Antarctica is a continent located in the very south of the Earth, the center of Antarctica roughly coincides with the south geographic pole. Antarctica is washed by the waters of the Southern Ocean (previously this ocean was considered the southern parts of the Indian, Pacific and Atlantic Oceans). The area of the continent is about 14.4 million km² (of which 1.6 million km² are ice shelves). Antarctica is also called the part of the world consisting of the continent Antarctica and the adjacent islands.
Antarctica was discovered on January 16 (28), 1820 by the Russian expedition led by Thaddeus Bellingshausen and Mikhail Lazarev, who, on sloops Vostok and Mirny, approached it at 69°21′ S. 2°14′ W. (area of the modern Bellingshausen Ice Shelf). The first to enter the continental part were the captain of the Norwegian ship “Antarctica” Christensen and the science teacher Karlsten Borchgrevink on January 24, 1895.
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Topography and Ice Sheet.
Antarctica is the highest continent on Earth, with an average surface elevation of over 2,000 meters above sea level and reaching 4,000 meters in the center of the continent. Most of this height is a permanent ice sheet of the continent, under which the continental relief is hidden and only ~5 % of its area is ice-free – mainly in West Antarctica and the Transantarctic Mountains: islands, coastal areas, the so-called “dry valleys” and individual ridges and mountain peaks (nunataks) that rise above the ice surface. Transantarctic mountains that cross almost the entire continent divide Antarctica into two parts – West Antarctica and East Antarctica, which have different origins and geological structure. In the east there is a high (the highest elevation of the ice surface ~4,100 m above sea level) ice-covered plateau. The western part consists of a group of mountainous islands connected by ice. On the Pacific coast there are the Antarctic Andes, the height of which exceeds 4000 m; the highest point of the continent – 4892 m above sea level – the Vinson Massif of the Sentinel Ridge. West Antarctica is also home to the continent’s deepest depression, the Bentley Trench, probably of rift origin. The Bentley Depression, filled with ice, reaches a depth of 2555 m below sea level.
The Antarctic ice sheet is the largest on our planet and exceeds the nearest in size Greenland ice sheet by approximately 10 times in area. It concentrates~30 million km³ of ice, i.e. 90% of all land ice. It has the form of a dome with increasing steepness of the surface towards the coast, where in many places it is framed by ice shelves. The average thickness of the ice layer is 2500-2800 m, reaching a maximum value in some areas of East Antarctica – 4800 m. Ice accumulation on the ice sheet leads, as in the case of other glaciers, to ice flowing into the ablation (destruction) zone, which is the continental coast (see Fig. 3); the ice is chipping away in the form of icebergs. The annual volume of ablation is estimated at 2500 km³.
A specific feature of Antarctica is the large area of ice shelves (low (blue) areas of West Antarctica), amounting to ~10% of the area above sea level; these glaciers are the sources of icebergs of record sizes, significantly exceeding the size of icebergs of the Greenland outlet glaciers; for example, in 2000, the largest known at this time (2005) iceberg B-15 of over 10,000 km² broke away from the Ross Ice Shelf Glacier. In winter (northern hemisphere summer), the area of sea ice around Antarctica increases to 18 million km² and decreases to 3-4 million km² in summer.
The ice cover of Antarctica was formed about 14 million years ago, apparently facilitated by the rupture of the seal connecting South America and the Antarctic Peninsula, which led in turn to the formation of the Antarctic Circumpolar Current (Western Winds Current) and the isolation of Antarctic waters from the World Ocean – these waters form the so-called Southern Ocean.
Antarctica is a tectonically calm continent with little seismic activity, the manifestations of volcanism are concentrated in West Antarctica and are associated with the Antarctic Peninsula, which arose during the Andean Period of mountain building. Some of the volcanoes, especially the island ones, have erupted in the last 200 years. The most active volcano in Antarctica is Erebus. It has been called “the volcano guarding the way to the South Pole.”
Antarctica has an extremely harsh cold climate. In East Antarctica there is an absolute cold pole, where temperatures down to -89.2 °C were recorded (Vostok station area).
Another peculiarity of East Antarctica meteorology is runoff (catabatic) winds, caused by its dome-shaped relief. These stable southerly winds arise on sufficiently steep slopes of the ice sheet due to cooling of the air layer near the ice surface, the density of the surface layer increases and it flows down the slope under the action of gravity. The thickness of the air flow layer is usually 200-300 m; due to the large amount of ice dust carried by the wind, horizontal visibility in such winds is very low. The strength of the runoff wind is proportional to the steepness of the slope and reaches its greatest strength in coastal areas with a high slope toward the sea. Runoff winds reach their maximum strength in Antarctic winter – from April to November they blow almost continuously around the clock, from November to March – at night or when the Sun is low above the horizon. In summer during the daytime hours due to heating of the near-surface air layer by the Sun, the runoff winds near the coast stop.
Data on temperature changes from 1981 to 2007 show that the temperature background in Antarctica changed unevenly. For West Antarctica, an increase of temperature was observed in general, whereas no warming was detected for East Antarctica and even some negative trend was noted. It is unlikely that the process of melting of Antarctica will increase significantly in the 21st century. On the contrary, the amount of snow falling on the Antarctic ice sheet is expected to increase with rising temperatures. However, due to warming, more intense destruction of the ice shelves and acceleration of the movement of Antarctic outlet glaciers that release ice into the world’s oceans is possible.
Due to the fact that not only average annual temperatures, but in most areas even summer temperatures in Antarctica do not exceed zero degrees Celsius, precipitation there falls only in the form of snow (rain is an extremely rare phenomenon). It forms a glacial (snow is compressed under its own weight) cover with a thickness of more than 1700 m, reaching 4300 m in some places. Antarctic ice concentrates up to 90% of all fresh water on Earth.
In the 1990s, Russian scientists discovered an ice-free subglacial lake Vostok – the largest of the Antarctic lakes, with a length of 250 km and a width of 50 km, the lake holds about 5400 thousand km³ of water.
In January 2006, geophysicists Robin Bell and Michael Studinger of the U.S. Lamont-Dogerty Geophysical Observatory discovered the second and third largest subglacial lakes, 2,000 km² and 1,600 km² respectively, located at a depth of about 3 km from the continental surface. They said it could have been done earlier if data from the 1958-1959 Soviet expedition had been analyzed more thoroughly. In addition to these data, satellite data, radar readings and measurements of the gravitational force on the surface of the continent were used.
In total, more than 140 subglacial lakes were discovered in Antarctica in 2007.
The biosphere in Antarctica is represented in four “life arenas”: coastal islands and ice, coastal oases on the mainland (such as the “Banger Oasis”), nunatak arenas (Mount Amundsen near Mirny, Mount Nansen on Victoria Land, etc.) and the ice sheet arena.
Plants and animals are most common in the littoral zone. Terrestrial vegetation in ice-free areas exists mainly in the form of various types of mosses and lichens and does not form a closed cover (Antarctic moss-lichen deserts).
Antarctic animals are completely dependent on the coastal ecosystem of the Southern Ocean: due to the scarcity of vegetation, all significant food chains of coastal ecosystems begin in the waters surrounding Antarctica. Antarctic waters are particularly rich in zooplankton, primarily krill. Krill directly or indirectly form the basis of the food chain of many species of fish, cetaceans, squids, seals, penguins and other animals; there are no fully terrestrial mammals in Antarctica; invertebrates are represented by about 70 species of arthropods (insects and spiders) and soil-dwelling nematodes.
Of the land animals, there are seals (Weddell’s seals, crab seals, sea leopards, Ross’s seals, sea elephants) and birds (several species of petrels, two species of skuas, Adelie penguins and emperor penguins).
In freshwater lakes of mainland coastal oases – “dry valleys” – there are oligotrophic ecosystems inhabited by blue-green algae, roundworms, oar-footed crustaceans (cyclops) and daphnia, while birds (petrels and skuas) fly in here occasionally.
Nunataks are characterized only by bacteria, algae, lichens and strongly depressed mosses, while only skuas occasionally fly into the ice sheet, following humans.
There is a suggestion that subglacial lakes in Antarctica, such as Lake Vostok, have extremely oligotrophic ecosystems, virtually isolated from the outside world.
In 1994, scientists reported a rapid increase in the number of plants in Antarctica, which seems to confirm the hypothesis of global climate warming on the planet.
The Antarctic Peninsula with its adjacent islands has the most favorable climatic conditions on the continent. It is here that the region’s only flowering plants, the Antarctic meadowsweet and kito colobanthus, grow.
The first ship to cross the southern polar circle belonged to the Dutch; it was commanded by Dirk Heeritz, who sailed in Jacob Mague’s squadron. In 1559, in the Strait of Magellan, Geeritz’s vessel lost sight of the squadron after a storm and sailed south. When it went down to 64° S., high land was discovered there. In 1671 La Roche discovered South Georgia; in 1739 Bouvet Island was discovered; in 1772 in the Indian Ocean Yves-Joseph Kerglen, a French naval officer, discovered an island named after him.
Almost simultaneously with the Kerglen voyage from England, James Cook set out on his first voyage to the southern hemisphere, and already in January 1773 his vessels Adventure and Resolution crossed the southern polar circle at the meridian 37°33′ E. After a difficult struggle with the ice, he reached 67°15′ S., where he was forced to turn north. In December 1773 Cook sailed again to the southern ocean, crossed it on December 8, and on the parallel of 67°5′ S. was wiped out by ice. Cook then proceeded southward and at the end of January 1774 reached 71°15′S, just SSW of Tierra del Fuego. Here an impenetrable wall of ice prevented him from proceeding further. Cook was one of the first to reach the South Polar Seas and, encountering solid ice at several points, declared that it was impossible to penetrate further. He was believed, and for 45 years no polar expeditions were undertaken.
In 1819 the Russian sailors F.F. Bellingshausen and M.P. Lazarev on the military sloops Vostok and Mirny, visited South Georgia and tried to penetrate deep into the Southern Arctic Ocean. For the first time, in January 1820, almost on the Greenwich meridian, they reached 69°21′ S.; then, having gone beyond the polar circle, Bellingshausen passed along it eastward to 19° E., where he crossed it again and reached almost the same latitude (69°6′) again in February 1820. Further eastward it ascended only to the 62° parallel and continued along the edge of the floating ice. Then, on the meridian of the Balleny Islands, Bellingshausen reached 64°55′, in December 1820 reached 161°W, passed the southern polar circle and reached 67°15′ S., and in January 1821 reached 69°53′ S. Near the meridian of 81° he discovered the high shore of Peter I Island, and passing further eastward, inside the southern polar circle – the coast of Alexander I. Thus, Bellingshausen was the first to make a complete voyage around Antarctica at latitudes from 60° to 70°.
After that, the study of the continent’s coast and interior began. Numerous explorations were made by British expeditions led by Ernest Shackleton (about them he wrote the book “The Most Terrible Crusade”). In 1911-1912 between the expeditions of the Norwegian explorer Roald Amundsen and the Englishman Robert Scott there was a real race to conquer the South Pole. Amundsen was the first to reach the South Pole, a month after him, Robert Scott’s party arrived at the cherished point and died on the way back.
Since the middle of the XX century the study of Antarctica on an industrial basis began. Numerous permanent bases were established on the continent by different countries, conducting meteorological, glaciological and geological research all year round. December 14, 1958 the third Soviet Antarctic expedition, led by Evgeny Tolstikov, reached the South Pole of Inaccessibility and founded there a temporary station “Pole of Inaccessibility.
Because of the harshness of the climate, Antarctica has no permanent population. However, scientific stations are located there. The temporary population of Antarctica varies from 4,000 people in summer (Russians about 150) to 1,000 people in winter (Russians about 100).
Antarctica is assigned a top-level Internet domain of .aq and a telephone prefix of +672.