<P> The Labrador, Norwegian, Greenland, and Barents Seas and Denmark and Davis Straits are strongly influenced by the cyclones in the North Atlantic storm track, which is most active in winter . As a result, these regions receive more precipitation in winter than in summer . Annual precipitation totals increase quickly from about 400 mm (16 in) in the northern to about 1400 mm (55 in) in the southern part of the region (Serreze and Hurst 2000). Precipitation is frequent in winter, with measurable totals falling on an average of 20 days each January in the Norwegian Sea (USSR 1985). The Bering Sea is influenced by the North Pacific storm track, and has annual precipitation totals between 400 mm and 800 mm (16 and 31 in), also with a winter maximum . </P> <P> Sea ice is frozen sea water that floats on the ocean's surface . It is the dominant surface type throughout the year in the Arctic Basin, and covers much of the ocean surface in the Arctic at some point during the year . The ice may be bare ice, or it may be covered by snow or ponds of melt water, depending on location and time of year . Sea ice is relatively thin, generally less than about 4 m (13 feet), with thicker ridges (NSIDC). NOAA's North Pole Web Cams having been tracking the Arctic summer sea ice transitions through spring thaw, summer melt ponds, and autumn freeze - up since the first webcam was deployed in 2002--present . </P> <P> Sea ice is important to the climate and the ocean in a variety of ways . It reduces the transfer of heat from the ocean to the atmosphere; it causes less solar energy to be absorbed at the surface, and provides a surface on which snow can accumulate, which further decreases the absorption of solar energy; since salt is rejected from the ice as it forms, the ice increases the salinity of the ocean's surface water where it forms and decreases the salinity where it melts, both of which can affect the ocean's circulation (NSIDC). </P> <P> The map at right shows the areas covered by sea ice when it is at its maximum extent (March) and its minimum extent (September). This map was made in the 1970s, and the extent of sea ice has decreased since then (see below), but this still gives a reasonable overview . At its maximum extent, in March, sea ice covers about 15 million km2 (5.8 million sq mi) of the Northern Hemisphere, nearly as much area as the largest country, Russia (UNEP 2007). </P>

How does salinity of the artic ocean change with the seasons