Abstract:

Cyclones generated south of the Arctic and migrating northward into the polar region are often accompanied by strong wind, precipitation and warming events during their development and migration. These cyclones transport heat and matter from mid-low to high latitudes, impacting the atmosphere, ocean, and sea ice in the polar region. An automatic cyclone recognition and tracking algorithm based on mean sea level pressure was used to automatically identify and track cyclones passing through the 70°N latitude from the south to the north. We found there were more cyclones in spring and winter than in summer and autumn. The annual number of cyclones decreased. Decreasing trends were also found in the numbers of cyclones in spring, autumn and winter. Strong cyclones were likely to occur in winter and weak cyclones occurred frequently in summer. Cyclone trajectories concentrated over the ocean in winter and over land in summer.  The cyclones travel northward over an average span of 9.2° in latitude. Winter cyclones traveled over an average of 10.2°, while summer cyclones traveled over an average of 7.3° in latitude. On the interannual scale, the annual averaged northward range in latitude increased over our study period. The range in spring and winter also increased, while the range in summer and autumn decreased. On the interdecadal scale, the annual averaged northward range, as well as the ranges in summer and winter de-creased from 1979–1988 to 1989–1998. They increased between 1999–2008, and decreased again after 2008. In contrast, no clear trends were detected for spring and autumn.

Key words: Arctic, cyclones, passing through 70°N, northward migration, main features