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[[Archivo:Greenland Ice Mass Trend.jpg|thumb|250px|Masa de la [[capa de hielo de Groenlandia]]]]
[[Archivo:Greenland Ice Mass Trend.jpg|thumb|250px|Masa de la [[capa de hielo de Groenlandia]]]]


El '''deshielo ártico''' es la conjunción de la [[disminución de la banquisa ártica]] y el deshielo de la [[capa de hielo de Groenlandia]] últimamente. El area de la banquisa seguirá disminuyendo en el futuro, según los modelos informáticos, aunque no hay consenso sobre cuando se desehelará durante los veranos. Hasta el momento los análisis científicos no han detectado que jamás el Oceano Ártico se deshelase estacionalmente durante los últimos 700.000 años, a pesar de haber habido períodos más cálidos.<ref>{{cita publicación|apellido=Overpeck |nombre=Jonathan T. |url=http://atoc.colorado.edu/~dcn/reprints/Overpeck_etal_EOS2005.pdf |formato=pdf |título=Arctic System on Trajectory to New, Seasonally Ice-Free State |revista=[[Eos (journal)|Eos, Transactions, American Geophysical Union]] |volumen=86 |número=34 |páginas=309–316 |fecha=2005-08-23 |fechaaceso=2007-12-24}}</ref><ref name="Ottera">{{cita publicación|apellido=Butt |nombre=F. A. |coautores=H. Drange, A. Elverhoi, O. H. Ottera & A. Solheim |url=http://www.nersc.no/~oddho/Thesis/chapter3.pdf |título=The Sensitivity of the North Atlantic Arctic Climate System to Isostatic Elevation Changes, Freshwater and Solar Forcings |editorial=Quaternary Science Reviews |volumen=21 |number=14-15 |páginas=1643–1660 |fecha=2002 |oclc=108566094 |fechaaceso=}}</ref> Los científicos siguen estudiando las causas y consecuencias como la alteración de la circulación atmosférica, calentamiento del [[océano Ártico]]<ref name=BBCNews> {{Cita noticia |apellido=Black |nombre=Richard |título='Drastic' shrinkage in Arctic ice |url=http://news.bbc.co.uk/2/hi/science/nature/5344208.stm |editorial=BBC News |obra=Science/Nature |fecha=2006-09-14 |fechaacceso=2007-09-16}}</ref> o alteración de la [[corriente marina]] como la [[corriente del Golfo]]<ref>{{Cita noticia |url=http://www.foxnews.com/story/0,2933,311753,00.html |título=Study: Circulation Shift May Be Melting Arctic Sea Ice |fecha=2007-11-24 |editorial=Fox News |fechaacceso=2007-11-27}}</ref>
El '''deshielo ártico''' es la conjunción de la [[disminución de la banquisa ártica]] y el deshielo de la [[capa de hielo de Groenlandia]] últimamente. El área de la banquisa seguirá disminuyendo en el futuro, según los modelos informáticos, aunque no hay consenso sobre cuando se desehelará durante los veranos. Hasta el momento los análisis científicos no han detectado que jamás el Oceano Ártico se deshelase estacionalmente durante los últimos 700.000 años, a pesar de haber habido períodos más cálidos.<ref>{{cita publicación|apellido=Overpeck |nombre=Jonathan T. |url=http://atoc.colorado.edu/~dcn/reprints/Overpeck_etal_EOS2005.pdf |formato=pdf |título=Arctic System on Trajectory to New, Seasonally Ice-Free State |revista=[[Eos (journal)|Eos, Transactions, American Geophysical Union]] |volumen=86 |número=34 |páginas=309–316 |fecha=23 de agosto 2005 |fechaaceso=24 de diciembre 2007}}</ref><ref name="Ottera">{{cita publicación|apellido=Butt |nombre=F. A. |coautores=H. Drange, A. Elverhoi, O. H. Ottera & A. Solheim |url=http://www.nersc.no/~oddho/Thesis/chapter3.pdf |título=The Sensitivity of the North Atlantic Arctic Climate System to Isostatic Elevation Changes, Freshwater and Solar Forcings |editorial=Quaternary Science Reviews |volumen=21 |number=14-15 |páginas=1643–1660 |fecha=2002 |oclc=108566094 |fechaaceso=}}</ref> Los científicos siguen estudiando las causas y consecuencias como la alteración de la circulación atmosférica, calentamiento del [[océano Ártico]]<ref name=BBCNews> {{Cita noticia |apellido=Black |nombre=Richard |título='Drastic' shrinkage in Arctic ice |url=http://news.bbc.co.uk/2/hi/science/nature/5344208.stm |editorial=BBC News |obra=Science/Nature |fecha=2006-09-14 |fechaacceso=16 de septiembre 2007}}</ref> o alteración de la [[corriente marina]] como la [[corriente del Golfo]]<ref>{{Cita noticia |url=http://www.foxnews.com/story/0,2933,311753,00.html |título=Study: Circulation Shift May Be Melting Arctic Sea Ice |fecha=24 de noviembre 2007 |editorial=Fox News |fechaacceso=27 de noviembre 2007}}</ref>
El [[grupo intergubernamental de expertos sobre el cambio climático]] reportó: "el calentamiento ártico, indicado como temperaturas máximas y mínimas diarias, ha sido equivalente al de cualquier otra parte del mundo.".<ref name="tar_wg2">{{cita libro |nombre=James J. |apellidos=McCarthy |coautores=[[Intergovernmental Panel on Climate Change]] Working Group II. |título=Climate Change 2001: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change | url = http://www.grida.no/climate/ipcc_tar/wg2/597.htm#16131 |editorial=Cambridge University Press |ubicación=New York |isbn=0521807689 |fecha=2001 |fechaacceso=2007-12-24}}</ref> Al reducirse la superficie de hielo disminuye el efecto [[albedo]] y refleja menos energía solar al espacio, por lo tanto, se aceleración la reducción.<ref name="Black">{{Cita noticia |apellido=Black |nombre=Richard |url=http://news.bbc.co.uk/2/hi/science/nature/4315968.stm |título=Earth - melting in the heat? |editorial=BBC News |fecha=2007-05-18 |fechaacceso=2008-01-03}}</ref>
El [[grupo intergubernamental de expertos sobre el cambio climático]] reportó: "el calentamiento ártico, indicado como temperaturas máximas y mínimas diarias, ha sido equivalente al de cualquier otra parte del mundo.".<ref name="tar_wg2">{{cita libro |nombre=James J. |apellidos=McCarthy |coautores=[[Intergovernmental Panel on Climate Change]] Working Group II. |título=Climate Change 2001: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change | url = http://www.grida.no/climate/ipcc_tar/wg2/597.htm#16131 |editorial=Cambridge University Press |ubicación=New York |isbn=0521807689 |fecha=2001 |fechaacceso=24 de diciembre 2007}}</ref> Al reducirse la superficie de hielo disminuye el efecto [[albedo]] y refleja menos energía solar al espacio, por lo tanto, se aceleración la reducción.<ref name="Black">{{Cita noticia |apellido=Black |nombre=Richard |url=http://news.bbc.co.uk/2/hi/science/nature/4315968.stm |título=Earth - melting in the heat? |editorial=BBC News |fecha=2007-05-18 |fechaacceso=3 de enero 2008}}</ref>


En verano de 2007 la banquisa alcanzó su mínima extensión con una deshielo dramáticamente rápido. Durante el invierno de 2007-2008 la mayoría de la banquisa derretida se "recongeló" y se acercó a la extensión de anteriores años. Sin embargo, en las zonas de hielo perenne el espesor que se midió era más delgado que en el invierno anterior.<ref name="Meier">Zabarenko, Deborah. [http://www.reuters.com/article/scienceNews/idUSN1822988120080318?pageNumber=1&virtualBrandChannel=0 "Thickest, oldest Arctic ice is melting: NASA data"], Reuters ([[2008-03-18]]).</ref> El templado verano de 2008 la banquisa estuvo en la linea del de 2007, aunque ligeramente superior.
En verano de 2007 la banquisa alcanzó su mínima extensión con una deshielo dramáticamente rápido. Durante el invierno de 2007-2008 la mayoría de la banquisa derretida se "recongeló" y se acercó a la extensión de anteriores años. Sin embargo, en las zonas de hielo perenne el espesor que se midió era más delgado que en el invierno anterior.<ref name="Meier">Zabarenko, Deborah. [http://www.reuters.com/article/scienceNews/idUSN1822988120080318?pageNumber=1&virtualBrandChannel=0 "Thickest, oldest Arctic ice is melting: NASA data"], Reuters ([[18 de marzo]] [[2008]]).</ref> El templado verano de 2008 la banquisa estuvo en la linea del de 2007, aunque ligeramente superior.


Sin embargo cuando se observa la extensión de la banquisa en los meses fríos de los últimos años, la hipótesis del calentamiento global parece debilitarse. En los meses de marzo y abril de 2008 su extensión ha sido la segunda mayor de los últimos 10 años, y según los datos emitidos por el [http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm IARC-JAXA] el 11 de diciembre del 2008 la extensión alcanzó los 11.678.894 km², la mayor del siglo XXI en las mismas fechas.
Sin embargo cuando se observa la extensión de la banquisa en los meses fríos de los últimos años, la hipótesis del calentamiento global parece debilitarse. En los meses de marzo y abril de 2008 su extensión ha sido la segunda mayor de los últimos 10 años, y según los datos emitidos por el [http://www.ijis.iarc.uaf.edu/en/home/seaice_extent.htm IARC-JAXA] el 11 de diciembre del 2008 la extensión alcanzó los 11.678.894 km², la mayor del siglo XXI en las mismas fechas.


== Modelado, historia, predicciones ==
{{seealso|Ecología e historia de la banquisa ártica}}
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Computer models predict that the sea ice area will continue to shrink in the future, although recent work has called into question their ability to accurately predict sea ice changes.<ref>{{cite journal |last=Eisenman |first=Ian |authorlink= |coauthors=Untersteiner, Norbert; Wettlaufer, J.S.| year=2007 |title=On the reliability of simulated Arctic sea ice in Global Climate Models | journal=Geophysical Research Letters | volume=34 | pages=L10501 | doi=10.1029/2007GL029914 | url=http://pantheon.yale.edu/%7Ejw378/articles/EUW_revised_2007.pdf }}</ref> Current [[climate model]]s frequently underestimate the rate of shrinkage.<ref>{{cite doi|10.1029/2007GL029703}}</ref> In 2007 the [[Intergovernmental Panel on Climate Change|IPCC]] reported that “the projected reduction <nowiki>[in global sea ice cover]</nowiki> is accelerated in the Arctic, where some models project summer sea ice cover to disappear entirely in the high-emission A2 scenario in the latter part of the 21st century.″ <ref>{{cite book |first=G.A., and others |last=Meehl |coauthors=Intergovernmental Panel on Climate Change Working Group I.
|title=Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Chapter 10 |url=http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter10.pdf |publisher=[[Cambridge University Press]] |location=New York |date=2007}}</ref> There is currently no scientific evidence that a seasonally ice-free Arctic Ocean existed anytime in the last 700,000 years, although there were periods when the Arctic was warmer than it is today.<ref name="overpeck">{{cite journal |last=Overpeck |first=Jonathan T. |url=http://atoc.colorado.edu/~dcn/reprints/Overpeck_etal_EOS2005.pdf |format=pdf |title=Arctic System on Trajectory to New, Seasonally Ice-Free State |journal=[[Eos (journal)|Eos, Transactions, American Geophysical Union]] |volume=86 |issue=34 |pages=309–316 |date=2005-08-23 |accessdate=2007-12-24}}</ref><ref name="Ottera">{{cite journal |last=Butt |first=F. A. |coauthors=H. Drange, A. Elverhoi, O. H. Ottera & A. Solheim |url=http://www.nersc.no/~oddho/Thesis/chapter3.pdf |title=The Sensitivity of the North Atlantic Arctic Climate System to Isostatic Elevation Changes, Freshwater and Solar Forcings |publisher=Quaternary Science Reviews |volume=21 |number=14-15 |pages=1643–1660 |date=2002 |oclc=108566094 |accessdate=}}</ref> Scientists are studying possible causal factors such as direct changes resulting from the greenhouse effect as well as indirect changes such as unusual wind patterns, rising Arctic temperatures,<ref name=BBCNews>
{{cite news |last=Black |first=Richard |title='Drastic' shrinkage in Arctic ice |url=http://news.bbc.co.uk/2/hi/science/nature/5344208.stm |publisher=''[[BBC News]]'' |work=Science/Nature |date=2006-09-14 |accessdate=2007-09-16}}</ref> or shifting water circulation<ref>{{cite news |url=http://www.foxnews.com/story/0,2933,311753,00.html |title=Study: Circulation Shift May Be Melting Arctic Sea Ice |date=2007-11-24 |publisher=Fox News |accessdate=2007-11-27}}</ref> (such as increasing inflows of warm, fresh water to the Arctic Ocean from rivers.)

According to the [[Intergovernmental Panel on Climate Change]], "warming in the Arctic, as indicated by daily maximum and minimum temperatures, has been as great as in any other part of the world."<ref name="tar_wg2">{{cite book |first=James J. |last=McCarthy |coauthors=Intergovernmental Panel on Climate Change Working Group II.
|title=Climate Change 2001: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change |url=http://www.grida.no/climate/ipcc_tar/wg2/597.htm#16131 |publisher=[[Cambridge University Press]] |location=New York |isbn=0521807689 |date=2001 |accessdate=2007-12-24}}</ref> Reduction of the area of Arctic sea ice means less solar energy is reflected back into space, thus [[Effects of global warming#Retreat of sea ice|accelerating the reduction]].<ref name="Black">{{cite news |last=Black |first=Richard |url=http://news.bbc.co.uk/2/hi/science/nature/4315968.stm |title=Earth - melting in the heat? |publisher=''BBC News'' |date=2007-05-18 |accessdate=2008-01-03}}</ref> Studies have shown that recent warming in the polar regions was due to the net effect human influence through [[greenhouse gas]]es and [[ozone depletion]], which has a cooling effect opposed to the influence of greenhouse gases.<ref name="Nature Geoscience">{{cite journal |last = Gillett |first = Nathan P. |coauthors = Stone, Dáithí A.; Stott, Peter A.; Nozawa, Toru; Karpechko, Alexey Yu.; Hegerl, Gabriele C.; Wehner, Michael F.; Jones, Philip D. |title = Attribution of polar warming to human influence |journal =Nature Geoscience |volume = 1 |publisher = [[Nature Publishing Group]] |date = 2008-10-30 |url = http://www.nature.com/ngeo/journal/vaop/ncurrent/abs/ngeo338.html |doi = 10.1038/ngeo338 |accessdate = 2008-11-01 |pages = 750}}</ref>

[[File:Seaice-1870-part-2009.png|thumb|right|1870-2000 Northern hemisphere [[Measurement_of_sea_ice#Sea_Ice_Extent|sea ice extent]] in million square kilometers. Blue shading indicates the pre-satellite era; data then is less reliable. In particular, the near-constant level extent in Autumn up to 1940 reflects lack of data rather than a real lack of variation.]]

Reliable measurement of sea ice edge begin within the satellite era in the late 1970s. Before this the region was less well monitored by a combination of ships, buoys and aircraft <ref>[http://www.igsoc.org/annals/46/a46a251.pdf|Meier, W.N., J.C. Stroeve, and F. Fetterer. 2006. Whither Arctic sea ice? A clear signal of decline regionally, seasonally and extending beyond the satellite record. Annals of Glaciology 46: 428-434.]</ref> On top of the long-term negative trend in recent years, attributed to [[global warming]], there is considerable interannual variation <ref>http://www.jpl.nasa.gov/news/news.cfm?release=2007-131</ref>. Some of this variation may be related to effects such as the [[arctic oscillation]], which may itself be related to global warming <ref>{{cite journal |last=Fyfe |first=J.C |coauthors=G.J. Boer and G.M. Flato |date=June 1, 1999 |title=The Arctic and Antarctic Oscillations and their Projected Changes Under Global Warming |journal=Geophysical Research Letters |volume=26 |issue=11 |pages=1601–4 |doi=10.1029/1999GL900317}}</ref>; some of the variation is essentially random "weather noise".

The Arctic sea ice September minimum extent reached new record lows in 2002, 2005, and 2007 (39.2 percent below below the 1979-2000 average). In 2007, Arctic sea ice broke all previous records by early August—a month before the end of melt season, with the biggest decline ever in Arctic sea ice minimum extent, more than a million square kilometers.<ref>[http://nsidc.org/sotc/sea_ice.html NSIDC "State of the Cryosphere, Is the Cryosphere sending signals about climate change?"]</ref> In the first time in human memory, the fabled Northwest Passage opened completely.<ref>http://nsidc.org/news/press/2007_seaiceminimum/20071001_pressrelease.html NSIDC 1 October 2007 "Arctic Sea Ice Shatters All Previous Record Lows - Diminished summer sea ice leads to opening of the fabled Northwest Passage"</ref> The dramatic 2007 melting surprised and concerned scientists.<ref>[http://www.nasa.gov/vision/earth/environment/arctic_minimum.html NASA "Remarkable' Drop in Arctic Sea Ice Raises Questions"]</ref><ref name= "NASA - Monitoring Sea Ice">.[http://earthobservatory.nasa.gov/Features/SeaIce/page2.php NASA Earth Observatory - Monitoring Sea Ice]</ref>

In 2008 and 2009, Arctic sea ice minimum extent was higher than 2007, but it did not return to the levels of previous years.<ref>[http://nsidc.org/news/press/20091005_minimumpr.html NSIDC"Arctic sea ice extent remains low; 2009 sees third-lowest mark"]</ref> Additionally, studies show a dramatic decline in ice age and thickness.<ref>[http://nsidc.org/news/press/20091005_minimumpr.html NSIDC 6 October 2009]</ref> The [[Catlin Arctic Survey]] reported an average thickness of 1.8 meters across the northern Beaufort Sea, an area that had traditionally contained older, thicker ice.<ref>[http://www.catlinarcticsurvey.com/latestfromtheice Catlin Arctic Survey "SURVEY DATA SUPPORTS RAPID ICE LOSS - LARGELY OPEN ARCTIC SEAS IN SUMMER WITHIN TEN YEARS"]</ref>
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== Efectos ==
[[archivo:NOAA-barrow-ice.jpg|left|thumb|Retiro temprano de hielo, [[Barrow, Alaska]]]]
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The effects of Arctic shrinkage include a [[Polar_ice_packs#Extent_and_trends_of_polar_ice_packs|marked decrease in Arctic sea ice]]; melting [[permafrost]], leading to [[Arctic methane release|the release of methane]], a potent greenhouse gas<ref>{{cite doi|10.1029/2003GL018680}}</ref>; the release of methane from [[clathrates]], leading to longer time-scale methane release;<ref>{{cite doi|10.1007/BF00144504}}</ref> the observed increase in [[Greenland ice sheet#The_melting_ice_sheet|melt on the Greenland Ice Sheet]] in recent years; and potential changes in patterns of ocean circulation. Scientists worry that some of these effects may cause positive feedbacks which could accelerate the rate of global warming.
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==== Banquisa====
La [[banquisa]] (mar de hielo) en la región ártica <!--region is in itself important in maintaining global [[climate]] due to its [[albedo]] (reflectivity).<ref name="NSIDC Sea Ice">{{cite web | publisher=NSIDC | url=http://www.nsidc.org/seaice/intro.html | title=All About Sea Ice | accessdate=2009-01-10}}</ref> Melting of this [[sea ice]] will therefore exacerbate [[global warming]] due to [[positive feedback]] effects, where warming creates more warming by increased solar absorption.<ref name="NSIDC Sea Ice" /><ref>{{cite web | url=http://www.unep.org/geo/geo_ice/PDF/GEO_C5_LowRes.pdf | title=Global Outlook for Ice and Snow, Chapter 5: Ice in the Sea | page=75–76 | publisher=United Nations Environment Programme}}</ref> An important feedback in the [[Arctic]] currently is [[ice-albedo feedback]]. The loss of the Arctic sea ice may represent a [[tipping point (climatology)|tipping point]] in global warming, when [[runaway climate change|'runaway']] climate change starts.<ref>{{cite doi|10.1029/2005GL025080}}</ref><ref>{{cite doi|10.1029/2004GC000854}}</ref> This would be due to the release of [[methane]] from [[permafrost]] and [[clathrate gun hypothesis|clathrates]] in the region, and also because of [[ice-albedo feedback]] effects. However, recent research has challenged the notion of ice-albedo feedback causing an imminent Arctic sea ice tipping point.<ref>http://environmentalresearchweb.org/cws/article/research/37591</ref><ref name="Eisenman2009">{{cite journal |last=Eisenman |first=Ian |authorlink= |coauthors=Wettlaufer, J.S. |year=2009 |month= |title=Nonlinear threshold behavior during the loss of Arctic sea ice |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=106 |issue=1 |pages=28&ndash;32 |doi=10.1073/pnas.0806887106 |url=http://pantheon.yale.edu/%7Ejw378/articles/E&W_Bif_PNAS.pdf |accessdate= |quote= }}</ref>

[[Image:Polar Bear Habitat.png|thumb|right| Projected change in polar bear habitat from 2001–2010 to 2041–2050]]
April 3, 2007, the [[National Wildlife Federation]] urged the U.S. Congress to place [[polar bear]]s under the [[Endangered Species Act]].<ref>{{cite news |url=http://www.sciencedaily.com/releases/2008/04/080402210456.htm |title=Protection For Polar Bears Urged By National Wildlife Federation |date=2008-04-03 |publisher=''[[Science Daily]]'' |accessdate=2008-04-03}}</ref>
Four months later, the [[United States Geological Survey]] completed a year-long study<ref>{{cite web |first=Eric |last=DeWeaver |coauthor=U.S. Geological Survey |url=http://www.usgs.gov/newsroom/special/polar_bears/docs/USGS_PolarBear_DeWeaver_GCM-Uncertainty.pdf |format=pdf |title=Uncertainty in Climate Model Projections of Arctic Sea Ice Decline: An Evaluation Relevant to Polar Bears |publisher=[[United States Department of the Interior]] |oclc=183412441 |year=2007 |accessdate=}}</ref> which concluded in part that the floating [[Arctic sea ice]] will continue its rapid shrinkage over the next 50 years, consequently wiping out much of the polar bear [[habitat]]. The bears would disappear from Alaska, but would continue to exist in the [[Canadian Arctic Archipelago]] and areas off the northern Greenland coast.<ref>{{cite news |first=John |last=Broder |coauthors= Revkin, Andrew C. |title=Warming Is Seen as Wiping Out Most Polar Bears |url=http://www.nytimes.com/2007/09/08/science/earth/08polar.html?_r=1&hp=&adxnnl=1&oref=slogin&adxnnlx=1190574637-aS0VOr2klykTSNwK91tiDg |work= |publisher=''The New York Times'' |date=2007-07-08 |accessdate=2007-09-23}}</ref> Secondary ecological effects are also resultant from the shrinkage of sea ice; for example, [[Polar Bear]]s are denied their historic length of seal hunting season due to late formation and early thaw of [[pack ice]].
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==== Pérdida de permafrost ====
{{main|Salida de metano ártico}}
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Sea ice loss has melting effects on permafrost<ref>http://www.cgd.ucar.edu/ccr/dlawren/publications/lawrence.grl.submit.2008.pdf</ref>, both in the sea<ref>http://e360.yale.edu/content/feature.msp?id=2081</ref>, and on land<ref name="ucar.edu">http://www.ucar.edu/news/releases/2008/permafrost.jsp</ref> and consequential effects on [[Arctic methane release|methane release]], and wildlife.<ref>{{cite web |url=http://www.ucar.edu/news/releases/2008/permafrost.jsp. |title=Permafrost Threatened by Rapid Retreat of Arctic Sea Ice, NCAR Study Finds |publisher=University Corporation for Atmospheric Research |date=2008-06-10 |accessdate=2008-06-11}}</ref> Some studies imply a direct link, as they predict cold air passing over ice is replaced by warm air passing over the sea. This warm air carries heat to the permafrost around the Arctic, and melts it.<ref name="ucar.edu" /> This thawing of the permafrost might accelerate methane release from areas like Siberia.<ref>http://news.nationalgeographic.com/news/2008/12/081219-methane-siberia.html</ref>
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==== Fusil de clatratos ====
{{main|Hipótesis del fusil de clatratos}}
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[[Sea ice]] serves to stabilise [[methane]] deposits on and near the shoreline,<ref>{{cite doi|10.1029/2005GL022751}}</ref> preventing the [[clathrate]] breaking down and outgassing [[methane]] into the atmosphere. Any methane released to the atmosphere will then causing further warming.
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==== Fusión de la cubierta de hielo de Groenlandia ====
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Models predict a sea-level contribution of about {{convert|5|cm|in|0}} from melting in Greenland during the 21st century.<ref>[[Intergovernmental Panel on Climate Change|IPCC]] [[AR4]] chapter 10 [http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-chapter10.pdf] Table 10.7</ref> It is also predicted that Greenland will become warm enough by 2100 to begin an almost complete melt during the next 1,000 years or more.<ref>{{cite journal |author1=Gregory JM |authorlink=Jonathan M. Gregory |author2=Huybrechts P |author3=Raper SC |title=Climatology: threatened loss of the Greenland ice-sheet |journal=Nature |volume=428 |issue=6983 |pages=616 |year=2004 |month=April |pmid=15071587 |doi=10.1038/428616a |url=http://homepages.vub.ac.be/~phuybrec/pdf/Nature.Green.2004.pdf |quote=The Greenland ice-sheet would melt faster in a warmer climate and is likely to be eliminated — except for residual glaciers in the mountains — if the annual average temperature in Greenland increases by more than about 3 °C. This would raise the global average sea-level by 7 metres over a period of 1000 years or more. We show here that concentrations of greenhouse gasses will probably have reached levels before the year 2100 that are sufficient to raise the temperature past this warming threshold.}}</ref><ref>{{cite web |publisher=Intergovernmental Panel on Climate Change | url = http://www.grida.no/climate/ipcc_tar/wg1/432.htm#fig1116 | title = Regional Sea Level Change | format = Figure 11.16}}</ref>
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==== Efecto de la circulación oceánica ====
{{seealso|:en:Shutdown of thermohaline circulation|Evento oceánico anóxico}}
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Although this is now thought unlikely in the near future, it has also been suggested that there could be a [[shutdown of thermohaline circulation]], similar to that which is believed to have driven the [[Younger Dryas]], an [[abrupt climate change]] event. There is also potentially a possibility of a more general disruption of [[ocean circulation]], which may lead to an [[ocean anoxic event]], although these are believed to be much more common in the distant past. It is unclear whether the appropriate pre-conditions for such an event exist today.
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== Control del deshielo ártico ==

=== Geoingeniería ===
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{{seealso|Arctic geoengineering|Geoengineering}}

Geoengineering approaches offer interventions which may increase Arctic ice, or reduce its decline.<ref>{{cite web|url=http://www.cosis.net/abstracts/EGU2008/09934/EGU2008-A-09934.pdf?PHPSESSID=|title=Geoengineering: a critical review|last=Lenton|first=T|coauthors=N. Vaughan|accessdate=2009-02-23}}</ref> These operate either by regional effects (Arctic geoengineering) or global effects (geoengineering). Several specific Arctic geoengineering schemes have been proposed to reduce Arctic shrinkage. Further, scientists such as [[Paul Crutzen]] have argued for general geoengineering proposals such as using [[stratospheric sulfur aerosols (geoengineering)|stratospheric sulfur aerosols]] to be used, which will affect the [[Arctic]] if deployed in or near this region.

According to [[John Holdren]], Assistant to the President of the United States for Science and Technology, complete loss of summer sea ice in the Arctic would be a milestone that could justify geoengineering in order to purposely cool the climate. Holdren believes that complete loss of summer sea ice in the Arctic could signal an increased chance of "really intolerable consequences."<ref>
Borenstein, Seth. [http://abcnews.go.com/Technology/GlobalWarming/wireStory?id=7295178 “Obama Looking at Cooling Air to Fight Warming”], Associated Press via ABC News. (2009-04-09).</ref>
-->
== Estudios ==
=== Nacional ===
Países individuales dentro de la zona ártica: [[Canadá]], [[Dinamarca]] ([[Groenlandia]]), [[Finlandia]], [[Islandia]], [[Noruega]], [[Rusia]], [[Suecia]], [[EE.UU.]] ([[Alaska]]) conducen estudios independientes <!-- through a variety of organizations and agencies, public and private, such as Russia's Arctic and Antarctic Research Institute. Countries who do not have Arctic claims, but are close neighbors, conduct Arctic research as well, such as the Chinese Arctic and Antarctic Agency.
-->
=== Internacional ===
<!--
International cooperative research between nations has become increasingly important:
* [http://www.damocles-eu.org/about_damocles.shtml DAMOCLES] (Developing Arctic Modeling and Observing Capabilities for Long-term Environmental Studies): European integrated project "specifically concerned with the potential for a significantly reduced sea ice cover, and the impacts this might have on the environment and on human activities, both regionally and globally".
* [[European Space Agency]] (ESA) is scheduled to launch [[CryoSat#CryoSat_II|CryoSat-2]] in 2009. It will provide satellite data on Arctic ice cover change rates.<ref name="esa">{{cite web|url=http://www.esa.int/esaLP/ESAOMH1VMOC_LPcryosat_0.html|title=ESA's ice mission CryoSat-2|date=11 September 2008|publisher=esa.int|accessdate=2009-06-15}}</ref>
* [[International Arctic Buoy Program]]: deploys and maintains buoys that provide real-time position, pressure, temperature, and interpolated ice velocity data
* [[International Arctic Research Center]]: Main participants are the United States and [[Japan]].
* [[International Arctic Science Committee]]: [[non-governmental]] [[organization]] (NGO) with diverse membership, including 18 countries from 3 continents.
* 'Role of the Arctic Region', in conjunction with the [[International Polar Year]], was the focus of the second international conference on Global Change Research, held in [[Nynäshamn]], [[Sweden]], October, 2007.<ref>{{cite web |first=Annakarin |last=Svenningsson |title=Global Environmental Change - The Role of the Arctic Region |url=http://www.innovations-report.de/html/berichte/veranstaltungen/bericht-92741.html |work= |publisher=innovations-report.de |date=2007-10-14 |accessdate=2007-10-16}}</ref><ref>{{cite web |first=Corinne |last=Wininger |url=http://www.innovations-report.com/html/reports/environment_sciences/report-93680.html |title=E SF, VR, FORMAS sign MOU to promote Global Environmental Change Research |publisher=innovations-report.de |date=2007-10-26 |accessdate=2007-11-26}}</ref>
* SEARCH ([[Study of Environmental Arctic Change]]): Supported by the [[Arctic Research Office]], a division of the United States' [[National Oceanic and Atmospheric Administration]] (NOAA), and the [[Russian Academy of Sciences]].
-->
== Reclamaciones territoriales ==
{{Main|Territorial claims in the Arctic}}
<!--
Growing evidence that global warming is shrinking polar ice has added to the urgency of several nations' [[Territorial claims in the Arctic|Arctic territorial claims]] in hopes of establishing resource development and new shipping lanes, in addition to protecting sovereign rights.<ref name=WashPost>
{{cite news |first=Mike |last=Eckel |title=Russia: Tests Show Arctic Ridge Is Ours |url=http://www.washingtonpost.com/wp-dyn/content/article/2007/09/20/AR2007092001703.html |work=[[The Associated Press]] |publisher=[[The Washington Post]] |date=2007-09-20 |accessdate=2007-09-21}}</ref>

Danish Foreign Minister [[Per Stig Møller]] and Greenland's Premier [[Hans Enoksen]] invited foreign ministers from Canada, Norway, Russia and the United States to [[Ilulissat|Ilulissat, Greenland]] for a summit in May 2008 to discuss how to divide borders in the changing Arctic region, and a discussion on more cooperation against climate change affecting the Arctic.<ref name="EUX">{{cite news |title=Denmark aims for meeting of Arctic nations to discuss borders |url=http://www.eux.tv/article.aspx?articleId=14443 |format=online |work=Denmark-Diplomacy |publisher=[[EUX.TV]] the Europe channel |date=2007-09-13 |accessdate=2007-09-16}}</ref> At the [[Arctic Ocean Conference]], Foreign Ministers and other officials representing the five countries announced the [[Ilulissat Declaration]] on May 28, 2008.<ref>{{cite news |title=Conference in Ilulissat, Greenland: Landmark political declaration on the future of the Arctic |url=http://www.um.dk/en/servicemenu/News/ConferenceInIlulissatGreenlandLandmarkPoliticalDeclarationOnTheFutureOfTheArctic.htm |publisher=Ministry of Foreign Affairs of Denmark |date=2008-05-28 |accessdate=2008-06-06}}</ref><ref>{{cite web |url=http://www.um.dk/NR/rdonlyres/BE00B850-D278-4489-A6BE-6AE230415546/0/ArcticOceanConference.pdf |title=The Ilulissat Declaration |date=28 de mayo 2008 |publisher=um.dk |accessdate=2008-06-06}}</ref>
-->
== Referencias ==
== Referencias ==
{{listaref|2}}
{{listaref|2}}
<div class="references-small">
* {{cite journal |title=[http://www.economist.com/world/international/displaystory.cfm?story_id=9660012 International - The Arctic - Drawing lines in melting ice] |journal=The Economist |volume=384 |number=8542 |date=2007 |pages=47 |oclc=166288931}}
* {{cite journal |last=Miller |first=PA |coauthors=SW Laxon, DL Feltham |date=2007 |title=Consistent and Contrasting Decadal Arctic Sea Ice Thickness Predictions from a Highly Optimized Sea Ice Model |journal=Journal of Geophysical Research |volume=112 |number=C7 |pages=C07020–2 |doi=10.1029/2006JC003855 |oclc=170040287}}
* {{cite journal |last=Oyugi |first=JO |coauthors=H Qiu, D. Safronetz |date=2007 |title=Global Warming and the Emergence of Ancient Pathogens in Canada's Arctic Regions |journal=Medical Hypotheses |volume=68 |number=3 |pages=709 |oclc=110702580 |doi=10.1016/j.mehy.2006.09.006 |pmid=17064851 |issue=3}}
* {{cite journal |last=Schiermeier |first=Q |date=2007 |title=Polar Research: the New Face of the Arctic |journal=Nature |volume=446 |number=7132 |pages=133–135 |oclc=110702580 |doi=10.1038/446133a |pmid=17344829 |issue=7132}}
* {{cite journal |last=Stroeve |first=J |coauthors=MM Holland, W Meier, T Scambos, M Serreze |date=2007 |title=The Cryosphere – L09501 – Arctic Sea Ice Decline: Faster Than Forecast |journal=Geophysical Research Letters |volume=34 |number=9 |pages=n.p. |doi=10.1029/2007GLO29703 |oclc=110702580 |doi_brokendate=2008-06-25}}
* {{cite journal |last=Xu |first=J |coauthors=G Wang, B Zhang |date=2007 |title=Climate Change Comparison between Arctic and Other Areas in the Northern Hemisphere Since the Last Interstade |journal=Journal of Geographical Sciences |volume=17 |number=1 |pages=43–50 |oclc=91622949 |doi=10.1007/s11442-007-0043-8}}
</div>

== Enlacese externos ==
* [http://www.arctic.noaa.gov/detect/Página web del cambio en el Ártico, casi en tiempo real]
* [http://iabp.apl.washington.edu/ International Arctic Buoy Programme]
* [http://www.iarc.uaf.edu/ International Arctic Research Center]
* [http://www.arcticportal.org/iasc/ International Arctic Science Committee]
* [http://www.panda.org/about_wwf/where_we_work/europe/what_we_do/arctic/index.cfm World Wildlife Foundation's International Arctic Programme]
* [http://instaar.colorado.edu/meetings/AW2008/index.html 38th Annual International Arctic Workshop 2008]
* [http://www.geus.dk/publications/bull/nr10/nr10_p61-64.pdf Cambios climáticos radicales pasados en el océano Ártico y la firma geofísica en el Lomonosov Ridge al norte de Groenlandia]


[[Categoría:Océano Ártico]]
[[Categoría:Océano Ártico]]
[[Categoría:Glaciología]]
[[Categoría:Glaciología]]
[[Categoría:Calentamiento global]]
[[Categoría:Calentamiento global]]
[[Categoría:Controversias científicas]]


[[ar:انكماش القطب الشمالي]]
[[ar:انكماش القطب الشمالي]]

Revisión del 03:21 1 dic 2009

Temperaturas árticas desde 1987 a 2007
La extensión de la banquisa se mide según la máxima extensión que permanece helada todo el verano, incluso en verano. Aquí se muestra el alcance en 2007, 2005 y la media entre 1979 y 2000.
Masa de la capa de hielo de Groenlandia

El deshielo ártico es la conjunción de la disminución de la banquisa ártica y el deshielo de la capa de hielo de Groenlandia últimamente. El área de la banquisa seguirá disminuyendo en el futuro, según los modelos informáticos, aunque no hay consenso sobre cuando se desehelará durante los veranos. Hasta el momento los análisis científicos no han detectado que jamás el Oceano Ártico se deshelase estacionalmente durante los últimos 700.000 años, a pesar de haber habido períodos más cálidos.[1]​[2]​ Los científicos siguen estudiando las causas y consecuencias como la alteración de la circulación atmosférica, calentamiento del océano Ártico[3]​ o alteración de la corriente marina como la corriente del Golfo[4]​

El grupo intergubernamental de expertos sobre el cambio climático reportó: "el calentamiento ártico, indicado como temperaturas máximas y mínimas diarias, ha sido equivalente al de cualquier otra parte del mundo.".[5]​ Al reducirse la superficie de hielo disminuye el efecto albedo y refleja menos energía solar al espacio, por lo tanto, se aceleración la reducción.[6]​

En verano de 2007 la banquisa alcanzó su mínima extensión con una deshielo dramáticamente rápido. Durante el invierno de 2007-2008 la mayoría de la banquisa derretida se "recongeló" y se acercó a la extensión de anteriores años. Sin embargo, en las zonas de hielo perenne el espesor que se midió era más delgado que en el invierno anterior.[7]​ El templado verano de 2008 la banquisa estuvo en la linea del de 2007, aunque ligeramente superior.

Sin embargo cuando se observa la extensión de la banquisa en los meses fríos de los últimos años, la hipótesis del calentamiento global parece debilitarse. En los meses de marzo y abril de 2008 su extensión ha sido la segunda mayor de los últimos 10 años, y según los datos emitidos por el IARC-JAXA el 11 de diciembre del 2008 la extensión alcanzó los 11.678.894 km², la mayor del siglo XXI en las mismas fechas.

Modelado, historia, predicciones

Véase también: Ecología e historia de la banquisa ártica

Efectos

Retiro temprano de hielo, Barrow, Alaska

Banquisa

La banquisa (mar de hielo) en la región ártica

Pérdida de permafrost

Artículo principal: Salida de metano ártico

Fusil de clatratos

Artículo principal: Hipótesis del fusil de clatratos

Fusión de la cubierta de hielo de Groenlandia

Efecto de la circulación oceánica

Véanse también: [[::en:Shutdown of thermohaline circulation|:en:Shutdown of thermohaline circulation]] y Evento oceánico anóxico.

Control del deshielo ártico

Geoingeniería

Estudios

Nacional

Países individuales dentro de la zona ártica: Canadá, Dinamarca (Groenlandia), Finlandia, Islandia, Noruega, Rusia, Suecia, EE.UU. (Alaska) conducen estudios independientes

Internacional

Reclamaciones territoriales

Artículo principal: Territorial claims in the Arctic

Referencias

  1. ↑ Overpeck, Jonathan T. (23 de agosto de 2005). «Arctic System on Trajectory to New, Seasonally Ice-Free State» (pdf). Eos, Transactions, American Geophysical Union 86 (34): 309-316.  Parámetro desconocido |fechaaceso= ignorado (se sugiere |fechaacceso=) (ayuda)
  2. ↑ Butt, F. A.; H. Drange, A. Elverhoi, O. H. Ottera & A. Solheim (2002). The Sensitivity of the North Atlantic Arctic Climate System to Isostatic Elevation Changes, Freshwater and Solar Forcings 21 (14-15). Quaternary Science Reviews. pp. 1643-1660. OCLC 108566094. 
  3. ↑ Black, Richard (14 de septiembre de 2006). «'Drastic' shrinkage in Arctic ice». Science/Nature (BBC News). Consultado el 16 de septiembre de 2007. 
  4. ↑ «Study: Circulation Shift May Be Melting Arctic Sea Ice». Fox News. 24 de noviembre de 2007. Consultado el 27 de noviembre de 2007. 
  5. ↑ McCarthy, James J.; Intergovernmental Panel on Climate Change Working Group II. (2001). Climate Change 2001: Impacts, Adaptation and Vulnerability. Contribution of Working Group II to the Third Assessment Report of the Intergovernmental Panel on Climate Change. New York: Cambridge University Press. ISBN 0521807689. Consultado el 24 de diciembre de 2007. 
  6. ↑ Black, Richard (18 de mayo de 2007). «Earth - melting in the heat?». BBC News. Consultado el 3 de enero de 2008. 
  7. ↑ Zabarenko, Deborah. "Thickest, oldest Arctic ice is melting: NASA data", Reuters (18 de marzo 2008).
  • «International - The Arctic - Drawing lines in melting ice». The Economist 384 (8542): 47. 2007. OCLC 166288931. 
  • Miller, PA; SW Laxon, DL Feltham (2007). «Consistent and Contrasting Decadal Arctic Sea Ice Thickness Predictions from a Highly Optimized Sea Ice Model». Journal of Geophysical Research 112 (C7): C07020-2. OCLC 170040287. doi:10.1029/2006JC003855. 
  • Oyugi, JO; H Qiu, D. Safronetz (2007). «Global Warming and the Emergence of Ancient Pathogens in Canada's Arctic Regions». Medical Hypotheses 68 (3): 709. OCLC 110702580. PMID 17064851. doi:10.1016/j.mehy.2006.09.006.  |number= y |issue= redundantes (ayuda)
  • Schiermeier, Q (2007). «Polar Research: the New Face of the Arctic». Nature 446 (7132): 133-135. OCLC 110702580. PMID 17344829. doi:10.1038/446133a.  |number= y |issue= redundantes (ayuda)
  • Stroeve, J; MM Holland, W Meier, T Scambos, M Serreze (2007). «The Cryosphere – L09501 – Arctic Sea Ice Decline: Faster Than Forecast». Geophysical Research Letters 34 (9): n.p. OCLC 110702580. doi:10.1029/2007GLO29703 (inactivo 2008-06-25). 
  • Xu, J; G Wang, B Zhang (2007). «Climate Change Comparison between Arctic and Other Areas in the Northern Hemisphere Since the Last Interstade». Journal of Geographical Sciences 17 (1): 43-50. OCLC 91622949. doi:10.1007/s11442-007-0043-8. 

Enlacese externos

Obtenido de «https://es.wikipedia.org/w/index.php?title=Deshielo_ártico&oldid=31883301»