Polar Regions

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Antarctica, the coldest and second-smallest continent (after Australia), is centered on the South Pole and is situated almost entirely within the Antarctic Circle at 66 1/2° S. Some 97% of the total area of about 13,924,000 sq km (5,376,000 sq mi) is covered by ice, and the continent contains about 90% of the world's ice and 70% of the fresh water. Antarctica is bounded by the Southern Ocean. The nearest points of land are the southern tip of South America, South Georgia, the South Sandwich Islands, the South Orkney Islands, and the South Shetland Islands. All of these islands are located within the Antarctic Convergence, which encircles Antarctica at approximately 1,600 km (1,000 mi) from the coast and divides the cold Antarctic waters from the warmer waters of the four oceans, in a zone of perpetual turbulence.

The Southern Ocean, which totally encircles Antarctica, was delimited in 2000 as a result of a decision of the International Hydrographic Organization. It was delimited from the southern parts of the Atlantic, Indian, and Pacific Oceans, and extends from the Antarctic coast north to 60° s latitude. The Southern Ocean encompasses 360° of longitude, and is slightly more than twice the size of the United States, or 20,327,000 sq mi (52,646,000 sq km). It is smaller than the Atlantic, Indian, and Pacific Oceans, but larger than the Arctic Ocean.

Some 200 million years ago, Antarctica was joined to South America, Africa, India, and Australia in a large single continent, Gondwanaland; subsequent geological changes caused the breakup into separate continental masses. Recent geological studies and fossil finds indicate that Antarctica once had a tropical environment, but that its present ice sheet is at least 20 million years old.

The Transantarctic Mountains divide the continent into two parts: the larger East Antarctic ice sheet, with land mostly above sea level; and the smaller West Antarctic ice sheet, with land mostly below sea level. The highest point is the Vinson Massif (4,897 m/16,066 ft), in the Ellsworth Mountains of West Antarctica. The South Pole lies at an altitude of about 3,000 m (9,800 ft). The Antarctic ice sheet averages 2,160 m (7,090 ft) in depth and is 4,776 m (15,670 ft) deep at its thickest point. Glaciers form ice shelves along nearly half the coastline. The larger ice shelvesthe Amery in the east, Ross in the south, and Ronne in the northwestmove seaward at speeds of from 900 to 1,300 m (2,9504,250 ft) per year. Sea ice up to 3 m (10 ft) thick forms a belt about 500 km (300 mi) wide that encircles the continent in winter. Ice-free areas are located generally along the coast and include the dry valleys in southern Victoria Land and the Bunger Oasis in Wilkes Land. Largely ice-free areas where much scientific activity takes place are on the coast of the Antarctic Peninsula, and on Ross Island in McMurdo Sound.

An increased amount of calving of the Antarctic ice shelves became an issue of international concern beginning in 2000. In March 2000, the largest iceberg ever recorded split offfrom the Ross Ice Shelf. Known as B-15, the iceberg was approximately the size of Connecticutit weighed about 2 billion tons and measured some 4,250 sq mi (11,007 sq km) before breaking up into five smaller sections. In March 2002, the Larson B ice shelf collapsed, causing 720 billion tons of ice to float into the South Atlantic Ocean. The Larson ice shelf was reduced to 60% of its former size.

Although Antarctica produces icebergs as part of a natural process, many scientists hold that global warming is one factor responsible for the increase in calving. Since the 1950s, ocean temperatures have increased by an average of half a degree Fahrenheit near the surface, and a tenth of a degree at deep levels. The Antarctic waters are warming more than four times faster than those in the rest of the world, with temperatures rising some 2.5° since 1950. These warmer waters could be melting the undersides of Antarctica's ice shelves. (See GLOBAL CLIMATE CHANGE below)

The severity of the Antarctic cold varies with location and altitude. East Antarctica has the coldest climate; the Antarctic Peninsula in the west has the mildest, with summer temperatures generally remaining above freezing. The mean annual temperature of the interior regions is 57° c (71° f); mean temperatures at the coastal McMurdo station range from 28° c (18° f) in August to 3° c (27° f) in January. The world's record low temperature of 89.2° c (128.6° f) was registered at what was the Soviet's Vostok station on 24 August 1960; highs of 15° c (59° f) have been measured on the northernmost Antarctic Peninsula. The interior is a vast desert, with annual precipitation averaging below 3 cm (1 in). The coastland is considerably more humid, with annual precipitation of about 25 cm (10 in) along the coasts of East Antarctica and the Antarctic Peninsula. Adélie Coast, in the southeast near the South Magnetic Pole, has recorded average wind speeds of 64 km/hr (40 mph), with gusts of nearly 320 km/hr (200 mph).

Because of its polar location, Antarctica has six months of continuous daylight from mid-September to mid-March, with the maximum 24 hours of light received at the summer solstice on 22 December; and six months of continuous darkness from mid-March to mid-September, with the winter solstice occurring on 22 June. In summer, the continent receives more solar radiation than even the Equator over a 24-hour period.

Although Antarctica has no native humans or large terrestrial mammals, it does have a varied marine life ranging from microscopic plankton to the largest whales and including about 100 species of fish. Land life includes bacteria, lichens, mosses, two kinds of flowering plants (in the ice-free areas), penguins, and some flying birds. Six types of sealthe crabeater, Weddell, elephant, leopard, fur, and Rossthrive in Antarctica and together number about 32.7 million, with the crabeaters accounting for nearly 94% of the total. The once-numerous fur seals were reduced by uncontrolled slaughter (about 1 million were killed on South Georgiaalone in 182022) to near extinction by 1870. This ended the Antarctic fur-sealing industry; since then, the number of fur seals has gradually increased, to more than 1 million, mostly on South Georgia. In 1972, the 12 nations active in the Antarctic signed the Convention for the Conservation of Antarctic Seals, which prohibits the killing of fur, elephant, and Ross seals, and sets annual quotas for the harvest of crabeater, leopard, and Weddell seals. The treaty entered into force in 1978, and as of 2005 had been rati fied by 16 nations. In 1982, the Convention on the Conservation of Antarctic Marine Living Resources entered into force, assuring the protection of ecosystems found in the Antarctic waters; as of 2005, 31 countries and the European Union (EU) were parties to the treaty.

Exploitation by humans threatens the survival of the Antarctic whalesthe sperm, blue, humpback, fin, minke, and seiwhich decreased in number from more than 1,500,000 at the beginning of the 20th century to fewer than 700,000 by the mid-1980s. Since 1972, the International Whaling Commission (IWC) has set quotas by species on the taking of whales, and the survival of all species of Antarctic whales seemed assured by the early 1980s. In 1982, the IWC approved a moratorium on the commercial killing of all whales that began in 1985. However, Japanese fishermen caught 3,087 whales in 1985 and 2,769 in 1986. Japan promised to end commercial whaling in 1988 but announced plans to harvest 300 minke (nonendangered) whales in Antarctic waters for "research" purposes during the winter of 198788; these plans were criticized by the IWC. In 2003, the IWC voted to uphold the ban on commercial whaling, despite a proposal from Japan to allow for an allocation of 50 minke whales. As of June 2005 there were 66 members of the IWC. Canada is a former member of the IWC but is generally adheres to IWC regulations and decisions. In August 2003, Iceland conducted a whale hunt for 38 minke whales for what it deemed to be research purposes. Whale meat not used for research was to be sold commercially in Iceland. It was the first whale hunt since Iceland ceased whaling operations in 1989. Iceland is a member of the IWC.


The ancient Greeks reasoned that there must be an "Antarctic" (opposite the Arctic) to balance the large land mass in the Northern Hemisphere, but it was not until the 19th century that definite proof was found that the continent existed. British Capt. James Cook had crossed the Antarctic Circle and circumnavigated the continent without sighting land (177275). In 1820, however, two other British mariners, William Smith and James Bransfield, discovered and mapped the Antarctic Peninsula, which was also explored by the American sea captain Nathaniel Palmer and the Englishman James Weddell, who discovered the sea that bears his name. Russian Adm. Fabian von Bellingshausen sailed around Antarctica during his 181921 voyage and found Queen Maud Land and Peter I Island.

On 7 February 1821, US Capt. John Davis made the first known landing on the continent at Hughes Bay, in the northwest. Many other British and US sealers explored the area, including 11 shipwrecked Englishmen who spent the winter of 1821 on King George Island, in the South Shetlands. Palmer and Benjamin Pendleton led a pioneering expedition in 182830 that included James Eights, the first American scientist to visit Antarctica. In 1837, a French expedition under J. S. C. Dumont d'Urville discovered the Adélie Coast (named for his wife) in eastern Antarctica. A year later, Lt. Charles Wilkes of the US Navy sailed along the coast of eastern Antarctica for about 2,400 km (1,500 mi), thereby definitely establishing that Antarctica was a continent, not a cluster of islands. During his 183943 Antarctic voyage, British Capt. James C. Ross discovered Victoria Land and the sea and the ice shelf that were later named in his honor.

With the decline of the fur seal industry, Antarctic exploration was neglected for about 50 years, until Norwegian and Scottish whalers began operating in the area. A Norwegian whaling captain, Carl Anton Larsen, explored the east coast of the Antarctic Peninsula in 1892 and found the first fossils. Thus began a period of intensive exploration during which 9 countries sent 16 expeditions to Antarctica. Another Norwegian captain, Leonard Kristensen, landed at Cape Adare, on McMurdo Sound, in 1895. It was there that a British expedition, led by a Norwegian, Carsten Egeberg Borchgrevink, established a base in 1899; Borchgrevink became the first explorer to probe inland by sledge. Swedish, Scottish, Belgian, and French expeditions also arrived, and four British expeditions set up bases on Ross Island. From there, Sir Ernest Henry Shackleton sledged to within 156 km (97 mi) of the South Pole on 9 January 1909.

This feat encouraged five national expeditions to compete for the goal in 1911, and the competition narrowed to a "race to the pole" between Capt. Robert F. Scott and Roald Amundsen of Norway. Amundsen and four companions, with sledges and 52 dogs, left their base on the Ross Ice Shelf on 20 October, scaled 3,000-m (10,000-ft) glaciers in the Queen Maud Mountains, ascended to the icy plateau, and located the South Pole by celestial observation on 14 December. They returned to their base by late January 1912. Meanwhile, Scott's party of five explorers, who had left McMurdo Sound on 1 November, reached the pole on 18 January 1912, only to find that Amundsen had beaten them there by more than a month. Disheartened, they met with mishaps on the return journey and, weakened by food shortages and exhausted from man-hauling their sledges, they all perished on the ice in late March. Another expedition that ended badly was led in 191415 by Shackleton, who lost his ship Endurance in heavy pack ice in the Weddell Sea and, with five companions, made a perilous 1,300-km (800-mi) journey in an open whale boat to South Georgia Island, where he got help to rescue his stranded men. Shackleton died at South Georgia in 1922, while preparing another expedition.

Technological advances were applied to Antarctic exploration after World War I. An Australian, Sir Hubert Wilkins, in 1928 became the first man to fly an airplane along the Antarctic Peninsula. The following year, US Navy Adm. Richard Evelyn Byrd flew over the South Pole, with his Norwegian-American pilot Bernt Balchen; Byrd established the Little America base on the Ross Ice Shelf, and was the first explorer to coordinate airplanes, radios, aerial cameras, and other technological aids for the purpose of exploration. Another American, Lincoln Ellsworth, was the first to complete a transantarctic flight, from the Antarctic Peninsula to the Ross Ice Shelf, in 1935. American, British, German, and Norwegian scientific expeditions did considerable aerial mapping of the continent throughout the 1930s; research in oceanography and marine biology by a British expedition resulted in the discovery of the Antarctic Convergence. The US expedition of 193941, headed by Byrd, established two continuing bases in the Antarctic, but the program ended with the outbreak of World War II.

Scientific Research

After the war, the United States took the lead in conducting scientific research in Antarctica. The Navy's Operation Highjump (194647), the largest expedition ever made to the continent, involved 4,700 men, 13 ships, and 25 airplanes to map extensive coastal areas by aerial photography. The Antarctic Research Expedition (194748), headed by Finn Ronne, was a privately sponsored US expedition to the continent. A major joint international expedition (194952), mounted by the United Kingdom, Norway, and Sweden, initiated the use of geophysical methods on a large scale to determine the thickness of ice caps. The former USSR also mounted expeditions, in 194647 and 195152.

The greatest scientific undertaking involving the Antarctic was the International Geophysical Year (IGY) of 1957/58, in which 67 nations participated. The purpose of the IGY's Antarctic program was to study the effects of the continent's huge ice mass on global weather, the oceans, the aurora australis, and the ionosphere. More than 50 Antarctic stations were established by 12 countries: Argentina, Australia, Belgium, Chile, France, Japan, New Zealand, Norway, South Africa, the United Kingdom, the United States, and the former USSR. The United States built a supply base and airfield on Ross Island, a station at the South Pole that was provisioned by air, and four other stations. The former USSR had 4 bases, the United Kingdom 14, Argentina 8, and Chile 6. The South Pole was the terminus of three pole-to-pole observation chains along three meridians, and the US station at Little America analyzed meteorological reports from all over the world. Valuable information was gleaned from meteorological and seismic observations, studies of the upper atmosphere, magnetic measurements, and ice-sheet core drillings. The first surface transantarctic crossing, between the Weddell and Ross seas, was accomplished by the Commonwealth Transantarctic Expedition. After the IGY, very little of the continent remained to be explored.

An important result of the IGY's success was the continuation of significant research programs in Antarctica after 1958. Old stations were either closed or replaced with new buildings, and new stations were opened. The United States constructed a year-round scientific village at McMurdo Sound, heated and lighted by a small atomic power plant that also used waste heat to distill seawater (the atomic reactor was replaced by diesel-powered units in 1972). Besides McMurdo Station, the United States maintains two other year-round stations, at the South Pole and on Anvers Island, offthe Antarctic Peninsula. Other countries maintaining year-round stations are the former USSR 7, Argentina 6, the United Kingdom 4, Chile 3, Australia 3, Japan 2, and 1 each by Brazil, China, the Federal Republic of Germany (FRG), France, India, Italy, New Zealand, Poland, and South Africa.

Transportation services are essential to Antarctic operations; for example, transportation expenses accounts for about half of the United States's yearly expenditure in Antarctica The United States, along with Argentina and New Zealand, routinely uses aircraft to carry both passengers and priority supplies to Antarctic stations. However, only four airfields can handle wheeled aircraft, those of Argentina, Chile, the former USSR, and the United States. France reportedly built a fully equipped airport on the Adélie Coast. Air transport to other bases is by ski-equipped aircraft. The United States has a fleet of transport airplanes which can carry large loads virtually anywhere in Antarctica. Transport between stations in the interior is provided mainly by tractor-trains and ski-equipped light aircraft. The longest surface supply route is from the former Soviet's Mirnyy station on the east coast to Vostok station in the interior, a distance of nearly 1,400 km (860 mi). Most nations operating in Antarctica rely on shipping for long-distance transportation and employ icebreakers to clear channels of pack ice. When conditions are favorable, ships offload cargo directly onto land or the ice shelf; when harbors are blocked by ice, tractors and helicopters carry passengers and cargo to shore.

Territorial Claims and International Cooperation

Seven nations have made separate territorial claims in Antarctica. Five of the claims begin at 60° S latitude and continue in the shape of a pie wedge to the South Pole. The exceptions are the claims of the United Kingdom, which start at 50° S in order to include the South Sandwich and South Georgia Islands of the Falkland chain; and of Norway, the northern and southern boundaries of which are undefined. The United Kingdom, the first nation to claim a "slice" of the continent (in 1908), was followed by New Zealand (1923), France (1924), Australia (1933), Norway (1939), Chile (1940), and Argentina (1943). The claims of Argentina and Chile overlap with each other and with that of the United Kingdom. Neither the United States nor the former USSR has claimed any Antarctic territory, and neither recognizes the claims of other nations. Since international law requires "effective occupation" as the basis for ownership, and since no nation has met the criteria by sustaining such permanent occupation in Antarctica, these territorial claims have not been recognized by other countries, by the UN, or by any other international body.

In order to clarify the issue of territorial claims and to form a legal framework for the activities of nations in Antarctica, the 12 countries that had participated in the IGY signed the Antarctic Treaty on 1 December 1959: Argentina, Australia, Belgium, Chile, France, Japan, New Zealand, Norway, South Africa, the former USSR, the United Kingdom, and the United States. All 12 had rati fied the treaty by 23 June 1961, when it duly entered into force. Other nations that conduct Antarctic research are entitled to consultative membership; as of 2003, 27 nations had consultative status. As of January 2005, there were 45 nations party to the treaty: Poland (1961), Czech Republic (1962), Slovak Republic (1962), Denmark (1965), the Netherlands (1967), Romania (1971), Brazil (1975), Bulgaria (1978), Germany (1979), Uruguay (1980), Papua New Guinea (1981), Italy (1981), Peru (1981), Spain (1982), China (1983), India (1983), Hungary (1984), Sweden (1984), Finland (1984), Cuba (1984), the Republic of Korea (1986), Austria(1987), the Democratic People's Republic of Korea (1987), Ecuador (1987), Greece (1987), Canada (1988), Colombia (1989), Switzerland (1990), Guatemala (1991), Ukraine (1992), Turkey(1996), Venezuela (1999), and Estonia (2001).

The Antarctic Treaty provides that "Antarctica shall be used for peaceful purposes only," and prohibits military bases, weapons testing (including nuclear explosions), and disposal of radioactive wastes. It seeks to foster freedom of scientific investigation and cooperation between nations, with the free exchange of scientific programs, observations, results, and personnel guaranteed. The treaty neither recognizes nor nullifies any preexisting territorial claims, but it does forbid any new claim or enlargement of any existing claim. The document specifies that contracting parties have the right to designate observers, and that such observers shall at all times have the right to inspect any station or installation. The treaty provides for the peaceful settlement of all disputes by the parties concerned or by the International Court of Justice. It also specifies periodic meetings between member states to exchange information and to enact measures in furtherance of treaty objectives. In 1991 the treaty was reviewed and renewed by 39 nations. The nations agreed to maintain the unique status of Antarctica for another 50 years. The nations also agreed to establish regulations and guidelines with respect to Antarctica's mineral and natural resources.

Scientific research has continued under the provisions of the treaty, but the emphasis has shift ed from short-term reconnaissance to long-term, large-scale investigations of Antarctic phenomena. Detailed study of the ice sheet has brought about increased understanding of global weather and climatic changes. The largest cooperative program completed to date has been the International Antarctic Glaciological Project (197181), conducted by Australia, France, the former USSR, the United Kingdom, and the United States. The principal objectives are to measure precisely the East Antarctic ice sheet by means of core drillings through the ice to bedrock at several coastal and interior locations, and to make extensive aerial surveys of the area. Another collaborative project, Polar Experiment (POLEX)South (197585), mounted by Argentina, the former USSR, and the United States, expanded on existing national research programs on the atmosphere, ocean currents, and the ice sheet. The Dry Valley Drilling Project (197176), a joint project conducted by Japan, New Zealand, and the United States, included geophysical exploration and bedrock drilling in the McMurdo Sound area. The Ross Ice Shelf Project, an ongoing US endeavor begun in 1973, has incorporated contributions from at least 12 other nations to measure the surface and under-ice topography, ice thickness, gravity, and seismic activity of the Ross Ice Shelf. Another US project, inaugurated in November 1983, involved the most intensive study yet of the relationship between the West Antarctica ice sheet and the global climate. A Soviet exploration project (197580) in the Filchner Ice Shelf of West Antarctica used aerial photography and geological surveys to evaluate the area's mineral resources. During the austral summers of 198386, international research resulted in significant discoveries of plant and animal fossils in Antarctica that provided new data on the geologic, climatic, and oceanic history of the Southern Hemisphere; enabled glaciologists to learn more about cycles of ice ages; and facilitated studies of Antarctic sea-ice algae and bacteria thought to be vital to the advancement of genetic engineering. In addition, a satellite link was established between the United States and the McMurdo and South Pole stations. In the late 1980s, some of the most compelling research in Antarctica was focused on study of the springtime depletion of stratospheric ozonea phenomenon popularly termed "the ozone hole"allowing high levels of potentially harmful ultraviolet radiation to reach the earth's surface.


Estimates of Antarctica's mineral deposits are imprecise. A US Geological Survey study has concluded that the continent may contain some 900 major mineral deposits, but that only about 20 of these are likely to be found in ice-free areas. Two minerals, iron ore and coal, have been discovered in quantities that, were they accessible, would be commercially attractive. Small amounts of copper, chromium, platinum, nickel, gold, and hydrocarbons have also been found. Mineral exploration has been limited to comparatively small ice-free areas, but the Dufek Massif in the Pensacola Mountains of the Transantarctic Range shows the most potential for discovery of valuable metals. Offshore deposits of oil and natural gas show the greatest economic promise: traces of natural gas were discovered in a core taken from the Weddell Sea in 1972. However, the difficulty of operating in the harsh Antarctic climate, the inaccessibility of the deposits, and the high cost involved in mining and transportation make mineral exploitation of Antarctica unlikely for some time, if ever.


The northernmost area of the earth's surface, the Arctic may be defined as all land and water within the Arctic Circle at 66° 31n N. However, the regional boundary may also be considered the 10° C (50° F) atmospheric isotherm for the warmest month (July), which extends well below the Arctic Circle in some places and coincides roughly with the tree line. The region, centered around the North Pole, includes the ice-covered Arctic Ocean basin, which is surrounded by the northern mainland and islands of North America and Eurasia, with outlets to the Bering Sea and the North Atlantic Ocean. The Arctic Ocean, with an area of about 14 million sq km (5.4 million sq mi), comprises nearly two-thirds of the total area. Principal land masses are the northern reaches of the former USSR, Scandinavia, Greenland, Canada, and Alaska.

Unlike Antarctica, the Arctic region has a year-round habitable climate at its fringes, a permanent population, and established territorial sovereignty over all land areas. The Arctic also is of great strategic importance because of its central location between North America and Eurasia; the northern tip of Canada lies only about 4,000 km (2,500 mi) from what was the Soviet city of Murmansk on the great circle route. As a consequence of such proximity, the Arctic region is the site of many radar stations maintained by Canada, the former USSR, and the United States to monitor air traffic and to provide early warning of an air attack.

The continental shelf around the Arctic basin occupies more than half the ocean area, a much larger proportion than in any other ocean; the edge of the continental shelf near Franz Josef Land lies about 1,500 km (930 mi) from the Eurasian mainland. The landmasses that extend above the Arctic Circle exhibit three major types of landforms: rugged uplands and deep fj ords formed by glaciation; swampy coastal plains and high ice plateaus covered by glacial deposits; and folded mountains, including the high peaks of the Canadian Rocky Mountains, Alaska's Brooks Range, and the rounded slopes of the Ural Mountains of the former USSR. Principal rivers flowing into the Arctic Ocean are the Mackenzie, in Canada, and the Ob', Yenisey, Lena, and Kolyma, in the former USSR. Major seas in the Arctic include the Chukchi, East Siberian, Laptev, Kara, Barents, Norwegian, Greenland, and Beaufort.

The Arctic Ocean remains frozen throughout the year (except for its fringes during summer) and is virtually icelocked from October to June. The vast Arctic ice pack expands from an average area of 7.8 million sq km (3 million sq mi) in summer to an average of 14.8 million sq km (5.7 million sq mi) during winter. The average thickness of the ice pack is estimated at 33.5 m (9.811.5 ft). Ice "islands" up to 60 m (200 ft) thick and 30 km (19 mi) wide break away from the moving ice pack offNorth America and float slowly in erratic circles before disintegrating or exiting to the North Atlantic. Smaller fragments called icebergs break offglaciers in Greenland and northeastern Canada and move southward via the East Greenland and Labrador currents into Atlantic shipping lanes. An estimated 1,000 icebergs each year cross 55° n, and nearly 400 reach the Grand Banks offNewfoundland. A few icebergs have traveled as far as 4,000 km (2,500 mi) over a three-year period and have been sighted as far south as Bermuda.

The most recent Ice Age climaxed about 15,000 years ago, when continental ice sheets covered most of the Northern Hemisphere. The retreat of the glaciers was stabilized some 8,500 years ago in Europe and 7,000 years ago in North America. The warming period that followed reached its maximum in historic times during ad 8001000, making possible the Viking colonization of Arctic lands, and from the 1880s to the 1940s, when extensive Arctic exploration occurred. However, a minor cooling trend that began in the 1940s had severe effects in the Arctic, increasing the ice-covered area substantially and reducing the annual mean air temperatures by several degrees, thereby shortening the summer season along the Arctic coast of Eurasia by nearly a month.

The Arctic experiences alternating six-month periods of winter darkness and summer daylight, including 24 hours of daylight within the Arctic Circle during the summer equinox (hence the designation "land of the midnight sun"). The region is subject to long, cold winters and short, cool summers. The snow cover is relatively light, averaging 2050 cm (820 in) and lasting for about 10 months over the frozen ocean. Air temperatures above the pack ice average 30° c (22° f) in January and near 0° c (32° f) in July. Annual mean temperatures on land vary from 12° c (10° f) at Barrow, Alaska, and 16° c (3° f) on Resolute Island, in northern Canada, to 0° c (32° f) at Murmansk, in what was the western USSR. Annual mean temperatures in Greenland are low because of the island's high elevation and vast interior ice sheet; they range from 40° c (40° f) in January to 10° c (14° f) in July, temperatures significantly colder than those of the North Pole. Total annual precipitation varies from 10 to 25 cm (410 in) on the Arctic ice pack to 45 cm (18 in) or more in Greenland.

A climate-dependent phenomenon is the presence of perennially frozen ground, or permafrost, which has impeded human use of land in the Arctic region. Permafrost, occurring wherever ground temperatures remain below freezing for two or more years, underlies most of the Arctic landmass of Alaska and Greenland, half of that in Canada and the former USSR, and parts of Scandinavia. It also has been found under coastal seabeds of the Arctic Ocean. The maximum thickness of permafrost has been measured at 500 m (1,640 ft) in Canada, 900 m (2,950 ft) in Alaska, and 1,500 m (4,920 ft) in the former USSR. Alternate freezing and thawing of the outer permafrost layer shortens the growing season during the summer and causes serious engineering problems for construction and mining operations in the Arctic region.

Vegetation on the Arctic tundra, or treeless plain, is limited to mosses, lichens, sedges, and a few flowering plants which blossom during the brief spring and summer seasons. The outer edges of the Arctic ice pack support a small number of animal species by providing an overhead platform for algae and plankton, which are eaten by fish that, in turn, serve as food for seals, walruses, and birds; the food chain is continued by foxes and polar bears which feed upon young seals. Altogether, the Arctic has about 20 species of land mammals, including the moose, caribou, reindeer, wolf, and squirrel. The arrival of migratory birds each spring increases the bird population enormously.

Principal fish are cod, herring, and capelin, a true Arctic fish; all of these have great commercial value, as do shrimp and crab. Since 15 October 1975, when Iceland extended its fishing zone to 200 nautical mi, all nations bordering the Arctic have done the same, and fish catch quotas are now under national management.

The ecological cycle of Arctic life has been damaged by human encroachment, but in recent years the natural environment has been increasingly protected by the five circumpolar countries (Canada, Denmark, Norway, the former USSR, and the United States). In 1956, the former USSR prohibited hunting of the polar bear, and in 1973 the five nations agreed to protect the bear's habitat. During construction in the 1970s of the trans-Alaska oil pipeline from Prudhoe Bay on the Arctic coast to the port of Valdez on the Gulf of Alaska, the US government required contractors to clean up the work site and to restore displaced vegetation; drillers were directed to trap and remove spilled oil. The pipeline carrying hot oil was suspended above ground level to prevent the permafrost from thawing, and crossings under the pipeline were provided at intervals for caribou and moose migrations. The Alaska Native Claims Settlement Act (1971) set aside about one-fourth of the state's area for wilderness preserves, wildlife refuges, and national parks. To prevent or control oil spills in the Arctic Ocean, Canada in 1970 authorized a 161-km (100-mi) offshore pollution control zone north of the 60° line. The former USSR has established nature preserves on several islands offthe Kola Peninsula, east of the Barents Sea, and on Wrangel Island. In 1973, Norway established nature reserves and national parks in its Svalbard territory in the Barents Sea, and the next year, Denmark designated the northeastern third of Greenland as a national park.

The 19-million acre Arctic National Wildlife Refuge (ANWR) lies in the northeast corner of Alaska, 1,300 miles south of the North Pole and entirely within the Arctic Circle. ANWR is located less than 100 mi east of Prudhoe Bay, the United States's largest oil field, which, together with three smaller fields, accounts for 25% of US domestic oil production. In the early 2000s, the debate over whether to begin petroleum exploration and drilling in ANWR, (regarded as the highest petroleum potential onshore yet to be explored in North America), or to preserve it as a wilderness area, was fierce.

Settlement and Exploration

The Arctic region was settled some 10,000 to 12,000 years ago, after the last Ice Age, by peoples of Central Asia, probably of Mongoloid stock, who pursued animal herds northward in the wake of retreating glaciers. The ancestors of the Lapps migrated to northern Scandinavia and the Kola Peninsula, while further east diverse peoples settled along the Arctic coast. At about the same time, the forebears of the American Indians came from Asia via a land bridge across the Bering Strait or traveled along the Aleutian Islands to North America. It is believed that the Eskimos arrived in Alaska much later.

These migratory peoples adapted to the harsh Arctic environment by inventing snowshoes, the kayak, the igloo, and primitive tools. They fashioned clothing and tents of caribou or reindeer skins, perfected efficient hunting techniques, and evolved distinctive forms of social organization. Gradually, over the course of centuries, these hunter-gatherers made the transition to herding and trading; especially for the Indians and Eskimos of Canada and the United States, however, intense contact with modern culture in the 20th century has meant abrupt change. In addition to Indians and Eskimos, principal indigenous Arctic population groups include the mixed Eskimo-Caucasian peoples of Greenland; the Lapps in Scandinavia; and the Samoyedic, Yakuts, Tungus-Manchurian, and Chukchi peoples of the former USSR. These aboriginal peoples constituted about half of the Arctic's total population.

The first explorers in Arctic waters were the Vikings (Northmen) from Scandinavia, who ventured into the North Atlantic as far as Greenland and the North American continent in the 10th and 11th centuries. It is generally accepted that the Norse chieft ain Leif Ericson explored part of the northeastern North American mainland, which he called Vinland, although its actual location is disputed. During the 16th and 17th centuries, European explorers such as Martin Frobisher, William Baffin, and William Barents probed the Arctic Ocean for the fabled Northwest Passage around North America to the Orient. Arctic geographical landmarks have been named after them and for Vitus Bering, the Danish explorer who sailed in the service of Russia in 1728 through the strait that bears his name. In the late 18th century, while developing trade routes for English fur companies, Alexander Mackenzie and Samuel Hearne followed Canadian rivers to reach the Arctic coast. In 1819, William Parry sailed west through the northern Canadian islands as far as M'Clure Strait before being stopped by heavy pack ice. That year, Swedish explorer Nils Nordenskjöld became the first to complete the Northeast Passage along the Russian Arctic coast. The disappearance in 1845 of Sir John Franklin's expedition spurred further exploration and the mapping of many Canadian islands in the Arctic Ocean. Norwegian explorer Roald Amundsen successfully transited the Northwest Passage for the first time, from 1903 to 1906.

Amundsen's accomplishment shift ed the emphasis of Arctic exploration to reaching the North Pole. American explorer Robert E. Peary came within 280 km (174 mi) of the goal in his 190506 expedition, and on 6 April 1909, he and his party, including four Eskimos, were the first men to reach the North Pole. In 1926, Adm. Richard E. Byrd, of Antarctic exploration fame, and his copilot Floyd Bennett were the first to fly over the pole, and Amundsen and Lincoln Ellsworth flew from Spitsbergen (now Svalbard) across the pole to Alaska. In 1958, the US atomic-powered submarine Nautilus was the first underwater vessel to navigate the North Pole, and in 1960, the Skate, a US submarine, became the first to surface at the pole. The Soviet icebreaker Arktika was the first surface vessel to reach it, in 1977.

Unresolved Arctic territorial disputes concern Norway's exclusive claim to the resources of the Svalbard continental shelf and conflicting Norwegian-Soviet claims in the Barents Sea. After the Antarctic Treaty was signed in 1959, hopes were raised for a similar agreement in regard to the Arctic, but the strategic importance of the Arctic region, its increasing economic value, and complex legal problems involving national sensitivities have thus far prevented the attainment of such an accord.

Arctic Development

The five nations with territories within the Arctic Circle have all developed the area's natural resources to some degree, but the former USSR has taken the lead both in populating the region and in exploiting its rich mineral deposits and other resources. The largest Arctic city is Murmansk, with a population of about 308,100 (2004), and there are some 30 other ex-Soviet cities and towns in the Arctic with more than 10,000 inhabitants. In contrast, the largest town on the North American mainland located north of the Arctic Circle is Inuvik, in Canada's Northwest Territories, with a population of 3,451 (2004); Godthaab, the capital of Greenland, has approximately 14,500 (2005) residents. The estimated population of what Russia terms its "far north" (including areas in eastern Siberia as far south as 55° N) is about 11 million (2004). The majority live in mining districts or coastal settlements based on fishing and military activities, and the rest are concentrated in northern river valleys, or scattered in the hinterlands. Canada's Yukon Territory, Northwest Territories, and Nunavut Territory (created in 1999), have over 40% of the country's land area but less than 1% of the total population. Alaska is the largest but fourth least populous of all the states of the United States (North Dakota, Vermont, and Wyoming have fewer people).

Beginning in the 1930s, with the establishment of the northern sea route to link coastal and river settlements, the Soviet government undertook the exceptionally costly task of fostering industrial development of the Arctic region. Because the harsh climate, the shortage of housing and amenities, and the low level of social services discouraged voluntary migration to the area, the Soviet government offered special resettlement inducements to workers, such as high wages and extensive fringe benefits. As a result, Soviet migration to the far north was nearly equal to the region's natural population increase between 1940 and 1970. However, labor turnover was rapid, with most new workers staying only one to three years. The most important economic activity was the mining of large nickel, copper, tin, platinum, cobalt, iron, and coal deposits. Eastern Siberia produced more than half the country's total output of nickel and much of the nation's copper, while the Kola Peninsula's apatite deposits provided at least two-thirds of the raw materials used to produce phosphate fertilizer. Eastern Siberia also produced about 90% of the former USSR's annual output of diamonds and tin. In addition, valuable oil fields and about two-thirds of proved Soviet natural gas reserves was located in western Siberia. Expansion of Soviet mining operations in the Arctic region continued into the 1980s and up until its collapse in the early 1990s. As of the mid-2000s, Russia was discussing further Arctic development, including mining.

The most significant economic development in the Arctic during the 1970s was the $4.5-billion trans-Alaska oil pipeline project and the exploitation of vast petroleum reserves (estimated at more than 10 billion barrels) at Alaska's Prudhoe Bay. Construction began on the 1,270-km (789-mi) pipeline to Valdez in 1974, and oil began to flow through the pipeline in 1977. Tens of thousands of American workers migrated to Alaska to take part in the project (earning the highest average wage rates in the United States), and many stayed there after its completion, thereby contributing to Alaska's population increase of 32.4% during the decade. Coal reserves estimated at 5 trillion tons are located on Alaska's North Slope; coal is mined at Healy, between Anchorage and Fairbanks. Gold, copper, lead, zinc, tin, platinum, tungsten, and uranium have been mined in the past, and there are known reserves of silver, lead, nickel, cobalt, mercury, molybdenum, and asbestos. However, the remoteness of mining sites and the high production costs continued to hinder mineral development (except for oil) in the 1980s and 1990s.

Valuable minerals produced in the Canadian Arctic include gold, silver, lead, zinc, copper, nickel, platinum, cadmium, and uranium. Canada also has proved oil reserves totaling 1.5 billion barrels in the Mackenzie River delta and offshore areas of the Beaufort Sea. Although Greenland also has considerable mineral resources, only lead, zinc, and coal have been mined in recent years. The two largest iron mines in Scandinavia are situated in the vicinity of Kiruna, in Swedish Lapland, and in Norway, near the Soviet border. Both Norway and the former USSR operate coal mines in Svalbard, and both have explored for offshore oil beneath the Barents Sea.

Lack of adequate transportation facilities long hampered Arctic development. Since World War II, however, a network of air, water, and land routes has been developed, and modern technology has made most polar areas accessible. Scheduled flights from many airfields scattered throughout the region link cities and remote towns in Alaska, Canada, and the former USSR. In Greenland, where the rugged terrain makes the building of airstrips both difficult and costly, there is scheduled jet helicopter service. Air transport serves both military and civilian needs in Norway's polar region and links Svalbard with the mainland. Although water transport is seasonal because of ice-blocked channels in winter, large quantities of cargo generally move by ship. Several hundred Russian vessels, including icebreakers, ply the 2,800-km (1,740-mi) northern sea route between Novaya Zemlya and the Bering Strait, moving an estimated 4 million tons of cargo annually during 24 months of navigability.

The former USSR and Norway use waterborne shuttles to supply Svalbard and to convey coal to their respective home ports. Canada's shipping service for Hudson Bay, the Arctic islands, and the Mackenzie River delta is provided by the coast guard and by private companies. The Alaskan ports of Prudhoe Bay and Barrow are served by ships for a two-month period during late summer. Inland waterways provide important supply links in the Soviet Arctic and northwestern Canada.

Land routes in the Arctic are relatively undeveloped in the colder regions. However, railroad lines in North America that penetrate the Arctic Circle include Alaska's heavily used AnchorageFairbanks line, and a Canadian railroad, providing a link to Churchill, on Hudson Bay. A number of Russian railroads serve the Arctic region, including the ports of Murmansk and Arkhangel'sk. Canada has Arctic highways that connect Inuvik with Dawson and with the Great Slave Lake towns of Hay River and Yellowknife. The most heavily traveled highway is Alaska's Arctic haul road between the Yukon River and Prudhoe Bay; this road was instrumental in hauling supplies and equipment to build the trans-Alaska oil pipeline. The Soviet Arctic has few roads, but the Murmansk area in the west connects with a well-developed Scandinavian road network.

Scientific Research

Scientific research in the Arctic region is directed mainly toward economic development and military applications. Research studies have dealt primarily with the Arctic's role in global air and water circulation and with such natural phenomena as pack ice, permafrost, geomagnetism, the aurora borealis, and other upper atmospheric conditions.

International cooperation has long played a vital role in Arctic research, dating back to the 1882/83 and 1932/33 International Polar Years. The most intensive multinational scientific study of the Arctic was accomplished during the International Geophysical Year (1957/58), in which some 300 Arctic stations were set up to monitor polar phenomena. The United States and the former USSR each launched two drift ing stations on the pack ice to gather data on Arctic currents and the topography of the Arctic seabed. It was found that little marine life existed on the Arctic Ocean floor and that rocks were scattered in profusion on the ocean bottom. The land stations obtained detailed information on the aurora borealis, ionosphere, and polar magnetic field. During 196975, Canada and the United States jointly conducted an Arctic ice experimental program involving manned and unmanned drift ing stations to determine the dynamics of sea-ice movement within the polar environment.

Scientific efforts by the former USSR in the Arctic have exceeded the combined activities of all the other circumpolar nations. By the late 1970s, the former USSR operated at least 100 polar stations and more than a dozen specially equipped sea and air vehicles to collect data on weather, ocean currents, and sea ice, with the aim of maintaining shipping services over the northern sea route. Drift ing ice stations maintained year-round make a variety of meteorological observations and conduct oceanographic and geophysical experiments. Each year, Russia mounts air expeditions to hundreds of sites along the ice pack, emplacing nearly two dozen automatic buoys to radio data on environmental conditions to the mainland.

US Arctic research centers mainly on Alaska but extends also to northern Canada, Greenland, and the Arctic Ocean. Civilian research is coordinated by the National Science Foundation (NSF), which awards funds for research to universities; the principal research centers are at Fairbanks and Barrow. Small outposts to gather weather information have been established at US military facilities in Alaska and at radar stations on the 4,800-km (3,000-mi) Distant Early Warning (DEW) line extending from Alaska to Greenland.

The United States operates an average of one drift ing ice station per year in the Arctic Ocean, supplemented by automatic data buoys. Ice reconnaissance flights are conducted, as well as ocean surveys by icebreakers and submarines in the Bering and Greenland seas. In the early 1980s, the NSF conducted a six-year project, called Processes and Resources of the Bering Sea Shelf (PROBES), to study the marine ecosystem of the Bering Sea in order to predict the environmental impact of both natural events and human activities. In 1987, the NSF initiated a follow-up program, Inner Shelf Transfer and Recycling (ISHTAR), conducted in the Bering and Chukchi seas to study the ways in which seasonal and annual variations in the northward transport of water influence life processes. In 1985, scientists from the National Oceanic and Atmospheric Administration (NOAA) embarked on a study of a 5,200-sq km (2,000-sq mi) polynya (open water in pack ice that is a source of heat in an extremely cold area) in the Bering Sea, hoping to assess its effects on weather patterns, wind behavior, and ocean currents. In the summer of 1981, the United States cooperated with Denmark and Switzerland to obtain ice cores from the bottom of the Greenland ice sheet, which represents a record of the climate over the past 130,000 years. Other recent US programs include studies of the geology and geophysics of the Arctic basin and research in Alaska on so-called surging glaciers, which move forward at the unusually rapid rate of several miles a year.

Other circumpolar nations have concentrated their Arctic research on the land and continental shelf. Canada's ongoing Polar Continental Shelf Project, begun in 1959, makes intensive studies of the North American continental shelf, Arctic islands, and Arctic Ocean. From March to October of each year, Canada also conducts aerial surveys of sea ice in the Arctic Ocean, Baffin Bay, and Beaufort Sea. Norway's Polar Institute, in Oslo, supervises mapping and scientific surveys of Svalbard, Jan Mayen, and the Arctic Ocean. In Greenland, the United States participates in geophysical and weather studies at Thule Air Base. Scientists from Russia, the United Kingdom, France, and other countries also conduct geological and biological research on the Danish dependency.


Recent shift s in the global climate, while not proven to be caused by humans, by 2006 conformed to a prevailing scientific view: without significant changes in emissions rates, global warming from the buildup of carbon dioxide and other greenhouse gases is likely to lead to substantial, and largely irreversible, transformations of climate, ecosystems, and coastlines later in the 21st century. The Earth's average surface temperature rose approximately 1 degree Fahrenheit over the 20th century, to about 59 degrees Fahrenheit, but the rate of warming from the 1970s until the mid-2000s was three times the average rate of warming since 1900. Seas have risen from some six to eight inches globally over the 20th century and the rate of rise increased markedly in the 1990s. The 1990s were the warmest decade on record, with 1998 the warmest year on record. Although there is a debate about the pace and extent of climate change, one thing remains clear: an increase in the levels of greenhouse gases will cause more global warming. The impact of such change on wildlife, agriculture, disease, local weather, and the height of the world's oceans is also debated.

In April 2006, the journal Nature published a study of estimates that foresaw a probable warming of some 5 degrees Fahrenheit should the concentration of carbon dioxide reach twice the 280-parts-per-million figure that had been the norm on Earth for at least 400,000 years. This figure is both far higher than conservative warming rates focused on by climate change skeptics, and far lower than the rates projected by those fearful of further climate change. As a result, by approximately 2100, sea levels could be several feet higher than they were in 2005, resulting in retreating shorelines as the Antarctic and Arctic ice sheets erode.

Many scientists say that to avoid a doubling of carbon dioxide concentrations, energy efficiency must be increased drastically in the near future. They argue that by the mid-21st century, there must be a complete transformation of energy technology. Nevertheless, some scientists report that they lack incontrovertible evidence to connect recent weather to the human influence on climate. However, the Intergovernmental Panel on Climate Change (IPCC), a worldwide network of 2,500 leading scientists and experts sponsored by the UN, reported in 2001 that most of the warming observed over the last 50 years is attributable to human activities. These scientists project a global warming of between 1.4 and 5.8 degrees C (2.5 to 10.4 degrees F) as early as 2100, the fastest rate of change since the end of the last ice age. In addition to the rise in sea levels and flooding of low-lying coastal areas and islands, rainfall patterns would change, increasing the threat of drought or floods, and a more variable climate would bring more extreme weather conditions, such as intense storms and heat waves. According to the IPCC, Arctic sea ice has thinned by 40% in recent decades in summer and autumn, and decreased in extent by 10-15% since the 1950s in spring and summer. Global snow cover has shrunk by 10% since the 1960s, and mountain glaciers have sharply retreated. The Northern Hemisphere has seen earlier plant flowering, earlier bird arrival and earlier emergence of insects.

The 1992 UN Convention on Climate Change-ratified by 186 nations-holds that developed countries, which account for some 20% of the global population and about 60% of annual emissions of carbon dioxide, should lead efforts to reduce greenhouse gas emissions. Forty-one industrialized nations listed in Annex 1 of the Convention agreed to a voluntary aim of returning their greenhouse gas emissions to 1990 levels by the year 2000. This goal was not met by many. States parties then launched a new round of talks to decide on stronger and more detailed commitments for industrialized countries. The outcome was the Protocol to the Convention agreed in Tokyo, Japan, in 1997. The Kyoto Protocol contains legally binding targets by which developed countries must reduce their combined emissions of six greenhouse gases by at least 5% by the period 2008-12, calculated as an average over those five years. Cuts in the three most important gases-carbon dioxide, methane, and nitrous oxide-are to be measured primarily against a base year of 1990. By reducing greenhouse gas emissions to 5% below 1990 levels, the Kyoto Protocol will result in 2010 emissions levels that are about 20% below what they would have been in the absence of the Protocol. The legally binding emissions commitments under the Kyoto Protocol apply only to developed countries, leaving to the future the question of similar commitments for developing countries. The Protocol entered into force on 16 February 2005, with the ratification of 55 nations and by including developed nation parties accounting for at least 55% of 1990 carbon dioxide emissions. Shares of 1990 carbon dioxide emissions included: United States, 36.1%; European Union, 24.2%; Russian Federation, 17.4%; and Japan, 8.5%. As of April 2006, 163 nations had ratified the Protocol, including all EU members, the Russian Federation, and Japan. The United States at that date was a signatory to the Protocol, but had not ratified it.