Editing Antarctic ice sheet (section)

== Ice loss and accumulation ==
{{excerpt|Climate change in Antarctica#Observed changes in ice mass}}

=== Near-future sea level rise ===
{{excerpt|Climate change in Antarctica#21st-century ice loss and sea-level rise}}

==== Weakening Antarctic circulation ====
[[File:Pellichero 2018 Southern Ocean mixed layer.jpg|thumb|Normally, some seasonal meltwater from the Antarctic ice sheet helps to drive the lower-cell circulation.<ref name="Pellichero2018">{{cite journal |last1=Pellichero |first1=Violaine |last2=Sallée |first2=Jean-Baptiste |last3=Chapman |first3=Christopher C. |last4=Downes |first4=Stephanie M. |date=3 May 2018 |title=The southern ocean meridional overturning in the sea-ice sector is driven by freshwater fluxes |journal=Nature Communications |volume=9 |issue=1 |page=1789 |doi=10.1038/s41467-018-04101-2 |pmid=29724994 |pmc=5934442 |bibcode=2018NatCo...9.1789P }}</ref> However, climate change has greatly increased meltwater amounts, which threatens to destabilize it.<ref name="IPCC AR6 WG1 Ch.9" />{{rp|1240}}]]
Ice loss from Antarctica also generates more fresh [[meltwater]], at a rate of 1100–1500 billion tons (GT) per year.<ref name="IPCC AR6 WG1 Ch.9" />{{rp|1240}} This meltwater then mixes back into the Southern Ocean, which makes its water fresher.<ref>{{Cite journal |last1=Pan |first1=Xianliang L. |last2=Li |first2=Bofeng F. |last3=Watanabe |first3=Yutaka W. |date=10 January 2022 |title=Intense ocean freshening from melting glacier around the Antarctica during early twenty-first century |journal=Scientific Reports |language=en |volume=12 |issue=1 |pages=383 |doi=10.1038/s41598-021-04231-6 |issn=2045-2322 |pmc=8748732 |pmid=35013425|bibcode=2022NatSR..12..383P }}</ref> This freshening of the Southern Ocean results in increased stratification and stabilization of its layers,<ref>{{Cite journal |last1=Haumann |first1=F. Alexander |last2=Gruber |first2=Nicolas |last3=Münnich |first3=Matthias |last4=Frenger |first4=Ivy |last5=Kern |first5=Stefan |date=September 2016 |title=Sea-ice transport driving Southern Ocean salinity and its recent trends |url=https://www.nature.com/articles/nature19101 |journal=Nature |language=en |volume=537 |issue=7618 |pages=89–92 |doi=10.1038/nature19101 |pmid=27582222 |bibcode=2016Natur.537...89H |hdl=20.500.11850/120143 |s2cid=205250191 |issn=1476-4687|hdl-access=free }}</ref><ref name="IPCC AR6 WG1 Ch.9" />{{rp|1240}} and this has the single largest impact on the long-term properties of Southern Ocean circulation.<ref name="Li2023" /> These changes in the Southern Ocean cause the upper cell circulation to speed up, accelerating the flow of major currents,<ref name="Ocean warming and accelerating Sout">{{cite journal | last1=Shi | first1=Jia-Rui | last2=Talley | first2=Lynne D. | last3=Xie | first3=Shang-Ping | last4=Peng | first4=Qihua | last5=Liu | first5=Wei | title=Ocean warming and accelerating Southern Ocean zonal flow | journal=Nature Climate Change | publisher=Springer Science and Business Media LLC | volume=11 | issue=12 | date=2021-11-29 | issn=1758-678X | doi=10.1038/s41558-021-01212-5 | pages=1090–1097| bibcode=2021NatCC..11.1090S | s2cid=244726388 }}</ref> while the lower cell circulation slows down, as it is dependent on the highly saline [[Antarctic bottom water]], which already appears to have been observably weakened by the freshening, in spite of the limited recovery during 2010s.<ref name="Silvano2018">{{Cite journal |last1=Silvano |first1=Alessandro |last2=Rintoul |first2=Stephen Rich |last3=Peña-Molino |first3=Beatriz |last4=Hobbs |first4=William Richard |last5=van Wijk |first5=Esmee |last6=Aoki |first6=Shigeru |last7=Tamura |first7=Takeshi |last8=Williams |first8=Guy Darvall |date=18 April 2018 |title=Freshening by glacial meltwater enhances the melting of ice shelves and reduces the formation of Antarctic Bottom Water |journal=Science Advances |volume=4 |issue=4 |pages=eaap9467 |doi=10.1126/sciadv.aap9467 |pmid=29675467 |pmc=5906079 }}</ref><ref>{{Cite journal |last1=Ribeiro |first1=N. |last2=Herraiz-Borreguero |first2=L. |last3=Rintoul |first3=S. R. |last4=McMahon |first4=C. R. |last5=Hindell |first5=M. |last6=Harcourt |first6=R. |last7=Williams |first7=G. |date=15 July 2021 |title=Warm Modified Circumpolar Deep Water Intrusions Drive Ice Shelf Melt and Inhibit Dense Shelf Water Formation in Vincennes Bay, East Antarctica |journal=Journal of Geophysical Research: Oceans |language=en |volume=126 |issue=8 |doi=10.1029/2020JC016998 |bibcode=2021JGRC..12616998R |s2cid=237695196 |issn=2169-9275 }}</ref><ref name="Aoki2020">{{Cite journal |last1=Aoki |first1=S. |last2=Yamazaki |first2=K. |last3=Hirano |first3=D. |last4=Katsumata |first4=K. |last5=Shimada |first5=K. |last6=Kitade |first6=Y. |last7=Sasaki |first7=H. |last8=Murase |first8=H. |date=15 September 2020 |title=Reversal of freshening trend of Antarctic Bottom Water in the Australian-Antarctic Basin during 2010s |journal=Scientific Reports |language=en |volume=10 |issue=1 |page=14415 |doi=10.1038/s41598-020-71290-6 |pmid=32934273 |pmc=7492216 }}</ref><ref>{{cite journal |last1=Gunn |first1=Kathryn L. |last2=Rintoul |first2=Stephen R. |last3=England |first3=Matthew H. |last4=Bowen |first4=Melissa M. |title=Recent reduced abyssal overturning and ventilation in the Australian Antarctic Basin |journal=Nature Climate Change |date=25 May 2023 |volume=13 |issue=6 |pages=537–544 |doi=10.1038/s41558-023-01667-8 |bibcode=2023NatCC..13..537G |language=en |issn=1758-6798|doi-access=free}}</ref><ref name="IPCC AR6 WG1 Ch.9" />{{rp|1240}} Since the 1970s, the upper cell has strengthened by 3–4 [[sverdrup]] (Sv; represents a flow of 1 million [[cubic meter]]s per second), or 50–60% of its flow, while the lower cell has weakened by a similar amount, but because of its larger volume, these changes represent a 10–20% weakening.<ref name="Lee2023">{{Cite journal |last1=Lee |first1=Sang-Ki |last2=Lumpkin |first2=Rick |last3=Gomez |first3=Fabian |last4=Yeager |first4=Stephen |last5=Lopez |first5=Hosmay |last6=Takglis |first6=Filippos |last7=Dong |first7=Shenfu |last8=Aguiar |first8=Wilton |last9=Kim |first9=Dongmin |last10=Baringer |first10=Molly |date=13 March 2023 |title=Human-induced changes in the global meridional overturning circulation are emerging from the Southern Ocean |journal=Communications Earth & Environment |volume=4 |issue=1 |page=69 |doi=10.1038/s43247-023-00727-3 |bibcode=2023ComEE...4...69L |doi-access=free }}</ref><ref name="NOAA2023">{{cite web |date=29 March 2023 |title=NOAA Scientists Detect a Reshaping of the Meridional Overturning Circulation in the Southern Ocean |url=https://www.aoml.noaa.gov/noaa-scientists-detect-reshaping-of-the-meridional-overturning-circulation-in-southern-ocean/ |publisher=[[NOAA]] }}</ref>
[[File:NOAA SMOC changes.png|thumb|upright=1.25|left|Since the 1970s, the upper cell of the circulation has strengthened, while the lower cell weakened.<ref name="NOAA2023" />]]
While these effects weren't fully caused by climate change, with some role played by the natural cycle of [[Interdecadal Pacific Oscillation]],<ref name="Zhou2023">{{cite journal |last1=Zhou |first1=Shenjie |last2=Meijers |first2=Andrew J. S. |last3=Meredith |first3=Michael P. |last4=Abrahamsen |first4=E. Povl |last5=Holland |first5=Paul R. |last6=Silvano |first6=Alessandro |last7=Sallée |first7=Jean-Baptiste |last8=Østerhus |first8=Svein |title=Slowdown of Antarctic Bottom Water export driven by climatic wind and sea-ice changes |date=12 June 2023 |journal=Nature Climate Change |volume=13 |issue=6 |pages=701–709 |doi=10.1038/s41558-023-01667-8 |bibcode=2023NatCC..13..537G |doi-access=free }}</ref><ref name="Silvano-Meijers2023">{{cite web |last1=Silvano |first1=Alessandro |last2=Meijers |first2=Andrew J. S. |last3=Zhou |first3=Shenjie |date=17 June 2023 |title=Slowing deep Southern Ocean current may be linked to natural climate cycle—but melting Antarctic ice is still a concern |url=https://theconversation.com/slowing-deep-southern-ocean-current-may-be-linked-to-natural-climate-cycle-but-thats-no-reason-to-stop-worrying-about-melting-antarctic-ice-205341 |publisher=[[The Conversation (website)|The Conversation]] }}</ref> they are likely to worsen in the future. As of early 2020s, [[climate model]]s' best, limited-confidence estimate is that the lower cell would continue to weaken, while the upper cell may strengthen by around 20% over the 21st century.<ref name="IPCC AR6 WG1 Ch.9">{{Cite book |last1=Fox-Kemper |first1=B. |last2=Hewitt |first2=H.T.|author2-link=Helene Hewitt |last3=Xiao |first3=C. |last4=Aðalgeirsdóttir |first4=G. |last5=Drijfhout |first5=S.S. |last6=Edwards |first6=T.L. |last7=Golledge |first7=N.R. |last8=Hemer |first8=M. |last9=Kopp |first9=R.E. |last10=Krinner |first10=G. |last11=Mix |first11=A. |date=2021 |editor1-last=Masson-Delmotte |editor1-first=V. |editor2-last=Zhai |editor2-first=P. |editor3-last=Pirani |editor3-first=A. |editor4-last=Connors |editor4-first=S.L. |editor5-last=Péan |editor5-first=C. |editor6-last=Berger |editor6-first=S. |editor7-last=Caud |editor7-first=N. |editor8-last=Chen |editor8-first=Y. |editor9-last=Goldfarb |editor9-first=L. |chapter=Ocean, Cryosphere and Sea Level Change |title=Climate Change 2021: The Physical Science Basis. Contribution of Working Group I  |volume=2021 |publisher=Cambridge University Press |pages=1239–1241 |doi=10.1017/9781009157896.011|bibcode=<!--- not 2021AGUFM.U13B..09F --> |chapter-url=https://www.ipcc.ch/report/ar6/wg1/chapter/chapter-9/  |url=https://www.ipcc.ch/report/ar6/wg1/ |series=Sixth Assessment Report of the Intergovernmental Panel on Climate Change |isbn=9781009157896 }}</ref> A key reason for the uncertainty is limited certainty about future ice loss from Antarctica and the poor and inconsistent representation of ocean stratification in even the [[Coupled Model Intercomparison Project|CMIP6]] models - the most advanced generation available as of early 2020s.<ref name="Bourgeois2022">{{cite journal |last1=Bourgeois |first1=Timothée |last2=Goris |first2=Nadine |last3=Schwinger |first3=Jörg |last4=Tjiputra |first4=Jerry F. |date=17 January 2022 |title=Stratification constrains future heat and carbon uptake in the Southern Ocean between 30°S and 55°S |journal=Nature Communications |volume=13 |issue=1 |page=340 |doi=10.1038/s41467-022-27979-5 |pmid=35039511 |pmc=8764023 |bibcode=2022NatCo..13..340B }}</ref> One study suggests that the circulation would lose half its strength by 2050 under the worst [[climate change scenario]],<ref name="Li2023">{{cite journal |last1=Li |first1=Qian |last2=England |first2=Matthew H. |last3=Hogg |first3=Andrew McC. |last4=Rintoul |first4=Stephen R. |last5=Morrison |first5=Adele K. |title=Abyssal ocean overturning slowdown and warming driven by Antarctic meltwater |journal=Nature |date=29 March 2023 |volume=615 |issue=7954 |pages=841–847 |doi=10.1038/s41586-023-05762-w |pmid=36991191 |bibcode=2023Natur.615..841L |s2cid=257807573 }}</ref> with greater losses occurring afterwards.<ref name="Logan2023">{{cite web |last1=Logan |first1=Tyne |date=29 March 2023 |title=Landmark study projects 'dramatic' changes to Southern Ocean by 2050 |url=https://www.abc.net.au/news/2023-03-30/dramatic-south-ocean-circulation-changes-study/102154690 |publisher=[[ABC News (Australia)|ABC News]] }}</ref>

It is possible that the South Ocean overturning circulation may not simply continue to weaken in response to increased warming and freshening, but will eventually collapse outright, in a way which would be difficult to reverse and constitute an example of [[tipping points in the climate system]]. This would be similar to some projections for [[Atlantic meridional overturning circulation]] (AMOC), which is also affected by the ocean warming and by meltwater flows from the declining [[Greenland ice sheet]].<ref>{{Cite journal |last1=Bakker |first1=P |last2=Schmittner |first2=A |last3=Lenaerts |first3=JT |last4=Abe-Ouchi |first4=A |last5=Bi |first5=D |last6=van den Broeke |first6=MR |last7=Chan |first7=WL |last8=Hu |first8=A |last9=Beadling |first9=RL |last10=Marsland |first10=SJ |last11=Mernild |first11=SH |last12=Saenko |first12=OA |last13=Swingedouw |first13=D |last14=Sullivan |first14=A |last15=Yin |first15=J |date=11 November 2016 |title=Fate of the Atlantic Meridional Overturning Circulation: Strong decline under continued warming and Greenland melting |journal=Geophysical Research Letters |volume=43 |issue=23 |pages=12,252–12,260 |doi=10.1002/2016GL070457|bibcode=2016GeoRL..4312252B |hdl=10150/622754 |s2cid=133069692 |hdl-access=free }}</ref> However, [[Southern Hemisphere]] is only inhabited by 10% of the world's population, and the Southern Ocean overturning circulation has historically received much less attention than the AMOC. Some preliminary research suggests that such a collapse may become likely once global warming reaches levels between {{convert|1.7|C-change|F-change}} and {{convert|3|C-change|F-change}}, but there is far less certainty than with the estimates for most other [[tipping points in the climate system]].<ref name="GTPR2023">{{cite report |last1=Lenton |first1=T. M. |last2=Armstrong McKay |first2=D.I. |last3=Loriani |first3=S. |last4=Abrams |first4=J.F.  |last5=Lade |first5=S.J. |last6=Donges |first6=J.F. |last7=Milkoreit |first7=M. |last8=Powell |first8=T. |last9=Smith |first9=S.R. |last10=Zimm |first10=C. |last11=Buxton |first11=J.E. |last12=Daube |first12=Bruce C. |last13=Krummel |first13=Paul B. |last14=Loh |first14=Zoë |last15=Luijkx |first15=Ingrid T. |year=2023 |title=The Global Tipping Points Report 2023 |url=https://global-tipping-points.org/download/4608/ |publisher=University of Exeter }}</ref> Even if initiated in the near future, the circulation's collapse is unlikely to be complete until close to 2300,<ref name="Liu2022">{{cite journal |last1=Liu |first1=Y. |last2=Moore |first2=J. K. |last3=Primeau |first3=F. |last4=Wang |first4=W. L. |date=22 December 2022 |title=Reduced CO2 uptake and growing nutrient sequestration from slowing overturning circulation |journal=Nature Climate Change |volume=13 |pages=83–90 |doi=10.1038/s41558-022-01555-7 |osti=2242376 |s2cid=255028552 }}</ref> Similarly, impacts such as the reduction in [[precipitation]] in the [[Southern Hemisphere]], with a corresponding increase in the [[Northern Hemisphere|North]], or a decline of [[fisheries]] in the Southern Ocean with a potential [[ecosystem collapse|collapse]] of certain [[marine ecosystem]]s, are also expected to unfold over multiple centuries.<ref name="Logan2023" />

=== Long-term future  ===
{{excerpt|Climate change in Antarctica#Long-term sea level rise|paragraphs=1-3}}

{{excerpt|East Antarctic ice sheet#Long-term future|files=no}}