Editing Antarctic ice sheet (section)

{{Short description|Earth's southern polar ice cap}}
{{Infobox glacier
| child         = test
| name          = Antarctic Ice Sheet 
| other_name    = 
| photo         = AA bedrock surface.4960.tif
| photo_width   = 
| photo_alt     = 
| photo_caption = South facing visualization of the Antarctic ice sheet from the [[Pacific]] sector of the [[Southern Ocean]] ([[West Antarctic ice sheet]], foreground; [[Antarctic Peninsula]], to the left; [[East Antarctic ice sheet]], background).<ref name=SVS2013>{{cite web |last1=Starr |first1=Cindy |date=4 June 2013 |title=Antarctic Bedrock: Bedmap2 Surface Elevation |url=http://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=4060 |website=Scientific Visualization Studio |publisher=NASA |quote=Since 2009, NASA's mission Operation IceBridge (OIB) has flown aircraft over the Antarctic Ice Sheet carrying laser and ice-penetrating radar instruments to collect data about the surface height, bedrock topography and ice thickness.}}</ref><ref name="Fretwell2013"/>
| map_image     = Antarctica.svg
| map_width     = 
| map_alt       = 
| map_caption   = Geographic map of [[Antarctica]], with the grounded [[ice sheet]] in white, its floating [[ice shelves]] in gray, and ice-free [[land]] in brown.
| type          = [[Ice sheet]]
| location      = [[Antarctica]]
| coordinates   = 
| coords_ref    = 
| area          = {{convert|14|e6km2|abbr=on}}<ref name=NSFfactsheet/>
| length        = 
| width         = 
| thickness     = {{convert|2.2|km|abbr=on}} on average,<ref name=NSFfactsheet/> {{convert|4.9|km|abbr=on}} at [[Astrolabe Subglacial Basin|maximum]]<ref name="Fretwell2013">{{Cite journal|last1=Fretwell|first1=P.|last2=Pritchard|first2=H. D.|last3=Vaughan|first3=D. G.|last4=Bamber|first4=J. L.|last5=Barrand|first5=N. E.|last6=Bell|first6=R.|last7=Bianchi|first7=C.|last8=Bingham|first8=R. G.|last9=Blankenship|first9=D. D.|date=2013-02-28|title=Bedmap2: improved ice bed, surface and thickness datasets for Antarctica|journal=The Cryosphere|volume=7|issue=1|pages=375–393|doi=10.5194/tc-7-375-2013|issn=1994-0424|doi-access=free|bibcode=2013TCry....7..375F|hdl=1808/18763|hdl-access=free}}</ref>
| elevation_max = 
| elevation_min = 
| terminus      = 
| status        = Ongoing net loss of ice, regionally variable<ref name="IMBIE2018">{{cite journal |title=Mass balance of the Antarctic Ice Sheet from 1992 to 2017 |journal=Nature |date=13 June 2018 |volume=558 |issue=7709 |pages=219–222 |doi=10.1038/s41586-018-0179-y |author1=IMBIE team |pmid=29899482 |bibcode=2018Natur.558..219I |hdl=1874/367877 |hdl-access=free }}</ref><ref name="Rignot2019" />
| embedded      = 
}}

The '''Antarctic ice sheet''' is a [[continental glacier]] covering 98% of the [[Antarctica|Antarctic]] [[continent]], with an area of {{convert|14|e6km2|abbr=off}} and an average thickness of over {{convert|2|km|mi}}. It is the largest of [[Ice sheet#Earth's current two ice sheets|Earth's two current ice sheets]], containing {{convert|26.5|e6km3|cumi|abbr=off}} of ice, which is equivalent to 61% of all [[fresh water]] on Earth. Its surface is nearly continuous, and the only ice-free areas on the continent are the dry valleys, [[nunataks]] of the [[List of mountain ranges#Antarctica|Antarctic mountain ranges]], and sparse coastal [[bedrock]]. However, it is often subdivided into the [[East Antarctic ice sheet]] (EAIS), [[West Antarctic ice sheet]] (WAIS), and [[Antarctic Peninsula]] (AP), due to the large differences in [[topography]], [[ice flow]], and [[glacier mass balance]] between the three regions.

Because the East Antarctic ice sheet is over 10 times larger than the West Antarctic ice sheet and located at a higher [[elevation]], it is less vulnerable to climate change than the WAIS. In the 20th century, EAIS had been one of the only places on Earth which displayed limited cooling instead of warming, even as the WAIS warmed by over 0.1&nbsp;°C/decade from 1950s to 2000, with an average warming trend of >0.05&nbsp;°C/decade since 1957 across the whole continent. As of early 2020s, there is still net mass gain over the EAIS (due to increased [[precipitation]] freezing on top of the ice sheet), yet the ice loss from the WAIS glaciers such as [[Thwaites Glacier|Thwaites]] and [[Pine Island Glacier]] is far greater.

By 2100, net ice loss from Antarctica alone would add around {{convert|11|cm|in|round=5|abbr=on}} to the global [[sea level rise]]. Further, the way WAIS is located deep below the sea level leaves it vulnerable to [[marine ice sheet instability]], which is difficult to simulate in [[ice sheet model]]s. If instability is triggered before 2100, it has the potential to increase total sea level rise caused by Antarctica by tens of centimeters more, particularly with high overall warming. Ice loss from Antarctica also generates fresh [[meltwater]], at a rate of 1100–1500 billion tons (GT) per year. This meltwater dilutes the saline [[Antarctic bottom water]], which weakens the lower cell of the [[Southern Ocean overturning circulation]] and may even contribute to its collapse, although this will likely take place over multiple centuries.

[[Paleoclimate]] research and improved modelling show that the West Antarctic ice sheet is very likely to disappear even if the warming does not progress any further, and only reducing the warming to {{convert|2|C-change|F-change}} below the temperature of 2020 may save it. It is believed that the loss of the ice sheet would take between 2,000 and 13,000 years, although several centuries of high emissions may shorten this to 500 years. {{convert|3.3|m|ftin|abbr=on}} of sea level rise would occur if the ice sheet collapses but leaves ice caps on the mountains behind, and {{convert|4.3|m|ftin|abbr=on}} if those melt as well. [[Isostatic rebound]] may also add around {{convert|1|m|ftin|abbr=on}} to the global sea levels over another 1,000 years. On the other hand, the East Antarctic ice sheet is far more stable and may only cause {{convert|0.5|m|ftin|abbr=on}} - {{convert|0.9|m|ftin|abbr=on}} of sea level rise from the current level of warming, which is a small fraction of the {{Convert|53.3|m|ft|abbr=on}} contained in the full ice sheet. Around {{convert|3|C-change|F-change}}, vulnerable locations like [[Wilkes Basin]] and [[Aurora Basin]] may collapse over a period of around 2,000 years, which would add up to {{convert|6.4|m|ftin|abbr=on}} to sea levels. The loss of the entire ice sheet would require global warming in a range between {{convert|5|C-change|F-change}} and {{convert|10|C-change|F-change}}, and a minimum of 10,000 years.