Arctic Ocean

Three forms of ice are found in the Arctic Ocean: land ice, river ice, and sea ice. Land ice enters the ocean in the form of icebergs, which are created when pieces of glaciers break off. In the Arctic Ocean, icebergs are created primarily along the coasts of Greenland. The freezing of fresh water, and its subsequent transport into the ocean by rivers, produces nearshore concentrations of river ice over small areas of the Siberian and North American shelves. Sea ice is formed by the freezing of seawater. It is the most extensive form of ice in the Arctic Ocean. In winter a permanent cap of sea ice covers all of the ocean surface, except for the area north-east of Iceland and north of Scandinavia. In summer the ice cover shrinks to expose narrow bands of relatively open water along the coasts of most of Siberia, Alaska, and Canada. The ice cap is composed of pack ice—that is, pieces of ice that pile up and are pressed in ridges or hummocks that may be more than 10 m (33 ft) in depth.

Fish, in commercially exploitable quantities, are found only in the warmer marginal seas of the Arctic Ocean, notably in the North Sea (herring, cod, and flounder) and the Barents Sea (primarily cod). Sea mammals, including various species of seal and whale, were hunted to near extinction before being protected by quotas set during the 1900s. Tin is actively mined off the coast of eastern Siberia, and petroleum and natural gas are extracted north of Alaska and Canada and in the North Sea.