The climate of Antarctica is the coldest on the whole of Earth. Antarctica has the lowest naturally occurring temperature ever recorded on the ground on Earth: −89.2 °C (−128.6 °F) at Vostok Station.[1] It is also extremely dry (technically a desert), averaging 166 mm (6.5 in) of precipitation per year. Even so, on most parts of the continent the snow rarely melts and is eventually compressed to become the glacial ice that makes up the ice sheet. Weather fronts rarely penetrate far into the continent. Most of Antarctica has an ice cap climate (Köppen EF) with very cold, generally extremely dry weather throughout the year and no month averaging above 0 °C (32 °F). Some fringe coastal areas have a polar climate (Köppen ET) with a short summer averaging above freezing, and much higher precipitation.
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The lowest naturally occurring temperature on Earth was −89.2°C (−128.6°F); recorded on Thursday, July 21, 1983 at Vostok Station. For comparison, this is 11 °C colder than subliming dry ice. The highest temperature ever recorded in Antarctica was 14.6°C (58.3°F) in two places, Hope Bay and Vanda Station, on January 5, 1974. The mean annual temperature of the interior is −57°C (−70°F). The coast is warmer. Monthly means at McMurdo Station range from −28°C (−18.4°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 December 25, 2011.[2] Along the Antarctic Peninsula, temperatures as high as 15°C (59°F) have been recorded, though the summer temperature is usually around 2°C (36°F). 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 in Antarctica, averaged over the entire continent, is about 166 mm (6.5 in) per year (Vaughan et al., J Climate, 1999). The actual rates vary widely, from high values over the Peninsula (meters/yards per year) to very low values (as little as 50 mm (2 in) per year) in the high interior. Areas that receive less than 250 mm (10 in) of precipitation per year are classified as deserts. Almost all Antarctic precipitation falls as snow. 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 in the continent.
The weather in Antarctica can be highly variable, and the weather conditions can often change dramatically in short periods of time. There are three classifications for describing weather conditions in Antarctica. At least one of the following criteria must be met for each category.
Nearly all of Antarctica is covered by an ice sheet that is, on average, at least 1.6 kilometres 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 30 million cubic kilometres of ice — the seas would rise by over 60 metres.[3] 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. Warmer temperatures are expected to lead to more snow, which would increase the amount of ice in Antarctica, offsetting approximately one third of the expected sea level rise from thermal expansion of the oceans.[4] During a recent decade, East Antarctica thickened at an average rate of about 1.8 centimetres per year while West Antarctica showed an overall thinning of 0.9 centimetres per year (Davis et al., Science 2005) doi:10.1126/science.1110662. 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.
| Surface | Area (km²) |
Percent | Mean ice thickness (m) |
Volume (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 | .57 | 670 | 53,100 | .18 |
| Glacier ice (total) | 13,586,380 | 2,160 | 30,109,800¹ | ||
| Rock outcrop | 331,690 | 2.38 | |||
| Antarctica (total) | 13,918,070 | 100.00 | 2,160 | 30,109,800¹ | 100.00 |
| ¹The total ice volume is different from the sum of the component parts because individual figures have been rounded. | |||||
| Region | Area (km²) |
Mean ice thickness (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 | 1,600 |
| West 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 | 1,300 |
| Antarctic Peninsula | |||
| Inland ice sheet | 300,380 | 610 | 183,200 |
| Ice shelves | 144,750 | 300 | 43,400 |
| Ice rises | 1,570 | 300 | 500 |
| Ross 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 |
Most of the coastline of Antarctica is ice shelves (floating ice sheet) or ice walls (grounded ice). Melting or breakup of floating shelf ice does not affect global sea levels, and happens regularly as shelves grow. Known changes in coastline ice:
The George VI Ice Shelf, which may be on the brink of instability,[5] has probably existed for approximately 8000 years, after melting 1500 years earlier.[6] Warm ocean currents may have been the cause of the melting.[7] The idea that it was warmer in Antarctica 10,000 years ago is supported by ice cores, though the timing is not quite right.
The continent-wide average surface temperature trend of Antarctica is positive and significant at >0.05°C/decade since 1957.[8][9][10][11] The West Antarctic ice sheet has warmed by more than 0.1°C/decade in the last 50 years, and 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.[12][13][14]
The British Antarctic Survey, which has undertaken the majority of Britain's scientific research in the area, has the following positions: [2]
The area of strongest cooling appears at the South Pole, and the region of strongest warming lies along the Antarctic Peninsula. A possible explanation is that loss of UV-absorbing ozone may have cooled the stratosphere and strengthened the polar vortex, a pattern of spinning winds around the South Pole. The vortex acts like an atmospheric barrier, preventing warmer, coastal air from moving in to the continent's interior. A stronger polar vortex might explain the cooling trend in the interior of Antarctica. [3]
In their latest study (September 20, 2007) NASA researchers have confirmed that Antarctic snow is melting farther inland from the coast over time, melting at higher altitudes than ever and increasingly melting on Antarctica's largest ice shelf.[15]
There is also evidence for widespread glacier retreat around the Antarctic Peninsula.[16]
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