A 5-year satellite climatology of winter sea ice leads in the western Arctic

Abstract

The distribution of openings (leads and polynyas) in polar sea ice is not well known. This study estimates the large-scale distribution and variability of leads in the Arctic of the western hemisphere in winter, using a 5-year record of Defense Meteorological Satellite Program thermal- and visible-band imagery. The occurrence (density) and orientation of leads are derived from gridded maps made at 10-day intervals. Their mean value and interannual, seasonal, and monthly variabilities are estimated. Lead densities are observed to be highest in early winter, decreasing 20% from November through April. The highest densities are observed in the central Canada Basin, and the lowest are in the East Siberian Sea. There is limited interannual variability in the positions of maximum and minimum densities. Preferred lead orientations are identified as generally north-south in the Beaufort Sea sector and east-west in the East Siberian Sea sector, with transitional orientations in the intermediate area. The mean distributions of lead density and orientation are observed to be associated with large-scale mean fields of ice divergence and shear, respectively.