On the relevance of serial cyclone clustering for Arctic sea ice.

Short-term changes in Arctic sea-ice concentration (SIC) are largely driven by weather, and strong ice loss typically occurs during intense Arctic cyclones causing unusually warm and stormy conditions. Such conditions are prolonged when several cyclones follow rapidly on each other. Here, we analyze changes in SIC for such periods of serial cyclone clustering utilizing satellite observations and reanalysis data from 1979-2024. While cyclones generally decrease SIC compared to non-cyclone conditions, cyclone clusters impact the ice approximately 2.5 times longer and cause two times stronger overall SIC-reductions than solitary cyclones. The amount of SIC-loss due to cyclone clusters scales with the intensity and number of clustered cyclones, and intensified SIC-loss occurs from 2004-2024 compared to 1979-1999, even within fixed SIC-categories. These findings highlight the relevance of accumulated impacts of clustered weather events for Arctic sea-ice variability and emphasize the need to understand drivers of serial cyclone clustering in the Arctic.