Climate of Antarctica

Surface temperature of Antarctica in winter and summer from the European Centre for Medium-Range Weather Forecasts

The climate of Antarctica is the coldest on Earth. Antarctica's lowest air temperature record was set on 21 July 1983, with −89.2 °C (−128.6 °F) at Vostok Station.[1] Satellite measurements have identified even lower ground temperatures, down to −93.2 °C (−135.8 °F) at the cloud free East Antarctic Plateau.[2] It is also extremely dry (technically a desert), averaging 166mm (6.5 in) of precipitation per year. On most parts of the continent the snow rarely melts and is eventually compressed to become 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 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.[3][4] 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's surface was −93.2 °C (−135.8 °F) at 81°48′S 63°30′E / 81.8°S 63.5°E / -81.8; 63.5, 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.[5][6] 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 1.5 m (4.9 ft) above the ground surface.

The highest temperature ever recorded in Antarctica was 17.5 °C (63.5 °F) at Hope Bay on 24 March 2015.[7] There are reservations about this value.[8] The mean annual temperature of the interior is −57 °C (−70.6 °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.[9] At the South Pole, the highest temperature ever recorded was −12.3 °C (9.9 °F) on 25 December 2011.[10] Along the Antarctic Peninsula, temperatures as high as 15 °C (59 °F) have been recorded, 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.

Precipitation

Map of average annual precipitation on Antarctica (mm liquid equivalent)

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 (15 to 25 feet a year[11]) to very low values (as little as 50 mm (2 in) per year) (source needed) 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.

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.[12][13][14]

See Antarctica Weather Danger Classification

Ice cover

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 of ice — the seas would rise by over 60 metres.[15] 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.[16] 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.[17] 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
(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.
Regional ice data (from Drewry and others, 1982; Drewry, 1983)
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

Ice shelves

Antarctic ice shelves, 1998

About 75% of the coastline of Antarctica is ice shelves. The utmost parts consist of floating ice until the grounding line of land based glaciers is reached, which is determined through affords 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; however, melting or breakup of floating shelf ice does not directly affect global sea levels.[18]

Known changes in coastline ice:

The George VI Ice Shelf, which may be on the brink of instability,[20] has probably existed for approximately 8000 years, after melting 1500 years earlier.[21] Warm ocean currents may have been the cause of the melting.[22]

Global warming

Antarctic Skin Temperature Trends between 1981 and 2007, based on thermal infrared observations made by a series of NOAA satellite sensors. Skin temperature trends do not necessarily reflect air temperature trends.

The continent-wide average surface temperature trend of Antarctica is positive and significant at >0.05 °C/decade since 1957.[23][24][25][26] 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.[23][24][25]

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, another study co-author. Some of the effects also could be natural variability, he said.[27]

The British Antarctic Survey, which has undertaken the majority of Britain's scientific research in the area, stated in 2009:

September 20, 2007 NASA map showing previously un-melted snowmelt

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.

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.[28]

There is also evidence for widespread glacier retreat around the Antarctic Peninsula.[29]

Researchers reported December 21, 2012 in Nature Geoscience that from 1958 to 2010, the average temperature at the mile-high Byrd Station rose by 2.4 degrees Celsius, with warming fastest in its winter and spring. The spot which is in the heart of the West Antarctic Ice Sheet is one of the fastest-warming places on Earth.[30][31][32]

See also

References

Notes

  1. ↑ The Coldest Place on Earth: -90°C and below from Landsat 8 and other satellite thermal sensors, Ted Scambos, Allen Pope, Garrett Campbell, and Terry Haran, American Geophysical Union fall meeting, 9 December 2013.
  2. ↑ Coldest spot on Earth identified by satellite, Jonathan Amos, BBC News, 9 December 2013.
  3. ↑ Budretsky, A.B. (1984). "New absolute minimum of air temperature". Bulletin of the Soviet Antarctic Expedition (in Russian) (Leningrad: Gidrometeoizdat) (105).
  4. ↑ "World: Lowest Temperature - ASU World Meteorological Organization". asu.edu.
  5. ↑ Natasha Vizcarra (2013-12-09). "Landsat 8 helps unveil the coldest place on Earth". National Snow and Ice Data Center. Retrieved 2013-12-27.
  6. ↑ Jonathan Amos (2013-12-09). "Coldest spot on Earth identified by satellite". BBC News Science & Environment. Retrieved 2013-12-27.
  7. ↑ http://www.ogimet.com/cgi-bin/gsynres?ind=88963&decoded=yes&ndays=2&ano=2015&mes=03&day=25&hora=00
  8. ↑ "Weather Extremes : Possible New Continental Heat Record for Antarctica - Weather Underground". wunderground.com.
  9. ↑ "Antarctica Climate data and graphs, South Pole, McMurdo and Vostok". coolantarctica.com.
  10. ↑ Matthew A. Lazzara (2011-12-28). "Preliminary Report: Record Temperatures at South Pole (and nearby AWS sites…)". Retrieved 2011-12-28.
  11. ↑ http://www.eurekalert.org/pub_releases/2015-11/agu-wac110415.php
  12. ↑ "Weathering The Conditions" (PDF). The Antarctic Sun. 18 October 1997. p. 8. Retrieved June 8, 2015.
  13. ↑ Jim Scott. "Weather and Travel" (PDF). Welcome to McMurdo Station. McMurdo Station. p. 6. Retrieved June 8, 2015.
  14. ↑ "Field Manual" (PDF). Antarctica New Zealand. New Zealand Government. p. 37. Retrieved June 8, 2015.
  15. ↑ "Climate Change 2001: The Scientific Basis". Grida.no. Retrieved 2011-03-27.
  16. ↑ "Climate Change 2001: The Scientific Basis". Grida.no. Retrieved 2011-03-27.
  17. ↑ Davis; et al. (2005). "Snowfall-Driven Growth in East Antarctic Ice Sheet Mitigates Recent Sea-Level Rise,". Science 308 (5730): 1898–1901. Bibcode:2005Sci...308.1898D. doi:10.1126/science.1110662. PMID 15905362.
  18. ↑ E. Rignot, S. Jacobs, J. Mouginot, B. Scheuchl. "Ice-Shelf Melting Around Antarctica". Science 341: 266–270. Bibcode:2013Sci...341..266R. doi:10.1126/science.1235798.
  19. ↑ NASA (14 May 2015). "NASA Study Shows Antarctica’s Larsen B Ice Shelf Nearing Its Final Act".
  20. ↑ Dr Mike Bentley and Dr Dominic Hodgson. "Millennial-scale variability of George VI Ice Shelf, Antarctic Peninsula". Natural Environment Research Council. Archived from the original on 12 September 2002. Retrieved 8 June 2015.
  21. ↑ Bentley, M.J. (1), Hjort, C. (2) Ingolfsson, O. (3) and Sugden, D.E. (4). "Holocene Instability of the George VI Ice Shelf, Antarctic Peninsula". Archived from the original on 20 October 2004. Retrieved June 8, 2015.
  22. ↑ "Press Release – New Year?s Honours for British Antarctic Survey Personnel". British Antarctic Survey. 2006-01-05. Retrieved 2011-03-27.
  23. 1 2 Tenney Naumer. "Climate Change: The Next Generation". climatechangepsychology.blogspot.com.
  24. 1 2 Retrieved=2009-01-22
  25. 1 2 Retrieved=2009-01-22
  26. ↑ "Global warming hitting all of Antarctica: scientists". The Sydney Morning Herald.
  27. ↑ Antarctica study challenges warming skeptics, Jan 21, 2009
  28. ↑ "NASA - NASA Researchers Find Snowmelt in Antarctica Creeping Inland". nasa.gov.
  29. ↑ IPCC 2007, Intergovernmental Panel on Climate Change, Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge University Press, 2007, page 376.
  30. ↑ West Antarctica warming fast; Temperature record from high-altitude station shows unexpectedly rapid rise December 21, 2012 Science News
  31. ↑ "Map of Antarctica and annual spatial footprint of the Byrd temperature record. : Central West Antarctica among the most rapidly warming regions on Earth : Nature Geoscience : Nature Publishing Group". nature.com.
  32. ↑ Bromwich, D. H.; Nicolas, J. P.; Monaghan, A. J.; Lazzara, M. A.; Keller, L. M.; Weidner, G. A.; Wilson, A. B. (2012). "Central West Antarctica among the most rapidly warming regions on Earth". Nature Geoscience 6 (2): 139–145. Bibcode:2013NatGe...6..139B. doi:10.1038/ngeo1671.

Sources

Further reading

External links

Climate

Climate change in Antarctica

Antarctic ice

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