An area of open water, surrounded by sea ice. They are generally found in the same region year after year. These patches can vary from a few square kilometres, to thousands of square kilometres. The North Water polynya in Canada's Arctic is estimated at more than 50,000 square kilometres. It's in the northern end of Baffin Bay between Ellesmere Island and Greenland. Polynyas are formed by a combination of factors, including currents, tides and winds. Because of their exposure to the sun's rays, polynyas are hosts for animals and plants, and are sometimes referred to as oases of the Arctic.
Large enclosed openings in the ice cover, due to currents or upwelling. They are biologically important in that they provide open water in winter used by birds and mammals and present an ice edge with increased productivity.
irregularly shaped areas of persistent open water that are sustained by winds or ocean heat; they often occur near coasts, fast ice, or ice shelves. Satellite view of polynyas (dark areas) near Oates Coast, Antarctica (solid white area at bottom of photo). (Photo courtesy of NASA.)