Arctic Ocean

The Arctic Ocean is divided by the underwater Lomonosov Ridge into two principal basins—the Canadian and the Eurasian. The ridge runs from the New Siberian Islands to Ellesmere Island, passing about 60 miles (100 km) from the North Pole.

Both basins are generally more than 6,000 feet (1,800 m) deep; in many places, they reach twice that depth. The greatest known depth, 18,399 feet (5,608 m), is in the Molloy Deep, between Svalbard and Greenland. At the North Pole the ocean is 13,410 feet (4,087 m) deep.

The central basins are ice-covered the year round. Ice thickness varies from about nine feet (2.7 m) in winter to less than six feet (1.8 m) in summer. During the warm season, as air and water temperatures rise, the ice cracks and separates into large slabs, called pancake ice. Travel across this ice is almost impossible. In winter, dog sledges and vehicles can move more freely across the solidly frozen ice pack; light airplanes can take off and land.

Most icebergs of the North Atlantic come from the glaciers in Greenland. Bergs that drift far out to sea may become a menace to shipping.

Bordering most Arctic lands is the continental shelf, a gently sloping seaward extension of the continents. The shelf is covered by the shallow parts of numerous seas, including the Chukchi, East Siberian, Laptev, Kara, Barents, Norwegian, Greenland, and Beaufort seas. These Arctic seas are slightly warmer than the central basins and are rich in fish and smaller marine life.