80°S 60°E / 80°S 60°E / -80; 60

East Antarctic ice sheet
TypeIce sheet
Thickness~2.2 km (1.4 mi) (average)[1], ~4.9 km (3.0 mi) (maximum) [2]

The East Antarctic Ice Sheet (EAIS) lies between 45° west and 168° east longitudinally. It was first formed around 34 million years ago,[3] and it is the largest ice sheet on the entire planet, with far greater volume than the Greenland ice sheet or the West Antarctic Ice Sheet (WAIS), from which it is separated by the Transantarctic Mountains. The ice sheet is around 2.2 km (1.4 mi) thick on average and is 4,897 m (16,066 ft) at its thickest point.[2] It is also home to the geographic South Pole and the Amundsen–Scott South Pole Station.

The surface of the EAIS is the driest, windiest, and coldest place on Earth. Lack of moisture in the air, high albedo from the snow as well as the surface's consistently high elevation[4] results in the reported cold temperature records of nearly −100 °C (212 °F).[5][6] Because of that, it has been practically the only place on Earth to have experienced little-to-no warming caused by greenhouse gas emissions in the recent years.[4]

The East Antarctic ice sheet is most likely to first see sustained losses of ice at its most vulnerable locations such as Totten Glacier and Wilkes Basin. Those areas are sometimes collectively described as East Antarctica's subglacial basins, and it is believed that once the warming reaches around 3 °C (5.4 °F), then they would start to collapse over a period of around 2,000 years,[7][8] This collapse would ultimately add between 1.4 m (4 ft 7 in) and 6.4 m (21 ft 0 in) to sea levels, depending on the ice sheet model used.[9] The EAIS as a whole holds enough ice to raise global sea levels by 53.3 m (175 ft).[2] However, it would take global warming in a range between 5 °C (9.0 °F) and 10 °C (18 °F), and a minimum of 10,000 years for the entire ice sheet to be lost.[7][8]

Description

Location and diagram of Lake Vostok, a prominent subglacial lake beneath the East Antarctic Ice Sheet.

East Antarctic Ice Sheet is located directly above the East Antarctic Shield - a craton (stable area of the Earth's crust) with the area of 10,200,000 km2 (3,900,000 sq mi), which accounts for around 73% of the entire Antarctic landmass.[10] East Antarctica is separate from West Antarctica due to the presence of Transantarctic Mountains, which span nearly 3,500 km (2,200 mi) from the Weddell Sea to the Ross Sea, and have a width of 100–300 km (62–186 mi).[1]

The ice sheet has an average thickness of around 2.2 km (1.4 mi). The thickest ice in Antarctica is located near Adelie Land close to the ice sheet's southeast coast, at the Astrolabe Subglacial Basin, where it measured 4,897 m (16,066 ft) around 2013.[1][2] Much of the ice sheet is already located at a high elevation: in particular, Dome Argus Plateau has an average height of around 4 km (2.5 mi), and yet it is underlain by the Gamburtsev Mountain Range, which has the average height of 2.7 km (1.7 mi) and is about equivalent in size to the European Alps.[11][12] Consequently, the ice thickness over these mountains ranges from around 1 km (0.62 mi) over their peaks to about 3 km (1.9 mi) over the valleys.[13]

South Pole research station.

These high elevations are an important reason for why the ice sheet is the driest, windiest, and coldest place on Earth. Dome A in particular sets reported cold temperature records of nearly −100 °C (212 °F).[5][6][4] The only ice-free areas of East Antarctica are where there is too little annual precipitation to form an ice layer, which is the case in the so-called Dry Valleys of the Southern Victoria Land. Another exception are the subglacial lakes, which occur so deep beneath the ice that the pressure melting point is well below 0 °C (32 °F).[13]

Many countries have made territorial claims in Antarctica. Within EAIS, the United Kingdom, France, Norway, Australia, Chile and Argentina all claim a portion (sometimes overlapping) as their own territory.[14]

Geologic history

Polar climatic temperature changes throughout the Cenozoic, showing glaciation of Antarctica toward the end of the Eocene, thawing near the end of the Oligocene and subsequent Miocene re-glaciation.

While relatively small glaciers and ice caps are known to have been present in Antarctica since at least the time of Late Palaeocene, 60 million years ago,[15] a proper ice sheet did not begin to form until the Eocene–Oligocene extinction event about 34 million years ago, when the atmospheric CO2 levels fell to below 750 parts per million. It was initially unstable, and did not grow to consistently cover the entire continent until 32.8 million years ago, when the CO2 levels had further declined to below 600 ppm.[3]

Afterwards, the East Antarctic Ice Sheet declined substantially during the Middle Miocene Climatic Optimum 15 million years ago, yet started to recover about 13.96 million years ago.[15] Since then, it had been largely stable, experiencing "minimal" change in its surface extent over the past 8 million years.[16] While it had still thinned by at least 500 m (1,600 ft) during the Pleistocene period, and by less than 50 m (160 ft) since Last Glacial Maximum, the land area covered by ice in East Antarctica remained largely the same.[17] Contrastingly, the smaller West Antarctic ice sheet is thought to have largely collapsed as recently as during the Eemian period, about 125,000 years ago.[18][19][20][21][22]

Recent climate change

East Antarctica had demonstrated cooling in the 1980s and 1990s, even as the West Antarctica warmed (left-hand side). This trend had largely reversed in 2000s and 2010s (right-hand side).[23]

Because East Antarctica is already cooler than West Antarctica, and is also located at substantially greater elevation,[4] it had been less sensitive to climate change, and had actually experienced cooling in the 1980s and 1990s, even as the West Antarctic Ice Sheet has warmed by more than 0.1 °C/decade since the 1950s.[24] After 2000, the trend had reversed due to local changes in atmospheric circulation: the warming of West Antarctica locations slowed or partially reversed between 2000 and 2020, while the East Antarctica interior had demonstated clear warming. This change in circulation had occurred partly due to natural variability, and partly as the result of the ozone layer beginning to recover following the Montreal Protocol.[23][25] The continent-wide average surface temperature trend of Antarctica is positive and statistically significant at >0.05 °C/decade since 1957.[24]

Aerial view of ice flows at Denman Glacier, one of the relatively few glaciers in the East Antarctica known to be losing mass.[26]

The limited warming and already low temperatures over East Antarctica mean that as of early 2020s, the majority of observational evidence shows it continuing to gain mass.[27][28][29][30] for instance, GRACE satellite data indicated East Antarctica mass gain of 60 ± 13 billion tons per year between 2002 to 2010.[27] Some analyses have suggested it already begun to lose mass in 2000s,[31][32], but they over-extrapolated some observed losses onto the poorly-observed areas, and a more complete observational record shows continued mass gain.[29]

If countries cut greenhouse gas emissions significantly (lowest trace), then sea level rise by 2100 can be limited to 0.3–0.6 m (1–2 ft).[33] If the emissions instead accelerate rapidly (top trace), sea levels could rise 5 m (16+1⁄2 ft) by the year 2300. Higher levels of sea level rise would involve ice loss from the East Antarctica.[33]

Because it is currently gaining mass, East Antarctic Ice Sheet is not expected to play a role in the 21st century sea level rise. However, it is still subject to adverse change, such as the retreat of Denman Glacier,[26][34] or the flow of warmer ocean current into ice cavities beneath the stabilizing ice shelves like the Fimbulisen ice shelf in the Queen Maud Land.[35] If global warming were to reach higher levels, then the EAIS would play an increasingly larger role in sea level rise occurring after 2100. According to the most recent reports of the Intergovernmental Panel on Climate Change (SROCC and the IPCC Sixth Assessment Report), the most intense climate change scenario, where the anthropogenic emissions increase continuously, RCP8.5, would result in Antarctica alone losing a median of 1.46 m (4 ft 9 in) (confidence interval between 60 cm (2.0 ft) and 2.89 m (9 ft 6 in)), which would involve some loss from the EAIS in addition to the erosion of the WAIS. This Antarctica-only sea level rise would be in addition to ice losses from the Greenland ice sheet and mountain glaciers, as well as the thermal expansion of ocean water.[36]

Long-term future

Retreat of Cook Glacier - a key part of the Wilkes Basin - during the Eemian ~120,000 years ago and an earlier Pleistocene interglacial ~330,000 years ago. These retreats would have added about 0.5 m (1 ft 8 in) and 0.9 m (2 ft 11 in) to sea level rise.[37]

If the warming were to remain at elevated levels for a long time, the East Antarctic Ice Sheet would eventually become the dominant contributor to sea level rise, simply because it contains far more ice than any other large ice mass. First, though, it would see sustained erosion at the so-called subglacial basins, such as Totten Glacier and Wilkes Basin, which are located in vulnerable locations below the sea level. Estimates suggest that they would be committed to disappearance once the global warming reaches 3 °C (5.4 °F), although the plausible temperature range is between 2 °C (3.6 °F) and 6 °C (11 °F). Once it becomes too warm for these subglacial basins, their collapse would unfold over a period of around 2,000 years, although it may be as fast as 500 years or as slow as 10,000 years.[7][8] The loss of all this ice would ultimately add between 1.4 m (4 ft 7 in) and 6.4 m (21 ft 0 in) to sea levels, depending on the ice sheet model used. Isostatic rebound of the newly ice-free land would also add 8 cm (3.1 in) and 57 cm (1 ft 10 in), respectively.[9] Evidence from the Pleistocene shows that partial loss can also occur at lower warming levels: Wilkes Basin is estimated to have lost enough ice to add 0.5 m (1 ft 8 in) to sea levels between 115,000 and 129,000 years ago, during the Eemian, and about 0.9 m (2 ft 11 in) between 318,000 and 339,000 years ago, during the Marine Isotope Stage 9.[37]

The entire East Antarctic Ice Sheet holds enough ice to raise global sea levels by 53.3 m (175 ft).[2] Its complete melting is also possible, but it would require very high warming and a lot of time: in 2022, an extensive assessment of tipping points in the climate system published in the Science Magazine concluded that the ice sheet would most likely be committed to complete disappearance only once the global warming reaches about 7.5 °C (13.5 °F), with the minimum and the maximum range between 5 °C (9.0 °F) and 10 °C (18 °F). It would also take a minimum of 10,000 years for the entire ice sheet to be lost. If it were to disappear, then the change in ice-albedo feedback would increase the global temperature by 0.6 °C (1.1 °F), while the regional temperatures would increase by around 2 °C (3.6 °F). The loss of the subglacial basins alone would only add about 0.05 °C (0.090 °F) to global temperatures due to their relatively limited area.[7][8]

See also

References

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  12. ↑ Robin Bell (12 November 2008). "Dispatches from the Bottom of the Earth: An Antarctic Expedition in Search of Large Mountains Encased in Ice". Scientific American. Retrieved 15 January 2024.
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  17. ↑ Yusuke Suganuma; Hideki Miura; Albert Zondervan; Jun'ichi Okuno (August 2014). "East Antarctic deglaciation and the link to global cooling during the Quaternary: evidence from glacial geomorphology and 10Be surface exposure dating of the Sør Rondane Mountains, Dronning Maud Land". Quaternary Science Reviews. 97: 102–120. Bibcode:2014QSRv...97..102S. doi:10.1016/j.quascirev.2014.05.007.
  18. ↑ Voosen, Paul (2018-12-18). "Discovery of recent Antarctic ice sheet collapse raises fears of a new global flood". Science. Retrieved 2018-12-28.
  19. ↑ Turney, Chris S. M.; Fogwill, Christopher J.; Golledge, Nicholas R.; McKay, Nicholas P.; Sebille, Erik van; Jones, Richard T.; Etheridge, David; Rubino, Mauro; Thornton, David P.; Davies, Siwan M.; Ramsey, Christopher Bronk (2020-02-11). "Early Last Interglacial ocean warming drove substantial ice mass loss from Antarctica". Proceedings of the National Academy of Sciences. 117 (8): 3996–4006. Bibcode:2020PNAS..117.3996T. doi:10.1073/pnas.1902469117. ISSN 0027-8424. PMC 7049167. PMID 32047039.
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  23. 1 2 Xin, Meijiao; Clem, Kyle R; Turner, John; Stammerjohn, Sharon E; Zhu, Jiang; Cai, Wenju; Li, Xichen (2 June 2023). "West-warming East-cooling trend over Antarctica reversed since early 21st century driven by large-scale circulation variation". Environmental Research Letters. 18 (6): 064034. doi:10.1088/1748-9326/acd8d4.
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  26. 1 2 Brancato, V.; Rignot, E.; Milillo, P.; Morlighem, M.; Mouginot, J.; An, L.; Scheuchl, B.; Jeong, S.; Rizzoli, P.; Bueso Bello, J.L.; Prats-Iraola, P. (2020). "Grounding line retreat of Denman Glacier, East Antarctica, measured with COSMO-SkyMed radar interferometry data". Geophysical Research Letters. 47 (7): e2019GL086291. Bibcode:2020GeoRL..4786291B. doi:10.1029/2019GL086291. ISSN 0094-8276.
  27. 1 2 King, M. A.; Bingham, R. J.; Moore, P.; Whitehouse, P. L.; Bentley, M. J.; Milne, G. A. (2012). "Lower satellite-gravimetry estimates of Antarctic sea-level contribution". Nature. 491 (7425): 586–589. Bibcode:2012Natur.491..586K. doi:10.1038/nature11621. PMID 23086145. S2CID 4414976.
  28. ↑ IMBIE team (13 June 2018). "Mass balance of the Antarctic Ice Sheet from 1992 to 2017". Nature. 558 (7709): 219–222. Bibcode:2018Natur.558..219I. doi:10.1038/s41586-018-0179-y. hdl:2268/225208. PMID 29899482. S2CID 49188002.
  29. 1 2 Zwally, H. Jay; Robbins, John W.; Luthcke, Scott B.; Loomis, Bryant D.; Rémy, Frédérique (29 March 2021). "Mass balance of the Antarctic ice sheet 1992–2016: reconciling results from GRACE gravimetry with ICESat, ERS1/2 and Envisat altimetry". Journal of Glaciology. 67 (263): 533–559. doi:10.1017/jog.2021.8. Although their methods of interpolation or extrapolation for areas with unobserved output velocities have an insufficient description for the evaluation of associated errors, such errors in previous results (Rignot and others, 2008) caused large overestimates of the mass losses as detailed in Zwally and Giovinetto (Zwally and Giovinetto, 2011).
  30. ↑ NASA (7 July 2023). "Antarctic Ice Mass Loss 2002-2023".
  31. ↑ Chen, J. L.; Wilson, C. R.; Blankenship, D.; Tapley, B. D. (2009). "Accelerated Antarctic ice loss from satellite gravity measurements". Nature Geoscience. 2 (12): 859. Bibcode:2009NatGe...2..859C. doi:10.1038/ngeo694. S2CID 130927366.
  32. ↑ Rignot, Eric; Mouginot, Jérémie; Scheuchl, Bernd; van den Broeke, Michiel; van Wessem, Melchior J.; Morlighem, Mathieu (22 January 2019). "Four decades of Antarctic Ice Sheet mass balance from 1979–2017". Proceedings of the National Academy of Sciences. 116 (4): 1095–1103. Bibcode:2019PNAS..116.1095R. doi:10.1073/pnas.1812883116. PMC 6347714. PMID 30642972.
  33. 1 2 "Anticipating Future Sea Levels". EarthObservatory.NASA.gov. National Aeronautics and Space Administration (NASA). 2021. Archived from the original on 7 July 2021.
  34. ↑ Amos, Jonathan (2020-03-23). "Climate change: Earth's deepest ice canyon vulnerable to melting". BBC.
  35. ↑ Lauber, Julius; Hattermann, Torr; de Steur, Laura; Darelius, Elin; Auger, Matthis; Anders Nost, Ole; Moholdt, Geir (21 September 2023). "Warming beneath an East Antarctic ice shelf due to increased subpolar westerlies and reduced sea ice". Nature Geoscience. 16: 877–885.
  36. ↑ Fox-Kemper, B.; Hewitt, H.T.; Xiao, C.; Aðalgeirsdóttir, G.; Drijfhout, S.S.; Edwards, T.L.; Golledge, N.R.; Hemer, M.; Kopp, R.E.; Krinner, G.; Mix, A. (2021). Masson-Delmotte, V.; Zhai, P.; Pirani, A.; Connors, S.L.; Péan, C.; Berger, S.; Caud, N.; Chen, Y.; Goldfarb, L. (eds.). "Chapter 9: Ocean, Cryosphere and Sea Level Change" (PDF). Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, UK and New York, NY, USA: 1270–1272.
  37. 1 2 Crotti, Ilaria; Quiquet, Aurélien; Landais, Amaelle; Stenni, Barbara; Wilson, David J.; Severi, Mirko; Mulvaney, Robert; Wilhelms, Frank; Barbante, Carlo; Frezzotti, Massimo (10 September 2022). "Wilkes subglacial basin ice sheet response to Southern Ocean warming during late Pleistocene interglacials". Nature Communications. 13: 5328. doi:10.1038/s41467-022-32847-3.
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