.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 largely covered by sea ice throughout the year. The Arctic Ocean's temperature and salinity vary seasonally as the ice cover melts and freezes;[3] 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.[4] The coastline length is 45,390 km (28,200 mi).[4] It is surrounded by the land masses of Eurasia, North America, Greenland, and several islands. It includes Baffin Bay[citation needed], Barents Sea, Beaufort Sea, Chukchi Sea, East Siberian Sea, Greenland Sea, Hudson Bay[citation needed], Hudson Strait[citation needed], 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[1] and Labrador Sea[citation needed]. 
According to the International Hydrographic Organization,[5] the limits of the Arctic Ocean proper are (see the map):
- A great circle line running from Cape Morris Jesup, the northernmost point of Greenland (83°38′N 32°40′W / 83.633°N 32.667°W) to the northernmost point of Spitsbergen (south of which line lies the Greenland Sea).
- Parallel 80° North to North East Land (Nordaustlandet).
- The north shore of Nordaustlandet to its easternmost point, Cape Leigh Smith (80°05′N 28°00′E / 80.083°N 28°E).
- A line running from Cape Leigh Smith to Cape Kohlsaat, the easternmost point of Franz Josef Land (81°14′N 65°10′E / 81.233°N 65.167°E, south of which line lies the Barents Sea].
- A line running from Cape Kohlsaat to Cape Molotov (Arctic Cape), the northernmost point of Komsomolets Island (81°13′N 95°15′E / 81.217°N 95.25°E, south of which line lies the Kara Sea).
- A line running from Arctic Cape to the northernmost point of Kotelny Island (76°10′N 138°50′E / 76.167°N 138.833°E, south of which line lies the Laptev Sea).
- A line running from the northernmost point of Kotelny Island to the northernmost point of Wrangel Island (71°40′N 179°30′W / 71.667°N 179.5°W, south of which line lies the East Siberian Sea).
- A line running from the northernmost point of Wrangel Island to Point Barrow, the northernmost point of Alaska (71°23′N 156°29′W / 71.383°N 156.483°W, south of which line lies the Chuckchi Sea).
- A line running from Point Barrow to Cape Land's End on Prince Patrick Island, Northwest Territories (76°27′N 121°59′W / 76.45°N 121.983°W, south of which line lies the Beaufort Sea).
- The northwest coast of Prince Patrick Island north to Cape Leopold M'Clintock, its northernmost point (77°33′N 116°23′W / 77.55°N 116.383°W).
- A line running from Cape Leopold M'Clintock to Cape Murray on Brock Island (77°57′N 115°04′W / 77.95°N 115.067°W).
- The northwest coast of Brock Island north to its northernmost point (78°05′N 114°20′W / 78.083°N 114.333°W).
- A line running from the northernmost point of Brock Island to Cape Mackay on Borden Island, its westernmost point (78°20′N 113°18′W / 78.333°N 113.3°W).
- The northwest coast of Borden Island north to Cape Malloch (78°46′N 110°24′W / 78.767°N 110.4°W, the northernmost point of the Northwest Territories).
- A line running from Cape Malloch to Cape Isachsen on Ellef Ringnes Island, Nunavut, its northwestern most point (79°20′N 105°24′W / 79.333°N 105.4°W).
- A line running from Cape Isachsen to the northwestern most point of Meighen Island (80°05′N 100°10′W / 80.083°N 100.167°W).
- A line running from the northwestern most point of Meighen Island to Cape Stallworthy on Axel Heiberg Island, its northernmost point (81°23′N 93°33′W / 81.383°N 93.55°W).
- A line running from Cape Stallworthy to Cape Colgate on Ellesmere Island, its westernmost point (81°37′N 91°55′W / 81.617°N 91.917°W).
- The north coast of Ellesmere Island north to Cape Columbia, its northernmost point (83°05′N 70°21′W / 83.083°N 70.35°W).
- A line running from Cape Columbia to Cape Morris Jesup (south of which line lies the Lincoln Sea).
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).
The Arctic Ocean contains a major choke point in the southern Chukchi Sea,[7] which provides northern access to the Pacific Ocean via the Bering Strait between North America and the Russian city of Arkhangelsk. The Arctic Ocean also 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 temperatures much of the time. The Arctic is a major source of very cold air that inevitably 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 Murmansk, Arkhangelsk, Churchill and Prudhoe Bay.[7]
The Arctic Ocean is encompassed by the Arctic shelves, one of which, the Siberian Shelf, is the largest on Earth.
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.[10] | |
 |  |
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 0 °C (32 °F). 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 continent.
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 20 to 50 cm (7.9 to 20 in) 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 10-20 °C (50-68 °F);[11] the surface waters of the northernmost[12] Arctic ocean warmed, seasonally at least, enough to support tropical lifeforms[13] requiring surface temperatures of over 22 °C (72 °F).[14]
No comments:
Post a Comment