West Antarctica, or Lesser Antarctica, one of the two major regions of

Antarctica Antarctica () is Earth's southernmost and least-populated continent. Situated almost entirely south of the Antarctic Circle and surrounded by the Southern Ocean (also known as the Antarctic Ocean), it contains the geographic South Pole. ...

, is the part of that continent that lies within the

Western Hemisphere The Western Hemisphere is the half of the planet Earth that lies west of the Prime Meridian (which crosses Greenwich, London, United Kingdom) and east of the 180th meridian.- The other half is called the Eastern Hemisphere. Geopolitically, ...

, and includes the

Antarctic Peninsula The Antarctic Peninsula, known as O'Higgins Land in Chile and Tierra de San Martin in Argentina, and originally as Graham Land in the United Kingdom and the Palmer Peninsula in the United States, is the northernmost part of mainland Antarctica. ...

. It is separated from

East Antarctica East Antarctica, also called Greater Antarctica, constitutes the majority (two-thirds) of the Antarctic continent, lying primarily in the Eastern Hemisphere south of the Indian Ocean, and separated from West Antarctica by the Transantarctic ...

by the

Transantarctic Mountains The Transantarctic Mountains (abbreviated TAM) comprise a mountain range of uplifted rock (primarily sedimentary) in Antarctica which extends, with some interruptions, across the continent from Cape Adare in northern Victoria Land to Coats L ...

and is covered by the

West Antarctic Ice Sheet The West Antarctic Ice Sheet (WAIS) is the segment of the Antarctic ice sheet, continental ice sheet that covers West Antarctica, the portion of Antarctica on the side of the Transantarctic Mountains that lies in the Western Hemisphere. It is cla ...

. It lies between the

Ross Sea The Ross Sea is a deep bay of the Southern Ocean in Antarctica, between Victoria Land and Marie Byrd Land and within the Ross Embayment, and is the southernmost sea on Earth. It derives its name from the British explorer James Clark Ross who ...

(partly covered by the

Ross Ice Shelf The Ross Ice Shelf is the largest ice shelf of Antarctica (, an area of roughly and about across: about the size of France). It is several hundred metres thick. The nearly vertical ice front to the open sea is more than long, and between high ...

), and the

Weddell Sea The Weddell Sea is part of the Southern Ocean and contains the Weddell Gyre. Its land boundaries are defined by the bay formed from the coasts of Coats Land and the Antarctic Peninsula. The easternmost point is Cape Norvegia at Princess Martha C ...

(largely covered by the Filchner-Ronne Ice Shelf). It may be considered a giant

peninsula A peninsula is a landform that extends from a mainland and is only connected to land on one side. Peninsulas exist on each continent. The largest peninsula in the world is the Arabian Peninsula. Etymology The word ''peninsula'' derives , . T ...

, stretching from the

South Pole The South Pole, also known as the Geographic South Pole or Terrestrial South Pole, is the point in the Southern Hemisphere where the Earth's rotation, Earth's axis of rotation meets its surface. It is called the True South Pole to distinguish ...

towards the tip of South America. West Antarctica is largely covered by the

Antarctic ice sheet The Antarctic ice sheet is a continental glacier covering 98% of the Antarctic continent, with an area of and an average thickness of over . It is the largest of Earth's two current ice sheets, containing of ice, which is equivalent to 61% of ...

, but there have been signs that

climate change Present-day climate change includes both global warming—the ongoing increase in Global surface temperature, global average temperature—and its wider effects on Earth's climate system. Climate variability and change, Climate change in ...

is having some effect and that this ice sheet may have started to shrink slightly. Over the past 50 years, the west coast of the Antarctic Peninsula has been – and still is – one of the most rapidly warming parts of the planet, and the coasts of the Peninsula are the only parts of West Antarctica that become (in summer) ice-free. These constitute the Marielandia Antarctic tundra and have the warmest climate in Antarctica. The rocks are clad in

moss Mosses are small, non-vascular plant, non-vascular flowerless plants in the taxonomic phylum, division Bryophyta (, ) ''sensu stricto''. Bryophyta (''sensu lato'', Wilhelm Philippe Schimper, Schimp. 1879) may also refer to the parent group bryo ...

es and

lichen A lichen ( , ) is a hybrid colony (biology), colony of algae or cyanobacteria living symbiotically among hypha, filaments of multiple fungus species, along with yeasts and bacteria embedded in the cortex or "skin", in a mutualism (biology), m ...

s that can cope with the intense cold of winter and the short growing-season.

Location and description

Lying on the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five Borders of the oceans, oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean, or, depending on the definition, to Antarctica in the south, and is ...

side of the Transantarctic Mountains, West Antarctica comprises the

(with

Graham Land Graham Land is the portion of the Antarctic Peninsula that lies north of a line joining Cape Jeremy and Cape Agassiz. This description of Graham Land is consistent with the 1964 agreement between the British Antarctic Place-names Committee ...

and

Palmer Land Palmer Land () is the portion of the Antarctic Peninsula, Antarctica that lies south of a line joining Cape Jeremy and Cape Agassiz. This application of Palmer Land is consistent with the 1964 agreement between the Advisory Committee on Antarctic N ...

) and

Ellsworth Land Ellsworth Land is a portion of the Antarctica, Antarctic continent bounded on the west by Marie Byrd Land, on the north by the Bellingshausen Sea, on the northeast by the base of the Antarctic Peninsula, and on the east by the western margin of t ...

Marie Byrd Land Marie Byrd Land (MBL) is an unclaimed region of Antarctica. With an area of , it is the largest unclaimed territory on Earth. It was named after the wife of American naval officer Richard E. Byrd, who explored the region in the early 20th centu ...

and

King Edward VII Land King Edward VII Land or King Edward VII Peninsula is a large, ice-covered peninsula which forms the northwestern extremity of Marie Byrd Land in Antarctica. The peninsula projects into the Ross Sea between Sulzberger Bay and the northeast corner ...

, offshore islands such as

Adelaide Island Adelaide Island is a large, mainly ice-covered island, long and wide, lying at the north side of Marguerite Bay off the west coast of the Antarctic Peninsula. The Ginger Islands lie off the southern end. Mount Bodys is the easternmost mounta ...

, and

ice shelves An ice shelf is a large platform of glacial ice floating on the ocean, fed by one or multiple tributary glaciers. Ice shelves form along coastlines where the ice thickness is insufficient to Displacement (fluid), displace the more dense surround ...

, notably the Filchner-Ronne Ice Shelf on the

, and the

on the

. West Antarctica was named in the early 20th century. That usage became standard following the

International Geophysical Year The International Geophysical Year (IGY; ), also referred to as the third International Polar Year, was an international scientific project that lasted from 1 July 1957 to 31 December 1958. It marked the end of a long period during the Cold War w ...

(1957–1958) and explorations which disclosed that the Transantarctic Mountains provide a useful regional border between West Antarctica and

. The

Advisory Committee on Antarctic Names The Advisory Committee on Antarctic Names (ACAN or US-ACAN) is an advisory committee of the United States Board on Geographic Names responsible for recommending commemorative names for features in Antarctica. History The committee was established ...

approved the name in 1962. West Antarctica is mostly covered by a massive ice sheet referred to as the

. In recent decades, this

ice sheet In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacier, glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are the Antarctic ice sheet and the Greenland ice sheet. Ice s ...

has shown signs of decreasing mass. The geologic history of West Antarctica was summarized in a 2020 publication.

Marielandia Antarctic tundra

The parts of West Antarctica not covered with ice (

Antarctic oasis An Antarctic oasis is a large area naturally free of snow and ice in the otherwise ice-covered continent of Antarctica. Geology In Antarctica there are, in addition to mountaintops and nunataks, other natural snow- and ice-free areas often ...

), which are the coasts of the

, constitute a

biodiversity Biodiversity is the variability of life, life on Earth. It can be measured on various levels. There is for example genetic variability, species diversity, ecosystem diversity and Phylogenetics, phylogenetic diversity. Diversity is not distribut ...

region known as Marielandia Antarctic

tundra In physical geography, a tundra () is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. There are three regions and associated types of tundra: #Arctic, Arctic, Alpine tundra, Alpine, and #Antarctic ...

(after

). This area has the warmest climate in Antarctica and the

and

-covered rocks are free of snow during the summer months, although the weather is still intensely cold and the growing season very short.

References

{{Authority control . Tundra Geography of Antarctica

Location and description

Marielandia Antarctic tundra

See also

References