Diferencies ente revisiones de «Indlandsis de L'Antártida»

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[[Archivu:Antarctic Temperature Trend 1981-2007.jpg|miniatura|Tendencies de temperatura de la superficie antártica ente 1981 y 2007, sobre la base d'observaciones termales [[infrarroxa]]s d'una serie de sensores de satélite [[NOAA]]. La temperatura de superficie non necesariamente reflexa la temperatura del aire.<ref>{{cita web | url=http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17838 | autor=[[NASA]] | títulu=Dos décades de cambeos de temperatura n'Antártica | editorial=Earth Observatory Newsroom | fecha=2007 | fechaacceso=14 d'agostu de 2008 | idioma= | urlarchivu=https://web.archive.org/web/20080920041805/http://earthobservatory.nasa.gov/Newsroom/NewImages/images.php3?img_id=17838 | fechaarchivu=20 de setiembre de 2008 }} Imaxe NASA de Robert Simmon, sobre la base de datos de Joey Comiso, GSFC.</ref>]]
 
La '''cubierta de xelu''' o '''indlandsis antárticu''' ye unu de los dos [[casquete polar|casquetes polares]] (o calotas polares) de la [[Tierra]]. Cubre cerca del 98&nbsp;% del [[Antártida|continente antárticu]] y ye la masa singular de [[xelu]] más grande de la Tierra, con siquier 14&nbsp;millones de [[kilómetros cuadraos|km²]] y contién 30&nbsp;millones de [[kilómetros cúbicos|km³]] de xelu.<ref>Esos 30 millones de [[kilómetros cúbicos|km³]] equivalen a un cubu de 310.72&nbsp;km de llau, o a 70&nbsp;metros d'altor d'agua en tolos océanos del planeta.</ref><!--That is, approximately 61 percent of all [[fresh water]] on the Earth is held in the Antarctic ice sheet, an amount equivalent to 70 m of water in the world's oceans. In [[East Antarctica]], the ice sheet rests on a major land mass, but in [[West Antarctica]] the bed can extend to more than 2,500 m below síaseya level. The land in this area would be seabed if the ice sheet were not there.-->
 
La so antigüedá ye de 33.6&nbsp;millones d'años.<!--
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Ice enters the sheet through precipitation as snow. This snow is then compacted to form glacier ice which moves under gravity towards the coast. Most of it is carried to the coast by fast moving [[ice stream]]s. The ice then passes into the ocean, often forming vast floating [[ice shelves]]. These shelves then melt or [[Ice calving|calve]] off to give [[iceberg]]s that eventually melt.
 
If the transfer of the ice from the land to the síaseya is balanced by snow falling back on the land then there will be non net contribution to global [[Sía level rise|sía level]]s. A 2002 analysis of [[NASA]] satellite data from 1979-1999 showed that areas of Antarctica where ice was increasing outnumbered areas of decreasing ice roughly 2:1.<ref>{{cite web
| last = Ramanujan
| first = Krishna
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West Antarctica has warmed by more than 0.1&nbsp;°C/decade in the last 50 years, and this warming 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.<ref name=steigblog/><ref name=steigbiog/><ref name=steig2009/>
 
Despite this warming total Antarctic síaseya ice anomalies have been steadily increasing since 1978 (NSIDC (2006)). 2007 showed the largest positive anomaly of síaseya ice in the southern hemisphere since records have been kept starting in 1979 and 2008 is currently on pace to surpass last years record.<ref name=cryospheretoday>{{cite web
| title = The Cryosphere Today
| url = http://arctic.atmos.uiuc.edu/cryosphere/
}}</ref>
The atmospheric warming cannot be directly linked to the recent mass losses in [[West Antarctica]]. This mass loss is more likely to be due to increased melting of the ice shelves because of changes in ocean circulation patterns. This in turn causes the ice streams to speed up.<ref name=payne2004>{{cite journal |author=Payne A.J., Vieli A., Shepherd A.P., Wingham D.J., Rignot Y. |title=Recent dramatic thinning of largest West Antarctic ice stream triggered by oceans |journal=[[Geophys. Res. Lett.]] |volume=31 |pages=L23401 |year=2004 |doi=10.1029/2004GL021284}}</ref>
The melting and disappearance of the floating ice shelves will only have a small effect on síaseya level, which is due to salinity differences.<ref>[http://www.physorg.com/news5619.html Peter Noerdlinger, PHYSORG.COM "Melting of Floating Ice Will Raise Sía Level"]</ref><ref>{{cite journal |last=Noerdlinger |first=P.D. |coauthors=Brower, K.R. |year=2007 |month=July |title=The melting of floating ice raises the ocean level |journal=Geophysical Journal International |volume=170 |issue=1 |pages=145–150 |doi=10.1111/j.1365-246X.2007.03472.x |accessdate=22 de xineru de 2009 }}</ref><ref>{{cite journal |last=Jenkins |first=A. |coauthors=Holland, D. |year=2007 |month=August |title=Melting of floating ice and síaseya level rise |journal=Geophysical Research Letters |volume=34 |issue=16 |doi=10.1029/2007GL030784 |accessdate=22 de xineru de 2009 |pages=L16609 }}</ref>
The most important consequence of their increased melting is the speed up of the ice streams on land which are buttressed by these ice shelves.
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