Antarctica

For other uses, see Antarctica (disambiguation).

Antarctica

Area	14,200,000 km2 5,500,000 sq mi
Population	1,000 to 5,000 (seasonal)
Population density	<0.01/km2 <0.03/sq mi
Demonym	Antarctic
Internet TLD	.aq
Largest settlements	McMurdo Station Other research stations
UN M49 code	010

Antarctica (/ænˈtɑːrktɪkə/ ) is Earth's southernmost continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean, it contains the geographic South Pole. Antarctica is the fifth-largest continent, being nearly twice the size of Australia, and has an area of 14,200,000 km² (5,500,000 sq mi). Most of Antarctica is covered by ice, with an average thickness of 1.9 km (1.2 mi).

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 over 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.

The continental mass of 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 km (800 mi) of the coast. The first confirmed landing was by a Norwegian team in 1895.

During the summer months 5,000 people reside at research stations, a figure that drops to around 1,000 in the winter. 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.

Etymology

A speculative representation of Antarctica labelled as 'Terra Australis Incognito' on Jan Janssonius's Zeekaart van het Zuidpoolgebied (1657), Het Scheepvaartmuseum

The name given to the world's southernmost continent originates from the word antarctic, which originates from the Middle French antartique or antarctique ('opposite to the Arctic') and the Latin antarcticus ('opposite to the north'). Antarcticus is derived from the Greek ἀντι- ('anti-') and ἀρκτικός ('of the Bear', 'northern'). The Greek philosopher Aristotle wrote in Meteorology about an "Antarctic region" in c. 350 BCE. The Greek geographer Marinus of Tyre reportedly used the name in his world map from the second century CE, now lost. The Roman authors Hyginus and Apuleius used for the South Pole the romanised Greek name polus antarcticus, from which derived the Old French pole antartike (modern pôle antarctique) attested in 1270, and from there the Middle English pol antartik, found in a treatise written by the English author Geoffrey Chaucer.

Until the discovery belief by Europeans in the existence of a Terra Australis—a vast continent in the far south of the globe to balance the northern lands of Europe, Asia and North Africa—had existed as an intellectual concept since classical antiquity. The belief of such a land lasted until the discovery of Australia.

During the early 19th century the explorer Matthew Flinders doubted the existence of a detached continent south of Australia, then called New Holland, and thus advocated for the "Terra Australis" name to be used for Australia instead. In 1824 the colonial authorities in Sydney officially renamed the continent of New Holland to Australia, leaving the term "Terra Australis" unavailable as a reference to Antarctica. Over the following decades, geographers had to make do with clumsy phrases such as "the Antarctic Continent". They searched for a more poetic replacement, suggesting various names such as Ultima and Antipodea. Antarctica was adopted in the 1890s, with the first use of the name being attributed to the Scottish cartographer John George Bartholomew.

Geography

Main article: Geography of Antarctica

See also: Extreme points of Antarctica and List of mountains in Antarctica

Eastern Antarctica is to the right of the Transantarctic Mountains and Western Antarctica is to the left.

Positioned asymmetrically around the South Pole and largely south of the Antarctic Circle (one of the five major circles of latitude that mark maps of the world), Antarctica is surrounded by the Southern Ocean. Rivers exist in Antarctica, the longest being the Onyx. Antarctica covers more than 14.2 million km² (5,500,000 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: As of 1983, 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 rest on rock, 13% is ice streams or the edge of glaciers, and the remaining 5% is exposed rock.

The lakes that lie at the base of the continental ice sheet occur mainly in the McMurdo Dry Valleys or various oases. 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. During the summer, the ice at the edges of the lakes can melt, and liquid moats temporarily form. Antarctica has both saline and freshwater lakes.

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, that averages 1.9 km (1.2 mi) in thickness. The ice sheet extends to all but a few oases, which, with the exception of the McMurdo Dry Valleys, are located in coastal areas. Several Antarctic ice streams flow to one of the many Antarctic ice shelves, a process known as ice-sheet dynamics.

Vinson Massif from the northwest, the highest peak in Antarctica

East Antarctica 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. There exist numerous islands surrounding Antarctica, most of which are volcanic and very young by geological standards. The most prominent exception to this are the islands of the Kerguelen Plateau, the earliest of which formed around 40 Ma.

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, which erupts around 10 times each day. Ash from eruptions has been found 300 kilometres (190 mi) from the crater. 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. The ice dome known as Dome Argus in East Antarctica is the highest of all Antarctic ice features, at 4,091 metres (13,422 ft). It is one of the world's coldest and driest places—temperatures there can reach −90 °C (−130 °F), and annual precipitation is 1–3 cm (0.39–1.18 in).

Geologic history

Main article: Geology of Antarctica

Further information: Geology of the Antarctic Peninsula

From the end of the Neoproterozoic era to the Cretaceous, Antarctica was part of the supercontinent Gondwana. Antarctica as we know it today was formed as Gondwana broke apart around 183 Ma, separating into Antarctica, South America and Australia. For a large proportion of the Phanerozoic, Antarctica experienced a tropical or temperate climate, and was covered in forests.

Palaeozoic era (540–250 Ma)

Glossopteris sp. leaf from the Permian of Antarctica

During the Cambrian period, Gondwana had a mild climate. West Antarctica was partially in the Northern Hemisphere, and during this period large amounts of sandstones, limestones and shales were deposited. East Antarctica was at the equator, where seafloor invertebrates and trilobites flourished in the tropical seas. By the start of the Devonian period (416 Ma), Gondwana was in more southern latitudes and the climate was cooler, though fossils of land plants are known from this time. Sand and silts were laid down in what is now the Ellsworth, Horlick and Pensacola Mountains.

Antarctica became glaciated during the Late Paleozoic icehouse beginning at the end of the Devonian period (360 Ma), though glaciation would substantially increase during the late Carboniferous. Antarctica drifted closer to the South Pole and the climate cooled, though flora remained. After deglaciation during the latter half of the Early Permian, the land became dominated by glossopterids (an extinct group of seed plants with no close living relatives), most prominently Glossopteris, a tree which is interpreted as growing in waterlogged soils, which formed extensive coal deposits. Other plants found in Antarctica during the Permian include Cordaitales, sphenopsids, ferns, and lycophytes. At the end of the Permian, the eruption of the Siberian Traps led to a dry, hot climate over much of Gondwana, and the collapse of the glossopterid forest ecosystems. There is no evidence of any tetrapods having lived in Antarctica during the Paleozoic.

Mesozoic era (250–66 Ma)

The continued warming dried out much of Gondwana. During the Triassic, Antarctica was dominated by seed ferns (pteridosperms) belonging to the genus Dicroidium, which grew as trees. Other associated Triassic flora included ginkgophytes, cycadophytes, conifers and sphenopsids. Tetrapods first appeared during the earliest Triassic, with the earliest known fossils found in the Fremouw Formation in the Transantarctic Mountains. Synapsids, known as "mammal-like reptiles", included species such as Lystrosaurus, and were common during the Early Triassic.

The Antarctic Peninsula began to form during the Jurassic period (206–146 Ma). Ginkgo trees, conifers, Bennettitales, horsetails, ferns and cycads were plentiful during this period. In West Antarctica, coniferous forests dominated throughout the Cretaceous period (146–66 Ma), though southern beech (Nothofagus) became prominent towards the end of the Cretaceous. Ammonites were common in the seas around Antarctica, and dinosaurs were also present, though only a few Antarctic dinosaur genera (Cryolophosaurus and Glacialisaurus, from the Early Jurassic Hanson Formation of the Transantarctic Mountains, and Antarctopelta, Trinisaura, Morrosaurus and Imperobator from Late Cretaceous of the Antarctic Peninsula) have been described.

Gondwana breakup (160–23 Ma)

Breakup of Gondwana at c. 150  Ma (left), c. 126 Ma (centre) and at c. 83 Ma (right)

Africa separated from Antarctica in the Jurassic, around 160 Ma, followed by the Indian subcontinent in the early Cretaceous (about 125 Ma). During the early Paleogene, Antarctica remained connected to southern South America via the Isthmus of Scotia as well as to southeastern Australia. Fauna from the La Meseta Formation in the Antarctic Peninsula, dating to the Eocene, is very similar to equivalent South American faunas; with marsupials, xenarthrans, litoptern and astrapotherian ungulates, as well as gondwanatheres and meridiolestidans. Marsupials are thought to have dispersed into Australia via Antarctica by the early Eocene.

Around 53 Ma, Australia-New Guinea separated from Antarctica. The Drake Passage opened between Antarctica and South America around 30 Ma, resulting in the creation of the Antarctic Circumpolar Current that completely isolated the continent. Models of Antarctic geography suggest that this, as well as a feedback loop caused by lowering CO₂ levels, caused the creation of small yet permanent polar ice caps. As CO₂ levels declined further, the ice began to spread rapidly, replacing the forests that until then had covered the continent. Since about 15 Ma, the continent has been mostly covered with ice.

Pliocene and Pleistocene

Fossil Nothofagus leaves in the Meyer Desert Formation of the Sirius Group show that intermittent warm periods allowed Nothofagus shrubs to cling to the Dominion Range until as late as 3–4 Ma (mid-late Pliocene). A 2014 study has estimated that during the Pleistocene, the East Antarctic Ice Sheet (EAIS) thinned by at least 500 m (1,600 ft), and that thinning since the Last Glacial Maximum for the EAIS area is less than 50 m (160 ft) and probably started around 12,000 years ago.

About 2,200 years ago, a volcano erupted under Antarctica's ice sheet, as detected by an airborne survey with radar images. The biggest eruption in the last 10,000 years, the volcanic ash was found deposited on the ice surface under the Hudson Mountains, close to Pine Island Glacier.

Present-day

The Antarctic Plate

The geology of Antarctica, largely obscured by the continental ice sheet, is being revealed by techniques such as remote sensing, ground-penetrating radar, and satellite imagery. Geologically, West Antarctica closely resembles the South American Andes. The Antarctic Peninsula was formed by geologic uplift and the transformation of sea bed sediments into metamorphic rocks.

West Antarctica was formed by the merging of several continental plates, which created a number of mountain ranges in the region, the most prominent being the Ellsworth Mountains. The presence of the West Antarctic Rift System has resulted in volcanism along the border between West and East Antarctica, along with the creation of the Transantarctic Mountains.

East Antarctica is geologically varied, dating from the Precambrian era, The formation of East Antarctica began during the Archean (4,000Ma–2500Ma), and stopped during the Cambrian. It is built on a craton of rock which is the basis of the Precambrian Shield. On top of this base are coal and sandstones, limestones and shales laid down during the Devonian and Jurassic periods to form the Transantarctic Mountains. In coastal areas such as the Shackleton Range and Victoria Land, some faulting has occurred.

Coal was first recorded near the Beardmore Glacier by Frank Wild on the Nimrod Expedition in 1907, and low-grade coal is known to exist across many parts of the Transantarctic Mountains. The Prince Charles Mountains contain deposits of iron ore. There exists oil and natural gas fields in the Ross Sea.

Climate

Main article: Climate of Antarctica

Blue ice covering Lake Fryxell, in the Transantarctic Mountains

Temperate conditions near the coast in December

Antarctica is the coldest, windiest and driest of Earth's continents. It was ice-free until about 34 Ma. 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 m (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.

Regional differences

East Antarctica is colder than its western counterpart because of its higher elevation. Weather fronts rarely penetrate far into the continent, leaving the centre cold and dry, with moderate wind speeds. Heavy snowfalls are common on the coastal portion of the continent, where snowfalls of up to 1.22 m (48 in) in 48 hours have been recorded. At the continent's edge, strong katabatic winds off the polar plateau often blow at storm force. During the summer, more solar radiation reaches the surface at the South Pole than at the equator, because of the 24 hours of sunlight received there each day.

Climate change

Main article: Climate change in Antarctica

The warming trend for Antarctica from 1957 to 2006, based on the analysis of weather station and satellite data; dark tints over West Antarctica indicates that the region warmed most per decade.

Over the second half of the 20th century, the Antarctic Peninsula was the fastest-warming place on Earth, closely followed by West Antarctica, but temperatures rose less rapidly during the early 21st-century. Conversely, the South Pole, located in East Antarctica, barely warmed during much of the 20th century, but temperatures rose three times the global average between 1990 and 2020. In February 2020, the continent recorded its highest temperature of 18.3 °C (64.9 °F), which was 0.8 °C (1.4 °F) higher than the previous record attained in March 2015.

There is some evidence that surface warming in Antarctica is due to human greenhouse gas emissions, but this is difficult to determine due to internal variability. A main component of climate variability in Antarctica is the Southern Annular Mode (a low-frequency mode of atmospheric variability of the southern hemisphere), which showed strengthened winds around Antarctica in summer of the later decades of the 20th century, associated with cooler temperatures over the continent. The trend was at a scale unprecedented over the last 600 years; the most dominant driver of this mode of variability is likely the depletion of ozone above the continent.

In 2002 the Antarctic Peninsula's Larsen-B ice shelf collapsed. Between 28 February and 8 March 2008, about 570 km² (220 sq mi) of ice from the Wilkins Ice Shelf on the southwest part of the peninsula collapsed, putting the remaining 15,000 km² (5,800 sq mi) of the ice shelf at risk. The ice was being held back by a "thread" of ice about 6 km (4 mi) wide, prior to its collapse on 5 April 2009.

Ice loss and global sea level

See also: Sea level rise and Antarctic sea ice

Pine Island Glacier, photographed in November 2011

Precipitation in Antarctica occurs in the form of snow, which accumulates and forms the giant ice sheet which covers the continent. Parts of this ice sheet form moving glaciers which flow towards the coast. Extensions of the outflowing glaciers, known as ice shelves, adjoin the continental shore.

Sea ice and ice shelves

Sea ice extent expands annually during the Antarctic winter, but most of it melts in the summer. This ice is formed from the ocean, and does not contribute to changes in sea level. The average extent of the sea ice around Antarctica has changed little since the satellites began to observe the Earth's surface in 1978, which is in contrast with the Arctic, which has seen rapid sea ice loss. A possible explanation is that thermohaline circulation transports warmed water to deeper layers in the Southern Ocean.

The melting of the ice shelves does not contribute much to sea-level rise, since the floating ice displaces its own mass of water, but they act to stabilize the land ice. They are vulnerable to warming water, which has caused large ice shelves to collapse into the ocean. This loss of ice shelf ''buttressing'' has been identified as the major cause of ice loss on the West Antarctic ice sheet, but has also been observed around the East Antarctic ice sheet.

The ice shelf on Pine Island Glacier lost approximately 20% of its area from 2017 to 2020, mostly in three dramatic breaks. Pine Island Glacier could collapse into the ocean; the glaciologist Ian Joughin at the University of Washington stated that “The processes we’d been studying in this region were leading to an irreversible collapse, but at a fairly measured pace. Things could be much more abrupt if we lose the rest of that ice shelf.”

Ice sheet loss and sea level rise

Ice mass loss since 2002

The loss of mass from Antarctica's ice sheet is partially offset by additional snow falling back onto the continent. A 2018 systematic review study estimated that ice loss across the entire continent was 43 gigatonnes per year on average during the period from 1992 to 2002, but accelerated to an average of 220 Gt per year during the five years from 2012 to 2017. The total contribution to sea level rise has been estimated as 8 to 14 mm (0.31 to 0.55 in) of sea level rise. Ice mass loss since 2002, as measured by NASA's GRACE and GRACE Follow-On satellite projects, has averaged 152 billion tons per year.

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). The continent stores around 70% of the world's fresh water as ice.

East Antarctica, which occupies most of the continent, is dominated by accumulated snow moves flows the sea as ice. Estimates of the mass balance of the East Antarctic Ice Sheet as a whole range from slightly positive to slightly negative. Increased ice outflow has been observed in some regions.

Future projections of ice loss depend on the speed of climate change mitigation and are uncertain. Tipping points have been identified in some regions; when a certain threshold warming is reached, these regions may start melting at a faster rate. If average temperatures were to begin to fall, the ice would not immediately be restored. A tipping point for the West Antarctic ice sheet is estimated to be between 1.5 and 2.0 °C of global warming. A full collapse would likely not take place unless warming reaches between 2 and 3 °C, and may occur within centuries under pessimistic assumptions. This full collapse would lead to 2 to 5 metres of sea level rise. At 3 °C, parts of the East Antarctic ice sheet are also projected to be fully lost, and total ice loss would lead to around 6 to 12 metres or more of sea level rise.

Ozone depletion

Main article: Ozone hole

Image of the largest hole in the ozone layer ever recorded, in September 2006

Scientists have studied the ozone layer in the atmosphere above Antarctica since the 1970s. In 1985, British scientists working on data they had gathered at Halley Station on the Brunt Ice Shelf discovered a large area of low ozone concentration over Antarctica. The 'ozone hole' covers almost the whole continent and was at its largest in September 2006; the longest-lasting event occurred in 2020. It is caused by the emission of chlorofluorocarbons (CFCs) into the atmosphere, which cause ozone to break down into other gases.

The ozone depletion over Antarctica, which is caused by the absorption of atmospheric ultraviolet (UV), can cause a cooling of around 6 °C (11 °F) in the stratosphere. This strengthens the polar vortex, and so prevents the outflow of the cold air near the South Pole, which in turn cools the continental mass of the East Antarctic ice sheet. The peripheral areas of Antarctica, especially the Antarctic Peninsula, are then subjected to higher temperatures, which accelerate the melting of the ice. The ozone hole above Antarctica is predicted to slowly disappear; by the 2060s, levels of ozone are expected to have returned to values last recorded in the1980s.

Models suggest that ozone depletion and the enhanced polar vortex effect also account for the period, lasting from when observation started in the early 1970s until 2014, of increasing the extent of offshore sea ice. Since 2014, the coverage of Antarctic sea ice has decreased rapidly.

Biodiversity

See also: Antarctic realm, Antarctic microorganism, and Wildlife of Antarctica

According to Ceridwen Fraser of the University of Otago in New Zealand, Antarctica's purely land-based species appear to be the descendants of ancestors who lived in geothermally-heated environments during the last ice age, when these areas were the only places on the continent not covered by ice.

Animals

Emperor penguins with juveniles

Invertebrate life of Antarctica includes species of microscopic mites such as Alaskozetes antarcticus, lice, nematodes, tardigrades, rotifers, krill and springtails. The few terrestrial vertebrates are limited to the sub-Antarctic islands. The flightless midge Belgica antarctica, the largest purely terrestrial animal in Antarctica, reaches 6 mm (1⁄4 in) in size.

Antarctic krill, which congregate in large schools, is the keystone species of the ecosystem of the Southern Ocean, being an important food organism for whales, seals, leopard seals, fur seals, squid, icefish, and many bird species, such as penguins and albatrosses. Some species of marine animals exist and rely, directly or indirectly, on the phytoplankton. Antarctic sea life includes penguins, blue whales, orcas, colossal squids and fur seals.

The emperor penguin is the only penguin that breeds during the winter in Antarctica; it and the Adélie penguin breed farther south than any other penguin. The snow petrel is one of only three birds that breed exclusively in Antarctica.

The Antarctic fur seal was very heavily hunted in the 18th and 19th centuries for its pelt by seal hunters from the United States and the United Kingdom. Leopard seals are apex predators in the Antarctic ecosystem, and migrate across the Southern Ocean in search of food.

A Census of Marine Life by some 500 researchers during the International Polar Year, was released in 2010. The research found that more than 235 marine organisms live in both polar regions, having bridged the gap of 12,000 km (7,456 mi). Large animals such as some cetaceans and birds make the round trip annually. Smaller forms of life such as sea cucumbers and free-swimming snails also found in both polar oceans. Factors that may aid in their distribution include temperature differences between the deep ocean at the poles and the equator of no more than 5 °C (9 °F) and the major current systems or marine conveyor belt which are able to transport eggs and larva.

Fungi

Orange lichen (Caloplaca) growing on the Yalour Islands, Wilhelm Archipelago

About 1,150 species of fungi have been recorded from Antarctica, of which about 750 are non-lichen-forming. Some of these species, having evolved under extreme conditions, have colonized structural cavities within porous rocks and have contributed to shaping the rock formations of the McMurdo Dry Valleys and surrounding mountain ridges.

The simplified morphology of such fungi, along with their similar biological structures, metabolism systems capable of remaining active at very low temperatures, and reduced life cycles, make them well suited to such environments. Their thick-walled and strongly melanised cells make them resistant to UV.

Those features can also be observed in algae and cyanobacteria, suggesting that these are adaptations to the conditions prevailing in Antarctica. This has led to speculation that life on Mars might have been similar to Antarctic fungi, such as Cryomyces antarcticus and Cryomyces minteri. Some of these species of fungi, which are apparently endemic to Antarctica, live in bird dung, and have evolved so they can grow inside extremely cold dung, but also pass through the intestines of warm-blooded animals.

Plants

About 400 Ma, Permian forests started to cover the continent, and tundra vegetation survived as late as 14 Ma, but the climate of present-day Antarctica does not allow extensive vegetation to form. A combination of freezing temperatures, poor soil quality, and a lack of moisture and sunlight inhibit plant growth, causing low species diversity and limited distribution. The flora largely consists of bryophytes (25 species of liverworts and 100 species of mosses). There are three species of flowering plants, all of which are found in the Antarctic Peninsula: Deschampsia antarctica (Antarctic hair grass), Colobanthus quitensis (Antarctic pearlwort) and the non-native Poa annua (annual bluegrass). Plant growth is restricted to a few weeks in the summer.

Other organisms

Of the 700 species of algae in Antarctica, most are phytoplankton. Multicoloured snow algae and diatoms are especially abundant in the coastal regions during the summer. Bacteria have been found as deep as 800 m (0.50 mi) under the ice. It is thought likely that there exists a native bacterial community within the subterranean water body of Lake Vostok. The existence of life there is thought to strengthen the argument for the possibility of life on Jupiter's moon Europa, which may have water beneath its water-ice crust. There exists a community of extremophile bacteria in the highly alkaline waters of Lake Untersee. The prevalence of highly resilient creatures in such inhospitable areas could further bolster the argument for extraterrestrial life in cold, methane-rich environments.

Conservation and environmental protection

Refuse littering the shoreline at Bellingshausen Station on King George Island, photographed in 1992

A whale in the Southern Ocean Whale Sanctuary

In the mid-1970s, a coalition of international environmental protection organisations launched a public campaign to pressure governments to prevent mining in Antarctica.

The passing of the 1978 Antarctic Conservation Act in the U.S. made it illegal to import alien plants or animals, or for U.S. citizens to extract any indigenous species. The overfishing of krill, which plays a large role in the Antarctic ecosystem, led officials to enact regulations on fishing. The Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR), an international treaty that came into force in 1980, requires that regulations managing all Southern Ocean fisheries consider potential effects on the entire Antarctic ecosystem. Despite these regulations, illegal fishing—particularly of the highly prized Patagonian toothfish which is marketed as Chilean Sea Bass in the U.S.—remains a problem.

In 1988, five years after the Antarctic Treaty Parties began negotiations, the Convention on the Regulation of Antarctic Mineral Resources (CRAMRA) was adopted. Australia and France announced in 1989 that they would not ratify the convention, proposing instead that a comprehensive regime to protect the Antarctic environment be negotiated in its place. After other countries followed their example, the Protocol on Environmental Protection to the Antarctic Treaty was negotiated, and on 14 January 1998 it entered into force. The Madrid Protocol bans all mining, designating the continent as a "natural reserve devoted to peace and science". It is the main instrument concerned with nature conservation and management of biodiversity in Antarctica. The Antarctic Treaty Consultative Meeting is advised on environmental and conservation issues in Antarctica by the Committee for Environmental Protection. A major concern within this committee is the risk to Antarctica from unintentional introduction of non-native species from outside the region. To protect the Antarctic marine environment, ships over 500 tonnes are subject to regulations under the International Code for Ships Operating in Polar Waters, adopted by the International Maritime Organization in 2017.

The pressure group Greenpeace established a base on Ross Island from 1987 to 1992, as part of its attempt to establish the continent as a World Park. The Southern Ocean Whale Sanctuary was established in 1994 by the International Whaling Commission. It covers 50 million km² (19 million sq mi), and completely surrounds the Antarctic continent. All commercial whaling is banned in the zone, though Japan has continued to hunt whales in the area, ostensibly for research purposes.

History of exploration

Main article: History of Antarctica

See also: List of Antarctic expeditions and Women in Antarctica

Captain James Cook's ships, HMS Resolution and Adventure, crossed the Antarctic Circle on 17 January 1773, in December 1773, and again in January 1774. Cook came within about 120 km (75 mi) of the Antarctic coast before retreating in the face of field ice in January 1773. In 1775, Cook called the existence of a polar continent "probable" and in another copy of his journal he wrote: "[I] firmly believe it and it's more than probable that we have seen a part of it".

19th century

Adélie Land, depicted by Jules Dumont d'Urville in his Voyage au Pôle Sud (1846)

Sealers were among the earliest to go closer to the Antarctic landmass, perhaps in the earlier part of the 19th century. The oldest known human remains in the Antarctic region was a skull, dated from 1819 to 1825, that belonged to a young woman on Yamana Beach at the South Shetland Islands. The woman, who was likely to have been part of a sealing expedition, was found in 1985.

The first person to sight Antarctica or its ice shelf was long thought to have been the British sailor Edward Bransfield, a captain in the Royal Navy, who discovered the tip of the Antarctic peninsula on 30 January 1820. However, a captain in the Imperial Russian Navy, Fabian Gottlieb von Bellingshausen recorded seeing an ice shelf on 27 January. The American sealer Nathaniel Palmer, whose sealing ship was in the region at this time, may have been the first to sight the Antarctic Peninsular.

The First Russian Antarctic Expedition, led by Bellingshausen and Mikhail Lazarev on the 985-ton sloop-of-war Vostok and the 530-ton support vessel Mirny, reached a point within 32 km (20 mi) of Queen Maud's Land and recorded sighting an ice shelf at 69°21′28″S 2°14′50″W. on 27 January 1820, This happened three days before Bransfield sighted the land of the Trinity Peninsula of Antarctica, as opposed to the ice of an ice shelf, and 10 months before Palmer did so in November 1820. The first documented landing on Antarctica was by the American sealer John Davis, apparently at Hughes Bay on 7 February 1821, although some historians dispute this claim, as there is no evidence Davis landed on the Antarctic continent rather than an offshore island.

On 22 January 1840, two days after the discovery of the coast west of the Balleny Islands, some members of the crew of the 1837–1840 expedition of the French explorer Jules Dumont d'Urville disembarked on the Dumoulin Islands, off the coast of Adélie Land, where they took some mineral, algae, and animal samples, erected the French flag and claimed French sovereignty over the territory. In 1847, the British naval officer John Ross failed to realise that what he referred to as "the various patches of land recently discovered by the English and American navigators on the verge of the Antarctic Circle"" were connected to form a single continent. The American explorer Mercator Cooper landed in East Antarctica on 26 January 1853.

The first confirmed landing on the continental mass of Antarctica occurred in 1895, when the Norwegian-Swedish whaling ship Antarctic reached Cape Adare.

20th century

The Nimrod Expedition of 1907–1909 (left to right): Frank Wild, Ernest Shackleton, Eric Marshall and Jameson Adams

During the Nimrod Expedition led by the British explorer Ernest Shackleton in 1907, parties led by Edgeworth David became the first to climb Mount Erebus and to reach the South Magnetic Pole. Douglas Mawson, who assumed the leadership of the Magnetic Pole party on their perilous return, retired in 1931. Between December 1908 and February 1909: Shackleton and three members of his expedition became the first humans to traverse the Ross Ice Shelf, the first to cross the Transantarctic Mountains (via the Beardmore Glacier), and the first to set foot on the South Polar Plateau. On 14 December 1911, An expedition led by Norwegian explorer Roald Amundsen from the ship Fram became the first to reach the geographic South Pole, using a route from the Bay of Whales and up the Axel Heiberg Glacier. One month later, the doomed Scott Expedition reached the pole.

The American explorer Richard E. Byrd led four expeditions to Antarctica during the 1920s, 1930s and 1940s, using the first mechanised tractors. His expeditions conducted extensive geographical and scientific research, and he is credited with surveying a larger region of the continent than any other explorer. In 1937, Ingrid Christensen became the first woman to step onto the Antarctic mainland. Caroline Mikkelsen had landed on an island of Antarctica, earlier in 1935.

The South Pole was next reached on 31 October 1956, when a U.S. Navy group led by Rear Admiral George J. Dufek successfully landed an aircraft there. Six women were flown to the South Pole as a publicity stunt in 1969. In the summer of 1996–1997 the Norwegian explorer Børge Ousland became the first person to cross Antarctica alone from coast to coast, helped by a kite on parts of the journey. Ousland holds the record for the fastest unsupported journey to the South Pole, taking 34 days.

Population

The first semi-permanent inhabitants of regions near Antarctica (areas situated south of the Antarctic Convergence) were British and American sealers who used to spend a year or more on South Georgia, from 1786 onward. During the whaling era, which lasted until 1966, the population of that island varied from over 1,000 in the summer (over 2,000 in some years) to some 200 in the winter. Most of the whalers were Norwegian, with an increasing proportion from Britain.

The "ceremonial" South Pole, at Amundsen–Scott Station

The continent of Antarctica has never had a permanent resident population, although staffed research stations are continuously maintained. The number of people conducting and supporting scientific research and other work on the continent and its nearby islands varies from about 1,000 in winter to about 5,000 in the summer. Some of the research stations are staffed year-round, the winter-over personnel typically arriving from their home countries for a one-year assignment. The Russian Orthodox Holy Trinity Church at the Bellingshausen Station on King George Island opened in 2004; it is manned year-round by one or two priests, who are similarly rotated every year.

The first child born in the southern polar region was a Norwegian girl, Solveig Gunbjørg Jacobsen, born in Grytviken on 8 October 1913. Emilio Marcos Palma was the first person born south of the 60th parallel south, the first born on the Antarctic mainland, and the only living human to be the first born on any continent.

The Antarctic Treaty prohibits any military activity in Antarctica, including the establishment of military bases and fortifications, military manoeuvres, and weapons testing. Military personnel or equipment are permitted only for scientific research or other peaceful purposes. The only documented military land manoeuvre has been the small Operation NINETY by the Argentine military in 1965.

Politics

The U.S. delegate Herman Phleger signs the Antarctic Treaty on in December 1959.

Sovereignty over regions of Antarctica is claimed by seven countries. While a few of these countries have mutually recognised each other's claims, the validity of these claims is not recognised universally.

New claims on Antarctica have been suspended since 1959, although in 2015 Norway formally defined Queen Maud Land as including the unclaimed area between it and the South Pole. Antarctica's status is regulated by the 1959 Antarctic Treaty and other related agreements, collectively called the Antarctic Treaty System. Antarctica is defined as all land and ice shelves south of 60° S for the purposes of the Treaty System. The treaty was signed by twelve countries including the Soviet Union (and later Russia), the United Kingdom, Argentina, Chile, Australia, and the United States. It set aside Antarctica as a scientific preserve, and established freedom of scientific investigation and environmental protection.

Territorial claims

Main article: Territorial claims in Antarctica

Date	Claimant	Territory	Claim limits	Map
1840	France	Adélie Land	142°02′E to 136°11′E
1908	United Kingdom	British Antarctic Territory	080°00′W to 020°00′W including overlaps: 80°00′W to 74°00′W claimed by Chile (1940) 74°00′W to 53°00′W claimed by Chile (1940) and Argentina (1943) 53°00′W to 25°00′W claimed by Argentina (1943)
1923	New Zealand	Ross Dependency	160°00′E to 150°00′W
1931	Norway	Peter I Island	68°50′S 90°35′W
1933	Australia	Australian Antarctic Territory	044°38′E to 136°11′E, and 142°02′E to 160°00′E
1939	Norway	Queen Maud Land	020°00′W to 044°38′E
1940	Chile	Chilean Antarctic Territory	090°00′W to 053°00′W including overlaps: 90°00′W to 74°00′W claimed by the United Kingdom (1908) 74°00′W to 53°00′W claimed by the United Kingdom (1908) and Argentina (1943)
1943	Argentina	Argentine Antarctica	074°00′W to 025°00′W including overlaps: 74°00′W to 53°00′W claimed by the United Kingdom (1908) and Chile (1940) 53°00′W to 25°00′W claimed by the United Kingdom (1908)
–	(Unclaimed territory)	Marie Byrd Land	150°00′W to 090°00′W (except Peter I Island)

The Argentine, British and Chilean claims overlap, and have caused friction. In 2012, after the British Foreign and Commonwealth Office designated a previously unnamed area Queen Elizabeth Land in tribute to Queen Elizabeth II's Diamond Jubilee. the Argentinean government formally protested against the claim. The UK passed some of the area it claimed to Australia and New Zealand after they achieved independence. The claims of Britain, Australia, New Zealand, France and Norway don't overlap, and are recognised by each other. Other members nations of the Antarctic Treaty don't recognize any claim, yet have shown some form of territorial interest in the past.

• Brazil has a designated 'zone of interest' that is not an actual claim.
• Peru has formally reserved its right to make a claim.
• Russia has inherited the Soviet Union's right to claim territory under the original Antarctic Treaty.
• South Africa has formally reserved its right to make a claim.
• United States reserved its right to make a claim in the original Antarctic Treaty.

The ISO 3166-1 alpha-2 code for Antarctica, AQ, is assigned to the entire continent regardless of jurisdiction.

Human activity

See also: Tourism in Antarctica and Research stations in Antarctica

Economic activity and tourism

The cruise ship Silver Cloud in Wilhelmina Bay

Deposits of coal, hydrocarbons, iron ore, platinum, copper, chromium, nickel, gold and other minerals have been found, but not in large enough quantities to extract. The Protocol on Environmental Protection to the Antarctic Treaty, which came into effect in 1998 and is due to be reviewed in 2048, restricts the exploitation of Antarctic resources, including minerals.

Tourists have been visiting Antarctica since 1957. Tourism is subject to the provisions of the Antarctic Treaty and Environmental Protocol; the self-regulatory body for the industry is the International Association of Antarctica Tour Operators (IAATO). Tourists arrive by small or medium ship at specific scenic locations with accessible concentrations of iconic wildlife. Over 74,000 tourists visited the region during the 2019/2020 season, of which 18,500 travelled on cruise ships but did not leave them to explore on land. The numbers of tourists fell rapidly after the start of the COVID-19 pandemic. Some nature conservation groups have expressed concern over the potential adverse effects caused by the influx of visitors, and have called for limits on the size of visiting cruise ships and a tourism quota. The primary response by Antarctic Treaty parties has been to develop guidelines that set landing limits and closed or restricted zones on the more frequently visited sites.

Overland sightseeing flights operated out of Australia and New Zealand until the Mount Erebus disaster in 1979, which killed all 257 people aboard. Qantas resumed commercial overflights to Antarctica from Australia in the mid-1990s.

Terrestrial research

An aerial view of McMurdo Station, the largest research station in Antarctica

In 2017, there were more than 4,400 scientists undertaking research in Antarctica, a number that fell to just over 1,100 in the winter. There are over 70 permanent and seasonal research stations on the continent; the largest, McMurdo Station, is capable of housing more than 1,000 people. Geologists primarily study plate tectonics, meteorites, and the breakup of Gondwana. Glaciologists study the history and dynamics of floating ice, seasonal snow, glaciers, and ice sheets. Biologists, in addition to researching the wildlife, are interested in how low temperatures and the presence of humans affect adaptation and survival strategies in organisms. Biomedical scientists have made discoveries concerning the spreading of viruses and the body's response to extreme seasonal temperatures.

The Polar Geospatial Center (PGC) was founded in 2007. It uses geospatial and remote sensing technology from satellites to provide up-to-date data about surface conditions across the continent. The centre can use Information from satellites to resolve images that are up to 30 cm (12 in) across.

In 2007 the Belgian-based International Polar Foundation unveiled the Princess Elisabeth station, the world's first zero-emissions polar science station in Antarctica, to research climate change. The prefabricated station was shipped to the South Pole from Belgium by the end of 2008 to monitor the health of the polar regions. The project includes research in climatology, glaciology and microbiology.

Astronomy

An Antarctic meteorite, Allan Hills 84001 on display at the Smithsonian Museum of Natural History

William Wales and William Bayly, astronomers who were on the second voyage of James Cook to the southern hemisphere, published their observations and findings in 1777. Modern astronomy on the continent began in the 1960s. The high elevation of the interior, the low temperatures, and the length of polar nights during the winter months, all allow for better astronomical observations at Antarctica than anywhere else on Earth. The view of space from Earth is improved by a thinner atmosphere at higher elevations, and a lack of water vapour in the atmosphere caused by freezing temperatures.

Astrophysicists at the Amundsen–Scott South Pole Station study cosmic microwave background radiation and neutrinos from space. The largest neutrino detector in the world, the IceCube Neutrino Observatory, lies at the Amundsen-Scott station. It consists of around 5,500 digital optical modules, some of which reach a depth of 2,450 m (8,040 ft), held in 1 km³ (0.24 cu mi) of ice.

Meteorites from Antarctica are important for studying material formed early in life of the Solar System; most are thought to come from asteroids, but some may have originated on larger planets. Most of those found have fallen onto the ice sheet over the last million years. The Adelie Land meteorite, discovered in 1912, was the first to be found. The motion of Antarctica's ice sheet tends to accumulate meteorites near mountain ranges, and wind erosion brings them to the surface after being for centuries beneath accumulated snowfall. Compared with those found in more temperate regions, Antarctic meteorites are well-preserved. They have helped to provide a better understanding of the abundance of meteorite types and their relationship with asteroids and comets. New types of meteorites and rare meteorites have been found, among which are rocks blasted off the Moon or Mars by impacts.

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Further reading

• Lucas, Mike (1996). Antarctica. New Holland Publishers. ISBN 978-1-85368-743-3.
• Mardon, Austin Albert; Mardon, Catherine (2009). The use of geographic remote sensing, mapping and aerial photography to aid in the recovery of blue ice surficial meteorites in Antarctica. Edmonton: Golden Meteorite Press. ISBN 978-18974-7-235-4 – via Internet Archive.
• Stewart, John (2011). Antarctica: An Encyclopedia. Jefferson, N.C. and London: McFarland. ISBN 978-0-7864-3590-6.

External links

• High resolution map (2018) – Reference Elevation Model of Antarctica (REMA)
• Antarctica. on In Our Time at the BBC
• Antarctic Treaty Secretariat, de facto government
• British Antarctic Survey (BAS)
• U.S. Antarctic Program Portal