Interannual Variations in the Summer Arctic Frontal Zone

Abstract:

A notable characteristic of the summertime Arctic is the existence of a narrow band of strong horizontal temperature gradients spanning the coastlines of Siberia, Alaska, and western Canada that extends through a considerable depth of the troposphere. Past research has associated this summer Arctic Frontal Zone (AFZ) with contrasts in atmospheric heating between the Arctic Ocean and snow-free land, with its regional strength strongly influenced by topography. However, little is known about its variability. We take advantage of output from the latest generation of global atmospheric reanalyses to better constrain and define the spatial and seasonal characteristics of the summer AFZ and evaluate the relative importance of different factors linked to its variability.

Interannual variations in AFZ strength are primarily dependent on factors affecting temperature over land, especially variability in cloud cover, surface wind direction, and snow cover extent. Local variability in sea ice concentration is also important through its control on temperatures over coastal seas. However, the relative importance of each factor is spatially heterogeneous, and while some factors (like snow cover) are particularly important to early AFZ development in May, other factors (like sea ice concentration) have greater influence on peak AFZ strength in July. Lastly, earlier retreat of both snow cover extent and sea ice concentration each spring and summer has changed the timing of summer AFZ development since 1979, but peak strength has not experienced significant change.