ARCTIC CYCLONES: AN IMPACT-TARGETED ASSESSMENT OF TRENDS

Abstract:

Among extreme events in the Arctic, cyclones arguably have the most direct impacts. Evidence for ongoing trends in cyclone occurrences in high latitudes is mixed, as are indications of future trends in projections by global climate models. Here we assess trends in Arctic cyclones over the past 40 years based on reanalysis output in a framework of coastal vulnerability. Specifically, the frequency of storms within a prescribed distance of the coast is evaluated with and without sea ice protecting the coastline. The procedure is repeated with an intensity-weighting of the cyclones. While trends of total occurrences are generally not statistically significant, trends of occurrences without sea ice are highly significant in regions such as Alaska where the open water season has lengthened. The increase is greatest in the late summer and autumn in regions near the boundary of minimum extent, but there are also detectable increases during the winter months in the Bering Sea and in the North Atlantic subarctic. The results point to the dominance of trends of sea ice over raw cyclone frequencies in the future trajectory of coastal impacts of high-latitude storms.