Cyclone Impacts on Sea Ice Concentration in the Atlantic Arctic Ocean: Annual Cycle and Recent Changes

We quantify sea ice concentration (SIC) changes related to synoptic cyclones separately for each month of the year in the Greenland, Barents and Kara Seas for 1979-2018. We find that these SIC changes can be statistically significant throughout the year. However, their strength varies from region to region and month to month, and their sign strongly depends on the considered time scale (before/during vs. after cyclone passages). Our results show that the annual cycle of cyclone impacts on SIC is related to varying cyclone intensity and traversed sea ice conditions. We further show that significant changes in these cyclone impacts have manifested in the last 40 years, with the strongest changes occurring in October and November. For these months, SIC decreases before/during cyclones have more than doubled in magnitude in the Barents and Kara Seas, while SIC increases following cyclones have weakened (intensified) in the Barents Sea (Kara Sea). We study how the sea ice cover in the Arctic Ocean changes due to the passage of low-pressure systems (cyclones). Our study covers all years between 1979 and 2018 and each individual month of the year. Our results show that the passage of cyclones can affect the sea ice year around, but the strength and the sign (less or more sea ice concentration due to cyclones) of this impact varies strongly. These variations in cyclone impacts throughout the year are related to variations in the strength of the cyclones and changes in the state of the sea ice cover (e.g., thinner vs. thicker ice). We further show that the cyclone impact on the Arctic sea ice has changed during the last 40 years. These changes are strongest in autumn, particularly in October and November. In these months, the strength of the destructive cyclone impacts on sea ice has more than doubled in some regions of the Arctic compared to previous times. In some regions, however, also the strength of ice preserving cyclone impacts (more sea ice due to cyclones) has intensified recently. Cyclones can significantly impact the sea ice in the Atlantic Arctic in all months of the year, but with strong spatiotemporal variationsImpacts are stronger in the cold season than in summer due to variations in cyclone intensity and traversed sea ice conditionsSignificant changes emerged throughout the year, recently strongest in the Barents Sea in autumn due to a reduced mean ice concentration