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Arctic Ocean
From Wikipedia, the free encyclopedia
(World Ocean)
- Arctic Ocean
- Atlantic Ocean
- Indian Ocean
- Pacific Ocean
- Southern Ocean
The Arctic Ocean, located in the Northern Hemisphere and mostly in the Arctic north polar region, is the smallest, and shallowest of the world's five major oceanic divisions.[1] The International Hydrographic Organization (IHO) recognizes it as an ocean, although some oceanographers call it the Arctic Mediterranean Sea or simply the Arctic Sea, classifying it as one of the mediterranean seas of the Atlantic Ocean.[2] Alternatively, the Arctic Ocean can be seen as the northernmost lobe of the all-encompassing World Ocean.
Almost completely surrounded by Eurasia and North America, the Arctic Ocean is partly covered by sea ice throughout the year[3] (and almost completely in winter). The Arctic Ocean's temperature and salinity vary seasonally as the ice cover melts and freezes;[4] its salinity is the lowest on average of the five major oceans, due to low evaporation, heavy freshwater inflow from rivers and streams, and limited connection and outflow to surrounding oceanic waters with higher salinities. The summer shrinking of the ice has been quoted at 50%.[1] The National Snow and Ice Data Center (NSIDC) use satellite data to provide a daily record of Arctic sea ice cover and the rate of melting compared to an average period and specific past years.
Geography
The Arctic Ocean occupies a roughly circular basin and covers an area of about 14,056,000 km2 (5,427,000 sq mi), almost the size of Russia.[5] The coastline is 45,390 km (28,200 mi) long.[5] It is surrounded by the land masses of Eurasia, North America, Greenland, and by several islands.
It is generally taken to include Baffin Bay, Barents Sea, Beaufort Sea, Chukchi Sea, East Siberian Sea, Greenland Sea, Hudson Bay, Hudson Strait, Kara Sea, Laptev Sea, White Sea and other tributary bodies of water. It is connected to the Pacific Ocean by the Bering Strait and to the Atlantic Ocean through the Greenland Sea and Labrador Sea.[1]
Extent
The International Hydrographic Organization defines the limits of the Arctic Ocean proper (that is, excluding the seas within the Ocean) as follows:[6]
Between Greenland and West Spitzbergen [sic] — The Northern limit of Greenland Sea.
Between West Spitzbergen and North East Land — the parallel of lat. 80°N.
From Cape Leigh Smith to Cape Kohlsaat — the Northern limit of Barentsz Sea [sic].
From Cape Kohlsaat to Cape Molotov — the Northern limit of Kara Sea.
From Cape Molotov to the Northern extremity of Kotelni Island — the Northern limit of Laptev Sea.
From the Northern extremity of Kotelni Island to the Northern point of Wrangel Island — the Northern limit of East Siberian Sea.
From the Northern point of Wrangel Island to Point Barrow — the Northern limit of Chuckchi Sea [sic].
From Point Barrow to Cape Land's End on Prince Patrick Island — the Northern limit of Beaufort Sea, through the Northwest coast of Prince Patrick Island to Cape Leopold M'Clintock, thence to Cape Murray (Brook Island) and along the Northwest coast to the extreme Northerly point; to Cape Mackay (Borden Island); through the Northwesterly coast of Borden Island to Cape Malloch, to Cape Isachsen (Ellef Ringnes Island); to the Northwest point of Meighen Island to Cape Stallworthy (Axel Heiberg Island) to Cape Colgate the extreme West point of Ellesmere Island; through the North shore of Ellesmere Island to Cape Columbia thence a line to Cape Morris Jesup (Greenland).
Underwater features
An underwater ridge, the Lomonosov Ridge, divides the deep sea North Polar Basin into two oceanic basins: the Eurasian Basin, which is between 4,000 and 4,500 m (13,000 and 15,000 ft) deep, and the Amerasian Basin (sometimes called the North American, or Hyperborean Basin), which is about 4,000 m (13,000 ft) deep. The bathymetry of the ocean bottom is marked by fault-block ridges, plains of the abyssal zone, ocean deeps, and basins. The average depth of the Arctic Ocean is 1,038 m (3,406 ft).[7] The deepest point is in the Eurasian Basin, at 5,450 m (17,880 ft).
The two major basins are further subdivided by ridges into the Canada Basin (between Alaska/Canada and the Alpha Ridge), Makarov Basin (between the Alpha and Lomonosov Ridges), Fram Basin (between Lomonosov and Gakkel ridges), and Nansen Basin (Amundsen Basin) (between the Gakkel Ridge and the continental shelf that includes the Franz Josef Land).
Water flow
The Arctic Ocean contains a major choke point in the southern Chukchi Sea,[8] which provides access to the Pacific Ocean through the Bering Strait between Alaska and Eastern Siberia. Subject to ice conditions, the Arctic Ocean provides the shortest marine link between the extremes of eastern and western Russia. There are several floating research stations in the Arctic, operated by the US and Russia.
The greatest inflow of water comes from the Atlantic by way of the Norwegian Current, which then flows along the Eurasian coast. Water also enters from the Pacific via the Bering Strait. The East Greenland Current carries the major outflow.
Ice covers most of the ocean surface year-round, causing subfreezing air temperatures much of the time. The Arctic is a major source of very cold air that moves toward the equator, meeting with warmer air at latitude 60°N and causing rain and snow. This flow is the lower portion of the polar cell, the highest (by latitude) of the three principal circulation cells of the Earth's atmosphere each spanning thirty degrees of latitude. Marine life abounds in open areas, especially the more southerly waters. The ocean's major ports are the cities of Murmansk, Arkhangelsk and Prudhoe Bay.[8]
Shelves
The Arctic Ocean is encompassed by the Arctic shelves, one of which, the Siberian Shelf, is the largest on Earth.
History
For much of European history, the North Polar regions remained largely unexplored and their geography conjectural. Pytheas of Massilia recorded an account of a journey northward in 325 BC, to a land he called "Eschate Thule," where the Sun only set for three hours each day and the water was replaced by a congealed substance "on which one can neither walk nor sail." He was probably describing loose sea ice known today as "growlers", or "bergy bits." His "Thule" may have been Iceland, though Norway is more often suggested.[9]
Early cartographers were unsure whether to draw the region around the North Pole as land (as in Johannes Ruysch's map of 1507, or Gerardus Mercator's map of 1595) or water (as with Martin Waldseemüller's world map of 1507). The fervent desire of European merchants for a northern passage to "Cathay" (China) caused water to win out, and by 1723 mapmakers such as Johann Homann featured an extensive "Oceanus Septentrionalis" at the northern edge of their charts.
The few expeditions to penetrate much beyond the Arctic Circle in this era added only small islands, such as Novaya Zemlya (11th century) and Spitsbergen (1596), though since these were often surrounded by pack-ice their northern limits were not so clear. The makers of navigational charts, more conservative than some of the more fanciful cartographers, tended to leave the region blank, with only fragments of known coastline sketched in.
This lack of knowledge of what lay north of the shifting barrier of ice gave rise to a number of conjectures. In England and other European nations, the myth of an "Open Polar Sea" was persistent. John Barrow, long time Second Secretary of the British Admiralty, promoted the exploration the region from 1818 to 1845 in search of this.