The Antarctic ice sheet is one of the two polar ice caps of the Earth. It covers about 98% of the Antarctic continent and is the largest single mass of ice on Earth. It covers an area of almost 14 million square kilometres (5.4 million square miles) and contains 26.5 million cubic kilometres (6,400,000 cubic miles) of ice. A cubic kilometer of ice weighs approximately one metric gigaton, meaning that the ice sheet weighs 26,500,000 gigatons. Approximately 61 percent of all fresh water on the Earth is held in the Antarctic ice sheet, an amount equivalent to about 58 m of sea-level rise. In East Antarctica, the ice sheet rests on a major land mass, while in West Antarctica the bed can extend to more than 2,500 m below sea level.
In contrast to the melting of the Arctic sea ice, sea ice around Antarctica was expanding as of 2013. The reasons for this are not fully understood, but suggestions include the climatic effects on ocean and atmospheric circulation of the ozone hole, and/or cooler ocean surface temperatures as the warming deep waters melt the ice shelves.
The icing of Antarctica began in the middle Eocene about 45.5 million years ago and escalated during the Eocene–Oligocene extinction event about 34 million years ago. CO2 levels were then about 760 ppm and had been decreasing from earlier levels in the thousands of ppm. Carbon dioxide decrease, with a tipping point of 600 ppm, was the primary agent forcing Antarctic glaciation. The glaciation was favored by an interval when the Earth's orbit favored cool summers but oxygen isotope ratio cycle marker changes were too large to be explained by Antarctic ice-sheet growth alone indicating an ice age of some size. The opening of the Drake Passage may have played a role as well though models of the changes suggest declining CO2 levels to have been more important.
The Western Antarctic ice sheet declined somewhat during the warm early Pliocene epoch, approximately 5 to 3 million years ago; during this time the Ross Sea opened up. But there was no significant decline in the land-based Eastern Antarctic ice sheet.
According to a 2009 study, the continent-wide average surface temperature trend of Antarctica is positive and significant at >0.05 °C/decade since 1957. West Antarctica has warmed by more than 0.1 °C/decade in the last 50 years, and this warming is strongest in winter and spring. Although this is partly offset by fall cooling in East Antarctica, this effect is restricted to the 1980s and 1990s.
Ice enters the sheet through precipitation as snow. This snow is then compacted to form glacier ice which moves under gravity towards the coast. Most of it is carried to the coast by fast moving ice streams. The ice then passes into the ocean, often forming vast floating ice shelves. These shelves then melt or calve off to give icebergs that eventually melt.
If the transfer of the ice from the land to the sea is balanced by snow falling back on the land then there will be no net contribution to global sea levels. The general trend shows that a warming climate in the southern hemisphere would transport more moisture to Antarctica, causing the interior ice sheets to grow, while calving events along the coast will increase, causing these areas to shrink. A 2006 paper derived from satellite data, measuring changes in the gravity of the ice mass, suggests that the total amount of ice in Antarctica has begun decreasing in the past few years. A 2008 study compared the ice leaving the ice sheet, by measuring the ice velocity and thickness along the coast, to the amount of snow accumulation over the continent. This found that the East Antarctic Ice Sheet was in balance but the West Antarctic Ice Sheet was losing mass. This was largely due to acceleration of ice streams such as Pine Island Glacier. These results agree closely with the gravity changes. An estimate published in November 2012 and based on the GRACE data as well as on an improved glacial isostatic adjustment model discussed systematic uncertainty in the estimates, and by studying 26 separate regions, estimated an average yearly mass loss of 69 ± 18 Gt/y from 2002 to 2010 (a sea-level rise of 0.16 ± 0.043 mm/y). The mass loss was geographically uneven, mainly occurring along the Amundsen Sea coast, while the West Antarctic Ice Sheet mass was roughly constant and the East Antarctic Ice Sheet gained in mass.
Antarctic sea ice anomalies have roughly followed the pattern of warming, with the greatest declines occurring off the coast of West Antarctica. East Antarctica sea ice has been increasing since 1978, though not at a statistically significant rate. The atmospheric warming has been directly linked to the mass losses in West Antarctica of the first decade of the twenty-first century. This mass loss is more likely to be due to increased melting of the ice shelves because of changes in ocean circulation patterns (which themselves may be linked to atmospheric circulation changes that may also explain the warming trends in West Antarctica). Melting of the ice shelves in turn causes the ice streams to speed up. The melting and disappearance of the floating ice shelves will only have a small effect on sea level, which is due to salinity differences. The most important consequence of their increased melting is the speed up of the ice streams on land which are buttressed by these ice shelves.
Using data largely collected during the 1970s, Drewry et al. (1992), estimated the potential sea-level contribution of the Antarctic ice sheets to be in the range of 60-72 m; for Bedmap1 this value was 57 m (Lythe et al., 2001), and for Bedmap2 it is 58 m.
The Amundsen Sea, an arm of the Southern Ocean off Marie Byrd Land in western Antarctica, lies between Cape Flying Fish (the northwestern tip of Thurston Island) to the east and Cape Dart on Siple Island to the west. Cape Flying Fish marks the boundary between the Amundsen Sea and the Bellingshausen Sea. West of Cape Dart there is no named marginal sea of the Southern Ocean between the Amundsen and Ross Seas. The Norwegian expedition of 1928–1929 under Captain Nils Larsen named the body of water for the Norwegian polar explorer Roald Amundsen while exploring this area in February 1929.The sea is mostly ice-covered, and the Thwaites Ice Tongue protrudes into it. The ice sheet which drains into the Amundsen Sea averages about 3 km (1.9 mi) in thickness; roughly the size of the state of Texas, this area is known as the Amundsen Sea Embayment (ASE); it forms one of the three major ice-drainage basins of the West Antarctic Ice Sheet.East Antarctic Ice Sheet
The East Antarctic Ice Sheet (EAIS) is one of two large ice sheets in Antarctica, and the largest on the entire planet. The EAIS lies between 45° west and 168° east longitudinally.
The EAIS holds enough ice to raise global sea levels by 53.3 m and is considerably larger in area and mass than the West Antarctic Ice Sheet (WAIS). It is separated from the WAIS by the Transantarctic Mountains. The EAIS is the driest, windiest, and coldest place on Earth, with temperatures reported down to nearly -100°C. The EAIS holds the thickest ice on Earth, at 15,700 ft (4,800 m). It is home to the geographic South Pole and the Amundsen-Scott South Pole Station.Gamburtsev Mountain Range
The Gamburtsev Mountain Range (also known as the Gamburtsev Subglacial Mountains) is a subglacial mountain range located in East Antarctica, just underneath the lofty Dome A, near the Southern Pole of Inaccessibility. The range was discovered by the 3rd Soviet Antarctic Expedition in 1958 and is named for Soviet geophysicist Grigoriy A. Gamburtsev. It is approximately 1,200 kilometres (750 mi) long, and the mountains are believed to be about 2,700 metres (8,900 ft) high, although they are completely covered by over 600 metres (2,000 ft) of ice and snow. The Gamburtsev Mountain Range is currently believed to be about the same size as the European Alps, and, as of 2008, it is unknown how the mountains were formed, though the current speculated age of the range is over 34 million years and possibly 500 million years. Current models suggest that the East Antarctic ice sheet was formed from the glaciers that began sliding down the Gamburtsev range at the end of the Eocene. Vostok Subglacial Highlands form an east extension of Gamburtsev Subglacial Mountains.Geography of Antarctica
The geography of Antarctica is dominated by its south polar location and, thus, by ice. The Antarctic continent, located in the Earth's southern hemisphere, is centered asymmetrically around the South Pole and largely south of the Antarctic Circle. It is washed by the Southern (or Antarctic) Ocean or, depending on definition, the southern Pacific, Atlantic, and Indian Oceans. It has an area of more than 14 million km².
Some 98% of Antarctica is covered by the Antarctic ice sheet, the world's largest ice sheet and also its largest reservoir of fresh water. Averaging at least 1.6 km thick, the ice is so massive that it has depressed the continental bedrock in some areas more than 2.5 km below sea level; subglacial lakes of liquid water also occur (e.g., Lake Vostok). Ice shelves and rises populate the ice sheet on the periphery.
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).Hudson Mountains
The Hudson Mountains is a group of parasitic cones, forming nunataks just above the Antarctic ice sheet in west Ellsworth Land. These mountains lie just east of Cranton Bay and Pine Island Bay at the eastern extremity of Amundsen Sea, and are bounded on the north by Cosgrove Ice Shelf and on the south by Pine Island Glacier.Ice sheet
An ice sheet, also known as a continental glacier, is a mass of glacial ice that covers surrounding terrain and is greater than 50,000 km2 (19,000 sq mi). The only current ice sheets are in Antarctica and Greenland; during the last glacial period at Last Glacial Maximum (LGM) the Laurentide ice sheet covered much of North America, the Weichselian ice sheet covered northern Europe and the Patagonian Ice Sheet covered southern South America.
Ice sheets are bigger than ice shelves or alpine glaciers. Masses of ice covering less than 50,000 km2 are termed an ice cap. An ice cap will typically feed a series of glaciers around its periphery.
Although the surface is cold, the base of an ice sheet is generally warmer due to geothermal heat. In places, melting occurs and the melt-water lubricates the ice sheet so that it flows more rapidly. This process produces fast-flowing channels in the ice sheet — these are ice streams.
The present-day polar ice sheets are relatively young in geological terms. The Antarctic Ice Sheet first formed as a small ice cap (maybe several) in the early Oligocene, but retreating and advancing many times until the Pliocene, when it came to occupy almost all of Antarctica. The Greenland ice sheet did not develop at all until the late Pliocene, but apparently developed very rapidly with the first continental glaciation. This had the unusual effect of allowing fossils of plants that once grew on present-day Greenland to be much better preserved than with the slowly forming Antarctic ice sheet.Kamb Ice Stream
Kamb Ice Stream (82°15′S 145°00′W), a glaciological feature of the West Antarctic Ice Sheet, formerly known as Ice Stream C, renamed in 2001 in honor of Caltech Glaciologist Dr. Barclay Kamb.Lambert Glacier
Lambert Glacier is a major glacier in East Antarctica. At about 60 miles (100 km) wide, over 250 miles (400 km) long, and about 2,500 m deep, it holds the Guinness world record for the world's largest glacier. It drains 8% of the Antarctic ice sheet to the east and south of the Prince Charles Mountains and flows northward to the Amery Ice Shelf. It flows in part of Lambert Graben and exits the continent at Prydz Bay.
This glacier was delineated and named in 1952 by American geographer John H. Roscoe who made a detailed study of this area from aerial photographs taken by Operation Highjump, 1946–47. He gave the name "Baker Three Glacier", using the code name of the Navy photographic aircraft and crew that made three flights in this coastal area in March 1947 resulting in geographic discoveries. The glacier was described in Gazetteer No. 14, Geographic Names of Antarctica (U.S. Board on Geographic Names, 1956), but the feature did not immediately appear on published maps. As a result the name Lambert Glacier, as applied by the Antarctic Names Committee of Australia in 1957 following mapping of the area by Australian National Antarctic Research Expeditions in 1956, has become established for this feature. It was named for Bruce P. Lambert, Director of National Mapping in the Australian Department of National Development.List of mountains of East Antarctica
The list of mountains of East Antarctica includes the highest mountains in East Antarctica.MacAyeal Ice Stream
MacAyeal Ice Stream (80°S 143°W), formerly Ice Stream E, is an ice stream in Antarctica flowing west to the juncture of Shirase Coast and Siple Coast between Bindschadler Ice Stream and Echelmeyer Ice Stream. It is one of several major ice streams draining from Marie Byrd Land into the Ross Ice Shelf. The ice streams were investigated and mapped by U.S. Antarctic Research Program personnel in a number of field seasons from 1983–84 onwards and named Ice Stream A, B, C, etc., according to their position from south to north. The name was changed from Ice Scream E by the Advisory Committee on Antarctic Names in 2002 to honor Douglas R. MacAyeal of the Department of Geophysical Sciences, University of Chicago, a U.S. Antarctic Program investigator in the Ross Sea area including study of the Ross Ice Shelf, the West Antarctic Ice Sheet and the Marie Byrd Land ice streams, 1989–2002. Shabtaie Ice Ridge sits between the MacAyeal and Bundschadler ice streams.Möller Ice Stream
Möller Ice Stream (82°20′S 63°30′W) is an Antarctic ice stream that drains an area of 66,000 square kilometres (25,000 sq mi) of the West Antarctic Ice Sheet as it flows north-northeast into the Ronne Ice Shelf to the west of Foundation Ice Stream. The drainage basin of this ice stream is separated by the Rambo Nunataks from the drainage basin of Foundation Ice Stream.The feature was delineated from U.S. Landsat imagery commissioned by the Institut für Angewandte Geodäsie, Frankfurt am Main, Germany, recorded January–March, 1986. It was named after German engineer Professor Dietrich Möller, Director of the Institute for Land Survey at the Technical University of Braunschweig from 1972, and Deputy Leader and in charge of geodetic work at Filchner Station on the Ronne Ice Shelf in 1979–80.Pine Island Glacier
Pine Island Glacier (PIG) is a large ice stream, and the fastest melting glacier in Antarctica, responsible for about 25% of Antarctica's ice loss. The glacier ice streams flow west-northwest along the south side of the Hudson Mountains into Pine Island Bay, Amundsen Sea, Antarctica. It was mapped by the United States Geological Survey (USGS) from surveys and United States Navy (USN) air photos, 1960–66, and named by the Advisory Committee on Antarctic Names (US-ACAN) in association with Pine Island Bay.The area drained by Pine Island Glacier comprises about 10% of the West Antarctic Ice Sheet. Satellite measurements have shown that the Pine Island Glacier Basin has a greater net contribution of ice to the sea than any other ice drainage basin in the world and this has increased due to recent acceleration of the ice stream.The ice stream is extremely remote, with the nearest continually occupied research station at Rothera, nearly 1,300 km (810 mi) away. The area is not claimed by any nations and the Antarctic Treaty prohibits any new claims while it is in force.Recovery Glacier
The Recovery Glacier (81°10′S 28°00′W) is a glacier flowing west along the southern side of the Shackleton Range in Antarctica. First seen from the air and examined from the ground by the Commonwealth Trans-Antarctic Expedition in 1957, it was so named because of the recovery of the expedition's vehicles which repeatedly broke into bridged crevasses on this glacier during the early stages of the crossing of Antarctica. It is at least 100 km (60 mi) long and 64 km (40 mi) wide at its mouth.Dana Floricioiu and Irena Hajnsek of the German Aerospace Centre spoke on the radar data showing the interior of the Recovery Glacier at the IEEE Geoscience and Remote Sensing Symposium in Cape Town, South Africa, in July 2009. The data comes from the German public-private satellite Terrasar-X and when combined with Radarsat-1 shows the changes in the glacier over 11 years.
The Recovery Ice Stream that drains part of the East Antarctic Ice Sheet into the glacier is nearly 800 km (500 mi) long and feeds the Filchner Ice Shelf over the Weddell Sea. The area contains four subglacial lakes, causing the ice flow rate to vary dramatically, ranging between 2 and 50 meters per year. The ice stream drains about 35 billion tons of water and ice into the ocean each year, while the entire East Antarctic ice sheet releases about 57 billion tons a year.The Blackwall Ice Stream joins Recovery Glacier between the Argentina Range and the Whichaway Nunataks.Scott Glacier (Transantarctic Mountains)
The Scott Glacier is a major glacier, 120 miles (190 km) long, that drains the East Antarctic Ice Sheet through the Queen Maud Mountains to the Ross Ice Shelf. The Scott Glacier is one of a series of major glaciers flowing across the Transantarctic Mountains, with the Amundsen Glacier to the west and the Leverett and Reedy glaciers to the east.Sea level rise
Since at least the start of the 20th century, the average global sea level has been rising. Between 1900 and 2016, the sea level rose by 16–21 cm (6.3–8.3 in). More precise data gathered from satellite radar measurements reveal an accelerating rise of 7.5 cm (3.0 in) from 1993 to 2017, which is a trend of roughly 30 cm (12 in) per century. This acceleration is due mostly to human-caused global warming, which is driving thermal expansion of seawater and the melting of land-based ice sheets and glaciers. Between 1993 and 2018, thermal expansion of the oceans contributed 42% to sea level rise; the melting of temperate glaciers, 21%; Greenland, 15%; and Antarctica, 8%. Climate scientists expect the rate to further accelerate during the 21st century.Projecting future sea level is challenging, due to the complexity of many aspects of the climate system. As climate research leads to improved computer models, projections have consistently increased. For example, in 2007 the Intergovernmental Panel on Climate Change (IPCC) projected a high end estimate of 60 cm (2 ft) through 2099, but their 2014 report raised the high-end estimate to about 90 cm (3 ft). A number of later studies have concluded that a global sea level rise of 200 to 270 cm (6.6 to 8.9 ft) this century is "physically plausible". A conservative estimate of the long-term projections is that each Celsius degree of temperature rise triggers a sea level rise of approximately 2.3 metres (4.2 ft/degree Fahrenheit) over a period of two millennia: an example of climate inertia.The sea level will not rise uniformly everywhere on Earth, and it will even drop in some locations. Local factors include tectonic effects and subsidence of the land, tides, currents and storms. Sea level rises can influence human populations considerably in coastal and island regions. Widespread coastal flooding is expected with several degrees of warming sustained for millennia. Further effects are higher storm-surges and more dangerous tsunamis, displacement of populations, loss and degradation of agricultural land and damage in cities. Natural environments like marine ecosystems are also affected, with fish, birds and plants losing parts of their habitat.Societies can respond to sea level rise in three different ways: to retreat, to accommodate and to protect. Sometimes these adaptation strategies go hand in hand, but at other times choices have to be made among different strategies. Ecosystems that adapt to rising sea levels by moving inland might not always be able to do so, due to natural or man-made barriers.Van der Veen Ice Stream
Van der Veen Ice Stream (83°50′S 130°00′W), formerly Ice Stream B1, is a large southeastern tributary to the Whillans Ice Stream in Marie Byrd Land, Antarctica. Named by Advisory Committee on Antarctic Names (US-ACAN) after Cornelis J. "Kees" van der Veen, Byrd Polar Research Center and Departments of Geological Sciences and Geography, Ohio State University; glacial theoretician and collaborator with Ian Whillans, 1986–2001, in many seminal reports on the dynamics of the West Antarctic Ice Sheet, including former Ice Stream B, now Whillans Ice Stream.West Antarctic Ice Sheet
The Western Antarctic Ice Sheet (WAIS) is the segment of the continental ice sheet that covers West (or Lesser) Antarctica, the portion of Antarctica on the side of the Transantarctic Mountains which lies in the Western Hemisphere. The WAIS is classified as a marine-based ice sheet, meaning that its bed lies well below sea level and its edges flow into floating ice shelves. The WAIS is bounded by the Ross Ice Shelf, the Ronne Ice Shelf, and outlet glaciers that drain into the Amundsen Sea.West Antarctica
West Antarctica, or Lesser Antarctica, one of the two major regions of Antarctica, is the part of that continent that lies within the Western Hemisphere, and includes the Antarctic Peninsula. It is separated from East Antarctica by the Transantarctic Mountains and is covered by the West Antarctic Ice Sheet. It lies between the Ross Sea (partly covered by the Ross Ice Shelf), and the Weddell Sea (largely covered by the Filchner-Ronne Ice Shelf). It may be considered a giant peninsula stretching from the South Pole towards the tip of South America.
West Antarctica is largely covered by the Antarctic ice sheet, but there have been signs that climate change is having some effect and that this ice sheet may have started to shrink slightly. The coasts of the Antarctic 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.Whillans Ice Stream
Whillans Ice Stream (83°40′S 145°00′W) is a glaciological feature of the West Antarctic Ice Sheet, formerly known as Ice Stream B, renamed in 2001 in honor of Ohio State University glaciologist Ian Whillans.