Arctic Ocean(redirected from Arctic Mediterranean Sea)
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Oceanography and Environment
Nearly landlocked, the Arctic Ocean is bordered by Greenland, Canada, Alaska, Russia, and Norway. The Bering Strait connects it with the Pacific Ocean and the Greenland Sea is the chief link with the Atlantic Ocean. The principal arms of the Arctic Ocean are the Beaufort, Chukchi, East Siberian, Laptev, Kara, Barents, and Greenland seas; the last is sometimes considered part of the Atlantic. The floor of the Arctic Ocean is divided by three submarine ridges—Alpha Ridge, Lomonosov Ridge, and the Arctic Mid-Oceanic Ridge; other submarine ridges, such as the Faeroe-Icelandic Ridge, act to separate the Arctic Ocean from the Atlantic.
The Arctic Ocean has the widest continental shelf of all the oceans; it extends c.750 mi (1,210 km) seaward from Siberia. From the shelf rise numerous islands, including the Arctic Archipelago, Novaya Zemlya, the New Siberian Islands, and Wrangel Island. The continental shelf encloses a deep oval basin (average depth 12,000 ft/3,658 m) that stretches between Svalbard and Alaska; E of Greenland the ring of the continental shelf is broken by the Greenland Sea. The greatest depth in the Arctic Ocean is at Molloy Deep, 18,599 ft (5,669 m), in the Fram Strait N of the Greenland Sea. (If the Greenland Sea is considered part of the Atlantic, the Arctic's deepest point is Litke Deep, 17,881 ft (5,449 m), in the Eurasian Basin.) Since the Arctic's connection with the Pacific Ocean is narrow and very shallow, its principal exchange of water is with the Atlantic Ocean through the Greenland Sea. Even there, though surface waters communicate freely and a strong subsurface current brings warm water from the Atlantic into the Arctic basin, exchange of deeper waters is barred by submarine ridges. Thus a near stagnant pool of very cold water is found at the bottom of the Arctic basin.
Because several major rivers in Siberia (Lena, Yenisei, Ob) and Canada (Mackenzie) bring in much water, and because evaporation is only slight, the outflow through the Greenland Sea is important. It creates the cold East Greenland Current, which flows south along the coast of E Greenland. A weaker current goes through Smith Sound and Baffin Bay and is known as the Labrador Current. Another weak current flows out of Bering Strait. The water that does not flow out by the Greenland Sea seems to be deflected by N Greenland and forms the current that gives rise to a circular current in the Arctic basin itself. This circular current causes the relatively light ice of the Siberian seas, which contrasts with the heavy-pressure ice phenomenon off Greenland and Ellesmere Island (in the Arctic Archipelago). The drift of ice southward and westward has been noted and utilized by explorers.
Once called the Frozen Ocean, the Arctic Ocean is covered with ice (2–14 ft/.6–4 m thick) throughout the year in most of its central and western portions, though since the 1980s the extent of the summer ice has been significantly reduced. Some of the ice pack remains in the Arctic basin, and some, carried out by the East Greenland Current, melts before going far enough south to reach the regular Atlantic shipping lanes; the icebergs that harass ships are generally brought from the fjords of W Greenland by the Labrador Current. It was long thought that no non-oceanic life could exist in the Arctic; however, despite drifting ice, ice packs, vast ice floes, and winter temperatures to −60℉ (−51℃), hares, polar bears, seals, gulls, and guillemots have been found as far north as 88°.
The cold Arctic currents give the shores of NE North America and NE Asia a much colder climate than the northwest shores of Europe and North America, which are warmed by the North Atlantic Drift and the Japan Current. The Arctic currents are also less saline and lighter than these warmer currents, and therefore the Arctic water is at the surface and the Atlantic current beneath, where they are exchanged in the Greenland Sea.
Exploration and Scientific Research
The Arctic basin was almost wholly unexplored until the Amundsen-Ellsworth flight over it in 1926. Arctic research was stimulated when it was recognized that the shortest air routes between the great cities of the Northern Hemisphere cross the Arctic Ocean. Improved technology has also facilitated research, with the development of aerial and satellite photography and photogrammetry for precise mapping, the sonic echo sounder for measuring ocean depths, and radio to maintain contact with the rest of the world. Detailed knowledge of drifts and ice floes, water depths, and the ocean floor has vastly increased. Soviet polar scientists investigated (1948–49) the Lomonosov Ridge, an undersea mountain range that influences the pattern of ice drift and the circulation and exchange of water in the Arctic Ocean. American scientists in 1959 discovered the existence of a submarine plateau rising 8,100 ft (2,469 m) from the ocean floor. In 1995 the U.S. navy agreed to lend its force of nuclear attack submarines for a series of civilian expeditions to the Arctic.
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. Such expectations have increased interest in the region's ocean resouces, and led the nations bordering the ocean to make territorial claims on vast sections of seabed.
For an account of exploration and for bibliography, see Arctic, the.
(also North Polar Sea; in Russian, Northern Ice Ocean), the smallest of the earth’s oceans, constituting 2.8 percent of the area of the world ocean. The Arctic Ocean has an area of 13.1 million sq km and a volume of roughly 17 million cu km (14.7 million sq km and 17.6 million cu km, respectively, according to some sources). Lying between Eurasia and North America, the Arctic Ocean is connected with the Atlantic through the Davis, Denmark, Faeroe-Iceland, and Faeroe-Shetland straits and with the Pacific through the Bering Strait. It was first identified as a separate ocean in 1650 by the Dutch geographer B. Varenius, who called it the Hyperboreal Ocean. In 1845 the London Geographical Society named it the Northern Ice Ocean. This name was officially adopted in the USSR by a decree of the Central Executive Committee on June 27, 1935.
Physical geography. In terms of its physical characteristics and the geological structure of its floor, the Arctic Ocean is divided into three parts: the North European Basin (Greenland, Norwegian, Barents, and White seas), the Arctic Basin, and the seas located within continental shelves (Kara, Laptev, East Siberian, Chukchi, and Beaufort seas and Baffin and Hudson bays).
ISLANDS. The Arctic Ocean ranks second after the Pacific in number of islands. With a few exceptions, the islands are found on the continental shelf and have continental origins. The largest islands and archipelagoes are Greenland, Iceland (on the boundary between the Arctic and Atlantic), the Canadian Arctic Archipelago, Spitsbergen, Franz Josef Land, Novaia Zemlia, Severnaia Zemlia, the Novosibirskie Islands, and Vrangel’ Island. The islands have a total area of about 4 million sq km.
COASTLINE. The Arctic Ocean has a varied coastline. Most of the coast of Scandinavia, Iceland, and Greenland is high and cut by fjords. In places the White, Barents, and Kara seas have an abrasion coastline broken by inlets; elsewhere the coast is low-lying and straight, with occasional deltas. Along the Laptev, East Siberian, Chukchi, and Beaufort seacoasts there are deltas or lagoons in places. The coastline of the Canadian Arctic Archipelago is for the most part low and even.
TOPOGRAPHY AND GEOLOGICAL STRUCTURE OF THE OCEAN FLOOR. The Arctic Ocean differs from other oceans in its lesser depths (average, 1,130 m; maximum, 5,449 m in the Nansen Basin) and in its extensively developed continental shelf, extending for 1,300 km in the Barents Sea. The North European Basin is separated from the Atlantic Ocean by a chain of rises (the Wyville Thompson, Faeroe-Iceland, and Greenland-Iceland sills) on which the Shetland and Faeroe islands and Iceland are situated. The eastern part of the basin floor is occupied by the shelves of the Barents and White Seas. The floor structure of the deep Norwegian and Greenland seas is characterized by a system of underwater ridges (Iceland, Mohn, and Knipovich). Together with the Gakkel’ Ridge in the Arctic Basin, these ridges constitute the northernmost segment of the world-encircling mid-oceanic ridge. The minimum depth of the ridge summits is 900–1,000 m. The North European Basin is connected with the Arctic Basin by the Fram Strait (between Greenland and Spitsbergen), reaching a maximum depth of 3,900 m in the Lena Trough.
A system of underwater ridges—Gakkel’, Lomonosov, and Mendeleev (with the Alpha Rise)—divides the Arctic Basin into several deep basins. The Lomonosov and Mendeleev ridges and the Alpha Rise differ from the volcanic Gakkel’ Ridge by their continental geostructure, formed by Early and Middle Mesozoic folds covered by a sedimentary mantle. (Some oceanographers regard these ridges as positive structures of the earth’s oceanic crust.) The ridges drop off steeply (as much as 22°) to the adjacent basins.
Beneath the marginal arctic seas is a relatively flat shelf dissected in many places by troughs, the chief channels for the removal of suspended material.
SEDIMENT. Bottom sediments differ in thickness and accumulate at a rapid rate. Typical of the continental shelf are terrigenous sediments varying greatly in texture. The ridges and deep basins are covered with clayey terrigenous sediments—dark brown and brown pelitic silts with a paucity of microfauna. In addition, there are sandy silts with foraminifers on the continental slopes. The thickness of the sedimentary layer in the deep basins reaches 1.5–2.5 km according to seismological findings, and the rate of sediment accumulation may be as much as 4–6 cm per 1,000 years in places. On the continental slope the rate of sediment accumulation declines to a maximum of 2–3 cm per 1,000 years, and sediments are up to 1.5 km thick. The ridges and their slopes have a discontinuous sedimentary cover 400–600 m thick.
Large fragmented material (boulders, pebbles, and gravel) dispersed by drifting ice or formed by the destruction of bedrock on the steep slopes and peaks of the underwater ridges is present in all types of Arctic Basin sediments. At great depths in the North European Basin the sediment is globigerina ooze.
CLIMATE. The characteristic features of the climate of the Arctic Ocean are determined by the ocean’s high latitude, which causes radiation cooling to exceed heat gain from the sun. The warm North Atlantic and Pacific currents also play an important part in forming the climate; the heat that they bring into the Arctic Ocean constitutes 60 percent of the heat transfer in the atmosphere, according to M. I. Budyko’s data. In the winter months (January to April) the arctic anticyclone is above the Arctic Basin. Cyclones from the Atlantic move northward through Baffin Bay and the Greenland Sea and eastward through the Norwegian, Barents, and Kara seas, frequently reaching the polar region. During the summer stable, but less powerful, anticyclones are observed over the Arctic Basin north of Alaska and the Chukchi Sea and over Greenland. Cyclonic activity develops primarily over northern Canada and northern Siberia and spreads to adjacent parts of the Arctic Ocean.
The trough of the Icelandic low prevails over the North European Basin throughout the year, and a maximum of atmospheric pressure occurs over Greenland. Therefore, northerly and northwesterly winds prevail above the western part of the basin, causing a severe arctic climate. Winds are primarily southerly and southwesterly in the eastern part of the basin. Because of these winds and the influence of the warm Norwegian Current the climate here is milder. A large number of deep cyclones pass through the North European Basin, producing abrupt changes in the weather and abundant precipitation and fog. During the autumn and, especially, winter the strong turbulence, high humidity, and low air temperatures often cause ships to become covered with ice, hindering navigation. The wind of the North European Basin is unstable (with average velocities of 4–6 m per sec), but winds of more than 15 m per sec seldom occur. In the coastal regions there is a marked seasonal (monsoon) pattern in the wind direction, and the wind velocity, as well as the number of days with storm winds, increases significantly, especially in winter.
The mean winter air temperature in different parts of the Arctic Ocean varies from – 2° to – 40°C; in summer the range is 0° to 6°C. The frequency of cloudy days may be as much as 90 percent in summer and 50 percent in winter. Atmospheric precipitation falls in the form of snow; rain, usually mixed with snow, occurs only rarely. Precipitation in the Arctic Basin does not exceed 150 mm a year; in the North European Basin it totals 250–300 mm a year. The snow cover is not thick and has an extremely uneven distribution. In summer the snow pack melts almost everywhere.
HYDROLOGICAL REGIME. The water and heat exchange between the Arctic Ocean and the adjacent oceans is largely governed by its positive freshwater balance. The large rivers that flow into the Arctic Ocean, among them the Severnaia Dvina, Ob’, Enisei, Khatanga, Lena, Kolyma, and Mackenzie, discharge about 5,000 cu km of fresh water a year into the ocean. Such a quantity of water could form a layer about 40 cm high in the Arctic Ocean—three times the height of the average layer that would be formed on the world ocean. Freshened by continental runoff to a salinity of less than 32‰, the cold surface water (below – 1 °C) and ice of the Arctic Ocean are carried into the Atlantic by the strong East Greenland and Labrador currents. The total transport volume of these currents is roughly 250,000 cu km a year. The outflow is compensated for by the inflow of warm (up to 10°C) and highly saline (34.9–35.2‰) water from the Atlantic and Pacific. Water from the Atlantic is transported by two branches of the North Atlantic Current— the Norwegian (135,000 cu km) and Irminger currents; the Bering Sea Current brings only about 30,000 cu km of water annually from the Pacific.
The principal water masses of the Arctic Ocean are surface, intermediate, abyssal, and bottom waters. Unlike the Arctic Basin, 95 percent of whose volume is occupied by relatively unchanged intermediate Pacific water, warm abyssal Atlantic water, and warm bottom water from the Norwegian Sea, more than 80 percent of the volume of the North European Basin is occupied by water of local origin—cold intermediate and bottom water. The bottom water in the North European Basin is the coldest (to – 1.3°C) and densest bottom water in the world ocean. The warm Atlantic water of the Norwegian Current and its branches, the West Spitsbergen and North Cape currents, occupies not more than 8 percent of the volume of the North European Basin.
One of the chief characteristics of the hydrological regime of the Arctic Ocean is the thick ice sheet that covers 11.4 million sq km in March and 7 million sq km in September. Only the Norwegian Sea and a small part of the Greenland and Barents seas are kept ice-free throughout the year by warm currents. The parts of the Arctic Ocean that are ice-free in summer are covered in winter with annual ice varying in thickness from 0.8 m to 2 m and with ice hummocks. The height of the above-water parts of the hummocks averages 2–3.5 m, sometimes reaching 5 m. The remainder of the Arctic Ocean, chiefly the Arctic Basin, is covered by drifting perennial ice with a maximum thickness of 4.5 m. The volume of ice in the Arctic Ocean totals about 26,000 cu km.
Icebergs, encountered in many parts of the ocean, are especially numerous in Baffin Bay. The “ice islands” formed from the shelf ice of the Canadian Arctic Archipelago may drift for six years or more in the Arctic Basin. Because of their thickness (as much as 30–35 m) drifting stations, such as the North Pole–6 Station, have been established on the ice islands. Ice conditions hinder navigation on the Northern Sea Route and the Northwest Passage, where ships may travel only two or three months out of the year, usually escorted by icebreakers.
The circulation of surface water and ice in the Arctic Ocean is determined primarily by wind action, which also has a significant effect on the ocean’s water exchange with the Atlantic and Pacific. In the Arctic Basin, the water and ice move in a clockwise direction at an average velocity of 2–5 cm per sec; in the North European Basin the circulation is counterclockwise, and the velocity increases to 10–20 cm per sec. The circulation of surface water and ice in the Arctic Ocean is governed by the Transarctic Current, which crosses the Arctic Basin from the Chukchi Sea to Fram Strait, by the eastern anticyclonic gyre north of Alaska, by the cold East Greenland Current moving south along the east coast of Greenland, and by the warm Norwegian Current and its branches. Tides, primarily semidiurnal, average not more than 1 m in the North European Basin and 0.5–0.6 m in the Arctic Basin. The maximum tidal fluctuations in the sea level (up to 6 m) are observed in inlets, for example, Iokanga Bay in the Barents Sea.
PLANT AND ANIMAL LIFE. The richness and diversity of the Arctic Ocean’s plant and animal life varies greatly depending on the temperature of the water. Bottom algae, including those of commercial importance (Laminaria, Fucus), are found in large numbers in areas influenced by warm waters along the coast of Iceland, Norway, and the Kola Peninsula and in the White Sea. The flora is much poorer in the cold waters of the Arctic Basin because the ice prevents the development of life in the littoral zone. However, phytoplankton, primarily diatomaceous, flourishes throughout the Arctic Ocean, including the ice-covered central region.
Animal life is more diverse in the North European Basin, inhabited by more than 2,000 species, including rorquals, the almost extinct Greenland whale, and such commercially important fish as herring, cod, sea perch, and haddock. Cryophiles such as the polar bear, walrus, seal, narwhal, and white whale are the predominant mammals in the Arctic Basin. Among the few fish species in the Arctic Basin are the Arctic pollack (Boreogadus), navaga, and Arctic cod (Arctogadus), as well as the freshwater fishes at river mouths. The overall density of the biomass decreases 5 to 10 times between the Atlantic and the pole.
Economic geography. The seas of the North European Basin and Baffin Bay are traditional areas for fishing and the hunting of marine mammals. Each year more than 12 million tons of herring, cod, halibut, sea perch, and other fish are caught in the Barents Sea, along the coast of Iceland, and in Baffin Bay. The hunting of marine mammals continues to be the primary source of livelihood of the indigenous coastal population of the northern parts of Greenland, Canada, and Alaska.
The importance of the Arctic Ocean for transportation, already great, is steadily growing. Shipping is carried on by the USSR along the Northern Sea Route and by the USA and Canada along the Northwest Passage. Navigation to Greenland, Iceland, northern Scandinavia, and Spitsbergen generally does not depend on ice conditions during the summer.
The most important arctic ports of the USSR are the year-around ice-free port at Murmansk (Barents Sea), Kandalaksha, Belomorsk, Arkhangel’sk (White Sea), Dikson (Kara Sea), Tiksi (Laptev Sea), and Pevek (East Siberian Sea). The major foreign ports are Tromsø and Trondheim on the Norwegian Sea and Churchill on Hudson Bay. The air space above the Arctic Ocean is crossed by air routes from Western Europe to the west coast of the USA (over Greenland and Canada) and to Japan (across Alaska).
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