Role of Arctic Cyclones of Different Origins in Poleward Heat Transport into the Arctic

Arctic cyclones of midlatitude origin (ACM) have a more asymmetric structure than Arctic cyclones of polar origin (ACP) in both summer and winter, with a southerly flow east of the cyclone center stronger than the northerly flow to the west. ACMs are also associated with more extensive tropospheric warm temperature anomalies east of the cyclone center than ACPs. We found that more frequent ACM occurrence in boreal winter leads to stronger eddy heat transport into the Arctic, while the ACP activity is not strongly related to poleward heat transport. In boreal summer, ACPs and ACMs contribute to eddy heat transport over different latitude bands.

Composite analysis suggests that the frequency and spatial distribution of ACMs and ACPs are closely related to the large-scale mean flow. In winter, strong zonal wind over Greenland Sea favors active ACPs that populate the central Arctic, while ACM activity tends to be higher than normal when the polar jet is displaced northward and extends further eastward toward the Nordic Seas and northern Europe. High ACP activity in summer is associated with a well-defined Arctic jet along the coast of the Arctic Ocean and a weaker polar jet in the midlatitudes. The Arctic Ocean is anomalously cold, and the Euro-Asia continent is anomalously warm. When summer ACMs are active, the polar jet extends from the North Atlantic through northern Europe to West Asia.

A negative relationship exists between ACP and ACM track densities, as environmental conditions in favor of one type tend to suppress the other type. The relationship is stronger in boreal summer and autumn and is weaker in winter and spring.