decline continue, understanding how Arctic ARs evolve is essential. While studies suggest an increase in Arctic ARs and storms, a comprehensive understanding of their changing behavior, seasonal patterns, and sea ice impacts remains incomplete. This study investigates the changing dynamics of Arctic ARs in response to a warming climate, examining the drivers of these changes and their impact on sea ice. Using the Community Earth System Model, Version 2 (CESM2), we find CESM2 effectively simulates Arctic ARs compared to ERA5. To analyze ARs under different climate conditions, we apply three detection methods: using present climate thresholds, scaling thresholds with projected future moisture changes, and calculating unique thresholds for each decade. Our results show increased AR frequency and intensity in the future, with changes strongly influenced by the chosen AR definition. Depending on the method, we find that AR frequency increases range from 30%–50% up to 400%, or even show decreases in some regions. During fall and winter, the North Atlantic experiences increased AR frequency, while more intense ARs occur in the North Pacific during summer. We also explore the effects of future ARs on sea ice, finding a net increase in sea ice loss, particularly in winter and spring. The extent of sea ice loss is highly sensitive to the AR detection method used.