The Arctic Ocean is at the extreme north of the Earth. It exists at and round the North Pole and most of it is frozen for the whole year round.  In winter explorers have trekked over the ice to the North Pole. The Arctic Ocean is smaller and shallower than the other Oceans and it is sometimes called the Arctic Sea. The corresponding ocean near the South Pole is the Southern Ocean.
One fact of great potential importance is now being studied—the Arctic Ocean is warming. Recorded temperatures, glacial regressions, and the appearance of observed species of fish in larger numbers, at higher latitudes, at earlier seasons, and for long periods prove that over the decades a "climatic improvement" has taken place. Similar changes have been reported in sub-Arctic latitudes. Whether this warming is a phase in a cycle or a permanent development has long been a question, but most scientists now believe that it is due to global warming. The warming may be affecting wind patterns above the region, amplifying the depletion of the ozone layer and possibly increasing precipitation. The area of the Arctic Ocean covered by year-round ice has decreased considerably since the late 1970s, and an increased amount of fresh water is entering the ocean from bordering rivers. Most researchers expect that, due to global warming, the ocean will become ice-free during the summer sometime between 2030 and 2070. Ice melting in the Arctic and Antarctic could raise sea levels and submerge many low lying cities.