Advancing the understanding of cyclone impacts on Arctic sea-ice concentration and sea-ice lead formation

Abstract

Cyclones are an important driver of heat and moisture transport into the Arctic and additionally cause high wind speeds and abrupt wind direction changes during their passage. The subsequent impacts on the Arctic sea ice cover consist of i) a thermodynamic stalling/enhancement of the seasonal sea-ice growth/melt, and ii) enhanced drift and deformation of sea ice. The statistical quantification of these cyclone impacts on the Arctic sea-ice cover is a very recent research topic. By conducting a climatological monthly analysis based on the ERA5 reanalysis and a cyclone tracking algorithm, we reveal a distinct seasonal cycle of cyclone impacts on sea-ice concentration in the Atlantic Arctic Ocean (strong impacts from autumn to spring, but weak impacts in summer). We further demonstrate that the cyclone impacts have changed significantly throughout the last four decades in a warming Arctic, magnitude-wise strongest in the Barents Sea in autumn. Still, open questions remain with respect to the impacts of cyclones on the Arctic sea ice in the present climate and regarding their possible changes in a warming Arctic. Specifically, the influence of cyclone passages on the formation of leads in the sea-ice cover has not been statistically analyzed so far. Thus, we extend our analysis to cyclone related changes in sea-ice lead fraction derived from horizontally high-resolved (down to 1km²) MODIS sea-ice observations. Our results indicate that cyclone passages significantly increase sea-ice lead fraction in large parts of the central Arctic Ocean. Mixed results are found for the Arctic marginal seas. The analysis of particular cyclone cases further suggests that groups of consecutive cyclones traversing the sea ice within short time are particularly effective in driving changes in sea-ice concentration and lead fraction. The statistical quantification of the importance of such a temporal clustering of cyclones for their sea-ice impacts is topic of ongoing research.