Antarctica

Antarctica (/ænˈtɑːrktɪkə/ or /ænˈtɑːrtɪkə/) is Earth's southernmost continent. Situated almost entirely south of the Antarctic Circle and is surrounded by the Southern Ocean, it contains the geographic South Pole. The fifth-largest continent—it is nearly twice the size of Australia—it has an area of 14,200,000 square kilometres (5,500,000 square miles). During the summer months 5,000 people reside at research stations, a figure that drops to around 1,000 in the winter. Most of Antarctica is covered by ice, with an average thickness of 1.9 km (1.2 mi; 6,200 ft).

Antarctica is on average the coldest, driest, and windiest of the continents, and has the highest average elevation. It is mainly a polar desert, with annual precipitation of 200 mm (8 in) along the coast and far less inland. About 70% of the world's freshwater reserves are frozen there, which if melted would raise global sea levels by about 60 metres (200 ft). Antarctica holds the record for the lowest measured temperature on Earth, −89.2 °C (−128.6 °F). The average temperature for the third quarter (the coldest part of the year) is −63 °C (−81 °F). Native species of animals include mites, nematodes, penguins, seals and tardigrades. Vegetation consists of tundra.

Antarctica was probably first seen in 1820, when the Russian expedition led by Fabian Gottlieb von Bellingshausen and Mikhail Lazarev sighted the Fimbul ice shelf. The continent was discovered in January 1840 by the United States Exploring Expedition, under Lieutenant Charles Wilkes; and a separate French expedition under Jules Dumont d'Urville. The Wilkes expedition—though it did not make a landing—remained long enough in the region to survey 1,300 kilometres (800 mi) of the coast. The first confirmed landing was by a Norwegian team in 1895.

Antarctica is governed by about 30 countries, all of which are parties to the 1959 Antarctic Treaty System. According to the terms of the treaty, military activity, mining, nuclear explosions and nuclear waste disposal are all prohibited.

Geography

Positioned asymmetrically around the South Pole and largely south of the Antarctic Circle, Antarctica is the southernmost continent and is surrounded by the Southern Ocean. Rivers exist in Antarctica, the longest being the Onyx. Antarctica covers more than 14 million km2 (5,400,000 sq mi), making it the fifth-largest continent, slightly less than 1.5 times the area of the United States. The coastline is almost 18,000 km (11,200 mi) long: Of the four coastal types, 44% of the coast is floating ice in the form of an Ice shelf, 38% consists of Ice walls that resting on rock, 13% is ice streams or the edge of glaciers, and the remaining 5% is exposed rock.

More than 70 lakes lie at the base of the continental ice sheet. Lake Vostok, discovered beneath Russia's Vostok Station in 1996, is the largest, and one of the largest sub-glacial lakes in the world. It was once believed that the lake had been sealed off for 500,000 to one million years, but there is a suggestion that every so often, there are large flows of water from one lake to another.

Antarctica is divided in two by the Transantarctic Mountains close to the neck between the Ross Sea and the Weddell Sea. The portion west of the Weddell Sea and east of the Ross Sea is called West Antarctica and the remainder East Antarctica. The vast majority of Antarctica is covered by the Antarctic ice sheet, a sheet of ice that averages 1.9 km (1.2 mi; 6,200 ft) in thickness. It extends to all but a few Antarctic oases, which, with the exception of the McMurdo Dry Valleys, are located in coastal areas. The continent has about 90% of the world's ice. If all of this ice were melted, sea levels would rise about 58 m (190 ft).

West Antarctica is covered by the West Antarctic Ice Sheet. The sheet is of concern because of the small possibility of its collapse. If the sheet were to break down, ocean levels would rise by several metres in a relatively short geological period of time, perhaps a matter of centuries. Several Antarctic ice streams flow to one of the many Antarctic ice shelves, a process known as ice-sheet dynamics.

East Antarctica lies on the Indian Ocean side of the Transantarctic Mountains and comprises Coats Land, Queen Maud Land, Enderby Land, Mac. Robertson Land, Wilkes Land, and Victoria Land. All but a small portion of this region lies within the Eastern Hemisphere. East Antarctica is largely covered by the East Antarctic Ice Sheet.

Vinson Massif, in the Ellsworth Mountains, is the highest peak in Antarctica at 4,892 m (16,050 ft). Mount Erebus on Ross Island is the world's southernmost active volcano. Minor eruptions are frequent, and lava flow has been observed. Other dormant volcanoes may potentially be active. In 2004, a potentially active underwater volcano was found in the Antarctic Peninsula by American and Canadian researchers.

In September 2018, researchers at the National Geospatial-Intelligence Agency released a high resolution terrain map (detail down to the size of a car, and less in some areas) of Antarctica, named the "Reference Elevation Model of Antarctica" (REMA).

Climate

Antarctica is the coldest, windiest and driest of Earth's continents. It was ice-free until about 34Ma. The lowest natural air temperature ever recorded on Earth was −89.2 °C (−128.6 °F) at the Russian Vostok Station in Antarctica on 21 July 1983. A lower air temperature of −94.7 °C (−138.5 °F) was recorded in 2010 by satellite—however, it may have been influenced by ground temperatures and was not recorded at a height of 2 metres (7 ft) above the surface as required for official air temperature records. Average temperatures can reach a minimum of between −80 °C (−112 °F) in the interior of the continent during winter and a maximum of over 10 °C (50 °F) near the coast in summer. Signy Island recorded a temperature of 19.8 °C (67.6 °F) in January 1982, the highest temperature ever recorded in the Antarctic region (including non-continental islands).

Antarctica is a polar desert with little precipitation; the South Pole receives on average less than 10 mm (0.4 in) of snow per year, and in most of the interior it is 20 mm (0.8 in) per year. In a few "blue ice" areas precipitation is lower than mass loss by sublimation, and so the local mass balance is negative. In the dry valleys, the same effect occurs over a rock base, leading to a barren and desiccated landscape. The continent is colder than the Arctic region, as much of the continent is over 3,000 m (9,800 ft) above sea level, where air temperatures are colder. The ocean's relative warmth of the Arctic Ocean, which covers the northern polar region, is transferred through the Arctic sea ice and moderates temperatures in the Arctic region. The Arctic is also warmer on average because the Earth is at its furthest distance from the Sun during the Antarctic winter, and at perihelion (its closest distance to the Sun) in the Arctic winter.

Antarctica (/ænˈtɑːrktɪkə/ or /ænˈtɑːrtɪkə/) is Earth's southernmost continent. Situated almost entirely south of the Antarctic Circle and is surrounded by the Southern Ocean, it contains the geographic South Pole. The fifth-largest continent—it is nearly twice the size of Australia—it has an area of 14,200,000 square kilometres (5,500,000 square miles). During the summer months 5,000 people reside at research stations, a figure that drops to around 1,000 in the winter. Most of Antarctica is covered by ice, with an average thickness of 1.9 km (1.2 mi; 6,200 ft).

Antarctica is on average the coldest, driest, and windiest of the continents, and has the highest average elevation. It is mainly a polar desert, with annual precipitation of 200 mm (8 in) along the coast and far less inland. About 70% of the world's freshwater reserves are frozen there, which if melted would raise global sea levels by about 60 metres (200 ft). Antarctica holds the record for the lowest measured temperature on Earth, −89.2 °C (−128.6 °F). The average temperature for the third quarter (the coldest part of the year) is −63 °C (−81 °F). Native species of animals include mites, nematodes, penguins, seals and tardigrades. Vegetation consists of tundra.

Antarctica was probably first seen in 1820, when the Russian expedition led by Fabian Gottlieb von Bellingshausen and Mikhail Lazarev sighted the Fimbul ice shelf. The continent was discovered in January 1840 by the United States Exploring Expedition, under Lieutenant Charles Wilkes; and a separate French expedition under Jules Dumont d'Urville. The Wilkes expedition—though it did not make a landing—remained long enough in the region to survey 1,300 kilometres (800 mi) of the coast. The first confirmed landing was by a Norwegian team in 1895.

Antarctica is governed by about 30 countries, all of which are parties to the 1959 Antarctic Treaty System. According to the terms of the treaty, military activity, mining, nuclear explosions and nuclear waste disposal are all prohibited.

Geography

Positioned asymmetrically around the South Pole and largely south of the Antarctic Circle, Antarctica is the southernmost continent and is surrounded by the Southern Ocean. Rivers exist in Antarctica, the longest being the Onyx. Antarctica covers more than 14 million km2 (5,400,000 sq mi), making it the fifth-largest continent, slightly less than 1.5 times the area of the United States. The coastline is almost 18,000 km (11,200 mi) long: Of the four coastal types, 44% of the coast is floating ice in the form of an Ice shelf, 38% consists of Ice walls that resting on rock, 13% is ice streams or the edge of glaciers, and the remaining 5% is exposed rock.

More than 70 lakes lie at the base of the continental ice sheet. Lake Vostok, discovered beneath Russia's Vostok Station in 1996, is the largest, and one of the largest sub-glacial lakes in the world. It was once believed that the lake had been sealed off for 500,000 to one million years, but there is a suggestion that every so often, there are large flows of water from one lake to another.

Antarctica is divided in two by the Transantarctic Mountains close to the neck between the Ross Sea and the Weddell Sea. The portion west of the Weddell Sea and east of the Ross Sea is called West Antarctica and the remainder East Antarctica. The vast majority of Antarctica is covered by the Antarctic ice sheet, a sheet of ice that averages 1.9 km (1.2 mi; 6,200 ft) in thickness. It extends to all but a few Antarctic oases, which, with the exception of the McMurdo Dry Valleys, are located in coastal areas. The continent has about 90% of the world's ice. If all of this ice were melted, sea levels would rise about 58 m (190 ft).

West Antarctica is covered by the West Antarctic Ice Sheet. The sheet is of concern because of the small possibility of its collapse. If the sheet were to break down, ocean levels would rise by several metres in a relatively short geological period of time, perhaps a matter of centuries. Several Antarctic ice streams flow to one of the many Antarctic ice shelves, a process known as ice-sheet dynamics.

East Antarctica lies on the Indian Ocean side of the Transantarctic Mountains and comprises Coats Land, Queen Maud Land, Enderby Land, Mac. Robertson Land, Wilkes Land, and Victoria Land. All but a small portion of this region lies within the Eastern Hemisphere. East Antarctica is largely covered by the East Antarctic Ice Sheet.

Vinson Massif, in the Ellsworth Mountains, is the highest peak in Antarctica at 4,892 m (16,050 ft). Mount Erebus on Ross Island is the world's southernmost active volcano. Minor eruptions are frequent, and lava flow has been observed. Other dormant volcanoes may potentially be active. In 2004, a potentially active underwater volcano was found in the Antarctic Peninsula by American and Canadian researchers.

In September 2018, researchers at the National Geospatial-Intelligence Agency released a high resolution terrain map (detail down to the size of a car, and less in some areas) of Antarctica, named the "Reference Elevation Model of Antarctica" (REMA).

Climate

Antarctica is the coldest, windiest and driest of Earth's continents. It was ice-free until about 34Ma. The lowest natural air temperature ever recorded on Earth was −89.2 °C (−128.6 °F) at the Russian Vostok Station in Antarctica on 21 July 1983. A lower air temperature of −94.7 °C (−138.5 °F) was recorded in 2010 by satellite—however, it may have been influenced by ground temperatures and was not recorded at a height of 2 metres (7 ft) above the surface as required for official air temperature records. Average temperatures can reach a minimum of between −80 °C (−112 °F) in the interior of the continent during winter and a maximum of over 10 °C (50 °F) near the coast in summer. Signy Island recorded a temperature of 19.8 °C (67.6 °F) in January 1982, the highest temperature ever recorded in the Antarctic region (including non-continental islands).

Antarctica is a polar desert with little precipitation; the South Pole receives on average less than 10 mm (0.4 in) of snow per year, and in most of the interior it is 20 mm (0.8 in) per year. In a few "blue ice" areas precipitation is lower than mass loss by sublimation, and so the local mass balance is negative. In the dry valleys, the same effect occurs over a rock base, leading to a barren and desiccated landscape. The continent is colder than the Arctic region, as much of the continent is over 3,000 m (9,800 ft) above sea level, where air temperatures are colder. The ocean's relative warmth of the Arctic Ocean, which covers the northern polar region, is transferred through the Arctic sea ice and moderates temperatures in the Arctic region. The Arctic is also warmer on average because the Earth is at its furthest distance from the Sun during the Antarctic winter, and at perihelion (its closest distance to the Sun) in the Arctic winter.