Western Antarctica
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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, it contains the geographic South Pole. Antarctica is the fifth-largest cont ...
, 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 antimeridian. The other half is called the Eastern Hemisphere. Politically, the te ...
, and includes the Antarctic Peninsula. It is separated from East Antarctica by the
Transantarctic Mountains The Transantarctic Mountains (abbreviated TAM) comprise a mountain range of uplifted (primarily sedimentary) rock in Antarctica which extend, with some interruptions, across the continent from Cape Adare in northern Victoria Land to Coats Land. ...
and is covered by the
West Antarctic Ice Sheet The Western Antarctic Ice Sheet (WAIS) is the segment of the continental ice sheet that covers West Antarctica, the portion of Antarctica on the side of the Transantarctic Mountains that lies in the Western Hemisphere. The WAIS is classified as ...
. 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), 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 ...
(largely covered by the Filchner-Ronne Ice Shelf). It may be considered a giant peninsula, stretching from the
South Pole The South Pole, also known as the Geographic South Pole, Terrestrial South Pole or 90th Parallel South, is one of the two points where Earth's axis of rotation intersects its surface. It is the southernmost point on Earth and lies antipod ...
towards the tip of South America. West Antarctica is largely covered by the Antarctic ice sheet, but there have been signs that
climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...
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 mosses and lichens 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 oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the contin ...
side of the Transantarctic Mountains, West Antarctica comprises the Antarctic Peninsula (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 an ...
and Palmer Land) and
Ellsworth Land Ellsworth Land is a portion of the Antarctic continent bounded on the west by Marie Byrd Land, on the north by Bellingshausen Sea, on the northeast by the base of Antarctic Peninsula, and on the east by the western margin of the Filchner–Ronne ...
, Marie Byrd Land 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 corne ...
, offshore islands such as Adelaide Island, and
ice shelves An ice shelf is a large floating platform of ice that forms where a glacier or ice sheet flows down to a coastline and onto the ocean surface. Ice shelves are only found in Antarctica, Greenland, Northern Canada, and the Russian Arctic. The b ...
, notably the Filchner-Ronne Ice Shelf on 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 ...
, and the Ross Ice Shelf on 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 ...
. West Antarctica was named in the early 20th century. That usage became standard following the International Geophysical Year (1957–1958) and explorations which disclosed that the Transantarctic Mountains provide a useful regional border between West Antarctica and East Antarctica. The Advisory Committee on Antarctic Names approved the name in 1962. West Antarctica is mostly covered by a massive ice sheet referred to as the
West Antarctic Ice Sheet The Western Antarctic Ice Sheet (WAIS) is the segment of the continental ice sheet that covers West Antarctica, the portion of Antarctica on the side of the Transantarctic Mountains that lies in the Western Hemisphere. The WAIS is classified as ...
. In recent decades, this
ice sheet In glaciology, an ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than . The only current ice sheets are in Antarctica and Greenland; during the Last Glacial Period at La ...
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 r ...
), which are the coasts of the Antarctic Peninsula, constitute a
biodiversity Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...
region known as Marielandia Antarctic
tundra In physical geography, tundra () is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. The term ''tundra'' comes through Russian (') from the Kildin Sámi word (') meaning "uplands", "treeless mou ...
(after Marie Byrd Land). This area has the warmest climate in Antarctica and the moss and lichen-covered rocks are free of snow during the summer months, although the weather is still intensely cold and the growing season very short.


See also

* Tectonic evolution of the Transantarctic Mountains *
West Antarctic Rift System The West Antarctic Rift System is a series of rift valleys between East and West Antarctica. It encompasses the Ross Embayment, the Ross Sea, the area under the Ross Ice Shelf and a part of Marie Byrd Land in West Antarctica, reaching to the ...


References

{{Authority control . Tundra Geography of Antarctica