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The Arctic Ocean, located in the Northern Hemispheremarker and mostly in the Arctic north polarmarker region, is the smallest, and shallowest of the world's five major oceanic divisions. 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 Oceanmarker. 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 (and almost completely in winter). The Arctic Ocean's temperature and salinity vary seasonally as the ice cover melts and freezes; 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%. 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.

The Arctic Ocean


Geography

The Arctic Ocean occupies a roughly circular basin and covers an area of about , almost the size of Russiamarker. The coastline is long. It is surrounded by the land masses of Eurasia, North America, Greenlandmarker, and by several islands. It is generally taken to include Baffin Baymarker, Barents Seamarker, Beaufort Seamarker, Chukchi Seamarker, East Siberian Seamarker, Greenland Seamarker, Hudson Baymarker, Hudson Straitmarker, Kara Seamarker, Laptev Seamarker, White Seamarker and other tributary bodies of water. It is connected to the Pacific Oceanmarker by the Bering Straitmarker and to the Atlantic Ocean through the Greenland Seamarker and Labrador Seamarker.

According to the International Hydrographic Organization, the limits of the Arctic Ocean proper (that is, excluding the seas within the Ocean) are (see the map):

Arctic region
An underwater ridge, the Lomonosov Ridge, divides the deep sea North Polar Basin into two oceanic basins: the Eurasian Basin, which is between deep, and the Amerasian Basin (sometimes called the North American, or Hyperborean Basin), which is about 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 . The deepest point is in the Eurasian Basin, at .

The two major basins are further subdivided by ridges into the Canada Basin (between Alaska/Canadamarker 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 Landmarker).

The Arctic Ocean contains a major choke point in the southern Chukchi Sea, 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 in the middle latitudes and causing rain and snow. Marine life abounds in open areas, especially the more southerly waters. The ocean's major ports are the cities of Murmanskmarker, Arkhangelskmarker and Prudhoe Baymarker.

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 BCE, 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 "growler", or "bergy bits." His "Thule" may have been Icelandmarker, though Norwaymarker is more often suggested.

Early cartographer 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" (Chinamarker) 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 Zemlyamarker (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 chart, 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. In the United Statesmarker in the 1850s and '60s, the explorers Elisha Kane and Isaac Israel Hayes both claimed to have seen part of this elusive body of water. Even quite late in the century, the eminent authority Matthew Fontaine Maury included a description of the Open Polar Sea in his textbook The Physical Geography of the Sea (1883). Nevertheless, as all the explorer who travelled closer and closer to the pole reported, the polar ice cap is quite thick, and persists year-round.

Fridtjof Nansen was the first to make a nautical crossing of the Arctic Ocean, in 1896. The first surface crossing of the ocean was led by Wally Herbert in 1969, in a dog sled expedition from Alaska to Svalbardmarker with air support.

Since 1937, Soviet and Russian manned drifting ice stations have extensively monitored the Arctic Ocean. Scientific settlements were established on the drift ice and carried thousands of kilometres by ice floes.

Climate

The images below compare the average late winter and late summer polar ice pack of the Arctic Ocean, averaged between the years 1978 and 2002, which denotes variation in amounts of ice pack during these time periods.
Extent of the Arctic ice-pack during the month of February, from 1978-2002.
Extent of the Arctic ice-pack during the month of September, from 1978-2002
Under the influence of the present ice age, the ocean is contained in a polar climate characterized by persistent cold and relatively narrow annual temperature ranges. Winters are characterized by continuous darkness (polar night), cold and stable weather conditions, and clear skies; summers are characterized by continuous daylight (midnight sun), damp and foggy weather, and weak cyclones with rain or snow.

The temperature of the surface of the Arctic Ocean is fairly constant, near the freezing point of seawater, slightly below . In the winter the relatively warm ocean water exerts a moderating influence, even when covered by ice. This is one reason why the Arctic does not experience the extremes of temperature seen on the Antarctic continentmarker.

There is considerable seasonal variation in how much pack ice of the Arctic ice pack covers the Arctic Ocean. Much of the ocean is also covered in snow for about 10 months of the year. The maximum snow cover is in March or April — about over the frozen ocean.

Climate has varied significantly in the past; as recently as 55 million years ago, during the Paleocene–Eocene Thermal Maximum the region reached an average annual temperature of ; the surface waters of the northernmost Arctic ocean warmed, seasonally at least, enough to support tropical lifeforms requiring surface temperatures of over .

Natural resources

Petroleum and natural gas field, placer deposits, polymetallic nodules, sand and gravel aggregate, fish, seals and whales can all be found in abundance in the region.

The political dead zone near the center of the sea is also the focus of a mounting dispute between the United States, Russia, Canada, Norway, and Denmarkmarker. It is significant for the global energy market because it may hold 25% or more of the world's undiscovered oil and gas resources.

Natural hazards

Ice islands occasionally break away from northern Ellesmere Island, and icebergs are formed from glaciers in western Greenland and extreme northeastern Canada. Permafrost is found on most islands. The ocean is virtually icelocked from October to June, and ships are subject to superstructure icing from October to May. Before the advent of modern icebreakers, ships sailing the Arctic Ocean risked being trapped or crushed by sea ice (although the Baychimo drifted through the Arctic Ocean untended for decades despite these hazards).

Animal and plant life

Endangered marine species include walruses and whales. The area has a fragile ecosystem which is slow to change and slow to recover from disruptions or damage.

The Arctic Ocean has relatively little plant life except for phytoplankton. Phytoplankton are a crucial part of the ocean and there are massive amounts of them in the Arctic. Nutrients from rivers and the currents of the Atlantic and Pacific oceans provide food for the Arctic phytoplankton. During summer, the Sun is out day and night, thus enabling the phytoplankton to photosynthesize for long periods of time and reproduce quickly. However, the reverse is true in winter where they struggle to get enough light to survive.

Environmental concerns

Sea cover in the Arctic Ocean, showing the median, 2005 and 2007 coverage
Decline of summer Arctic ice from 1979-2000 to 2002-05.


The polar ice pack is thinning, and in many years there will be seasonal hole in the ozone layer.Reduction of the area of Arctic sea ice reduces the planet's average albedo, possibly resulting in global warming in a positive feedback mechanism. Research shows that the Arctic may become ice free for the first time in human history between 2013 and 2040. Many scientists are presently concerned that warming temperatures in the Arctic may cause large amounts of fresh meltwater to enter the North Atlantic, possibly disrupting global ocean current patterns. Potentially severe changes in the Earth's climate might then ensue.

Other environmental concerns relate to the radioactive contamination of the Arctic Ocean from, for example, Russian radioactive waste dump sites in the Kara Sea and Cold War nuclear test sites such as Novaya Zemlya.

Major ports and harbors

Arctic Ocean ports


Some notable ports and harbours from west to east include:

See also



References

Further reading

  • Neatby, Leslie H., Discovery in Russian and Siberian Waters 1973 ISBN 0-8214-0124-6
  • Ray, L., and bacon, B., eds., The Arctic Ocean 1982 ISBN 0-333-31017-9
  • Thorén, Ragnar V. A., Picture Atlas of the Arctic 1969 ISBN 0-8214-0124-6


External links




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