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.