The Influence of the Arctic Frontal Zone on Summer Cyclone Activity Today and in the Future

• Main Author: Crawford-Alley, Alexander D.
• Format: Text
• Language: unknown
• Published: CU Scholar 2017
• Subjects: Arctic; Atmospheric Reanalyses; Climate Change; Climate Modeling; Extratropical Cyclones; Atmospheric Sciences; Physical and Environmental Geography; Arctic Ocean; Climate change; Global warming
• Online Access: https://scholar.colorado.edu/geog_gradetds/102; https://scholar.colorado.edu/cgi/viewcontent.cgi?article=1103&context=geog_gradetds

Extratropical cyclone activity over the central Arctic Ocean reaches its peak in summer. Along with local genesis, previous research has argued for the existence of two major external cyclone source regions contributing to this summer maximum: the Eurasian continent interior and a narrow band of strong horizontal temperature gradients along the Arctic coastline known as the Arctic frontal zone (AFZ). This study incorporates data from an atmospheric reanalysis and an advanced cyclone detection and tracking algorithm to critically evaluate the relationship between the summer AFZ and cyclone activity in the central Arctic Ocean. Next, it uses the Community Earth System Model Large Ensemble to assess how the AFZ, Arctic cyclone activity, and the relationship between them respond to a global warming scenario. Analysis of both individual cyclone tracks and seasonal fields of cyclone characteristics shows that the Arctic coast (and therefore the AFZ) is not a region of cyclogenesis. Rather, the AFZ acts as an intensification area for systems forming over Eurasia. As these systems migrate toward the Arctic Ocean, they experience greater deepening in situations when the AFZ is strong at midtropospheric levels. On a broader scale, intensity of the summer AFZ at midtropospheric levels has a positive correlation with cyclone intensity in the Arctic Ocean during summer, even when controlling for variability in the northern annular mode. Taken as a whole, these findings suggest that the summer AFZ can intensify cyclones that cross the coast into the Arctic Ocean, but focused modeling studies are needed to disentangle the relative importance of the AFZ, large-scale circulation patterns, and topographic controls. Under a strong warming scenario, the AFZ remains a significant cyclone intensifier, and changes to the AFZ are largely restricted to June. The AFZ develops earlier in the year and appears stronger in June. This strengthening is accompanied by enhanced cyclogenesis along the east Siberian coast in June, but no change is observed for overall cyclogenesis or cyclone frequency and intensity in the Arctic. Cyclone-associated precipitation rises in all summer months, but this is likely driven by thermodynamic changes, not changes to cyclone development.