Difference between revisions of "Climate of Antarctica"

[[File:Horlick Mountains.jpg|thumb|400px|Snow and ice surrounding the [[Horlick Mountains]]]]

The '''Climate of Antarctica''' is the coldest on the Earth.

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 explorers working in the continent.

If all the land-ice covering Antarctica were to melt — around 30 million cubic kilometers (7.2 million cubic miles) of ice — the seas would rise by over 60 meters (200 feet). This is, however, very unlikely to occur 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 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. During a recent decade, East Antarctica thickened at an average rate of about 1.8 centimeters per year while West Antarctica showed an overall thinning of 0.9 centimeters per year. Because ice flows, albeit slowly, the ice within the ice sheet is younger than the age of the sheet itself.

About 75% of the coastline of Antarctica is [[ice-shelf|ice shelves]]. The utmost parts consist of floating ice until the grounding line of land based glaciers is reached, which is determined through efforts such as Operation IceBridge. Ice shelves lose mass through [[iceberg]] breakup (calving), or basal melting (at the foot of the glacier, when warm ocean water impacts), and this can affect ice sheet stability when the land based glaciers start to retreat; melting or breakup of floating shelf ice does not directly affect global sea levels, however, when sea ice freezes, it preferentially expels salt, in the process becoming purer than the sea water it is floating in. Pure water is less dense than salty water, so when the ice melts it will overflow the "hole in the water" that the ice had occupied, and when it overflows, it raises the water level.

::''Main article: [[Global warming]]''

The continent-wide average surface temperature trend of Antarctica is positive and significant at >0.05 °C/decade since 1957. 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.

* [[Westarctica]]'s ice loss could contribute to 1.4 meters (4 feet 7 inches) sea level rise.

* [[Antarctica]] predicted to warm by around 3 °C (5.4 °F) over this century.

* Hole in ozone layer, which has shielded most of Antarctica from [[global warming]].

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 into the continent's interior. A stronger polar vortex might explain the cooling trend in the interior of Antarctica.

There is also evidence for widespread glacier retreat around the [[Antarctic Peninsula]].