Climate of Antarctica 1 Climate of Antarctica The climate of Antarctica is the coldest on the whole of Earth. Antarctica has the lowest naturally occurring temperature ever recorded on the surface on Earth: −89.2°C (−128.6°F) at Vostok Station. Satellites have recorded even lower temperatures, down to -93.2°C(-135.8°F). It is also extremely dry (technically a desert), averaging 166mm (6.5in) of precipitation per year. On most parts of the continent the snow rarely melts and is eventually compressed to Surface temperature of Antarctica in winter and become the glacial ice that makes up the ice sheet. Weather fronts summer from the European Centre for rarely penetrate far into the continent. Most of Antarctica has an ice Medium-Range Weather Forecasts cap climate (Köppen EF) with very cold, generally extremely dry weather. Temperature The lowest reliably measured temperature of a continuously occupied station on Earth of −89.2 °C (−128.6 °F) was on 21 July 1983 at Vostok Station.[1] 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 3,900 meters (12,800 feet). The lowest recorded temperature of any location on Earth surface was −93.2 °C (−135.8 °F) at 81.8°S 59.3°E [2], which is on an unnamed Antarctic plateau between Dome A and Dome F, on August 10, 2010. The temperature was deduced from radiance measured by the Landsat 8 satellite, and discovered during a National Snow and Ice Data Center review of stored data in December, 2013. This temperature is not directly comparable to the -89.2 quoted above, since it is a skin temperature deduced from satellite-measured upwelling radiance, rather than a thermometer-measured temperature of the air 1.5m above the ground surface. The highest temperature ever recorded in Antarctica was 14.6°C (58.3°F) in two places, Hope Bay and Vanda Station, on 5 January 1974. The mean annual temperature of the interior is −57°C (−70°F). The coast is warmer. Monthly means at McMurdo Station range from −26°C (−14.8°F) in August to −3°C (26.6°F) in January.[3] 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,Wikipedia:Please clarify though the summer temperature is below 0°C (32°F)in most 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.Wikipedia:Citation needed The Antarctic Peninsula has the most moderate climate. Higher temperatures occur in January along the coast and average slightly below freezing. Climate of Antarctica 2 Precipitation The total precipitation on 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. Map of average annual precipitation on Weather condition classification Antarctica (mm liquid equivalent) 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 described below: Condition 1 Windspeed over 55 knots (100 km/h) Visibility less than 30 metres (98 ft) Wind chill below −73 °C (−99 °F) Description: Dangerous conditions; outside travel is not permitted. Condition 2 Windspeed of 48 to 55 knots (90 to 100 km/h) Visibility 400 to 30 metres (1/4 of a mile to 100 feet) Wind chill of −60 °C (−76 °F) to −73 °C (−99 °F) Description: Unpleasant conditions; outside travel is permitted but not recommended. Condition 3 Windspeed below 48 knots (90 km/h) Visibility greater than 400 metres (1/4 of a mile) Wind chill above −60 °C (−76 °F) Description: Pleasant conditions; all outside travel is permitted. Ice cover Nearly all of Antarctica is covered by an ice sheet that is, on average, at least a mile thick (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 of ice — the seas would rise by over 60 metres. 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 Climate of Antarctica 3 sea level rise from thermal expansion of the oceans. 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.[4] 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) Surface Area Percent Mean ice Volume Percent (km²) thickness (km³) (m) 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. Regional ice data (from Drewry and others, 1982; Drewry, 1983) Region Area Mean Volume (km²) ice (km³) thickness (m) 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 Climate of Antarctica 4 Ice shelves 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: • Around the Antarctic Peninsula: • 1936–1989: Wordie Ice Shelf significantly reduced in size. • 1995: Prince Gustav Channel no longer blocked by ice. Last open from about 1900 years ago to 6500 years ago, probably due to warmth during the Holocene Climatic Optimum. • Parts of the Larsen Ice Shelf broke up in recent decades. • 1995: The Larsen A ice shelf disintegrated in January 1995. Antarctic ice shelves, 1998 • 2001: 3,250 km² of the Larsen B ice shelf disintegrated in February 2001. It had been gradually retreating before the breakup event. 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. The idea that it was warmer in Antarctica 10,000 years ago is supported by ice cores, though the timing is not quite right. Climate change The continent-wide average surface temperature trend of Antarctica is positive and significant at >0.05°C/decade since 1957.[7][8][9][10] 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. Research published in 2009 found that overall the continent had become warmer since the 1950s, a finding consistent with the influence of man-made climate change: "We can't pin it down, but it certainly is consistent with the influence of greenhouse gases from fossil fuels", said NASA scientist Drew Shindell, Antarctic Skin Temperature Trends between 1981 and 2007, based on thermal infrared observations made by a series of NOAA satellite sensors. Skin another study co-author. Some of the temperature trends do not necessarily reflect air temperature trends. effects also could be natural variability, he said.[11] The British Antarctic Survey, which has undertaken the majority of Britain's scientific research in the area, has the following positions: [12] • Ice makes polar climate sensitive by introducing a strong positive feedback loop.