Climate of Antarctica
The climate of Antarctica is the coldest on Earth. The continent is also extremely dry (it would be a desert virtually anywhere else on Earth, but it is mathematically impossible for any location on Earth that as a mean annual temperature of <14°C to be even a steppe, let alone a desert, under the Köppen classification scheme), averaging 166 mm (6.5 in) of precipitation per year. Snow rarely melts on most parts of the continent, and, after being compressed, 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, generally extremely dry weather.
The lowest air temperature record, the lowest reliably measured temperature on Antarctica was set on 21 July 1983, when −89.2 °C (−128.6 °F) was observed at Vostok Station. For comparison, this is 10.7 °C (19.3 °F) colder than subliming dry ice (at sea level pressure). The altitude of the location is 3,488 meters (11,444 feet).
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 −93.2 °C (−135.8 °F) to −98 °C (−144.4 °F). 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 –89.2 °C reading quoted above, since it is a skin temperature deduced from satellite-measured upwelling radiance, rather than a thermometer-measured temperature of the air 1.5 m (4.9 ft) above the ground surface.
The mean annual temperature of the interior is −57 °C (−70.6 °F). The coast is warmer; on the coast Antarctic average temperatures are around −10 °C (14.0 °F) (in the warmest parts of Antarctica) and in the elevated inland they average about −55 °C (−67.0 °F) in Vostok. Monthly means at McMurdo Station range from −26 °C (−14.8 °F) in August to −3 °C (26.6 °F) in January. At the South Pole, the highest temperature ever recorded was −12.3 °C (9.9 °F) on 25 December 2011. Along the Antarctic Peninsula, temperatures as high as 15 °C (59 °F) have been recorded,[clarification needed] though the summer temperature is below 0 °C (32 °F) 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.
The total precipitation on Antarctica, averaged over the entire continent, is about 166 millimetres (6.5 inches) per year (Vaughan et al., J Climate, 1999). The actual rates vary widely, from high values over the Peninsula (15 to 25 inches a year) to very low values (as little as 50 millimetres (2.0 inches) in the high interior (Bromwich, Reviews of Geophysics, 1988). Areas that receive less than 250 millimetres (9.8 inches) 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.
Nearly all of Antarctica is covered by a sheet of ice that is, on average, a mile thick or more (1.6 km). 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 30 million cubic kilometres (7.2 million cubic miles) of ice — the seas would rise by over 60 metres (200 feet). This is, however, very unlikely within the next few centuries. 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 a recent[when?] decade, East Antarctica thickened at an average rate of about 1.8 centimetres (0.71 in) per year while West Antarctica showed an overall thinning of 0.9 centimetres (0.35 in) 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.
|Percent||Mean ice thickness
|Inland ice sheet||11,965,700||85.97||2,450||29,324,700||97.00|
|Glacier ice (total)||13,586,380||2,160||30,109,800¹|
|¹The total ice volume is different from the sum of the component parts because individual figures have been rounded.|
|West Antarctica (excluding Antarctic Peninsula)|
|Inland ice sheet||1,809,760||1,780||3,221,400|
|Inland ice sheet||300,380||610||183,200|
|Ross Ice Shelf|
|Filchner-Ronne Ice Shelf|
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: 3,250 square kilometres (1,250 square miles) 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 in Antarctica is resulting in rising temperatures and increasing snowmelt and ice loss. A summary study in 2018 incorporating calculations and data from many other studies estimated that total ice loss in Antarctica due to climate change was 43 gigatons per year on average during the period from 1992 to 2002 but has accelerated to an average of 220 gigatons per year during the five years from 2012 to 2017.Some of Antarctica has been warming up; particularly strong warming has been noted on the Antarctic Peninsula. A study by Eric Steig published in 2009 noted for the first time that the continent-wide average surface temperature trend of Antarctica was slightly positive from 1957 to 2006. Over the second half of the 20th century, the Antarctic Peninsula was the fastest-warming place on Earth, closely followed by West Antarctica, but these trends weakened in the early 21st-century. Conversely, the South Pole in East Antarctica barely warmed last century, but in the last three decades the temperature increase there has been more than three times greater than the global average. In February 2020, the continent recorded its highest temperature of 18.3 °C (64.9 °F), which was a degree higher than the previous record of 17.5 °C (63.5 °F) in March 2015.
- Antarctic oscillation
- Antarctica cooling controversy
- Climate of the Arctic
- Effects of global warming
- Polar amplification
- Retreat of glaciers since 1850
- Southern Ocean
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- Antarctica Climate and Weather
Climate change in Antarctica
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