A 5-YEAR SATELLITE CLIMATOLOGY OF WINTER SEA-ICE LEADS IN THE WESTERNARCTIC

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 th ermal- and visible-band imagery. The occurrence (density) and orientat ion of leads are derived from gridded maps made at 10-day intervals. T heir mean value and interannual, seasonal, and monthly variabilities a re estimated. Lead densities are observed to be highest in early winte r, decreasing 20% from November through April. The highest densities a re observed in the central Canada Basin, and the lowest are in the Eas t Siberian Sea. There is limited interannual variability in the positi ons of maximum and minimum densities. Preferred lead orientations are identified as generally north-south in the Beaufort Sea sector and eas t-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.