Climate of Antarctica

The climate of Antarctica is the coldest and driest on Earth. Antarctica averages of precipitation per year and snow rarely melts on most parts of the continent. After Antarctic snow becomes compressed, it becomes the glacier ice that makes up the ice sheet. Weather fronts rarely penetrate far into the continent, because of the katabatic winds. Most of Antarctica has an ice-cap climate (Köppen classification EF) with very cold and dry weather.

Temperature The highest temperature ever recorded on Antarctica was recorded at Signy Research Station, Signy Island on 30 January 1982.

The highest temperature on the Antarctic mainland was at the Esperanza Base (Argentina) on 6 February 2020. The lowest air temperature record, the lowest reliably measured temperature on Antarctica was set on 21 July 1983, when a temperature of was observed at Vostok Station. For comparison, this is colder than subliming dry ice (at sea level pressure). The elevation of the location is .

Satellite measurements have identified even lower ground temperatures, with having been observed at the cloud-free East Antarctic Plateau on 10 August 2010.Coldest spot on Earth identified by satellite , Jonathan Amos, BBC News, 9 December 2013.

The lowest recorded temperature of any location on Earth's surface at was revised with new data in 2018 in nearly 100 locations, ranging from to . This unnamed part of the Antarctic plateau, between Dome A and Dome F, was measured on 10 August 2010, and the temperature was deduced from radiance measured by the Landsat 8 and other satellites. It was discovered during a National Snow and Ice Data Center review of stored data in December 2013 but revised by researchers on 25 June 2018. This temperature is not directly comparable to the reading quoted above, since it is a skin temperature deduced from satellite-measured upwelling radiance, rather than a thermometer-measured temperature of the air above the ground surface.

The mean annual temperature of the interior is . The coast is warmer; on the coast Antarctic average temperatures are around (in the warmest parts of Antarctica) and in the elevated inland they average about in Vostok. Monthly means at McMurdo Station range from in August to in January. At the South Pole, the highest temperature ever recorded was on 25 December 2011. Along the Antarctic Peninsula, temperatures as high as have been recorded, though the summer temperature is below most of the time. Severe low temperatures vary with latitude, elevation, and distance from the ocean. East Antarctica is colder than West Antarctica because of its higher elevation. The Antarctic Peninsula has the most moderate climate. Higher temperatures occur in January along the coast and average slightly below freezing.

Precipitation

The total precipitation on Antarctica, averaged over the entire continent, is about per year (Vaughan et al., J. Clim., 1999). The actual rates vary widely, from high values over the Peninsula ( a year) to very low values (as little as in the high interior (Bromwich, Reviews of Geophysics, 1988)). Areas that receive less than of precipitation per year are classified as deserts. Almost all Antarctic precipitation falls as snow. Rainfall is rare and mainly occurs during the summer in coastal areas and surrounding islands. Note that the quoted precipitation is a measure of its equivalence to water, rather than being the actual depth of snow. The air in Antarctica is also very dry. The low temperatures result in a very low absolute humidity, which means that dry skin and cracked lips are a continual problem for scientists and expeditioners working on the continent.

Weather condition classification

The weather in Antarctica can be highly variable, and the weather conditions can often change dramatically in short periods of time. There are various classifications for describing weather conditions in Antarctica; restrictions given to workers during the different conditions vary by station and nation.

Ice cover Nearly all of Antarctica is covered by a sheet of ice that is, on average, at least thick. Antarctica contains 90% of the world's ice and more than 70% of its fresh water. If all the land-ice covering Antarctica were to melt—around of ice—the seas would rise by over . The Antarctic is so cold that even with increases of a few degrees, temperatures would generally remain below the melting point of ice. Higher temperatures are expected to lead to more precipitation, which takes the form of snow. This would increase the amount of ice in Antarctica, offsetting approximately one third of the expected sea level rise from thermal expansion of the oceans. During the period from January 1992 to January 2003, East Antarctica thickened at an average rate of about per year while West Antarctica showed an overall thinning of per year. For the contribution of Antarctica to present and future sea level change, see sea level rise. Because ice flows, albeit slowly, the ice within the ice sheet is younger than the age of the sheet itself.

+ Morphometric data for Antarctica (from Drewry, 1983)SurfaceAreaMean icethickness (m)Volume(km2)Percent(km3)Percent Inland ice sheet 11,965,700 85.97 2,450 29,324,700 97.39 Ice shelves 1,541,710 11.08 475 731,900 2.43 Ice rises 78,970 0.57 670 53,100 0.18 Glacier ice (total) 13,586,380 2,160 30,109,800 Rock outcrop 331,690 2.38 Antarctica (total) 13,918,070 100.00 2,160 30,109,800 100.00

+ Regional ice data (from Drewry and others, 1982; Drewry, 1983) Region Area (km2) Mean icethickness (m) Volume (km3)East Antarctica Inland ice 9,855,570 2,630 25,920,100 Ice shelves 293,510 400 117,400 Ice rises 4,090 400 1,600West Antarctica (excluding Antarctic Peninsula) Inland ice sheet 1,809,760 1,780 3,221,400 Ice shelves 104,860 375 39,300 Ice rises 3,550 375 1,300Antarctic Peninsula Inland ice sheet 300,380 610 183,200 Ice shelves 144,750 300 43,400 Ice rises 1,570 300 500Ross Ice Shelf Ice shelf 525,840 427 224,500 Ice rises 10,320 500 5,100 Filchner-Ronne Ice Shelf Ice shelf 472,760 650 307,300 Ice rises 59,440 750 44,600

Ice shelves

About 75% of the coastline of Antarctica is ice shelf. The majority of ice shelf consists of floating ice, and a lesser amount consists of glaciers that move slowly from the land mass into the sea. Ice shelves lose mass through breakup of glacial ice (calving), or basal melting due to warm ocean water under the ice.

Melting or breakup of floating shelf ice does not directly affect global sea levels; however, ice shelves have a buttressing effect on the ice flow behind them. If ice shelves break up, the ice flow behind them may accelerate, resulting in increasing melt of the Antarctic ice sheet and an increasing contribution to sea level rise.

Known changes in coastline ice around the Antarctic Peninsula: 1936–1989: Wordie Ice Shelf significantly reduced in size. 1995: Ice in the Prince Gustav Channel disintegrated. Parts of the Larsen Ice Shelf broke up in recent decades. 1995: The Larsen A ice shelf disintegrated in January 1995. 2001: of the Larsen B ice shelf disintegrated in February 2001. It had been gradually retreating before the breakup event. 2015: A study concluded that the remaining Larsen B ice-shelf will disintegrate by the end of the decade, based on observations of faster flow and rapid thinning of glaciers in the area.

The George VI Ice Shelf, which may be on the brink of instability, has probably existed for approximately 8,000 years, after melting 1,500 years earlier. Warm ocean currents may have been the cause of the melting. Not only are the ice sheets losing mass, they are losing mass at an accelerating rate.

Climate change

See also Antarctic oscillation Antarctica cooling controversy Climate of the Arctic Effects of global warming Polar amplification Retreat of glaciers since 1850 Southern Ocean

References Notes

Sources

Climate of Antarctica

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