Antarctica

Antarctica I

INTRODUCTION

Antarctica, fifth largest of the Earth’s seven continents. The southernmost, coldest, windiest, highest, most remote, and most recently discovered continent, it surrounds the South Pole, the point at the southern end of the Earth’s axis. Almost completely covered by ice, Antarctica has no permanent human population. The continent is ringed by the Southern Ocean. The entire area south of the Antarctic Convergence, which serves as the northern boundary of the Southern Ocean, is referred to as the Antarctic region. Antarctica means “opposite to the Arctic,” the Earth’s northernmost region. The continent is shaped somewhat like a comma, with a round body surrounding the pole and a tail curving toward South America. The round portion, lying mainly in the Eastern Hemisphere, makes up East Antarctica. The tail and its thickened base, located entirely in the Western Hemisphere, form West Antarctica. Antarctica lies 1,000 km (600 mi) from South America, its nearest neighbor; 4,000 km (2,500 mi) from Africa; and 2,500 km (1,600 mi) from Australia. Antarctica’s latitude (location in relation to the equator) and high elevations make it the coldest continent. Air temperatures of the high inland regions fall below –80°C (-110°F) in winter and rise only to –30°C (–20°F) in summer. The warmest coastal regions reach the freezing point in summer but drop well below in winter. The last continent to be discovered, Antarctica remained hidden behind barriers of fog, storm, and sea ice until it was first sighted in the early 19th century. Because of the extreme cold and the lack of native peoples, forests, land animals, and obvious natural resources, the continent remained largely neglected for decades after discovery. Scientific expeditions and seal hunters had explored only fragments of its coasts by the end of the 19th century, while the interior remained unknown. Explorers first reached the South Pole in 1911, and the first permanent settlements—scientific stations—were established in the early 1940s. From that time the pace of exploration accelerated rapidly. Scientists continue to conduct research in Antarctica, and in recent years increasing numbers of tourists have visited Antarctica to appreciate the region’s majestic scenery and wildlife. Seven nations—Argentina, Australia, the United Kingdom, Chile, France, New Zealand, and Norway— claim territory in Antarctica. Other nations, including the United States and Russia, do not acknowledge these claims and make no claims of their own, but reserve rights to claim territory in the future. Since 1961 the continent has been administered under the Antarctic Treaty, an international agreement to preserve the continent for peaceful scientific study.

II

LAND AND CLIMATE

Antarctic Ice Sheet The continent of Antarctica is covered almost completely by a massive ice sheet, which contains about 90 percent of the world’s ice. Permanent floating slabs of ice called ice shelves fringe nearly half of Antarctica’s coastline. Image Makers/The Image Bank

With an area of 14 million sq km (5.4 million sq mi), Antarctica is larger than either Europe or Australia. Its average elevation of more than 2,000 m (6,500 ft) is over twice that of Asia, the next highest continent. However, much of this mass is ice. Below this ice, East Antarctica is a landmass about the size of Australia, and West Antarctica is a collection of islands. Only 2.4 percent of the total continental area is exposed rock. Exposed areas include the peaks of several mountain ranges and other smaller scattered outcrops, both of which poke through the ice cover, as well as dry valleys, glacier-carved areas that are kept clear of snow by gusty winds. Only about 2 percent of the coast is exposed cliffs or beaches; the rest is made up of ice cliffs that extend beyond the end of the continental rock. The Ross and Weddell seas indent the thickened base of West Antarctica where it meets East Antarctica, while the Amundsen and Bellingshausen seas lie at West Antarctica’s outer edge. Numerous bays also indent the outer edge of East Antarctica, creating a jagged coastline.

A

Land of Ice

Brunt Ice Shelf, Antarctica Antarctica's Brunt Ice Shelf floats atop the Weddell Sea. The ice shelves of Antarctica are a major source of icebergs. Graham Neden/Corbis

The total volume of the ice sheet covering Antarctica is estimated at 29 million cu km (7 million cu mi), or about 90 percent of the world’s ice. If the ice sheet melted, the oceans of the world would rise by 60 m (200 ft). Some 11 percent of the ice sheet consists of ice shelves—massive floating slabs of permanent ice fringing the continent—that are anchored to the rock and extend into the surrounding ocean. The largest, Ross Ice Shelf, is about the size of France. The Antarctic ice sheet has an average thickness of 2,160 m (7,090 ft); its greatest recorded depth is more than 4,700 m (15,400 ft). Antarctica’s ice sheet formed over millions of years. As new snow falls, it compresses the layers of older snow beneath it into ice. The physical characteristics of the ice sheet are constantly changing as new ice forms and slides outward toward the coasts. Large masses of moving ice known as glaciers move down the continent’s five major drainage systems in two ways. If there is a layer of water between the glacier and the bedrock beneath it, the whole glacier can slide under the force of gravity. Alternatively, the weight of the accumulated snow and ice can cause the ice crystals of the glacier to form into layers, which glide over one another. Glaciers flow either into ice shelves or directly out to the edges of the continent, where portions break off and form floating masses called icebergs (see Ice: Icebergs). Carried by circumpolar currents and prevailing winds, these icebergs drift westward around the continent and then northward to the Antarctic Convergence before gradually breaking up and melting upon contact with warmer waters. In addition to icebergs, ocean waters close to the continent contain floating sea ice, some attached to the land (fast ice) and some drifting with wind and currents (pack ice). Sea ice melts and freezes

seasonally, covering up to 21 million sq km (8 million sq mi) in late winter and only 5 million sq km (2 million sq mi) in summer.

B

Land Regions

Transantarctic Mountains The Transantarctic Mountains stretch across the entire continent of Antarctica, separating East Antarctica from West Antarctica. Most of the range is covered by Antarctica’s massive ice sheet. Some mountain peaks and exposed coastal areas remain ice-free. Galen Rowell/Corbis

During the Mesozoic Era (about 240 million to 65 million years ago) Antarctica was a central part of Gondwanaland, an ancient landmass that consisted of the present continents of South America, Africa, Antarctica, and Australia as well as the Indian subcontinent. Evidence from oceanic ridges surrounding Antarctica indicates that Gondwanaland began to break up about 150 million years ago. Antarctica gradually drifted towards the South Pole, arriving near its present polar position about 100 million years ago. Climatic cooling caused the gradual formation of the Antarctic ice sheet.

Antarctic Peninsula The Antarctic Peninsula is the northernmost extension of Antarctica, reaching beyond the Antarctic Circle toward South America. Shown here are Adélie penguins, which live much of their lives on the pack ice or in the waters adjoining the peninsula, returning to the land to breed. Art Wolfe/Tony Stone Images

East Antarctica makes up about two-thirds of the continent’s area. The land beneath the ice consists of a basement complex of ancient gneisses, schists, and other metamorphic rocks overlaid by sediments from the Cambrian and Permian periods. Containing evidence of tropical forests and deserts prior to the more recent glacial conditions, these layers reflect the region’s complex climatic history. Covering the land is a huge, complex ice dome rising from coastal plains to a high plateau more than 4,000 m (13,000 ft) in elevation. The Transantarctic Mountains stretch 3,500 km (2,200 mi) along the entire western flank of East Antarctica, separating it from West Antarctica. This range holds back the plateau ice of East Antarctica like a massive dam, penetrated by glaciers that flow into the Ross and FilchnerRonne ice shelves to the west. High peaks—some rising to more than 4,300 m (14,000 ft)—poke through the ice sheet, and other portions of the range are dry valleys that are free of ice. Toward the Indian and Pacific ocean coasts lie several minor ice domes and lower plateaus, some penetrated by other mountain ranges.

Deception Island, Antarctic Region Lying off of the tip of the Antarctic Peninsula, Deception Island is part of an archipelago known as the South Shetland Islands. The island is mountainous and uninhabited. © Microsoft Corporation. All Rights Reserved.

In East Antarctica, at the center of the continent, is the South Pole, also known as the south geographic pole. The South Pole is the point where all lines of longitude converge. Off the Adélie Coast of East Antarctica is the south magnetic pole, the location to which the south-seeking end of a compass needle points due to the Earth’s magnetic fields. Located on land when it was first reached in 1909, the south magnetic pole has migrated gradually out to sea with changes in the fields, a phenomenon known as polar wandering. The remaining third of the continent, West Antarctica, consists of a much lower, undulating ice sheet covering a complex of mountainous islands. The Antarctic Peninsula, the “tail” of land reaching toward South America, was formed by the same geologic processes that formed the Andes Mountains on that continent. Many islands, including the South Shetland Islands, lie off the Antarctic Peninsula. Deep trenches and basins beneath the ice separate the islands of West Antarctica. Vinson Massif, the highest point in Antarctica, has an elevation of 4,897 m (16,066 ft) and lies in the Sentinel Range near the Filchner-Ronne Ice Shelf. Several active volcanoes, including Mount Erebus on Ross Island, dot coastal and island areas. The multilayered land formations of West Antarctica, folded and transformed by geologic structural deformations, reveal a distinct, more turbulent geological history than that of East Antarctica. These formations consist of a Precambrian basement covered by volcanic sediments from the Carboniferous Period, Mesozoic Era, and Tertiary Period. These volcanic sediments are in turn covered by plant-bearing Jurassic and later Tertiary sediments.

C

Climate and Weather

Antarctica: Climate Map Antarctica, the coldest continent in the world, holds the record for the coldest temperature ever recorded on Earth: -89.2° C (-128.6° F). The interior of Antarctica is a windy polar desert with less than 50 mm (less than 2 in) of precipitation a year. Precipitation is greater in the milder coastal areas, averaging more than 200 mm (more than 8 in) annually, much of it in the form of snow dropped by cyclones. © Microsoft Corporation. All Rights Reserved.

Antarctica has several climates, all cold but differing considerably in severity. East Antarctica’s high plateau region yields the lowest year-round temperatures due to its relatively high elevation. The world’s lowest yearly air temperatures, typically –88°C (–126°F), are recorded in late August at Russia’s Vostok station. In coastal regions latitude is more significant than elevation. The higher the latitude— that is, the closer to the pole—the lower the average temperatures. The west coast of the Antarctic Peninsula and the neighboring islands have the mildest climates, with average January temperatures above freezing.

Polar Weather

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The entire region south of the Antarctic Circle, which is the parallel of latitude at 66°30’ south, experiences at least one day of continuous daylight during the Southern Hemisphere’s summer (around December 21) and one day of continuous darkness during the winter (around June 21). The interior of Antarctica has almost continuous daylight during the summer and darkness during the winter. In coastal areas farther north, there are fewer days of continuous daylight and darkness, and sunrises and sunsets occur more frequently. Precipitation falls mainly as snow or ice, with occasional rain in coastal areas. Very little precipitation falls on the high plateau. Average annual accumulations of 50 mm (2 in) there make it one of the world’s driest deserts. Successive low-pressure systems around the coasts and islands bring heavier snow, which is packed down by wind and its own weight to form ice. Winds are light and variable on the plateaus, rarely reaching more than 30 km/h (20 mph), but are strong and persistent closer to the coasts. Katabatic, or downslope, winds blow cold, dense air down the steep slopes from the interior highlands onto the lower ice slopes.

D

Optical Phenomena

Auroras Auroras are rapidly shifting patches and streams of colored lights appearing in the night sky, usually in winter and usually over the Arctic and Antarctic regions. In the northern hemisphere, this phenomenon is called aurora borealis; in the southern hemisphere, it is called aurora australis. Auroras occur when charged particles in the solar wind interact with gases in the earth’s atmosphere. Seen from space, auroras have a characteristic ring shape. National Geographic Society

Antarctica experiences many unique atmospheric optical phenomena. Most spectacular is the aurora australis (southern lights), caused by entry into the upper atmosphere of streams of charged particles (mainly protons and electrons) from the Sun. Deflected by the Earth’s magnetic field, the particles collide with atoms and molecules of atmospheric gases 100 to 140 km (60 to 90 mi) above the Earth’s surface. This produces light in characteristic rays, bands, and rings of various hues. Within the southern auroral zone—a wide circle about 4,000 km (about 2,000 mi) in diameter and centered

around the geomagnetic pole (the south end of the axis of the geomagnetic field that surrounds the Earth)—auroral displays are visible almost every winter night, including the 24-hour-long polar night. Refraction of light from the Sun and Moon by concentrations of ice crystals in the lower atmosphere produces iridescent clouds in the sky and rainbow-like halos around the Sun and Moon. Dry atmosphere chilled by contact with the cold surface of the Earth gives rise to spectacular mirages, in which distant objects are raised above the horizon to appear misleadingly close. Similar atmospheric distortions produce colored disks resembling the Sun and Moon—called parhelia, or sun dogs, and parselene respectively—as well as colored arches in the sky.

E

Vegetation

Almost completely covered by thick ice, Antarctica has very little land available for soils to form or vegetation to settle. Existing soils were formed late in the continent’s geologic history and have little organic content or water-holding capacity. Isolation from other continents makes it difficult for new types of vegetation to spread to Antarctica. Constant low temperatures, high winds, and lack of moisture discourage all but the hardiest plants, which may be capable of active growth for only a few days per year. These factors limit plant life in Antarctica almost entirely to protists (simple, often onecelled organisms), algae, lichens, and mosses. Only two known species of flowering plants, both found only on the Antarctic Peninsula and neighboring islands, grow in Antarctica. The continent has no equivalent of Arctic tundra, which supports a greater variety of plant life: Antarctica’s richest vegetation compares with the northernmost, scarcest Arctic polar desert vegetation. Nevertheless, patches of vegetation grow on all known rocky outcrops in Antarctica, to within 290 km (180 mi) of the South Pole. Snow algae grow on snow and ice surfaces close to the coast, especially along the Antarctic Peninsula where seabird droppings and sea spray provide nutrients. Antarctic waters support other types of vegetation. Coastal seaweeds thrive on and around islands near the Antarctic Convergence, but are inhibited farther south where sea ice scrapes the shores. The cold waters of the Southern Ocean support masses of phytoplankton—minute floating plants including diatoms, dinoflagellates, and other algae—that proliferate in summer, especially in areas where upwelling brings nutrient-rich waters to the surface (see Marine Life: Environmental Factors). Phytoplankton provides a rich source of food for marine animals.

F

Animal Life

Penguins on Paulet Island Several species of penguin inhabit the Antarctic region. Pictured here is a colony of Adélie penguins on Paulet Island, located off the tip of the Antarctic Peninsula. © Microsoft Corporation. All Rights Reserved.

The harsh climate and sparse vegetation of Antarctica’s land regions support only microscopic animals and primitive insects. Protozoa, nematodes, tardigrades, and other minute forms inhabit damp soils. Other invertebrate species include springtails and mites. The wingless midge, which grows up to 12 mm (0.47 in) long, is the largest land animal. In contrast to the land, the Southern Ocean supports a wide variety of animal life, which all depends directly or indirectly on the phytoplankton of the surface waters. Zooplankton—including krill, copepods, arrowworms, jellyfish, fish larvae, and larval forms of bottom-dwelling starfish, bristle worms, anemones, and mollusks—feed on phytoplankton. Zooplankton in turn provide food for fish and squid, both of which are abundant in Antarctic waters. Concentrated swarms of zooplankton (especially of krill and young fish), together with larger fish (especially of superfamily Notothenioidea) and squid, provide food for the seals, whales, and seabirds that are Antarctica’s major predators and most prominent animals. Seven species of whales and eight species of dolphins feed in the Southern Ocean; several penetrate far south into the pack ice during the summer. Seven species of seals breed within the Antarctic region, some on southern island shores and some exclusively within the pack ice region. About 40 species of seabirds—including 7 species of penguins, 4 species of albatross, 20 species of petrels, as well as cormorants, gulls, skuas, and terns—breed within the region, mainly on islands and continental coasts. Large marine animals played an important role in attracting humans to Antarctica: Sealers and whalers contributed substantially to the early exploration of the Southern Ocean and coastal regions. Fur seals and southern elephant seals of the islands near the Antarctic Convergence were hunted for skins and oil throughout the 19th century until economically profitable stocks were depleted. Hunting of elephant seals continued into the 1950s. From 1904 through the 1960s whalers hunted large migratory whales (blue, fin, sei, humpback, and sperm whales) for oil in Antarctic waters from whaling stations on several Antarctic islands and from floating factory ships. Beginning in the 1960s concern that seals and whales would be hunted to extinction prompted several measures to protect surviving populations. See the Management and Conservation section of this article, below.

G

Mineral Resources

Although only about 1 percent of the continent’s ice-free areas have been surveyed for minerals, evidence indicates that Antarctica contains rich mineral deposits. The Transantarctic Mountains contain huge deposits of coal as well as copper, lead, zinc, silver, tin, and gold. The Prince Charles Mountains of East Antarctica are rich in iron ore; the Antarctic Peninsula contains copper and molybdenum ores; and the Dufek Massif includes ores of chromium, platinum, copper, and nickel. It is also believed that deposits of petroleum and natural gas exist in the continental shelf regions, such as the area under the Ross Sea. Although Antarctica has prospects for mineral development, there are concerns about the potential environmental and political impacts of this development. In 1991 the signatory nations of the Antarctic Treaty agreed to a 50-year moratorium on commercial mining activity. The only mineral resources currently used are sand, gravel, and crushed rocks for constructing airstrips and building foundations at the scientific stations.

III

EXPLORATION

Iceberg Grotto in Antarctica Two members of a British expedition, led by Robert F. Scott between 1910 and 1913, explore an iceberg grotto in Antarctica. Their ship Terra Nova can be seen in the distance. Herbert Ponting/Popperfoto/Archive Photos

Long before Antarctica was discovered, medieval world maps showed a huge continent, Terra Australis, occupying more than half of the Southern Hemisphere. From the late 15th century several voyages dispelled beliefs about the continent’s vastness and its attachment to Africa, South America, and Australia. Over the next two centuries explorers came upon many of the islands within the present-day Antarctic region, including the South Sandwich Islands, South Georgia, and the Kerguelen Islands. In 1773 British navigator Captain James Cook traveled farther south than anyone before him, reaching latitude 71°10’ south. He explored the edge of the pack ice and was the first to cross the Antarctic Circle. Cook saw no land, but judged correctly that the massive icebergs around him could have accumulated only on land nearby. In July 1819 a Russian naval expedition led by Fabian Gottlieb von Bellingshausen complemented and enhanced Cook’s findings. Bellingshausen charted South Georgia and the South Sandwich Islands, then edged eastward along the pack ice, twice crossing the Antarctic Circle, until he was stopped by ice cliffs. In the following year he returned south to the ice’s edge, continuing eastward and pressing through pack ice very close to the continental coast. Later he discovered Peter I Island and Alexander Island. Like Cook, Bellingshausen sailed to within sight of Antarctica without the satisfaction of positive discovery. British naval officer Edward Bransfield sighted part of the present-day Antarctic Peninsula in 1820. Sealers of many nations, who had been exploring Antarctic and subantarctic (lying just north of the Antarctic Convergence) islands and waters since Cook’s voyage, had sighted the South Shetland Islands, other parts of the Antarctic Peninsula, and the South Orkney Islands by the early 1820s. In 1823 British navigator James Weddell explored the present-day Weddell Sea, setting a new farthestsouth record of latitude 74° south. Within the next 20 years sealers and whalers explored present-day Enderby Land on the eastern continental coast, Graham Land (now the northern part of the Antarctic Peninsula) and Adelaide Island off its coast, and the Sabrina Coast of East Antarctica and the neighboring Balleny Islands. Between 1838 and 1843 three naval scientific expeditions added substantially to knowledge about Antarctica’s coastline. French explorer Jules Dumont d’Urville discovered a part of the Antarctic Peninsula, which he named Terre Louis Philippe. He also discovered neighboring islands, now known as D’Urville and Joinville islands, and part of the East Antarctica coast, which he named Terre Adélie (Adélie Coast). American explorer Charles Wilkes penetrated the pack ice to explore the ice coast of present-day Wilkes Land. British explorer Sir James Clark Ross discovered the Ross Sea, reaching a new record latitude of 78° south. Ross charted the volcanic island and the massive ice shelf that now bear his name; he also discovered present-day Victoria Land and located the south magnetic pole, which at that time was positioned among Victoria Land’s mountains. From the 1870s to the 1890s German, Scottish, and Norwegian whalers explored the Antarctic Peninsula, discovering Bismarck Strait and several other new channels and islands. On January 24, 1895, Norwegian whaler Henryk John Bull made the first recorded landing on the continent outside the Antarctic Peninsula, at Cape Adare near the Ross Sea. In 1904 Norwegian whaler Carl Anton Larsen established the first Antarctic whaling station, on South Georgia.

In 1895 delegates to the Sixth International Geographical Congress in London, England, declared that exploration of the Antarctic region was the greatest geographical exploration still to be undertaken, and urged that scientific discovery of Antarctica begin before the close of the century. Within the next few years expeditions from six European nations took the field. From 1897 to 1899 a Belgian expedition explored the west coast of the Antarctic Peninsula by ship. The vessel became trapped for more than 13 months in the pack ice of Bellingshausen Sea, involuntarily becoming the first expedition to winter south of the Antarctic Circle. In 1899 members of a small British expedition led by Carsten Borchgrevink became the first people to spend the winter on the continent, at Cape Adare. The larger and more successful British National Antarctic Expedition (1901-1904), led by naval officer Robert Falcon Scott, spent two winters in McMurdo Sound in the southern Ross Sea, exploring inland, discovering the polar plateau, and making the first attempt to reach the South Pole. Although Scott failed to reach the pole, he achieved a new farthest-south record of 82°17’ south. Several other European expeditions traveled to Antarctica during this period. The German South Polar Expedition, which lasted from 1901 to 1903, became caught in pack ice 80 km (50 mi) from the shore of East Antarctica, wintering on board and freeing themselves the following summer. The Swedish National Expedition from 1901 to 1904 set up a base on Snow Hill Island on the eastern flank of the Antarctic Peninsula; despite losing their ship in the pack ice, the crew explored the area north and south of the island. The Scottish National Antarctic Expedition of 1902 to 1904 wintered on the South Orkney Islands and explored the unknown east coast on the Weddell Sea. The expedition’s meteorological observatory on Laurie Island, taken over by the Argentine navy upon Scottish departure, has since provided Antarctica's longest unbroken climatic record. Two French expeditions led by physician Jean-Baptiste Charcot wintered in the peninsula area in 1903 and 1908, discovering the Loubet Coast north of Adelaide Island and exploring south into Marguerite Bay and the Bellingshausen Sea.

A

Race to the South Pole

Race to the South Pole In the early 20th century British explorers Robert Falcon Scott and Ernest Shackleton made attempts to reach the South Pole, but severe weather, hunger, and sickness forced them to turn back before attaining their goal. The superior skill and technique of Norwegian explorer Roald Amundsen enabled him to take a shorter, steeper route to the pole, which he reached in December 1911. Scott reached the pole just weeks later on his second attempt but died on the return journey. © Microsoft Corporation. All Rights Reserved.

In 1908 British explorer Ernest Shackleton, who had accompanied Scott on his earlier expedition, led a British expedition expressly to reach the South Pole. Pioneering a route from McMurdo Sound across the Ross Ice Shelf, and through the Transantarctic Mountains by way of the Beardmore Glacier, he and three colleagues reached the polar plateau. Lack of food forced the party to turn back within 179 km (111 mi) of the pole. In addition to attaining a new farthest-south point, they returned from the mountains with samples of coal. Due to the type of vegetation necessary for the formation of coal, this finding confirmed that Antarctica had once been semitropical. Other members of the same expedition, under William Edgeworth David, reached the south magnetic pole in 1909. In 1910 Scott returned to McMurdo Sound, again to seek the pole. In October 1911 he and four companions left their base on Ross Island and began traveling along Shackleton's route, hauling their supplies on sleds. Scott’s party reached the pole on January 17, 1912, only to find that Roald Amundsen, a Norwegian explorer with experience on both Arctic and Antarctic expeditions, had reached the pole almost five weeks earlier. Scott and his party died on the return journey. Two of the men were injured along the route, and the rest died from starvation and exposure at a camp just short of their supply station. Amundsen originally sought the North Pole, but when that was conquered in 1909 he set his sights on the South Pole. He and his companions set out from the Bay of Whales on the Ross Ice Shelf near Roosevelt Island just four days before Scott’s team began their journey. Outmatching Scott's group in experience and technique and using efficient dog teams, Amundsen’s group climbed a steeper, shorter glacier (now Amundsen Glacier) to the plateau. They arrived at the pole on December 14, 1911, and arrived safely back at their base the following month.

Scott’s Team at the South Pole

British explorer Robert F. Scott reached the South Pole in January 1912, only to discover that Norwegian explorer Roald Amundsen had gotten there first. This photograph, along with other photographs and documents, was found with the bodies of Scott and his men, who all died on the return journey. Hulton Deutsch/Corbis

With the pole conquered, explorers began to take on new challenges. In 1912 Australian scientist Douglas Mawson led the Australian Antarctic Expedition to explore the coast of East Antarctica directly south of Australia. An overland party explored the area now known as George V Land, although two of Mawson’s companions died and Mawson returned to his base barely alive. Shackleton returned in 1915, intending to cross the continent from the Weddell Sea to the Ross Sea by way of the pole. But his ship never reached the continent; it became trapped by the ice and sank ten months later. Shackleton reached South Georgia in a lifeboat, and returned to rescue his stranded men three months later.

B

Aerial Exploration

Despite these numerous land and sea expeditions, by 1920 explorers had surveyed only 5 percent of Antarctica. Advances in aviation and aerial photography rapidly increased the rate of exploration, and by 1940 most of the coast and several inland areas had been sighted and named. Australian aviator Sir George Hubert Wilkins made the first Antarctic flight in 1928, traveling 1,000 km (600 mi) from Deception Island along the Antarctic Peninsula. In 1929 American aviator Richard Evelyn Byrd flew from the Bay of Whales on the Ross Ice Shelf to the South Pole and back, taking aerial photographs of many square kilometers of Antarctica’s interior. Byrd returned to the same area to conduct more aerial photographic surveys between 1933 and 1935. Scientific sledging parties gathered scientific data and astronomical fixes that supplemented Byrd’s aerial photography. Byrd’s expeditions established that mountains and high plateau lay in every direction behind the Ross Ice Shelf and that Antarctica was beyond doubt a single continent. Between 1929 and 1931 the British, Australian, and New Zealand Antarctic Research Expedition (BANZARE) used floatplanes to explore and photograph many kilometers of East Antarctica’s coast. Between 1929 and 1934 Norwegian whaler Lars Christensen equipped his expeditions with seaplanes, which flew over and photographed the remote island of Bouvetoya and stretches of the Antarctic coast from Enderby Land to Coats Land. In 1936 American explorer Lincoln Ellsworth crossed Antarctica by air, flying from Dundee Island at the tip of the Antarctic Peninsula to the Bay of Whales. In 1938 a German expedition flew over and photographed an extensive area of East Antarctica now known as Queen Maud Land (Dronning Maud Land).

C

Land Claims

In 1908 Britain revived long-standing territorial claims, based on discovery, to South Georgia, the South Shetland, South Orkney, and South Sandwich islands, as well as Graham Land, to justify the control and taxation of whaling in those areas. In 1923 Britain claimed the Ross Ice Shelf and adjacent

coasts (now Ross Dependency) for similar reasons. In 1924 France claimed Adélie Land, a narrow sector of East Antarctica where Dumont d'Urville had landed in 1840. In 1933 Britain claimed the sectors of East Antarctica that BANZARE had explored as an Australian territory; this area was formally declared the Australian Antarctic Territory in 1936. Spurred by the possibility of a German claim, Norway in 1939 claimed the sector of East Antarctica later called Queen Maud Land, along with Peter I Island and Bouvetoya. When Britain set up wartime stations in the peninsular region in 1943, Argentina and Chile lodged rival claims to the sector. Because U.S. policy for Antarctica states that all nations should have free access for peaceful pursuits, the U.S. government did not support claims made by American explorers and does not recognize any foreign territorial claims.

IV

MANAGEMENT AND CONSERVATION

First Crossing of Antarctica During the International Geophysical Year (1957-1958), British explorer Vivian Fuchs led the first crossing of Antarctica. Traveling by snow tractor, Fuchs traversed the 3,473 km (2,158 mi) from the Weddell Sea to the Ross Sea. Express Newspapers/Archive Photos

During the exploratory period of Antarctic history, scientific research was less important than discovery. In 1939 the U.S. Antarctic Service Expedition under Richard Byrd introduced the concept of permanent stations with science as a major objective. Two stations, at Bay of Whales and Stonington Island off the Antarctic Peninsula, opened in 1941, but closed after a year when the United States entered World War II. In 1943 Britain set up several permanent stations. Although the British stations were set up primarily to assert sovereignty against Argentine and Chilean claims in the maritime Antarctic, they were staffed by scientists. Establishment of these early bases began the era of scientific research that was closely coupled with political rivalry. During this period Argentina, Australia, Chile, and France established permanent

national expeditions, both to maintain territorial claims and to conduct scientific research. In 1946 the United States conducted Operation Highjump, the largest Antarctic expedition to date, involving massive exploration by means of ships, aircraft, and temporary land stations. This operation also gave U.S. military forces experience in polar conditions, seen as a necessity should a confrontation with Soviet troops occur in the Arctic region of the Union of Soviet Socialist Republics (USSR). Against the backdrop of the Cold War, a period of political tension between the Soviet Union and its associated nations and Western countries allied with the United States, the USSR declared its right to make an Antarctic territorial claim in 1950. The International Geophysical Year (IGY), a period of worldwide coordinated geophysical research from July 1957 to December 1958, proved a useful step toward resolving political disputes in Antarctica. Twelve nations (Argentina, Australia, Belgium, the United Kingdom, Chile, France, Japan, New Zealand, Norway, South Africa, the United States, and the USSR) agreed to cooperate on scientific research in Antarctica. Starting a year beforehand, survey parties established research stations on an unprecedented scale. During the IGY more than 5,000 scientists and support staff served at 49 Antarctic stations. Projects included studies of a wide range of geophysical topics such as upper atmosphere physics, meteorology, oceanography, glaciology, seismology, and geology. The IGY led to the establishment in 1958 of the Special (later Scientific) Committee on Antarctic Research (SCAR), a group designed to coordinate additional research; SCAR continues in that same function today.

A

Antarctic Treaty

Amundsen-Scott Base

Flags from the nations supporting the 1961 Antarctic Treaty are displayed in front of the Amundsen-Scott Base at the South Pole. The treaty dedicated the entire continent to peaceful scientific research and suspended territorial claims. Dr. David Millar/Photo Researchers, Inc.

The international cooperation and overall success of the IGY led the governments of the 12 nations to develop the Antarctic Treaty, an agreement to extend cooperation in Antarctica after the IGY ended. Concluded in 1959, the treaty asserts that Antarctica be used only for peaceful purposes; prohibits military measures, fortifications, and weapons testing; and requires freedom of scientific investigation and scientific cooperation to continue. It provides for exchanges of scientific personnel, plans for scientific programs, and scientific observations and results. It also provides for exchanges of observers, mutual inspection of stations and of ships and aircraft that are loading or discharging cargoes or personnel, and meetings of representatives to promote its objectives. The treaty prohibits nuclear explosions and disposal of nuclear waste in the treaty area (south of latitude 60° south). The treaty addressed long-standing territorial conflicts of interest over Antarctica. It made no ruling on the validity of existing claims by seven nations (Argentina, Australia, Britain, Chile, France, New Zealand, and Norway), and particularly on the overlapping claims of Argentina, Britain, and Chile. However, it forbids any new claims while the treaty is in effect and states that no member nations are required to recognize the claims of other nations. Although the United States and the USSR reserved the right to lodge future claims of their own, the indefinite freeze on territorial claims served to ease Cold War suspicions of each other’s activities in Antarctica. Starting primarily as a tentative exercise in scientific cooperation, the treaty gradually assumed a larger management role. The nations that signed the treaty became Antarctica’s governing body, the Antarctic Treaty System (ATS). Other interested nations have joined the ATS over the years. Those that take part in substantial scientific Antarctic research join the treaty administration as consultative parties, or full voting members. Other nations not engaged in substantial research but agreeing to abide by the treaty join as nonconsultative parties. By 1999, 43 states had signed the treaty; 27 of these had consultative status. Only two countries, Estonia and Pakistan, undertake Antarctic research without membership; both are members of SCAR. Members of the ATS meet yearly to exchange information, discuss matters of common interest, and agree on measures to further the principles and objectives of the Antarctic Treaty.

B

Conservation Measures

The ATS has drafted several significant resolutions aimed at resource conservation and protection. The Agreed Measures for the Conservation of Antarctic Fauna and Flora (1964) protects all life on Antarctica from nonscientific or nonsubsistence killing. The Convention on the Conservation of Antarctic Seals (1972) protects all seals south of the Antarctic Circle through yearly catch limits, restricted sealing seasons, and a ban on the killing of Ross and fur seals. The Conservation of Antarctic Marine Living Resources (1980) manages commercial fisheries in the Southern Ocean by imposing quotas and bans on particular species and fishing zones. The Protocol on Environmental Protection, also known as the

Madrid Protocol (1991), is a comprehensive set of measures for regulating human activities and preserving the environment of Antarctica. Whaling falls under the control not of the ATS, but of the International Whaling Commission (IWC). Established in 1946 to regulate the industry in all the world’s oceans, the IWC set progressively lower limits on whaling throughout the 1970s. In 1994 the IWC established an Antarctic whale sanctuary to protect primary feeding grounds.

V

SCIENTIFIC RESEARCH

McMurdo Base, Antarctica McMurdo is the largest scientific station in Antarctica, with laboratories and living quarters for scientists and visitors. During the summer months, McMurdo accommodates up to a thousand residents. © Microsoft Corporation. All Rights Reserved.

At the beginning of the 21st century, scientists from 27 nations operating at 43 stations participated in year-round research on Antarctica. Most stations are located on rocky shores or coastal ice slopes. A few stations sit farther inland on the ice cap, cut off from the outside world except by radio. Small stations have up to a dozen scientists and support staff, while larger stations may have two to three times as many. The largest is McMurdo, which may accommodate several thousand visitors in summer, including those on their way to inland stations or field camps. Life at the smaller stations is simple, with comfortable living quarters and a family atmosphere. Larger stations resemble hotels or barracks, with cafeteria meals and fewer home comforts. The largest stations are effectively small towns, with stores, cinemas, chapels, banks, offices, laboratories, garages, powerhouses, airstrips, and hostels for residents and visitors. Men far outnumber women in Antarctica. Although some people spend one or two years there at a time, most visit just for the summer months when good weather facilitates fieldwork. Many scientists who work indoors in laboratories or offices, perhaps servicing self-recording instruments or collecting data by radio from remote instruments, may hardly be aware of the cold world outside. Field scientists who travel in small parties by tractor or skidoo (motorized toboggan), surveying or collecting specimens and camping for weeks on end, live and work much closer to the challenges of Antarctica’s unique landscape and climate.

Scientists have studied extensively Antarctica’s ice sheet and the land beneath it. Geologists and solidearth geophysicists conduct research in plate tectonics, the study of the plates of the Earth’s crust. Antarctica is a valued source of fossils, which provide a record of the breakup of the supercontinent Gondwanaland, and meteorites, including those from the Moon and from Mars. Glaciologists measure the movement and the layers of the ice sheet. They use satellites to plot the slow movement of the ice surface. Ice cores drilled through the layers of the ice sheet have enabled French, Russian, and American scientists to trace changes in the 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 as a source of fresh water. Biologists study the plant and animal life of the Antarctic region. These scientists model the continent’s relatively simple ecosystems, study responses of plants and animals to hostile environments, and measure the impacts of people on the polar environment. Marine biologists study the local marine food chains. The atmosphere above the continent provides another important area of study. Antarctica provides important information for climatologists modeling atmospheric circulation, or the constant flow of warm air toward the poles and cold air toward the equator (see Meteorology: Energy Flow and Global Circulation). Antarctica’s relatively unpolluted, thin, and dry atmosphere allows scientists to study phenomena such as auroras, cosmic rays, and transmission of radio waves. Most notably, these scientists study the levels of ozone, the atmospheric gas that protects life on the Earth from the Sun’s harmful ultraviolet radiation. In 1985 they identified the so-called ozone hole, a region of depleted ozone that develops over Antarctica each spring and virtually disappears several months later. Continuous monitoring revealed that the size of the hole continued to increase. Largely due to the work of Antarctic scientists, many nations have reduced or eliminated the use of chlorofluorocarbons (CFCs), which have been linked to ozone depletion. In 1987, 36 nations, including the United States, signed the Montréal Protocol, a treaty to protect the ozone layer. In the 1990s further steps were taken to ban the production of CFCs. Many scientists believe that the presence of CFCs in the atmosphere peaked in 2001 and then began to decline. Nevertheless, U.S. government scientists reported in 2006 that the ozone hole over Antarctica had reached its greatest extent ever. They do not expect the ozone layer to recover until 2065. Finally, medical researchers study the scientists and support staff living in Antarctica. Physicians have made discoveries about the behavior of viruses in a cold, isolated environment. Immunologists study the ability of expeditioners to resist infection. Psychological and sleep studies are frequently conducted during the winter, when the extreme climate and lack of visitors isolate workers from the outside world.

VI

GROWING INTEREST

Until the middle of the 20th century only explorers visited Antarctica. With the establishment of the first research stations the continent became the preserve of scientists. More recently Antarctica has slipped into public awareness, both as a wilderness in need of conservation and as a venue for tourism. The two trends began together: Tourists from the 1960s onward drew attention to accumulating garbage and abandoned buildings littering Antarctica—relics of installations used and discarded by scientists. In the 1970s and 1980s growing environmental organizations such as Greenpeace and the World Wildlife Fund (WWF) effectively organized public opinion against practices at the bases that impacted the natural environment, such as construction near animal breeding grounds, improper disposal of containers and chemical wastes, and open burning of garbage. Largely as a result of public pressure, many stations cleaned up former dumping sites. They also began disposing of waste by shipping it back to the countries operating the bases. Environmental groups continue to oppose mining in Antarctica and to press for high standards of environmental protection. Some seek to have Antarctica managed as a world park, a status akin to a national park in the United States. This would protect Antarctica from mining, military activities, and permanent human settlement. Tourism has grown slowly since its beginning in 1958. In the late 1990s about 10,000 tourists visited Antarctica annually between November and March. Most travel by ship and only go ashore for brief periods, so they require very few facilities on land. Several thousand more tourists take sightseeing flights over the continent from Australia and New Zealand. Although some environmental groups feel that an increase in tourism would undoubtedly increase its impact, on its current scale tourism makes few demands on the environment and does not interfere significantly with scientific activities. In introducing nonscientists to the scenery, wildlife, and mystery of Antarctica, tourism may well be helping broaden public interest in Antarctica, thereby ensuring a safer future for this most remarkable area of the world.

Contributed By: Bernard Stonehouse Microsoft ® Encarta ® 2008. © 1993-2007 Microsoft Corporation. All rights reserved.