About Antarctica

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Continent located at the South Pole and surrounded by the Southern Ocean.
Discover the history and general characteristics, climate, wildlife by clicking below or in the tabs at the bottom of the page

General characteristics

 

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The Antarctic is the continent located at the South Pole and surrounded by the

Southern Ocean. Its surface area is about 12.5 million km², exposed rock representing only 2% of this surface. This is a continent covered by an ice sheet itself extending 14 million km² in summer, about 26 times that of metropolitan France.

With an average altitude of around 2.3 km, it is Earth’s highest continent. The ice sheet extends in certain sectors as immense ice shelves, spreading and floating on the Southern Ocean. The combined surface areas of these exceed 1.5 million km². The greatest diameter of the Antarctic is about 5500 km. The complete coastline amounts to a length of around 24 000 km, including the ice-shelves. The Transantarctic chain, a mountain range about 3000 km long, is a natural separation between the West and East of the ice sheet.

  • The East part of the continent, facing the Atlantic and Indian Oceans, is called the Eastern Antarctic. It takes the form of an immense dome of ice of about 10 million km² which culminates at over 4000 m for an average altitude of 2600 m.
  • The West part, the Western Antarctic, constitutes only 5% of the continent’s total surface area and culminates at about 2500 m; it is prolonged by the Antarctic Peninsula and 2 large ice-shelves, the Ross and Ronne.

The average ice-sheet thickness is 1300 m in the west and 2200 m in the east. The maximum thickness is nearly 5000 m. Most of the continent’s non-iced zones are found in the Antarctic Peninsula. It is the northernmost area of the Antarctic continent and almost the only part extending beyond the Antarctic Circle. It is a mountainous region, positioned along the continuation of the Andes range of South America.

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From Antiquity to 18th Century

The existence of an Antarctic continent as a balance to the Arctic was evoked in Antiquity by Aristotle. This idea was then abandoned until Magellan rounded the tip of South America in 1520 and observed ice-covered land to the south. From that time onwards geographers envisaged a continent known as Terra Australis seemingly stretching from Tierra del Fuego to what is now Australia.

In 1773, James Cook was the first navigator to cross the Antarctic Circle (66°33’39”S). He was halted by ice in January 1774 at the record latitude of 71°10’S. He was also the first explorer to sail completely round the continent (but without knowing it).

19th Century

The Russian Bellingshausen was the first to catch sight of the continent. He named it Alexander I Land in January 1820. Then it was the American sealer John Davis who was the first to berth at the continent in February 1821.

In 1838, French navigators led by Dumont d’Urville set off to look for the magnetic South Pole. On 21 January 1840, they landed on the continent at a place Dumont d’Urville named Adélie Land, in honour of his wife.

In 1897-98, the Belgica commanded by Adrien de Gerlache, carried out the first overwintering on the ice sheet of the Antarctic Peninsula. The following year saw the Norwegian Borchgrevink install the first base on the continent, at Cap Adare (east of Adélie Land), where he accomplished the first land-based overwintering operation.

20th Century

The geographical South Pole was reached on 14 December 1911 by the Norwegian Roald Amundsen, 1 month before British explorer Robert Falcon Scott and his team got there (16 January 1912). The return journey cost the lives of Scott and his 4 companions in misfortune.

Model of Port Martin, offered to IPEV by the French polar expeditions.

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In 1950, the Expéditions Polaires Françaises (EPF), founded by Paul-Emile Victor, built the Port-Martin station in Adélie Land. The buildings were destroyed by a fire in January 1952 and the French team set itself up on Petrel Island in the Geology Point Islands 5 km off the mainland, on the current site of the Dumont d’Urville station set up in January 1956.

During the International Geophysical Year of 1957, a large number of expeditions were run and 12 countries implanted 48 operational stations, mostly on the coasts but also some on the ice sheet (Russian Vostok base, American Amundsen-Scott base).

The Charcot base was constructed in 1957, 320 km from Dumont d’Urville and was definitively shut down in December 1959.

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The Antarctic Treaty was signed on 1 December 1959 and came into force on 23 June 1961. It brought to a halt all territorial claims over the continent.

Several factors, like high altitude, low solar radiation, the Antarctic Circumpolar Current and reflectivity of the ice (80% of light radiation is reflected back into the atmosphere), combine to make this the coldest of all Earth’s continents.

Temperature

Ant-Concordia-Science-AlexSALAM-2009-IPEV (4)Temperatures are relatively “mild” on the coast: -10°C, on average the seasonal extreme varying from 0 to -30°C. However, they plummet dramatically the further the distance towards the heart of the continental ice sheet. The annual average is between -20°C at 1000 m altitude and -55°C at the Russian research station Vostok (3500 m): -30°C for the warmest 2 months (January-February) and an average of -60°C the rest of the year with lowest point at –89.3°C, the lowest temperature ever measured on the Earth’s surface (at Vostok). At this temperature, any person dressed in normal clothing would die of cold in less than a minute.

Winds

The average wind speed is quite moderate in the central areas (10 to 20 km/h) but stronger at the coast (30 to 70 km/h) where winds gusting to record speeds are possible: 320 km/h has been measured at the Dumont d’Urville station.

Precipitation

It hardly snows in the Antarctic, seemingly a great paradox. Atmospheric depressions cannot easily penetrate into the interior of the continent and most precipitation thus occurs on the coast. The interior of the landmass is like a desert: over a surface area of 5 million km², annual precipitation is less than the equivalent of 5 cm of water and often less than 2 cm! It must have taken Nature a long time to build up the several-kilometre thick layer that constitutes the ice sheet.

The Antarctic came into being at least 3.8 billion years ago (Ga), the age of the most ancient rocks found there. Its growth then continued according to all the build-up and breakup processes undergone by a succession of supercontinents: Columbia  (1.8 – 1.6 Ga BP), Rodinia (1.3 – 0.93 Ga), Pannotia (0.68 – 0.55 Ga), then Gondwana (0.45 – 0.25 Ga). The breaking-up of Gondwana gradually led the Antarctic to become a separate entity, beginning its drift towards the South Pole around 60 million years (Ma) BP.

Some 30 Ma ago, the Antarctic had become separate and the opening-up of the Drake passage, south of Cape Horn, generated a circumpolar current which isolated the continent climatically by blocking the passage of temperate influences from the other oceans: Atlantic, Indian and Pacific.

It was around 14 Ma BP that the Antarctic became an ice sheet: a continent topped with a thick cap of ice. Nevertheless at depth the ice masses do flow, towards the ocean, and those in place today are considered to be no more than 900 000 years old.

There are two major geological domains in the Antarctic:

  • The oldest is on the East and consists of continental remnants in the form of nuclei of rocks called cratons surrounded by belts built up during continental-drift induced collisions and overlap. Erosion planed down all the top parts of these configurations. All that now remains are the deepest folded zones: indeed the “roots” of ancient mountain chains.
  • The western part, which has been reworked several times (by fusion then magmatism); hence it is younger. Two present-day mountain chains govern its morphology:

> The West Antarctic Cordillera, heavily marked by volcanoes and earthquakes, whose origin is comparable with that observed in the Andes.

> The Transantarctic Mountains generated by a rift (tearing of the lithosphere) cuts into the continent over 3 000 km and is punctuated with volcanoes. The best known of these, Mount Erebus, is still active and continually emits chlorine: possible influence on the ozone layer remains to be determined.

The Antarctic’s surface is 98% covered over with ice. Radar and satellite studies, combined with field observations, yield useful data for defining the topography of the ice sheet and determining ice thickness and monitoring any changes and developments.

The ice sheet: ice cap

The average thickness of the ice sheet is 1300 m in the West Antarctic and 2200 m in the Eastern part. Its maximum thickness reaches nearly 5000 m. Its base therefore lies more than 2500 m below sea level. It is fed by snow falls which are more abundant in the coastal regions. Precipitation in the interior of the continent is even only half that received by the hottest deserts. Year after year, the snow accumulates and changes into compact ice. Under the combined effect of this extra load and gravity, the ice flows away from the centre of the ice cap towards the continental periphery. These movements are very weak at the centre of the ice sheet, a few tens of centimetres per year, then pick up speed, reaching about 100 metres per year, in the voluminous glaciers which, at the coast, drain the continental ice out to the ocean.

Ice-shelves and icebergs

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The ice sheet extends in some areas as immense ice-shelves, spreading and floating on the Southern Ocean, and whose surface areas combined exceed 1.5 million km². The 3 largest ice-shelves are Amery, Ronne and Ross, with an area almost as large as France.

As they advance onto the ocean, ice-shelves fragment as blocks that can attain over 400 m thickness and can form tabular icebergs. Some can even be larger than Corsica.

Sea-ice

OLYMPUS DIGITAL CAMERAEvery winter, the ocean around the Antarctic freezes. Sea-water’s salinity means that surface freezing begins at –1.8°C. Ice at the formation stage is fragile and is destroyed at every storm. Subsequently, as the cold intensifies, the ice in the sea thickens to turn into the sea-ice with average thickness 40-60 cm. The maximum extent of the sea-ice, in September, can reach 20 million km², which doubles the frozen area of the Southern Hemisphere.

In the midst of expanses of sea-ice there are persistent or recurrent zones of open water called polynyas. These are linked to upwelling of warmer water from the depths. The most extensive is located is the eastern part of the Weddell Sea, measuring 250 000 km².

In February, nearing the end of the Austral summer, the sea-ice is completely broken up and most of the coasts are therefore freely accessible. Which means however that access to the continent is possible only during 2 to 3 months of summer. And that is uncertain because the condition of the ice formations depends heavily on the vagaries of the climate.

The annual rhythm of formation and melting of this immense quantity of ice bears a strong influence on the global ocean circulation, the heat exchanges between ocean and the atmosphere and the biology of the oceans of the Southern Hemisphere.

Ant-Astrolabe-Paysage-EduardoDAFORNO-2014-IPEV-117From an oceanographic point of view, the Antarctic Ocean or Southern Ocean is defined as an ocean traversed by the Antarctic circumpolar current, which moves from West to East around the Antarctic continent. Contrary to the other oceans, which are defined as expanses of water delimited by the continents, the Southern Ocean is the only one to be defined as a mass of water that surrounds a continent. This ring of water stretches to south of the 60th parallel South and over the whole of Earth’s circumference.

History

The name “Southern Ocean” and the boundary of 60°S were adopted in 2000 following a proposal and opinion poll organized by the International Hydrographic Organization (IHO). Before that, the waters covered by the Southern Ocean were considered to be southern parts of the Atlantic, Indian and Pacific Oceans, even if the term already existed. According to this definition its surface area exceeds 20 million km².

Ocean circulation

The circulation of this ocean is considered to be the main driving force behind the formation of deep-moving bodies of water in the World ocean, cooling more than half its volume by about 2°C. Water masses differing in temperature and salinity circulate from and around the continent, in equilibrium with the uprising of deep Atlantic water arriving from the Arctic. The Antarctic convergence is the best natural marker of the upper boundary of the Southern Ocean: it is a distinct region in the centre of the Antarctic Circumpolar Current which separates the very cold surface waters to the south from the warmer subantarctic waters to the north. This phenomenon effectively isolates the continent even further from the heat transport and exchange operating in the middle latitudes. Another current circulates even closer to the Antarctic: the Antarctic Coastal Current, which circulates from east to west, separated from the circumpolar current by the Antarctic Divergence.

Bathymetry

Southern Ocean is deep, between 4000 and 5000 m over most of its extent, with only few shallower areas. The maximum depth is reached at the South Sandwich trench (60°S, 24°W), at 7235 m. The Antarctic continental shelf is generally narrow. The part near the coastline coasts is also deep: from 400 to 800 m whereas the global average is only 133 m.

Climate

The sea temperature varies between about –1.8°C and 10°C. The oceanic zone covering from about 40°S to the Antarctic Circle is subjected to the strongest winds ever known on Earth. There is no lack of evocative terms for the conditions encountered when sailing to the Far South: through regions of the “Roaring forties” or the “Furious fifties“. In winter, the ocean freezes beyond 65°S in the Pacific sector, and from 55°S in the Atlantic sector, lowering the surface temperatures to well under 0°C and forming the sea-ice.

The opposite to the ice sheet, a lifeless desert, the marine environment is biologically extremely rich. Almost all the life in the Antarctic is concentrated in the sea or on its margins. The biomass is very high owing mainly to the water’s high nutrient and oxygen contents.

Plankton and Krill

The plankton is the basis for any aquatic food chain and is more abundant in polar than in tropical waters. The krill is made up of numerous crustacean species, feeding on plankton, the most frequent of which, Euphausia superba, is like a shrimp. In terms of biomass, krill probably constitutes the Earth’s most abundant element, possibly exceeded 500 million tonnes! In summer, these Crustacea can form swarms covering 500 km². The pink colour is detectable by satellite, not only by fishermen! The very core of the food web, krill provides the staple food for fish, whales, seals, penguins and other birds.

Fish

Out of the 20 000 species of fish in the world, less than 300 live in the Southern Ocean. The most characteristic of them, adapted to the polar environment, include the “icefish” (Champsocephalus gunnari, mackerel icefish) whose blood contains no haemoglobin, and Notothenia, a cod icefish which secretes .antifreeze substances.

Flora

The flora is scarcely developed on the Antarctic continent. Lichens and mosses are found on rocks, as are microscopic algae in often frozen ice or lakes, also 2 flowering plants in the more temperate Antarctic Peninsula.

However, many species of birds and marine mammals are present on the coast, the sea-ice and in the ocean.

Birds

About 40 species of birds, amounting to 200 million individuals, live in the Southern and subantarctic zones; half of them reproducing in summer on the very sparse lands and islands that border the continent. The species most represented are petrels, skuas, terns and of course penguins.

Ant-DumontDurville-Faune-CyrilGALLUT-2014-IPEV-34The penguins are birds that are unable to fly but extremely well adapted to the marine environment and to cold. Four species live in the Antarctic, but although chinstrap and gentoo penguins frequent the Peninsula, only the Adélie and Emperor penguins nest on the coastal shores. Penguins form groups, huddling together in thousands on the sea-ice or on the coast forming what are termed rookeries to keep warm. The emperor penguin is the largest and heaviest penguin. It is found in only a few tens of colonies, although each consists of thousands of individuals.

Mammals

Ant-Astrolabe-Faune-BrunoEtMarieCUSA-2014-IPEV-86Cetacea (whales, killer whales etc.) and 8 species of Pinnipedia (seals and sea lions), 4 of which reproduce near the continent. However, sea lions do not venture further than the Peninsula and there are no walrus. Several species belong particularly to the Antarctic: the crabeater seals, the most numerous, amount to 15 million individuals, whereas those from Weddell are the most impressive (3 m long and over 400 kg); leopard seals, rarer, feed mainly on penguins: they can swallow up to 20 per day!

The Antarctic, “land of international cooperation”, is a continent protected by a considerable armour of legal measures: the Antarctic Treaty system. Among other things this system guarantees the halting of territorial claims and very strict protection of the environment through the Madrid Protocol.

The Antarctic Treaty:

The scientific and political success of the International Geophysical Year (IGY) laid the foundation for the Treaty’s signature on 1 December 1959. A system set up by States wanting to pursue high-quality research on an exceptional field of study, the Antarctic Treaty freezes territorial claims south of the 60th parallel S. Only peaceful activities can be permitted. At the start 12 States were involved (South Africa, Argentina, Australia, Belgium, Chile, USA, France, Japan, Norway, New-Zealand, United Kingdom, Russia), then since 2009 the number has reached 47. Among these, 7 are known as “Claimant States”, that is they claim possession of a part of the continent (Adélie Land for France for example).

Set out below are texts related to protection of the fauna and flora of the Antarctic zone which are usually attached to the Antarctic Treaty system:

The Madrid Protocol:

In 1991, the Antarctic Treaty was supplemented by a protocol dealing with environmental protection, commonly known as the Madrid Protocol (the city where the final text was adopted, on 4 October 1991). The States that are party to the protocol undertake to ensure the overall protection of the environment in the Antarctic and dependent and associated ecosystems. The Antarctic is therefore designated a “natural reserve dedicated to Peace and Science”.

The Protocol came into force on 14 January 1998, 30 days after ratification by Japan, which brought the ratifications to the number necessary for its entry into force. France approved the Madrid Protocol through a law of 18 December 1992 before its publication in 1998 in the Journal Officiel de la République Française (decree of 18 September 1998). Since then the country has implemented the provisions of the Protocol principally by a law of 15 April 2003 on the protection of the environment in the Antarctic and a decree of application in 2005.

The Madrid Protocol in French law :

Conventions

Convention for the protection of Antarctic seals (CCAS – signed in 1972, in force from 1978)
Convention the conservation of Antarctic Marine Living Resources (CCAMLR, signed in 1980, in force from 1982).

Note: all the texts can be downloaded in pdf opposite