Difference between revisions of "Antarctica"
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[[Image:Antarctic region pol02.jpg|thumb|right|300px|Territorial claims on the Antarctic continent]]
[[Image:Antarctic region pol02.jpg|thumb|right|300px|Territorial claims on the Antarctic continent]]
'''Antarctica''' is the southernmost [[continent]] on Earth, covering the region of the [[South Pole]], the coldest continent on the earth, and the last continental landmass to be discovered by man. Although its northernmost part has gotten slightly warmer in recent years (see [[Antarctic Peninsula]]), overall it has been getting colder and accumulating more ice.
'''Antarctica''' is the southernmost [[continent]] on Earth, covering the region of the [[South Pole]], the coldest continent on the earth, and the last continental landmass to be discovered by man. Although its northernmost part has gotten slightly warmer in recent years (see [[Antarctic Peninsula]]), overall it has been getting colder and accumulating more ice. , the [[global warming theory]].
Revision as of 14:29, 20 February 2009
Antarctica is the southernmost continent on Earth, covering the region of the South Pole, the coldest continent on the earth, and the last continental landmass to be discovered by man. Although its northernmost part has gotten slightly warmer in recent years (see Antarctic Peninsula), overall it has been getting colder and accumulating more ice. Surprisingly, this may confirm the theory of global warming.
"Antarctica" comes from antarktikos (Greek ανταρκτικός), which means "opposite of the Arctic," and may have been based on the myths of the "Southern Land" (Terra Australis) which explorers have speculated about since ancient times and have long sought.
Antarctica is composed of two major, geologically distinct parts bridged by a vast ice sheet. East Antarctica, the larger of the two, is roughly the size of the U.S. and is composed of continental crust covered by an ice sheet that averages 1.6 miles thick. Rock exposures are limited to isolated coastal regions and to alpine elevations in the 2,000-mile long Transantarctic Mountains. West Antarctica, the smaller portion, is a mosaic of small blocks of continental crust covered by the West Antarctic Ice Sheet and an Andean-like mountain chain forming the Antarctic Peninsula. Most of the West Antarctic Ice Sheet is grounded below sea level, in places over 1.5 miles below sea level.
The continent itself is depressed more than half-a-mile to near sea level under the tremendous load of the ice sheet, with some regions well below sea level. The highest mountains rise to elevations of over 14,000 ft. about the height of the U.S. Rocky Mountains.
The present Antarctic ice sheet accounts for 90 percent of Earth's total ice volume. The ice sheet at the Pole, nearly two miles thick, is constantly shifting, carrying the Amundsen/Scott Research Facility at the Pole along with it at the rate of about 30 feet a year. Nearly 90 percent of the ice flowing across West Antarctica converges into ice streams that are the most dynamic, and perhaps unstable, components of the ice sheet. Recent glaciological observations have yielded evidence that some of these West Antarctic ice streams may be responding to climatic and sea level changes of the recent past, changes that could lead to more rapid retreat and global sea-level rise in the future. A few active volcanoes may also affect the ice sheet's behavior.
The Antarctic climate offers a formidable challenge to those who venture there in quest of scientific knowledge. It is the coldest, driest, highest (on average) and windiest continent on Earth. Absolute humidity is lower than on the Sahara. Annual snowfall in much of the interior is less than two inches. Winds that flow down the surface of the ice sheet toward the coast (katabatic winds) commonly reach speeds of 80 miles per hour, and maximum measured wind speeds have exceeded 180 miles per hour. Changes in the weather are dramatic: winds shift from calm to full-gale in a brief period of time. A drop of 65°F was once recorded in 12 minutes. Earth's lowest surface temperature (-126.9°F) was recorded at Russia's Vostok Station in the interior of Antarctica. Coastal locations in summer occasionally rise above the freezing point.
A lake (Lake Vostok) buried 11,000 ft. under the ice is the size of North America's Lake Huron.
Offshore cyclones occur with little warning. Winds typically reach hurricane strength within an hour and persist for several days. A concentration of storm formation and/or intensification occurs at approximately 50°S latitude and is associated with some of the most violent seas in the world ("the roaring forties"). The stretch of ocean between Antarctica and the tip of South America is considered the most hostile in the world and has claimed numerous ships over the centuries.
Meteorological observations have been recorded only in recent decades, and then only in scattered localities, so long-term temperature trends remain uncertain. The longest instrumental temperature records come from the relatively warm Antarctic Peninsula region, referred to by the "Frozen Chosen" as the "Banana Belt" of Antarctica. In historical time the fronts of the Larsen and George VI ice shelves, the two largest ice shelves in the region, have retreated at rates of nearly one-half mile per year. Another smaller ice shelf, the Wordie Ice Shelf, has completely vanished during the past several decades. Whether these changes are due to induced global warming or to natural (perhaps regional) climatic cycles remains uncertain.
Millions of square miles of sea ice surround Antarctica; the extent annually experiences a five-fold increase and decrease, with the winter maximum more than doubling the entire Antarctic region's area of ice coverage. Icebergs larger than the State of Connecticut have been observed. The temperature gradient associated with Antarctica's sea-ice zone is one of the strongest on Earth, and the seasonal variability in the extent of sea ice is an important regulator of the climate of the Southern Hemisphere. This is primarily because of the significant difference between sea ice and water in reflecting the sun's energy (albedo) and because the sea ice serves as a barrier to energy exchange between atmosphere and ocean. The extent of sea ice around Antarctica also regulates (and stimulates) primary productivity of microorganisms in surface waters, and the sea ice zone is one of the most dynamic biological systems on Earth. Global warming could cause a significant reduction in the extent of the sea ice; the potential climatic and biological impacts of a change remain problematic.
Ocean circulation and water mass production in the Antarctic region are unique owing to the strong influence of sea ice and ice shelves on temperature and salinity and to a virtual absence of geographic obstacles to circulation around the continent. A key ingredient of the global ocean is the very cold, saline water that forms in regions of the Antarctic's continental shelf. This water is supercooled by exposure to ice shelves (floating glacial ice still attached to the land), and its salinity is increased by salt that is expelled from freezing sea water during annual sea ice production. This water flows off the Antarctic continental shelf and into the global ocean as Antarctic Bottom Water, the coldest and saltiest water mass in the deep ocean and a primary driver in global ocean circulation. Elsewhere around Antarctica, relatively warm water masses flow onto the continental shelf and melt the undersides of ice shelves. This feedback between water masses and ice shelves is still not well understood.
Life forms on the Antarctic continent are sparse because of the severe climate. Nevertheless, biologists have found bacteria and yeast growing just 183 miles from the South Pole. A lichen was found in a sunny canyon 210 miles from the Pole, and a blue-green alga was observed in a frozen pond 224 miles from the Pole. Microbes related to lichens colonize in green and brown layers just beneath the surface of rocks facing the Sun. Mosses and liverworts grow in some ice-free areas along the coast. Two species of flowering plants a grass and an herb grow along the Antarctic Peninsula.
The native land animals are limited to arthropods (insects and the like), of which 76 species have been discovered. Nearly all of these species are found only in Antarctica. These springtails, midges and mites generally live along the coast among plant colonies. The southernmost known animal, a mite, has been found 315 miles from the South Pole.
Sea life, in contrast to the land, is bounteous. The immense numbers of birds and seals that live in Antarctica are, properly speaking, sea animals. They spend most of their time in or over the water, where they get their food. These animals come ashore only to breed.
About 45 species of birds live south of the Antarctic Convergence. Of the seven penguin species, the emperor and the Adélie are distributed widely around the entire coastline. Gentoo and chinstrap penguins occupy Antarctic Peninsula coasts. The population of birds in the Antarctic is estimated to be 350 million, of which about half are penguins. The total weight of birds is estimated in excess of 400,000 tons greater than the combined weight of Antarctic seals and whales.
Four species of seals breed almost exclusively in the Antarctic: the Weddell, crabeater, leopard, and Ross. Other species include the fur seal and the huge elephant seal. Most populous is the crabeater, estimated at 50 million to 75 million. Leopard and Weddell seals number 250,000 to 500,000 each.
Fishes peculiar to the Antarctic include the Antarctic cod and the icefish. These and other fishes have developed proteins in their blood that enable them to live in sea water as cold as 28°F that is, below the freezing temperature of fresh water. There is abundant and varied bottom life (starfish, urchins, shellfish) in most coastal waters.
Aside from phytoplankton (marine plants), a singularly important member of the Antarctic marine food chain is krill. This crustacean looks like a small shrimp and exists in huge numbers; vast swarms stretching several miles in length have been observed from ships, and some biologists believe the krill population may exceed 5 billion tons. Krill eat phytoplankton and small marine animals and in turn are eaten in great numbers by squid, birds, seals, and whales. There is evidence that depletion of the ozone layer affects phytoplankton productivity, and may therefore affect krill and the entire southern ocean food chain.
Remote, inaccessible, and inhospitable, Antarctica was the last continent to be discovered, and knowledge of the south polar region was accumulated slowly. Until the present century the interior of Antarctica was unknown, and even the continental margins had been seen in only a few places. Of the world's 61,000 nonfiction papers and books published about the Antarctic since the earliest papers dating from the 1600s, 91 percent have been published since 1951. However, the historian Kenneth J. Bertrand (Americans in Antarctica 1775-1948, American Geographical Society, 1971) writes that "the success of recent operations in unveiling Antarctica with the aid of modern technology does not negate the importance of earlier efforts. Present accomplishments have been built on the past, developed step by step since 1674, sometimes haltingly and sometimes failing."
Explorations have been conducted for a variety of motives and sometimes accidentally, as was the case of the first discovery south of the Antarctic Convergence (where temperate and polar waters meet) of South Georgia in the 1670s when a commercial ship was blown off course. The true nature of the Antarctic as a frigid region of ice and snow was convincingly proved for the first time by the second voyage of the English navigator, Captain James Cook, between 1772 and 1775. Until then, there was general belief in a large, still undiscovered continent in the southern hemisphere suitable for European settlement. Cook circumnavigated Antarctica, much of his course south of 60°S, and crossed the Antarctic Circle in three places. He failed to sight any part of the Antarctic continent, but disproved conclusively the existence of the mythical continent "Terra Australis Incognita" at latitudes north of 60°S. Mariners who followed Cook into high southern latitudes were attracted to the harsh environment by his reports of great numbers of whales and seals, particularly the latter.
In 1820-1821 the American sealer Nathaniel B. Palmer of Stonington, Connecticut, saw the Antarctic Peninsula from his sloop Hero and met the Russian Captain Thaddeus Bellingshausen commanding the two ships Vostok and Mirnyy on a major national expedition that circumnavigated Antarctica eastward. Three other great national expeditions were made between 1819 and 1843 by the French Admiral Dumont d'Urville, who discovered the Adélie and Clarie coasts in 1840; by U.S. Navy Lieutenant Charles Wilkes, who mapped 1,500 miles of Antarctica's coast south of Australia in 1839-1840, proving Antarctica a continent; and by Britain's Sir James Clark Ross, who discovered the Ross Sea, Ross Island, and the Ross Ice Shelf in 1841.
Historians have not settled the question of who was first to see land in Antarctica. British, Russian, and U.S. ships all were in the Antarctic Peninsula area in the early 1820s, and the first sighting occurred during that time. The first documented landing on the continent was on 24 January 1895, when the Norwegian whaling ship Antarctic landed a party at Cape Adare on the northern Ross Sea. The party consisted of Captain Leonard Kristensen, second mate Carstens Borchgrevinck, and H. J. Bull, who wrote a book about their adventure. Bull called being first on the Antarctic mainland "both strange and pleasurable," although he thought the crew would have preferred to find a Right Whale "even of small dimensions."
In 1895 a resolution by the Sixth International Geographical Congress in London promoted Antarctic exploration and set into motion a series of expeditions known now as the "Heroic Era." Before World War I halted this activity, 16 exploring expeditions from Australia, Belgium, England, France, Germany, Japan, Norway, Scotland and Sweden (but not the U.S.) had visited Antarctica. This activity is exclusive of whalers, discussed below. The magnitude of this activity was unprecedented for Antarctica, and, considering the state of technology and size of the world's population and wealth, it probably was greater than that of the mechanical age that followed and comparable to the operations initiated with the International Geophysical Year (IGY), 1957-1958. The best known of the Heroic Age expeditions were those led by Roald Amundsen (Norway) and Robert F. Scott (England), who separately reached the geographic South Pole (and were the first to do so) a few weeks apart on 14 December 1911 and 17 January 1912, respectively.
U.S. Antarctic activity in this century began with Richard E. Byrd's hugely popular, privately financed, expeditions in 1928-1930 and 1933-1935. Byrd's success led to Congressional appropriations of $10,000 in 1939 and $340,000 in 1940 (totaling about $4.1M in 1997 dollars) for the U.S. Antarctic Service, organized as a civilian entity under four cabinet agencies. Intended to be permanent but curtailed to a single winter and two summers because of World War II, the field work in 1939-1941 nevertheless was the largest Antarctic expedition up to that time, and it produced discoveries in a number of research disciplines.
After the War the U.S. Navy Antarctic Developments Project (Operation Highjump) in 1946-1947 was then (and remains) by far the largest Antarctic expedition, with more than 4,700 naval and marine personnel, 44 observers, 13 ships, and a number of aircraft. The expedition sighted more than 1.5-million square miles of Antarctica, half of it previously unexplored, and took 15,000 aerial trimetrogon (mapping) photographs. The following season the U.S. Navy Second Antarctic Developments Project (Operation Windmill) used ship-based helicopters to get geodetic ground control for the Highjump photographs. The expedition contributed to production of the first medium-scale maps of the region and influenced decisions regarding locations of stations for the International Geophysical Year the following decade. At a time when other nations had embarked on programs of permanent bases, the U.S. Navy Second Antarctic Developments Project also was a vehicle for continuing the U.S. presence in Antarctica.
Whaling, Sealing, Fishing
British sealers first crossed the Antarctic Convergence in 1778, and Americans in about 1792. Profits were enormous. Around 1797 the Neptune of New Haven, a ship worth perhaps $3,000, gathered 45,000 skins at the Falklands and Juan Fernandez, sold them for $90,000 in Canton, bought Chinese goods there and sold them for $260,000 in New York. As subantarctic seals were decimated the sealers pushed farther south. In 1820-1821, at least 30 American, 24 British, and 1 Australian vessels were hunting seals in the South Shetlands. The next year the numbers were perhaps doubled. Landings were said to have been made on the Antarctic Peninsula, the South Orkney Islands were discovered, and at least one and maybe three Americans traveled as far south as 66°S on the west side of the Antarctic Peninsula. James Weddell (British) discovered the Weddell Sea. Fur seals and then elephant seals (for their oil) were reduced almost to extinction by the mid-1800s, at which point the sealers for all practical purposes abandoned this activity. In 1978 the Antarctic Treaty nations agreed to prohibit the taking of fur, elephant and Ross seals, and to limit the annual catch of various other species. No seal hunting has taken place in the Antarctic since 1964 and the populations of fur and elephant seals have significantly regenerated themselves in the last half of the 20th century.
Whaling began in Antarctic waters in the 19th century. The industry enlarged greatly in the early 1900s, when steamships, harpoon guns, and shore processing stations (notably at South Georgia) were introduced. During the 1912-1913 season 10,760 whales were caught. After that time nearly all the whales caught in the world were taken in Antarctic waters. In 1931, the peak year, 40,199 whales were caught in the Antarctic, while 1,124 were caught in the rest of the world. The whaling industry declined after 1960. In the 1980-1981 season fewer than 6,000 whales were caught in the Antarctic; all were Minke whales, a relatively small-sized species. In 1994 the member nations of the International Whaling Commission declared Antarctic waters a whale sanctuary in which no commercial whaling is allowed.
International Geophysical Year
The IGY, 1 July 1957 to 31 December 1958, was a cooperative endeavor by scientists throughout the world to improve their understanding of the Earth and its environment. Much of the field activity took place in Antarctica, where 12 nations established some 60 research stations. Laurence M. Gould, who was Richard E. Byrd's chief scientist in Antarctica in the 1920s and 1930s and later chaired the National Academy of Sciences Polar Research Board and served on the National Science Board, called the IGY the most comprehensive scientific program ever undertaken and the first attempt at a total study of the environment. "No field of geophysics," he wrote in 1958, "can be understood or complete without specific data available only from this vast continent and its surrounding oceans."
The U.S. established six Antarctic IGY research stations: Little America (on the Ross Ice Shelf), Hallett (in Victoria Land), South Pole and Byrd (in Marie Byrd Land), plus Wilkes (on the coast of Wilkes Land, East Antarctica) and Ellsworth (on the Filchner Ice Shelf). Naval Air Facility, McMurdo Sound (now McMurdo Station), was set up as a logistics base from which to supply South Pole. Studies were directed toward geophysics and upper atmospheric physics and complemented simultaneous observations around the globe. Long traverses were made to collect data in glaciology, seismology, gravimetry, and meteorology. Geological and biological samples were also collected, although these disciplines were not formally part of the IGY.
Antarctic Treaty of 1959
International cooperation in the IGY stimulated the Antarctic Treaty , signed by the 12 Antarctic IGY nations at Washington, D.C., in 1959 and entered into force in 1961. The treaty establishes a legal framework for the area south of 60°S, which includes all of Antarctica. There are two types of Antarctic Treaty parties. Consultative nations, now 26 in number, are empowered to meet periodically and to influence operation of the treaty. Acceding nations, of which there now are 17, agree to abide by the treaty, but, not being among the original signatories and not having substantial programs in Antarctica, do not participate in the consultative process.
The treaty provides that Antarctica shall be used for peaceful purposes only; it prohibits military operations except in support of peaceful activities. It provides that freedom of scientific investigation and cooperation shall continue and that nations shall exchange program plans, personnel, observations, and results. The treaty seeks to resolve the issue of territorial claims by simply not recognizing, disputing, or establishing claims; and it prohibits assertion of new claims. It prohibits nuclear explosions and disposal of radioactive waste. It guarantees access by any treaty nation to inspect others' stations and equipment. Appendix VI further summarizes the treaty.
The consultative meetings provided for by the treaty have generated a series of recommendations, most of which have been formally adopted by the treaty nations, that provide rules for operating on and around the continent. One of the most significant is the Agreed Measures for the Conservation of Antarctic Fauna and Flora, ratified by the U.S. as Public Law 95-541, the Antarctic Conservation Act of 1978. Other advances have included the Convention for the Conservation of Antarctic Seals and the Convention on the Conservation of Antarctic Marine Living Resources. A failed recommendation of significance is the 1988 Convention on the Regulation of Antarctic Mineral Resource Activities, which would have permitted mining if the proponent were to demonstrate that the environment would not be damaged. Instead, a 1991 Antarctic Treaty meeting adopted a protocol for improved environmental protection that prohibits mining; the U.S. signed this protocol into law (PL104-227) in October 1996 and is preparing to deposit its instrument of ratification with the Antarctic Treaty system. The U.S. and other Antarctic Treaty nations are complying with the protocol on a voluntary basis pending its entry into force, which will occur only after all 26 of the nations initially signing the 1991 agreement ratify it.
Seven nations have asserted claims to pie-shaped sectors of Antarctica bounded by longitudinal lines: Great Britain (claim made formally in 1926), New Zealand (1923), Australia (1936), Norway (1939), Chile (1940), Argentina (no formal date), and France (1924). The initial claims were based on discovery, adjacency, or decree, and all but one of the claims extend from north of the coast to the South Pole. Three claims overlap. One sector is unclaimed. The claims occasionally have led to conflict; on 2 February 1952 the Argentine navy fired on the British when they tried to land at Hope Bay. Conflicts over other remote areas have not been unknown, including the U.K./Argentina war over the Falklands as recently as 1982. Other nations have acted to make claims, but not asserted them; for example, Germany sent an expedition for this purpose in 1938, and in 1939 Lincoln Ellsworth, heading his second Antarctic expedition (the first was a transantarctic flight in 1935), dropped from his plane a brass cylinder containing a note claiming territories for the U.S. "so far as this act allows."
Other than the claimant states, most nations do not recognize Antarctic claims. U.S. non-recognition, a cornerstone of the nation's Antarctic policy, dates to 1924, when Secretary of State Charles Evans Hughes wrote that discovery of lands unknown to civilization "does not support a valid claim of sovereignty unless the discovery is followed by an actual settlement of the discovered country." In 1934 the Assistant Secretary of State added: "I reserve all rights which the U.S. or its citizens may have with respect to this matter." President Franklin D. Roosevelt reaffirmed the U.S. stance in 1939: "The U.S. has never recognized any claims of sovereignty over territory in the Antarctic regions asserted by any foreign state." In 1947 Dean Acheson, then Under Secretary of State, wrote that the U.S. "has not recognized any claims of any other nations in the area and has reserved all rights which it may have in the area."
Despite the Antarctic Treaty provision that "no acts or activities taking place while the present Treaty is in force shall constitute a basis for asserting, supporting, or denying a claim to territorial sovereignty in Antarctica," some signatories have taken what appear to be assertive steps. For example, both Argentina and Chile publish their claimed Antarctic sectors on their official national maps, and both have established hotels and post offices. Chile has placed whole families in residence at its Antarctic stations, with schools, banks, and other evidence of "effective occupation," including the birth of a child. An Argentinian child was born at Argentina's Esperanza Station in the late 1970s.
- The Antarctic Treaty, from the U.S. State Dept. website
- Antarctica resources on the Internet, from the USGS
- NOAA's "South Pole Live" camera