Polynya

A polynya, a term borrowed from Russian, is an area of open water surrounded by sea ice, occurring within otherwise continuous pack ice or fast ice. Coastal polynyas form in two ways: sensible heat polynyas occur where upwelling warm water keeps the surface at or above freezing and slows ice formation, while latent heat polynyas form where katabatic winds drive newly formed ice away from a fixed coastline, so new ice keeps forming and being pushed out to sea. Mid-sea polynyas open instead under particular atmospheric conditions over pre-conditioned ocean areas, where polar cyclones and cold fronts create opposing winds that push pack ice away from a central point; the Weddell Polynya, over the Maud Rise seamount in the Lazarev Sea, is a well-known example. Coastal polynyas appear year after year near the Arctic and Antarctic coasts, including the North Water Polynya between Canada and Greenland and polynyas near Hudson Bay and Alaska, and both people and wildlife have long depended on them for food and survival.