Antarctica
Fifth largest of the earth's seven continents, located almost entirely S of lat 66°30' S (the Antarctic Circle), and surrounding the South Pole. It is mostly circular in shape with a long arm--the Antarctic Peninsula--reaching out toward South America, and with two large indentations, the Ross and the Weddell seas and their ice shelves. Its total area is about 14.2 million sq km (about 5.5 million sq mi) in summer. During the winter Antarctica doubles in size because of the large amount of sea ice that forms at its periphery. The true boundary of Antarctica is not the coastline of the continent itself but the Antarctic Convergence, which is a sharply defined zone in the S extremities of the Atlantic, Indian, and Pacific oceans between about lat 48° S and lat 60° S. At this point the colder waters flowing N from Antarctica mix with warmer waters moving S. The Antarctic Convergence marks a definite physical difference in the oceans. For these reasons, the water surrounding the Antarctic continent is considered an ocean in itself, often known as the Antarctic, or Southern, Ocean.
Antarctica has no native population. Its residents are scientific and support staffs who usually stay no more than a year at a time. The first person born in Antarctica was Emilio Palma, on Jan. 7, 1978, the son of the commander of Argentina's Esperanza Base.
Antarctica is more than 95% ice covered and contains about 90% of the world's fresh water. Because of its thick ice cover, it is the highest of all continents, with an average elevation of more than 1600 m (about 5250 ft). The highest point on the continent is Vinson Massif (5140 m/16,864 ft); the lowest point appears to be the Bentley Subglacial Trench (2499 m/8200 ft below sea level) in West Antarctica. This trench is covered with more than 3000 m (more than 9840 ft) of ice and snow. Lower points may exist under the ice, but they have not yet been discovered.
Seven nations have announced territorial claims to parts of Antarctica. Since the Antarctic Treaty of 1961 these claims have been held aside in the interests of international cooperation in scientific research. Neither the U.S. nor the USSR made a claim to Antarctica, and the claims to Antarctica made by Norway, France, Australia, New Zealand, Chile, Great Britain, and Argentina are not recognized.
Antarctica exists today in an ice age. Future economic development of the ice-covered landmass is highly unlikely. Resource exploitation on the continental shelf is possible, but certainly not for many years to come. Currently, the marine life--whale and krill, for example--in the oceans surrounding Antarctica is being developed economically.
Antarctica was a central part of the former supercontinent Gondwanaland. As Gondwanaland broke apart during the late Mesozoic and early Cenozoic eras (some 100 million years ago) to form the continents of the southern hemisphere, Antarctica drifted from the Tropical Zone to its present polar position.
Antarctica consists essentially of two geologic areas. The larger of these, East Antarctica, which is located mostly in the eastern hemisphere, is probably a Precambrian shield covered by thousands of meters of ice. West Antarctica, lying mostly within the western hemisphere, appears to be a continuation of the Andes of South America; glaciologists and geologists speculate that West Antarctica would become an island archipelago if the ice cover were removed.
The two areas of Antarctica are separated by the Transantarctic Mts., an uplift zone of mountains that extends across the entire continent, although portions are buried under the ice cover. Within these mountains are found many coal deposits and fossil remains related to the earlier tropical climate of Antarctica.
In East Antarctica the geologically stable Precambrian shield is generally covered by sedimentary or igneous deposits. The geologic structure of West Antarctica is less well known, but at least two active volcanoes are found in the area, the higher of which is Mt. Erebus (3794 m/12,448 ft). Antarctic soils are classified as dry polar desert soils, and their occurrence is limited to the several deglaciated (ice-free) valleys or oases and to parts of the N Antarctic Peninsula.
The ice cover of Antarctica is continuously moving. Great ice rivers drain the interior of the continent and form the ice shelves. Coastal valleys drain parts of the mainland into the sea. Large tabular icebergs are formed as the edges of the ice shelves and glaciers calve off into the sea. Ice also extends over vast areas of the sea in the form of permanent floating ice shelves; the largest of these formations, the Ross Ice Shelf, is the size of the state of Texas.
The snow and ice of Antarctica are the purest in the world. The general isolation of Antarctica from the remainder of the world has allowed it to avoid the industrial pollution common to the other continents. This ice and snow are readily available to be converted into water for human use. Most scientific stations use snow melters to heat the ice and convert it to water for station use.
Subglacial water was first detected in central Antarctica by radio waves in 1974. In 1996, with the help of satellite surveys and seismic measurements, it was determined that the fresh water trapped under the polar ice cap is at least 488 m (at least 1600 ft) deep, and covers and area of 12,950 sq km (5000 sq mi)--almost as large as Lake Ontario.
Antarctica is the coldest continent. The lowest temperature ever recorded anywhere on earth, -88.3° C (-126.9° F), was on Aug. 24, 1960, at the Soviet Union's Vostok Station. The continent is also characterized by heavy winds. In the interior, winds as high as 320 km/hr (200 mph) have been recorded. These winds flow downslope from the interior toward the coast and, combined with the low temperatures, create dangerous wind-chill conditions.
Three basic climatic regions can be distinguished in Antarctica. The interior is characterized by extreme cold and light snowfall; the coastal areas are characterized by somewhat milder temperatures and much higher precipitation rates; and the Antarctic Peninsula is characterized by a warmer and wetter climate, with above-freezing temperatures common.
Antarctica can be classified as a true desert; in the interior the average annual precipitation (in water) is only about 50 mm (about 2 in). Raging blizzards often occur, however, when winds pick up previously deposited snow and move it from place to place. Annual precipitation is much heavier along the coast, amounting to about 380 mm (about 15 in) in water. Here, heavy snowfalls occur when cyclonic storms pick up moisture from the surrounding seas; this moisture freezes and is deposited as snow over the coastal areas. Along the Antarctic Peninsula, especially the N end, rain is as common as snow.
The interior of Antarctica has almost continuous daylight during the austral summer and darkness during the austral winter. In coastal areas, which are farther N, long periods of sunshine occur during the summer, but sunrises and sunsets occur during much of the rest of the year.
The few plants that survive in Antarctica are restricted to the small ice-free areas. The continent has no trees, and vegetation is limited to about 350 species, mostly lichens, mosses, and algae. Lush beds of such vegetation exist in parts of the Antarctic Peninsula, and lichens have been discovered growing on isolated mountains within 475 km (295 mi) of the South Pole. Three species of flowering plants are also found on the Antarctic Peninsula.
No land-based vertebrates inhabit Antarctica. Invertebrates, especially mites and ticks, which can tolerate the lower temperatures, exist in the Antarctic Peninsula but are still considered rare. The surrounding ocean, however, abounds in living creatures. Large numbers of whales feed on the rich marine life, especially krill, a tiny, shrimplike animal. Six species of seals (including the crabeater, elephant, and leopard) and about 12 species of birds live and breed in the Antarctic. The most prominent inhabitant is the penguin, with a population numbering in the millions.. A flightless bird, the penguin lives in the pack ice and the oceans around Antarctica and breeds on the land or ice surfaces along the coast. Most typical are the Adélie and emperor species.
Antarctica is thought to have large deposits of valuable mineral resources. Coal in commercially attractive deposits has been found, but no other minerals are known to exist in potentially useful amounts. Large deposits of oil and natural gas are believed to exist in Antarctica's continental shelf.
Antarctica was not discovered until the early 19th century, largely because of its remoteness from the other continents. The ancient Greeks first theorized the existence of Antarctica when they realized that the southern hemisphere must have large continents to balance those in the northern hemisphere. The British explorer Capt. James Cook was the first explorer to cross the Antarctic Circle in the 1770s, but even though he circumnavigated Antarctica, he never sighted the continent. From deposits of rock in icebergs at sea, Cook realized that a southern continent existed, but it was not the lush, populated place some had expected.
From 1819 to 1821 a Russian expedition under the naval officer and explorer Fabian von Bellingshausen circumnavigated Antarctica and sighted some offshore islands. The party of American sealer Nathaniel Palmer (1799-1877) and that of British naval officers William Smith and Edward Branfield (c. 1795-1852) sailed near the tip of the Antarctic Peninsula probably in 1820. The first known landing was on Feb. 7, 1821, by another American sealer, Capt. John Davis. In 1823 the British whaler James Weddell (1787-1834) was the first to reach the southernmost point of the sea that bears his name.
Not until the 1840s, however, was Antarctica's continentality established. Three separate national expeditions--a French expedition under Jules Dumont d'Urville, a British expedition under Sir James Ross, and an American expedition under Capt. Charles Wilkes--sailed along enough coastline to realize that the ice-covered land they saw was truly a continental landmass.
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Library of Congress, George Grantham Bain Collection
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Erich Dagobert von Drygalski
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From the late 19th century until World War I, numerous expeditions visited Antarctica. With the encouragement of the International Geographical Congress, expeditions were sent out by several different nations, including Belgium, commanded by Adrien de Gerlache (1866-1934); Britain, commanded by Robert Scott and Carsten Borchgrevink (1864-1934); and Germany, commanded by Erich von Drygalski (1865-1949). Gerlache took his expedition, the first truly scientific Antarctic expedition, to the Pacific Ocean side of the Antarctic Peninsula, became caught in the ice, and spent the winter of 1897-98 there. The Borchgrevink expedition landed men at Cape Adare in 1899 and became the first group to spend the winter on land. The Scott expedition (1901-4) used Ross Island in McMurdo Sound as a base and explored the Ross Ice Shelf and Victoria Land. Drygalski, who was a geophysicist, led an expedition (1901-3) to the Indian Ocean coast of Antarctica. Both Scott and Drygalski carried captive balloons and used them for aerial observation of the surface of Antarctica. Also at this time were privately sponsored expeditions from Sweden under Otto Nordenskjöld, from Scotland under William Bruce (1867-1921), and from France under Jean Charcot (1867-1936).
The search for the South Pole was the dominant theme in the next series of Antarctic expeditions. From 1907 to 1909 Sir Ernest Shackleton led a British expedition to within 156 km (97 mi) of the South Pole before turning back because of exhausted supplies.
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Treasures of the NOAA Library Collection
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Roald Amundsen
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A second British expedition went into the field in 1910 under Robert Scott, as did a Norwegian expedition under Roald Amundsen. Using dogs to haul their sledges, Amundsen and a party of four reached the South Pole on Dec. 14, 1911. Scott's party of five reached the pole on Jan. 18, 1912, after hauling their sledges by hand over the roughest part of their route. All of Scott's party died on the return journey after the Norwegians returned to their base. Shackleton returned to Antarctica in 1914 to attempt a crossing of the continent, but his ship,
Endurance, became trapped in the ice and was crushed. He and his men made their way across ice floes to Elephant Island and were rescued in August of 1916.
In the 1920s aviation came to Antarctica. The Australian Sir George Wilkins and the American C. B. Eielson became the first to fly an airplane over the continent when they explored the Antarctic Peninsula from the air in 1928. The American explorer Richard E. Byrd established a large camp--Little America--on the Ross Ice Shelf on the Bay of Whales in early 1929 and in November flew to the South Pole. Byrd returned to Antarctica in 1933 with another expedition. Both expeditions included a scientific research staff.
Other aviation expeditions included those of Lincoln Ellsworth, an American, who flew across the continent in 1935; the Norwegians, who conducted extensive exploration along the coastlines; the Germans, who sent an aviation expedition in 1938-39; and the American U.S. Antarctic Service Expedition in 1939-41.
Following World War II, the U.S. sent the largest expedition ever to Antarctica. More than 4000 men participated in Operation Highjump with some 13 ships and more than 20 airplanes. Much of the coast was photographed by air for the preparation of maps.
Long-term systematic exploration and scientific investigation of Antarctica began with the International Geophysical Year (IGY)--July 1, 1957 to Dec. 31, 1958. Twelve nations established more than 60 scientific stations in Antarctica during the IGY and visited most parts of the continent. When the IGY came to a close, the 12 nations decided to continue their research during a year of International Geophysical Cooperation. Representatives of the 12 nations met in Washington, D.C., in 1959 to draft and sign the Antarctic Treaty, which dedicated the entire continent to peaceful scientific investigation; the treaty came into effect in 1961, suspending all territorial claims. In 1991, 24 nations approved a protocol to the treaty that would ban oil and other mineral exploration for a period of at least 50 years.
For additional information on individual explorers, see biographies of most of those whose names are not followed by dates.
Significant scientific research has been accomplished in Antarctica, including studies of glaciology, meteorology, geomagnetism, international weather control, seismology, and ionospheric physics. The nutrient-rich oceans that surround Antarctica are an important focus of research. Biologists have discovered that fish in Antarctic waters have an antifreeze component to their blood that allows them to live in subzero temperatures.. Studies conducted on the life cycles of penguins, seals, and krill (a potential world food source) have provided much new information on the ecology of these species. Internationally conducted studies have resulted in an improved understanding of krill reproduction and allowed scientists to improve their predictions of safe limits for krill harvesting.
Geologists have now visited most exposed rock areas of the continent, increasing knowledge of the basic geologic structure and history of Antarctica. Glacial geologists studying the remains of past glaciers have discovered that Antarctica once contained much more ice than it now does. Fossil finds in Antarctica have included such achievements as the discovery in 1982 of the first mammal remains found there and in 1986 of the first dinosaur fossil. Such fossils have by now provided a nearly complete sequential record of the breakup of the ancient supercontinent Gondwanaland. Volcanologists have extensively studied Mt. Siple and the active volcano Mt. Erebus. Geologists have collected thousands of meteorites (including a few rare moon fragments), which are especially valued for having been preserved in ice with little weathering or other deterioration.
The ice cover itself has long been the subject of intense study. Glaciologists from several countries have employed modern methods of investigation such as radio glaciology to obtain information on the landscape under the ice cover and to discover large lakes between the earth and the bottom of the ice. Satellites have been utilized to plot the slow movement of the ice surface. Ice cores drilled from Antarctica, including a complete core to the bottom of the Ross Ice Shelf and one through the ice of West Antarctica at Byrd Station, enabled French, Russian, and American scientists to trace changes in the continent's climate over a period of tens of thousands of years. French scientists have put radio transmitters on icebergs to plot their movement, and Australian and Saudi Arabian officials have considered the possibility of towing icebergs to arid regions for fresh water.
Continuous weather records by meteorologists have been taken for some 25 years and are providing an understanding of Antarctica's function in world climate. One such contribution has been the discovery, first noted by British scientists in 1985, that a so-called ozone hole develops each Antarctic spring in the stratosphere high above the continent and then more or less disappears by the end of the season. The meaning of this reduction in the ozone layer in the vicinity of the South Pole continues to be studied. It may be partly a natural phenomenon, but evidence indicates that the ozone loss is also related to the problem of the release of fluorocarbons into the atmosphere.
Physicians have made discoveries about the behavior of viruses in a cold isolated environment. Psychological and sleep studies are frequently conducted during the winter, when Antarctica is isolated from the outside world.
In 1997 scientists began drilling for sedimentary rock core samples in the southwest corner of the Ross Sea at Cape Roberts to determine whether expansion and contraction of the Antarctic ice cover caused fluctuations in worldwide sea levels before the current glaciation period. The site was chosen because it lies just inside a major rift system and is close to the South Pole. P.J.A.