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Greenland ice sheet
please note:
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{{Short description|Vast body of ice in Greenland, Northern Hemisphere}}{{Use dmy dates|date=January 2024}}- the content below is remote from Wikipedia
- it has been imported raw for GetWiki
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Description
{{See also|Greenland Ice Sheet Project|Greenland ice core project|}}Ice sheets form through a process of glaciation, when the local climate is sufficiently cold that snow is able to accumulate from year to year. As the annual snow layers pile up, their weight gradually compresses the deeper levels of snow to firn and then to solid glacier ice over hundreds of years. Once the ice sheet formed in Greenland, its size remained similar to its current state.JOURNAL, Strunk, Astrid, Knudsen, Mads Faurschou, Egholm, David L. E, Jansen, John D., Levy, Laura B., Jacobsen, Bo H., Larsen, Nicolaj K., 18 January 2017, One million years of glaciation and denudation history in west Greenland, Nature Communications, en, 8, 14199, 2017NatCo...814199S, 10.1038/ncomms14199, 5253681, 28098141, However, there have been 11 periods in Greenland's history when the ice sheet extended up to {{cvt|120|km|mi}} beyond its current boundaries; with the last one around 1 million years ago.(File:Aschwanden_2016_greenland_ice_flows.jpg|thumb|The pattern of ice flows at the Greenland ice sheet, with arrows pointing to outlet glaciers where ice calving occursJOURNAL, Aschwanden, Andy, Fahnestock, Mark A., Truffer, Martin, 1 February 2016, Complex Greenland outlet glacier flow captured, Nature Communications, 7, 10524, 2016NatCo...710524A, 10.1038/ncomms10524, 4740423, 26830316, )The weight of the ice causes it to slowly "flow", unless it is stopped by a sufficiently large obstacle, such as a mountain. Greenland has many mountains near its coastline, which normally prevent the ice sheet from flowing further into the Arctic Ocean. The 11 previous episodes of glaciation are notable because the ice sheet grew large enough to flow over those mountains. Nowadays, the northwest and southeast margins of the ice sheet are the main areas where there are sufficient gaps in the mountains to enable the ice sheet to flow out to the ocean through outlet glaciers. These glaciers regularly shed ice in what is known as ice calving. Sediment released from calved and melting ice sinks accumulates on the seafloor, and sediment cores from places such as the Fram Strait provide long records of glaciation at Greenland.Geological history
(File:Tan 2018 GrIS formation.png|thumb|Timeline of the ice sheet's formation from 2.9 to 2.6 million years ago)While there is evidence of large glaciers in Greenland for most of the past 18 million years, these ice bodies were probably similar to various smaller modern examples, such as Maniitsoq and Flade Isblink, which cover {{convert|76000|and|100000|km²|sqmi|-3}} around the periphery. Conditions in Greenland were not initially suitable for a single coherent ice sheet to develop, but this began to change around 10 million years ago, during the middle Miocene, when the two passive continental margins which now form the uplands of West and East Greenland experienced uplift, and ultimately formed the upper planation surface at a height of 2000 to 3000 meter above sea level.JOURNAL, Japsen, Peter, Green, Paul F., Bonow, Johan M., Nielsen, Troels F.D., Chalmers, James A., 5 February 2014, From volcanic plains to glaciated peaks: Burial, uplift and exhumation history of southern East Greenland after opening of the NE Atlantic, Global and Planetary Change, 116, 91–114, 2014GPC...116...91J, 10.1016/j.gloplacha.2014.01.012, JOURNAL, Solgaard, Anne M., Bonow, Johan M., Langen, Peter L., Japsen, Peter, Hvidberg, Christine, 27 September 2013, Mountain building and the initiation of the Greenland Ice Sheet, Palaeogeography, Palaeoclimatology, Palaeoecology, 392, 161–176, 2013PPP...392..161S, 10.1016/j.palaeo.2013.09.019, Later uplift, during the Pliocene, formed a lower planation surface at 500 to 1000 meters above sea level. A third stage of uplift created multiple valleys and fjords below the planation surfaces. This uplift intensified glaciation due to increased orographic precipitation and cooler surface temperatures, allowing ice to accumulate and persist. As recently as 3 million years ago, during the Pliocene warm period, Greenland's ice was limited to the highest peaks in the east and the south.JOURNAL, Koenig, S. J., Dolan, A. M., de Boer, B., Stone, E. J., Hill, D. J., DeConto, R. M., Abe-Ouchi, A., Lunt, D. J., Pollard, D., Quiquet, A., Saito, F., Savage, J., van de Wal, R., 5 March 2015, Ice sheet model dependency of the simulated Greenland Ice Sheet in the mid-Pliocene, Climate of the Past, 11, 3, 369–381, 2015CliPa..11..369K, 10.5194/cp-11-369-2015, free, Ice cover gradually expanded since then, until the atmospheric CO2 levels dropped to between 280 and 320 ppm 2.7–2.6 million years ago, by which time temperatures had dropped sufficiently for the disparate ice caps to connect and cover most of the island.Ice cores and sediment samples
(File:Yang_2022_GrIS_trends_120k.png|thumb|left|upright=1.2|For much of the past 120,000 years, the climate of Greenland has been colder than in the last few millennia of recorded history (upper half), allowing the ice sheet to become considerably larger than it is now (lower half).JOURNAL, Yang, Hu, Krebs-Kanzow, Uta, Kleiner, Thomas, Sidorenko, Dmitry, Rodehacke, Christian Bernd, Shi, Xiaoxu, Gierz, Paul, Niu, Lu J., Gowan, Evan J., Hinck, Sebastian, Liu, Xingxing, Stap, Lennert B., Lohmann, Gerrit, 20 January 2022, Impact of paleoclimate on present and future evolution of the Greenland Ice Sheet, PLOS ONE, 17, 1, e0259816, 10.1371/journal.pone.0259816, 35051173, 8776332, 2022PLoSO..1759816Y, free, )The base of the ice sheet may be warm enough due to geothermal activity to have liquid water beneath it.WEB, Vinas, Maria-Jose, 3 August 2016, NASA Maps Thawed Areas Under Greenland Ice Sheet,weblink 12 December 2023, NASA, 12 December 2023,weblink live, This liquid water, under pressure from the weight of ice above it, may cause erosion, eventually leaving nothing but bedrock below the ice sheet. However, there are parts of the Greenland ice sheet, near the summit, where the ice sheet slides over a basal layer of ice which had frozen solid to the ground, preserving ancient soil, which can then be recovered by drilling. The oldest such soil was continuously covered by ice for around 2.7 million years, while another, {{convert|3|km|mi|1}} deep ice core from the summit has revealed ice that is around ~1,000,000 years old.Sediment samples from the Labrador Sea provide evidence that nearly all of the south Greenland ice had melted around 400,000 years ago, during Marine Isotope Stage 11.JOURNAL, Irvalı, Nil, Galaasen, Eirik V., Ninnemann, Ulysses S., Rosenthal, Yair, Born, Andreas, Kleiven, Helga (Kikki) F., 18 December 2019, A low climate threshold for south Greenland Ice Sheet demise during the Late Pleistocene, Proceedings of the National Academy of Sciences, en, 117, 1, 190–195, 10.1073/pnas.1911902116, 0027-8424, 6955352, 31871153, free, Other ice core samples from Camp Century in northwestern Greenland, show that the ice there melted at least once during the past 1.4 million years, during the Pleistocene, and did not return for at least 280,000 years. These findings suggest that less than 10% of the current ice sheet volume was left during those geologically recent periods, when the temperatures were less than {{convert|2.5|C-change|F-change}} warmer than preindustrial conditions. This contradicts how climate models typically simulate the continuous presence of solid ice under those conditions.JOURNAL, Schaefer, Joerg M., Finkel, Robert C., Balco, Greg, Alley, Richard B., Caffee, Marc W., Briner, Jason P., Young, Nicolas E., Gow, Anthony J., Schwartz, Roseanne, 7 December 2016, Greenland was nearly ice-free for extended periods during the Pleistocene, Nature, en, 540, 7632, 252–255, 2016Natur.540..252S, 10.1038/nature20146, 27929018, 4471742, Analysis of the ~100,000-year records obtained from {{convert|3|km|abbr=on}} long ice cores drilled between 1989 and 1993 into the summit of Greenland's ice sheet, had provided evidence for geologically rapid changes in climate, and informed research on tipping points such as in the Atlantic meridional overturning circulation (AMOC).BOOK, Alley, Richard B, 2000, The Two-Mile Time Machine: Ice Cores, Abrupt Climate Change, and Our Future, Princeton University Press, 0-691-00493-5, (File:Radar reflector installation Greenland.jpg|thumb|Glaciologist at work)Ice cores provide valuable information about the past states of the ice sheet, and other kinds of paleoclimate data. Subtle differences in the oxygen isotope composition of the water molecules in ice cores can reveal important information about the water cycle at the time, while air bubbles frozen within the ice core provide a snapshot of the gas and particulate composition of the atmosphere through time.When properly analyzed, ice cores provide a wealth of proxies suitable for reconstructing the past temperature record,JOURNAL, Gkinis, V., Simonsen, S. B., Buchardt, S. L., White, J. W. C., Vinther, B. M., 1 November 2014, Water isotope diffusion rates from the NorthGRIP ice core for the last 16,000 years – Glaciological and paleoclimatic implications, Earth and Planetary Science Letters, 405, 132–141, EN, 10.1016/j.epsl.2014.08.022, 1404.4201, 2014E&PSL.405..132G, precipitation patterns,JOURNAL, Masson-Delmotte, V., Jouzel, J., Landais, A., Stievenard, M., Johnsen, S. J., White, J. W. C., Werner, M., Sveinbjornsdottir, A., Fuhrer, K., 1 July 2005, GRIP Deuterium Excess Reveals Rapid and Orbital-Scale Changes in Greenland Moisture Origin, Science, 309, 5731, 118–121, EN, 10.1126/science.1108575, 15994553, 2005Sci...309..118M, 10566001,weblink 13 December 2023, 19 May 2022,weblink live, volcanic eruptions,JOURNAL, Zielinski, G. A., Mayewski, P. A., Meeker, L. D., Whitlow, S., Twickler, M. S., Morrison, M., Meese, D. A., Gow, A. J., Alley, R. B., 13 May 1994, Record of Volcanism Since 7000 B.C. from the GISP2 Greenland Ice Core and Implications for the Volcano-Climate System, Science, 264, 5161, 948–952, EN, 10.1126/science.264.5161.948, 17830082, 1994Sci...264..948Z, 21695750, solar variation,JOURNAL, Adolphi, Florian, Muscheler, Raimund, Svensson, Anders, Aldahan, Ala, Possnert, Göran, Beer, Jürg, Sjolte, Jesper, Björck, Svante, Matthes, Katja, Thiéblemont, Rémi, 17 August 2014, Persistent link between solar activity and Greenland climate during the Last Glacial Maximum, Nature Geoscience, 7, 9, 662–666, EN, 10.1038/ngeo2225, 2014NatGe...7..662A, ocean primary production,JOURNAL, Kurosaki, Yutaka, Matoba, Sumito, Iizuka, Yoshinori, Fujita, Koji, Shimada, Rigen, Increased oceanic dimethyl sulfide emissions in areas of sea ice retreat inferred from a Greenland ice core, Communications Earth & Environment, 26 December 2022, 3, 1, 327, 10.1038/s43247-022-00661-w, 2022ComEE...3..327K, en, 2662-4435, free, (File:CC-BY icon.svg|50px) Text and images are available under a Creative Commons Attribution 4.0 International License {{Webarchive|url=https://web.archive.org/web/20171016050101weblink |date=16 October 2017 }}. and even changes in soil vegetation cover and the associated wildfire frequency.JOURNAL, Fischer, Hubertus, Schüpbach, Simon, Gfeller, Gideon, Bigler, Matthias, Röthlisberger, Regine, Erhardt, Tobias, Stocker, Thomas F., Mulvaney, Robert, Wolff, Eric W., 10 August 2015, Millennial changes in North American wildfire and soil activity over the last glacial cycle, Nature Geoscience, 8, 9, 723–727, EN, 10.1038/ngeo2495, 2015NatGe...8..723F,weblink 13 December 2023, 3 December 2023,weblink" title="web.archive.org/web/20231203124359weblink">weblink live, The ice cores from Greenland also record human impact, such as lead production during the time of Ancient GreeceJOURNAL, Wood, J.R., Other ways to examine the finances behind the birth of Classical Greece, 21 October 2022, Archaeometry, 65, 3, 570–586, 10.1111/arcm.12839, free, and the Roman Empire.JOURNAL, McConnell, Joseph R., Wilson, Andrew I., Stohl, Andreas, Arienzo, Monica M., Chellman, Nathan J., Eckhardt, Sabine, Thompson, Elisabeth M., Pollard, A. Mark, Steffensen, Jørgen Peder, 29 May 2018, Lead pollution recorded in Greenland ice indicates European emissions tracked plagues, wars, and imperial expansion during antiquity, Proceedings of the National Academy of Sciences, 115, 22, 5726–5731, 10.1073/pnas.1721818115, 29760088, 5984509, 2018PNAS..115.5726M, free,Recent melting
(File:Arctic Temperature Trend 1987-2007.jpg|thumb|Arctic temperature trend, 1981–2007)From the 1960s to the 1980s an area in the North Atlantic which included southern Greenland was one of the few locations in the world which showed cooling rather than warming.WEB,weblink Arctic Climate Impact Assessment, 2006-02-23, 2010-12-14,weblink" title="web.archive.org/web/20101214135239weblink">weblink dead, WEB, 16 July 2008, Arctic Climate Impact Assessment,weblink Union of Concerned Scientists, 5 December 2023, 5 December 2023,weblink live, This location was relatively warmer in the 1930s and 1940s than in the decades immediately before or after.JOURNAL, Vinther, B. M., Andersen, K. K., Jones, P. D., Briffa, K. R., Cappelen, J., Extending Greenland temperature records into the late eighteenth century, Journal of Geophysical Research,weblink 111, D11, D11105, 6 June 2006, 10.1029/2005JD006810, 2006JGRD..11111105V, free, 10 July 2007, 23 February 2011,weblink" title="web.archive.org/web/20110223042959weblink">weblink live, More complete data sets have established trends of warming and ice loss starting from 1900JOURNAL, Kjeldsen, Kristian K., Korsgaard, Niels J., Bjørk, Anders A., Khan, Shfaqat A., Box, Jason E., Funder, Svend, Larsen, Nicolaj K., Bamber, Jonathan L., Colgan, William, van den Broeke, Michiel, Siggaard-Andersen, Marie-Louise, Nuth, Christopher, Schomacker, Anders, Andresen, Camilla S., Willerslev, Eske, Kjær, Kurt H., 16 December 2015, Spatial and temporal distribution of mass loss from the Greenland Ice Sheet since AD 1900, Nature, en, 528, 7582, 396–400, 10.1038/nature16183, 26672555, 2015Natur.528..396K, 1874/329934, 4468824, (well after the start of the Industrial Revolution and its impact on global carbon dioxide levelsJOURNAL, Frederikse, Thomas, Landerer, Felix, Caron, Lambert, Adhikari, Surendra, Parkes, David, Humphrey, Vincent W., Dangendorf, Sönke, Hogarth, Peter, Zanna, Laure, Cheng, Lijing, Wu, Yun-Hao, 19 August 2020, The causes of sea-level rise since 1900, Nature, en, 584, 7821, 393–397, 10.1038/s41586-020-2591-3, 32814886, 221182575, ) and a trend of strong warming starting around 1979, in line with concurrent observed Arctic sea ice decline.IPCC, 2007. Trenberth, K.E., P.D. Jones, P. Ambenje, R. Bojariu, D. Easterling, A. Klein Tank, D. Parker, F. Rahimzadeh, J.A. Renwick, M. Rusticucci, B. Soden and P. Zhai, 2007: Observations: Surface and Atmospheric Climate Change. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.weblink {{Webarchive|url=https://web.archive.org/web/20171023052326weblink|date=23 October 2017}} In 1995–1999, central Greenland was already {{convert|2|C-change|F-change}} warmer than it was in the 1950s. Between 1991 and 2004, average winter temperature at one location, Swiss Camp, rose almost {{convert|6|C-change|F-change}}.CONFERENCE, Steffen, Konrad, Cullen, Nicloas, Huff, Russell, 85th American Meteorogical Union Annual Meeting, 13 January 2005, Climate variability and trends along the western slope of the Greenland ice sheet during 1991-2004,weblinkweblink" title="web.archive.org/web/20070614071743weblink">weblink 14 June 2007, Consistent with this warming, the 1970s were the last decade when the Greenland ice sheet grew, gaining about 47 gigatonnes per year. From 1980–1990 there was an average annual mass loss of ~51 Gt/y. The period 1990–2000 showed an average annual loss of 41 Gt/y, with 1996 being the last year the Greenland ice sheet saw net mass gain. As of 2022, the Greenland ice sheet had been losing ice for 26 years in a row,WEB, Stendel, Martin, Mottram, Ruth, 22 September 2022, Guest post: How the Greenland ice sheet fared in 2022,weblink Carbon Brief, 2022-10-22, 22 October 2022,weblink live, and temperatures there had been the highest in the entire past last millennium – about {{convert|1.5|C-change|F-change}} warmer than the 20th century average.JOURNAL, Hörhold, M., Münch, T., Weißbach, S., Kipfstuhl, S., Freitag, J., Sasgen, I., Lohmann, G., Vinther, B., Laepple, T., 18 January 2023, Modern temperatures in central–north Greenland warmest in past millennium, Nature, 613, 7506, 525–528, 10.1038/nature13456, 24965655, 2014Natur.510..525R, 4468457, (File:Cambios en la capa de hielo de Groenlandia.jpg|thumb|Until 2007, rate of decrease in ice sheet height in cm per year)Several factors determine the net rate of ice sheet growth or decline. These are:- Accumulation and melting rates of snow in and around the centre
- Melting of ice along the sheet's margins
- Ice calving into the sea from outlet glaciers also along the sheet's edges
Observed glacier retreat
(File:Measuring Elevation Changes on the Greenland Ice Sheet.ogg|thumb|This narrated animation shows the overall change in the elevation of the Greenland ice sheet between 2003 and 2012. The coastal areas of the ice sheet lost far more height, or "thinned", compared to the more inland regions.)File:Choi 2021 GIS glacier map.png|thumb|Greenland ice sheet has 215 marine-terminating glaciers whose retreat directly impacts sea level rise. As of 2021, 115 accounted for 79% of ice flow and could be simulated with good accuracy, 25 had their retreat underestimated and accounted for 13%, 67 lacked sufficient bathymetrybathymetryRetreat of outlet glaciers as they shed ice into the Arctic is a large factor in the decline of Greenland's ice sheet. Estimates suggest that losses from glaciers explain between 49% and 66.8% of observed ice loss since the 1980s. Net loss of ice was already observed across 70% of the ice sheet margins by the 1990s, with thinning detected as the glaciers started to lose height.JOURNAL, Moon, Twila, Joughin, Ian, 7 June 2008, Changes in ice front position on Greenland's outlet glaciers from 1992 to 2007, Journal of Geophysical Research: Earth Surface, 113, F2, 10.1029/2007JF000927, 2008JGRF..113.2022M, Between 1998 and 2006, thinning occurred four times faster for coastal glaciers compared to the early 1990s, falling at rates between {{cvt|1|m|ft|frac=2}} and {{cvt|10|m|ft|frac=2}} per year,WEB, Shukman, David, Greenland ice-melt 'speeding up', 28 July 2004,weblink The BBC, 22 December 2023, 22 December 2023,weblink" title="web.archive.org/web/20231222170116weblink">weblink live, while the landlocked glaciers experienced almost no such acceleration.JOURNAL, Sole, A., Payne, T., Bamber, J., Nienow, P., Krabill, W., 16 December 2008, Testing hypotheses of the cause of peripheral thinning of the Greenland Ice Sheet: is land-terminating ice thinning at anomalously high rates?, The Cryosphere, en, 2, 2, 205–218, 10.5194/tc-2-205-2008, 2008TCry....2..205S, 16539240, 1994-0424, free, One of the most dramatic examples of thinning was in the southeast, at Kangerlussuaq Glacier. It is over {{cvt|20|mi|km|frac=2}} long, {{cvt|4.5|mi|km|frac=2}} wide and around {{cvt|1|km|mi|frac=2}} thick, which makes it the third largest glacier in Greenland. Between 1993 and 1998, parts of the glacier within {{cvt|5|km|mi|frac=2}} of the coast lost {{cvt|50|m|ft|frac=2}} in height.JOURNAL, Thomas, Robert H., Abdalati, Waleed, Akins, Torry L., Csatho, Beata M., Frederick, Earl B., Gogineni, Siva P., Krabill, William B., Manizade, Serdar S., Rignot, Eric J., 1 May 2000, Substantial thinning of a major east Greenland outlet glacier, Geophysical Research Letters, 27, 9, 1291–1294, 10.1029/1999GL008473, 2000GeoRL..27.1291T, Its observed ice flow speed went from {{cvt|3.1-3.7|mi|km|frac=2}} per year in 1988–1995 to {{cvt|8.7|mi|km|frac=2}} per year in 2005, which was then the fastest known flow of any glacier.NEWS, Connor, Steve, 25 July 2005, Melting Greenland glacier may hasten rise in sea level,weblink The Independent, 30 April 2010, 27 July 2005,weblink" title="web.archive.org/web/20050727015231weblink">weblink The retreat of Kangerlussuaq slowed down by 2008,JOURNAL, Howat, Ian M., Ahn, Yushin, Joughin, Ian, van den Broeke, Michiel R., Lenaerts, Jan T. M., Smith, Ben, 18 June 2011, Mass balance of Greenland's three largest outlet glaciers, 2000–2010, Geophysical Research Letters, 27, 9, 10.1029/1999GL008473, 2000GeoRL..27.1291T, and showed some recovery until 2016–2018, when more rapid ice loss occurred.JOURNAL, Barnett, Jamie, Holmes, Felicity A., Kirchner, Nina, 23 August 2022, Modelled dynamic retreat of Kangerlussuaq Glacier, East Greenland, strongly influenced by the consecutive absence of an ice mélange in Kangerlussuaq Fjord, Journal of Glaciology, en, 59, 275, 433–444, 10.1017/jog.2022.70, Greenland's other major outlet glaciers have also experienced rapid change in recent decades. Its single largest outlet glacier is Jakobshavn Isbræ () in west Greenland, which has been observed by glaciologists for many decades.WEB, Ilulissat Icefjord,weblink UNESCO World Heritage Centre, United Nations Educational, Scientific, and Cultural Organization, 19 Jun 2021, 24 December 2018,weblink" title="web.archive.org/web/20181224225842weblink">weblink live, It historically sheds ice from 6.5% of the ice sheet (compared to 4% for Kangerlussuaq), at speeds of ~{{convert|20|m}} per day. While it lost enough ice to retreat around {{convert|30|km|abbr=on}} between 1850 and 1964, its mass gain increased sufficiently to keep it in balance for the next 35 years,JOURNAL, Pelto.M, Hughes, T, Fastook J., Brecher, H., Equilibrium state of Jakobshavns Isbræ, West Greenland, International Glaciological Society, Annals of Glaciology, 12, 781–783, 1989Processes accelerating glacier retreat
(File:Ciraci_2023_Petermann_fluctuations.jpg|thumb|Petermann Glacier experiences notable shifts from year to year not just at its calving front, but also at its grounding line, which renders it less stable. If such behaviour turns out to be widespread at other glaciers, this could potentially double their rates of ice loss.)Since the early 2000s, glaciologists have concluded that glacier retreat in Greenland is accelerating too quickly to be explained by a linear increase in melting in response to greater surface temperatures alone, and that additional mechanisms must also be at work.JOURNAL, Rignot, Eric, Gogineni, Sivaprasad, Joughin, Ian, Krabill, William, 1 December 2001, Contribution to the glaciology of northern Greenland from satellite radar interferometry, Journal of Geophysical Research: Atmospheres, 106, D24, 34007–34019, 10.1029/2001JD900071, 2001JGR...10634007R, JOURNAL, Rignot, E., Braaten, D., Gogineni, S., Krabill, W., McConnell, J. R., 25 May 2004, Rapid ice discharge from southeast Greenland glaciers, Geophysical Research Letters, 31, 10, 10.1029/2004GL019474, 2004GeoRL..3110401R, JOURNAL, Luckman, Adrian, Murray, Tavi, de Lange, Remko, Hanna, Edward, 3 February 2006, Rapid and synchronous ice-dynamic changes in East Greenland, Geophysical Research Letters, 33, 3, 10.1029/2005gl025428, 2006GeoRL..33.3503L, 55517773, 0094-8276, free, Rapid calving events at the largest glaciers match what was first described as the "Jakobshavn effect" in 1986:JOURNAL, Hughes, T., The Jakobshavn Effect, Geophysical Research Letters, 13, 1, 46–48, 1986, 10.1029/GL013i001p00046, 1986GeoRL..13...46H, thinning causes the glacier to be more buoyant, reducing friction that would otherwise impede its retreat, and resulting in a force imbalance at the calving front, with an increase in velocity spread across the mass of the glacier.JOURNAL, Thomas, Robert H., 2004, Force-perturbation analysis of recent thinning and acceleration of Jakobshavn Isbræ, Greenland, Journal of Glaciology, en, 50, 168, 57–66, 10.3189/172756504781830321, 2004JGlac..50...57T, 128911716, 0022-1430, free, JOURNAL, Thomas, Robert H., Abdalati, Waleed, Frederick, Earl, Krabill, William, Manizade, Serdar, Steffen, Konrad, 2003, Investigation of surface melting and dynamic thinning on Jakobshavn Isbrae, Greenland, Journal of Glaciology, 49, 165, 231–239, 10.3189/172756503781830764, 2003JGlac..49..231T, free, The overall acceleration of Jakobshavn Isbrae and other glaciers from 1997 onwards had been attributed to the warming of North Atlantic waters which melt the glacier fronts from underneath. While this warming had been going on since the 1950s,JOURNAL, Straneo, Fiammetta, Heimbach, Patrick, 4 December 2013, North Atlantic warming and the retreat of Greenland's outlet glaciers, Nature, 504, 7478, 36–43, 10.1038/nature12854, 24305146, 2013Natur.504...36S, 205236826, 1997 also saw a shift in circulation which brought relatively warmer currents from the Irminger Sea into closer contact with the glaciers of West Greenland.JOURNAL, Holland, D M., Younn, B. D., Ribergaard, M. H., Lyberth, B., 28 September 2008, Acceleration of Jakobshavn Isbrae triggered by warm ocean waters, Nature Geoscience, 1, 659–664, 10.1038/ngeo316, 10, 2008NatGe...1..659H, 131559096, By 2016, waters across much of West Greenland's coastline had warmed by {{convert|1.6|C-change|F-change}} relative to 1990s, and some of the smaller glaciers were losing more ice to such melting than normal calving processes, leading to rapid retreat.JOURNAL, Rignot, E., Xu, Y., Menemenlis, D., Mouginot, J., Scheuchl, B., Li, X., Morlighem, M., Seroussi, H., van den Broeke, M., Fenty, I., Cai, C., An, L., de Fleurian, B., 30 May 2016, Modeling of ocean-induced ice melt rates of five west Greenland glaciers over the past two decades, Geophysical Research Letters, 43, 12, 6374–6382, 10.1002/2016GL068784, 2016GeoRL..43.6374R, 1874/350987, 102341541, Conversely, Jakobshavn Isbrae is sensitive to changes in ocean temperature as it experiences elevated exposure through a deep subglacial trench.JOURNAL, Clarke, Ted S., Echelmeyer, Keith, 1996, Seismic-reflection evidence for a deep subglacial trough beneath Jakobshavns Isbræ, West Greenland, Journal of Glaciology, 43, 141, 219–232, 10.3189/S0022143000004081, JOURNAL, van der Veen, C.J., Leftwich, T., von Frese, R., Csatho, B.M., Li, J., 21 June 2007, Subglacial topography and geothermal heat flux: Potential interactions with drainage of the Greenland ice sheet,weblink Geophysical Research Letters, L12501, 34, 12, 5 pp, 2007GeoRL..3412501V, 10.1029/2007GL030046, 16 January 2011, free, 1808/17298, 54213033, 8 September 2011,weblink" title="web.archive.org/web/20110908122046weblink">weblink dead, This sensitivity meant that an influx of cooler ocean water to its location was responsible for its slowdown after 2015, in large part because the sea ice and icebergs immediately off-shore were able to survive for longer, and thus helped to stabilize the glacier.JOURNAL, Joughin, Ian, Shean, David E., Smith, Benjamin E., Floricioiu, Dana, 24 January 2020, A decade of variability on Jakobshavn Isbræ: ocean temperatures pace speed through influence on mélange rigidity, The Cryosphere, en, 14, 1, 211–227, 10.5194/tc-14-211-2020, 32355554, 2020TCry...14..211J, free, Likewise, the rapid retreat and then slowdown of Helheim and Kangerdlugssuaq has also been connected to the respective warming and cooling of nearby currents.JOURNAL, Joughin, Ian, Howat, Ian, Alley, Richard B., Ekstrom, Goran, Fahnestock, Mark, Moon, Twila, Nettles, Meredith, Truffer, Martin, Tsai, Victor C., 26 January 2008, Ice-front variation and tidewater behavior on Helheim and Kangerdlugssuaq Glaciers, Greenland, Journal of Geophysical Research: Earth Surface, 113, F1, 10.1029/2007JF000837, 2008JGRF..113.1004J, At Petermann Glacier, the rapid rate of retreat has been linked to the topography of its grounding line, which appears to shift back and forth by around a kilometer with the tide. It has been suggested that if similar processes can occur at the other glaciers, then their eventual rate of mass loss could be doubled.NEWS, Miller, Brandon, 8 May 2023, A major Greenland glacier is melting away with the tide, which could signal faster sea level rise, study finds,weblink 16 June 2023, CNN, en, 16 June 2023,weblink live, JOURNAL, Ciracì, Enrico, Rignot, Eric, Scheuchl, Bernd, 8 May 2023, Melt rates in the kilometer-size grounding zone of Petermann Glacier, Greenland, before and during a retreat, Proceedings of the National Academy of Sciences of the United States of America, PNAS, 120, 20, e2220924120, 10.1073/pnas.2220924120, 37155853, 10193949, 2023PNAS..12020924C, File:Inlandsis moulin Groenland 2009 Expédition ACarré.JPG|thumb|left|Meltwater rivers may flow down into moulins and reach the base of the ice sheet]]There are several ways in which increased melting at the surface of the ice sheet can accelerate lateral retreat of outlet glaciers. Firstly, the increase in meltwater at the surface causes larger amounts to flow through the ice sheet down to bedrock via moulins. There, it lubricates the base of the glaciers and generates higher basal pressure, which collectively reduces friction and accelerates glacial motion, including the rate of ice calving. This mechanism was observed at Sermeq Kujalleq in 1998 and 1999, where flow increased by up to 20% for two to three months.JOURNAL, Zwally, H. Jay, Abdalati, Waleed, Herring, Tom, Larson, Kristine, Saba, Jack, Steffen, Konrad, 12 July 2002, Surface Melt-Induced Acceleration of Greenland Ice-Sheet Flow, Science, 297, 5579, 218–222, EN, 10.1126/science.1072708, 12052902, 2002Sci...297..218Z, 37381126, free, WEB, Pelto, M., Moulins, Calving Fronts and Greenland Outlet Glacier Acceleration, RealClimate, 2008,weblink 27 September 2008, 27 July 2009,weblink" title="web.archive.org/web/20090727103900weblink">weblink live, However, some research suggests that this mechanism only applies to certain small glaciers, rather than to the largest outlet glaciers,JOURNAL, Das, Sarah B., Joughin, Ian, Behn, Mark D., Howat, Ian M., King, Matt A., Lizarralde, Dan, Bhatia, Maya P., 9 May 2008, Fracture Propagation to the Base of the Greenland Ice Sheet During Supraglacial Lake Drainage,weblink Science, 320, 5877, 778–781, EN, 10.1126/science.1153360, 18420900, 2008Sci...320..778D, 1912/2506, 41582882, free, 7 March 2022, 7 March 2022,weblink live, and may have only a marginal impact on ice loss trends.JOURNAL, Thomas, R., Frederick, E., Krabill, W., Manizade, S., Martin, C., 2009, Recent changes on Greenland outlet glaciers, Journal of Glaciology, en, 55, 189, 147–162, 10.3189/002214309788608958, 2009JGlac..55..147T, (File:Slater_2022_meltwater_plumes.png|thumb|An illustration of how meltwater forms a plume once it flows out into the ocean)Secondly, once meltwater flows into the ocean, it can still impact the glaciers by interacting with ocean water and altering its local circulation - even in the absence of any ocean warming. In certain fjords, large meltwater flows from beneath the ice may mix with ocean water to create turbulent plumes that can be damaging to the calving front.JOURNAL, Chauché, N., Hubbard, A., Gascard, J.-C., Box, J. E., Bates, R., Koppes, M., Sole, A., Christoffersen, P., Patton, H., 8 August 2014, Ice–ocean interaction and calving front morphology at two west Greenland tidewater outlet glaciers, The Cryosphere, 8, 4, 1457–1468, 10.5194/tc-8-1457-2014, 2014TCry....8.1457C, free, While the models generally consider the impact from meltwater run-off as secondary to ocean warming,JOURNAL, Morlighem, Mathieu, Wood, Michael, Seroussi, Hélène, Choi, Youngmin, Rignot, Eric, 1 March 2019, Modeling the response of northwest Greenland to enhanced ocean thermal forcing and subglacial discharge, The Cryosphere, 13, 2, 723–734, 10.5194/tc-13-723-2019, 2019TCry...13..723M, free, observations of 13 glaciers found that meltwater plumes play a greater role for glaciers with shallow grounding lines.JOURNAL, Fried, M. J., Catania, G. A., Stearns, L. A., Sutherland, D. A., Bartholomaus, T. C., Shroyer, E., Nash, J., 10 July 2018, Reconciling Drivers of Seasonal Terminus Advance and Retreat at 13 Central West Greenland Tidewater Glaciers, Journal of Geophysical Research: Earth Surface, 123, 7, 1590–1607, 10.1029/2018JF004628, 2018JGRF..123.1590F, Further, 2022 research suggests that the warming from plumes had a greater impact on underwater melting across northwest Greenland.JOURNAL, Slater, D. A., Straneo, F., 3 October 2022, Submarine melting of glaciers in Greenland amplified by atmospheric warming, Nature Geoscience, 15, 10, 794–799, 10.1038/s41561-022-01035-9, 2022NatGe..15..794S, Finally, it has been shown that meltwater can also flow through cracks that are too small to be picked up by most research tools - only {{cvt|2|cm|in|frac=2}} wide. Such cracks do not connect to bedrock through the entire ice sheet but may still reach several hundred meters down from the surface.JOURNAL, Chandler, David M., Hubbard, Alun, 19 June 2023, Widespread partial-depth hydrofractures in ice sheets driven by supraglacial streams, Nature Geoscience, 37, 20, 605–611, 10.1038/s41561-023-01208-0, 2023NatGe..16..605C, Their presence is important, as it weakens the ice sheet, conducts more heat directly through the ice, and allows it to flow faster.JOURNAL, Phillips, Thomas, Rajaram, Harihar, Steffen, Konrad, 23 October 2010, Cryo-hydrologic warming: A potential mechanism for rapid thermal response of ice sheets, Geophysical Research Letters, 48, 15, e2021GL092942, 10.1029/2010GL044397, 2010GeoRL..3720503P, 129678617, This recent research is not currently captured in models. One of the scientists behind these findings, Alun Hubbard, described finding moulins where "current scientific understanding doesn’t accommodate" their presence, because it disregards how they may develop from hairline cracks in the absence of existing large crevasses that are normally thought to be necessary for their formation.WEB, Hubbard, Alun, 29 June 2023, Meltwater is infiltrating Greenland's ice sheet through millions of hairline cracks – destabilizing its structure,weblink The Conversation (website), The Conversation, 22 December 2023, 22 December 2023,weblink live,Observed surface melting
{{multiple image| total_width = 450| width1 =| footer =| image1 = Satellite measurements of Greenland's ice cover from 1979 to 2009 reveals a trend of increased melting.ogv| alt1 = Satellite measurements of Greenland's ice cover from 1979 to 2009 reveals a trend of increased melting.| caption1 = Satellite measurements of Greenland's ice cover from 1979 to 2009 reveals a trend of increased melting.| width2 =| image2 = NASA's MODIS and QuikSCAT satellite data from 2007 confirm precision of different melt observations.ogv| alt2 = NASA's MODIS and QuikSCAT satellite data from 2007 were compared to confirm the precision of different melt observations.| caption2 = NASA's MODIS and QuikSCAT satellite data from 2007 were compared to confirm the precision of different melt observations.}}Currently, the total accumulation of ice on the surface of Greenland ice sheet is larger than either outlet glacier losses individually or surface melting during the summer, and it is the combination of both which causes net annual loss. For instance, the ice sheet's interior thickened by an average of {{convert|6|cm|abbr=on}} each year between 1994 and 2005, in part due to a phase of North Atlantic oscillation increasing snowfall.WEB, 7 November 2005, Satellite shows Greenland's ice sheets getting thicker,weblink The Register,weblink" title="web.archive.org/web/20170901014546weblink">weblink 1 September 2017, Every summer, a so-called snow line separates the ice sheet's surface into areas above it, where snow continues to accumulate even then, with the areas below the line where summer melting occurs.NEWS, Mooney, Chris, 29 August 2022, Greenland ice sheet set to raise sea levels by nearly a foot, study finds,weblink 29 August 2022, The Washington Post, As it thaws, scientists think the change will manifest itself at a location called the snow line. This is the dividing line between the high altitude, bright white parts of the ice sheet that accumulate snow and mass even during the summer, and the darker, lower elevation parts that melt and contribute water to the sea. This line moves every year, depending on how warm or cool the summer is, tracking how much of Greenland melts in a given period., 29 August 2022,weblink live, The exact position of the snow line moves around every summer, and if it moves away from some areas it covered the previous year, then those tend to experience substantially greater melt as their darker ice is exposed. Uncertainty about the snow line is one of the factors making it hard to predict each melting season in advance.JOURNAL, Ryan, J. C., Smith, L. C., van As, D., Cooley, S. W., Cooper, M. G., Pitcher, L. H., Hubbard, A., 6 March 2019, Greenland Ice Sheet surface melt amplified by snowline migration and bare ice exposure, Science Advances, 5, 3, 218–222, EN, 10.1126/sciadv.aav3738, 30854432, 6402853, 2019SciA....5.3738R, File:Melt Ponds on the Greenland Ice Sheet.jpg|thumb|left|Satellite image of dark melt pondsmelt pondsA notable example of ice accumulation rates above the snow line is provided by Glacier Girl, a Lockheed P-38 Lightning fighter plane which had crashed early in World War II and was recovered in 1992, by which point it had been buried under {{cvt|268|ft|m|frac=2}} of ice.WEB, Glacier Girl: The Back Story,weblink Air & Space Magazine, Smithsonian Institution, 21 June 2020, 21 June 2020,weblink live, Another example occurred in 2017, when an Airbus A380 had to make an emergency landing in Canada after one of its jet engines exploded while it was above Greenland; the engine's massive air intake fan was recovered from the ice sheet two years later, when it was already buried beneath {{cvt|4|ft|m|frac=2}}of ice and snow.WEB, Wattles, Jackie, 14 October 2020, How investigators found a jet engine under Greenland's ice sheet,weblink CNN Business,weblink 26 April 2023, While summer surface melting has been increasing, it is still expected that it will be decades before melting will consistently exceed snow accumulation on its own. It is also hypothesized that the increase in global precipitation associated with the effects of climate change on the water cycle could increase snowfall over Greenland, and thus further delay this transition. This hypothesis was difficult to test in the 2000s due to the poor state of long-term precipitation records over the ice sheet.JOURNAL, Bales, Roger C., Guo, Qinghua, Shen, Dayong, McConnell, Joseph R., Du, Guoming, Burkhart, John F., Spikes, Vandy B., Hanna, Edward, Cappelen, John, 27 March 2009, Annual accumulation for Greenland updated using ice core data developed during 2000–2006 and analysis of daily coastal meteorological data, Journal of Geophysical Research Atmospheres, 114, D6, 10.1029/2008JD011208, 2009JGRD..114.6116B,weblink 13 December 2023, 3 December 2023,weblink" title="web.archive.org/web/20231203082239weblink">weblink live, By 2019, it was found that while there was an increase in snowfall over southwest Greenland,JOURNAL, Auger, Jeffrey D., Birkel, Sean D., Maasch, Kirk A., Mayewski, Paul A., Schuenemann, Keah C., 6 June 2017, Examination of precipitation variability in southern Greenland, Journal of Geophysical Research Atmospheres, 122, 12, 6202–6216, 10.1002/2016JD026377, 2017JGRD..122.6202A, there had been a substantial decrease in precipitation over western Greenland as a whole.JOURNAL, Lewis, Gabriel, Osterberg, Erich, Hawley, Robert, Marshall, Hans Peter, Meehan, Tate, Graeter, Karina, McCarthy, Forrest, Overly, Thomas, Thundercloud, Zayta, Ferris, David, 4 November 2019, Recent precipitation decrease across the western Greenland ice sheet percolation zone,weblink The Cryosphere, en, 13, 11, 2797–2815, 10.5194/tc-13-2797-2019, 2019TCry...13.2797L, free, 7 March 2022, 22 January 2022,weblink live, Further, more precipitation in the northwest had been falling as rain instead of snow, with a fourfold increase in rain since 1980.JOURNAL, Niwano, M., Box, J. E., Wehrlé, A., Vandecrux, B., Colgan, W. T., Cappelen, J., 3 July 2021, Rainfall on the Greenland Ice Sheet: Present-Day Climatology From a High-Resolution Non-Hydrostatic Polar Regional Climate Model, Geophysical Research Letters, 48, 15, e2021GL092942, 10.1029/2021GL092942, 2021GeoRL..4892942N, Rain is warmer than snow and forms darker and less thermally insulating ice layer once it does freeze on the ice sheet. It is particularly damaging when it falls due to late-summer cyclones, whose increasing occurrence has been overlooked by the earlier models.JOURNAL, Doyle, Samuel H., Hubbard, Alun, van de Wal, Roderik S. W., Box, Jason E., van As, Dirk, Scharrer, Kilian, Meierbachtol, Toby W., Smeets, Paul C. J. P., Harper, Joel T., Johansson, Emma, Mottram, Ruth H., Mikkelsen, Andreas B., Wilhelms, Frank, Patton, Henry, Christoffersen, Poul, Hubbard, Bryn, 13 July 2015, Amplified melt and flow of the Greenland ice sheet driven by late-summer cyclonic rainfall, Nature Geoscience, 8, 8, 647–653, 10.1038/ngeo2482, 2015NatGe...8..647D, 1874/321802, 130094002, There has also been an increase in water vapor, which paradoxically increases melting by making it easier for heat to radiate downwards through moist, as opposed to dry, air.JOURNAL, Mattingly, Kyle S., Ramseyer, Craig A., Rosen, Joshua J., Mote, Thomas L., Muthyala, Rohi, 22 August 2016, Increasing water vapor transport to the Greenland Ice Sheet revealed using self-organizing maps, Geophysical Research Letters, 43, 17, 9250–9258, 10.1002/2016GL070424, 2016GeoRL..43.9250M, 132714399, File:Greenland Meltdown 08072012 12072012.jpg|350px|thumb|NASANASAAltogether, the melt zone below the snow line, where summer warmth turns snow and ice into slush and melt ponds, has been expanding at an accelerating rate since the beginning of detailed measurements in 1979. By 2002, its area was found to have increased by 16% since 1979, and the annual melting season broke all previous records. Another record was set in July 2012, when the melt zone extended to 97% of the ice sheet's cover,WEB, 23 September 2013, Greenland enters melt mode,weblink Science News, 14 August 2012, 5 August 2012,weblink" title="web.archive.org/web/20120805043523weblink">weblink live, and the ice sheet lost approximately 0.1% of its total mass (2900 Gt) during that year's melting season, with the net loss (464 Gt) setting another record.WEB, 2012, Arctic Report Card: Update for 2012; Greenland Ice Sheet,weblink 7 March 2022, 19 January 2022,weblink live, It became the first directly observed example of a "massive melting event", when the melting took place across practically the entire ice sheet surface, rather than specific areas.WEB, Barnes, Adam, 9 August 2021, 'Massive melting event' torpedoes billions of tons of ice the whole world depends on,weblink The Hill, Ice cores show that these widespread melt events were really rare prior to the 21st century, but since then, we have had several melt seasons., 24 August 2021, 25 August 2021,weblink live, That event led to the counterintuitive discovery that cloud cover, which normally results in cooler temperature due to their albedo, actually interferes with meltwater refreezing in the firn layer at night, which can increase total meltwater runoff by over 30%.JOURNAL, Van Tricht, K., Lhermitte, S., Lenaerts, J. T. M., Gorodetskaya, I. V., L'Ecuyer, T. S., Noël, B., van den Broeke, M. R., Turner, D. D., van Lipzig, N. P. M., 12 January 2016, Clouds enhance Greenland ice sheet meltwater runoff, Nature Communications, 7, 10266, 10.1038/ncomms10266, 26756470, 4729937, 2016NatCo...710266V, JOURNAL, Mikkelsen, Andreas Bech, Hubbard, Alun, MacFerrin, Mike, Box, Jason Eric, Doyle, Sam H., Fitzpatrick, Andrew, Hasholt, Bent, Bailey, Hannah L., Lindbäck, Katrin, Pettersson, Rickard, 30 May 2016, Extraordinary runoff from the Greenland ice sheet in 2012 amplified by hypsometry and depleted firn retention, The Cryosphere, en, 10, 3, 1147–1159, 10.5194/tc-10-1147-2016, 2016TCry...10.1147M, free, Thin, water-rich clouds have the worst impact, and they were the most prominent in July 2012.JOURNAL, Bennartz, R., Shupe, M. D., Turner, D. D., Walden, V. P., Steffen, K., Cox, C. J., Kulie, M. S., Miller, N. B., Pettersen, C., 3 April 2013, July 2012 Greenland melt extent enhanced by low-level liquid clouds, Nature, 83–86, 496, 7443, 10.1038/nature12002, 23552947, 2013Natur.496...83B, 4382849, (File:Greenland_river_July_2012.png|thumb|left|Rivers of meltwater flowing on 21 July 2012.)Ice cores had shown that the last time a melting event of the same magnitude as in 2012 took place was in 1889, and some glaciologists had expressed hope that 2012 was part of a 150-year cycle.WEB, Revkin, Andrew C., 25 July 2012, 'Unprecedented' Greenland Surface Melt – Every 150 Years?,weblink The New York Times, 23 December 2023, 3 January 2022,weblink live, JOURNAL, Meese, D. A., Gow, A. J., Grootes, P., Stuiver, M., Mayewski, P. A., Zielinski, G. A., Ram, M., Taylor, K. C., Waddington, E. D., 1994, The Accumulation Record from the GISP2 Core as an Indicator of Climate Change Throughout the Holocene, 266, 5191, 1680–1682, Science, 10.1126/science.266.5191.1680, 17775628, 1994Sci...266.1680M, 12059819, This was disproven in summer 2019, when a combination of high temperatures and unsuitable cloud cover led to an even larger mass melting event, which ultimately covered over {{convert|300,000|mi|km|1|abbr=on}} at its greatest extent. Predictably, 2019 set a new record of 586 Gt net mass loss.NEWS, Record melt: Greenland lost 586 billion tons of ice in 2019,weblink 6 September 2020, phys.org, en, 13 September 2020,weblink live, JOURNAL, Sasgen, Ingo, Wouters, Bert, Gardner, Alex S., King, Michalea D., Tedesco, Marco, Landerer, Felix W., Dahle, Christoph, Save, Himanshu, Fettweis, Xavier, 20 August 2020, Return to rapid ice loss in Greenland and record loss in 2019 detected by the GRACE-FO satellites, Communications Earth & Environment, 1, 1, 8, 10.1038/s43247-020-0010-1, 2020ComEE...1....8S, 221200001, en, 2662-4435, free, (File:CC-BY icon.svg|50px) Text and images are available under a Creative Commons Attribution 4.0 International License {{Webarchive|url=https://web.archive.org/web/20171016050101weblink |date=16 October 2017 }}. In July 2021, another record mass melting event occurred. At its peak, it covered {{convert|340,000 |mi|km|1|abbr=on}}, and led to daily ice losses of 88 Gt across several days.NEWS, Milman, Oliver, 30 July 2021, Greenland: enough ice melted on single day to cover Florida in two inches of water,weblink The Guardian, Greenland's vast ice sheet is undergoing a surge in melting...The deluge of melting has reached deep into Greenland's enormous icy interior, with data from the Danish government showing that the ice sheet lost 8.5bn tons of surface mass on Tuesday alone., 24 August 2021, 23 August 2021,weblink live, WEB, Turner, Ben, 2 August 2021, 'Massive melting event' strikes Greenland after record heat wave,weblink LiveScience.com, High temperatures on 28 July caused the third-largest single-day loss of ice in Greenland since 1950; the second and first biggest single-day losses occurred in 2012 and 2019. Greenland's yearly ice loss began in 1990. In recent years it has accelerated to roughly four times the levels before 2000., 24 August 2021, 25 August 2021,weblink live, High temperatures continued in August 2021, with the melt extent staying at {{convert|337,000|mi|km|1|abbr=on}}. At that time, rain fell for 13 hours at Greenland's Summit Station, located at {{convert|10,551|ft|m|1|abbr=on}} elevation.WEB, Carrington, Damian, 20 August 2021, Rain falls on peak of Greenland ice cap for first time on record,weblink The Guardian, Rain has fallen on the summit of Greenland's huge ice cap for the first time on record. Temperatures are normally well below freezing on the 3,216-metre (10,551ft) peak...Scientists at the US National Science Foundation's summit station saw rain falling throughout 14 August but had no gauges to measure the fall because the precipitation was so unexpected., 24 August 2021, 21 December 2021,weblink live, Researchers had no rain gauges to measure the rainfall, because temperatures at the summit have risen above freezing only three times since 1989 and it had never rained there before.NEWS, Patel, Kasha, 19 August 2021, Rain falls at the summit of Greenland Ice Sheet for first time on record,weblink Washington Post, Rain fell on and off for 13 hours at the station, but staff are not certain exactly how much rain fell...there are no rain gauges at the summit because no one expected it to rain at this altitude., 24 August 2021, 19 August 2021,weblink live, Due to the enormous thickness of the central Greenland ice sheet, even the most extensive melting event can only affect a small fraction of it before the start of the freezing season, and so they are considered "short-term variability" in the scientific literature. Nevertheless, their existence is important: the fact that the current models underestimate the extent and frequency of such events is considered to be one of the main reasons why the observed ice sheet decline in Greenland and Antarctica tracks the worst-case rather than the moderate scenarios of the IPCC Fifth Assessment Report's sea-level rise projections.NEWS, Sea level rise from ice sheets track worst-case climate change scenario,weblink 8 September 2020, phys.org, en, 6 June 2023,weblink live, NEWS, Ice sheet melt on track with 'worst-case climate scenario',weblink 8 September 2020, www.esa.int, en, 9 June 2023,weblink live, JOURNAL, Slater, Thomas, Hogg, Anna E., Mottram, Ruth, Ruth Mottram, 31 August 2020, Ice-sheet losses track high-end sea-level rise projections,weblink Nature Climate Change, en, 10, 10, 879–881, 2020NatCC..10..879S, 10.1038/s41558-020-0893-y, 1758-6798, 8 September 2020, 221381924, 22 January 2021,weblink" title="web.archive.org/web/20210122145652weblink">weblink live, Some of the most recent scientific projections of Greenland melt now include an extreme scenario where a massive melting event occurs every year across the studied period (i.e. every year between now and 2100 or between now and 2300), to illustrate that such a hypothetical future would greatly increase ice loss, but still wouldn't melt the entire ice sheet within the study period.Changes in albedo
(File:Greenland Albedo Change.png|thumb|Albedo change in Greenland)On the ice sheet, annual temperatures are generally substantially lower than elsewhere in Greenland: about {{convert|-20|°C|°F}} at the south dome (latitudes 63°–65°N) and {{convert|-31|°C|°F|0}} near the center of the north dome (latitude 72°N (the fourth highest "summit" of Greenland). On 22 December 1991, a temperature of {{convert|-69.6|C|F}} was recorded at an automatic weather station near the topographic summit of the Greenland Ice Sheet, making it the lowest temperature ever recorded in the Northern Hemisphere. The record went unnoticed for more than 28 years and was finally recognized in 2020.WEB, 22 September 2020, WMO verifies −69.6°C Greenland temperature as Northern hemisphere record,weblink World Meteorological Organization,weblink dead, 18 December 2023, These low temperatures are in part caused by the high albedo of the ice sheet, as its bright white surface is very effective at reflecting sunlight. Ice-albedo feedback means that as the temperatures increase, this causes more ice to melt and either reveal bare ground or even just to form darker melt ponds, both of which act to reduce albedo, which accelerates the warming and contributes to further melting. This is taken into account by the climate models, which estimate that a total loss of the ice sheet would increase global temperature by {{convert|0.13|C-change|F-change}}, while Greenland's local temperatures would increase by between {{convert|0.5|C-change|F-change}} and {{convert|3|C-change|F-change}}.JOURNAL, Wunderling, Nico, Willeit, Matteo, Donges, Jonathan F., Winkelmann, Ricarda, 27 October 2020, Global warming due to loss of large ice masses and Arctic summer sea ice, Nature Communications, en, 10, 1, 5177, 10.1038/s41467-020-18934-3, 33110092, 7591863, 2020NatCo..11.5177W, Even incomplete melting already has some impact on the ice-albedo feedback. Besides the formation of darker melt ponds, warmer temperatures enable increasing growth of algae on the ice sheet's surface. Mats of algae are darker in colour than the surface of the ice, so they absorb more thermal radiation and increase the rate of ice melt.NEWS, Shukman, David, 7 August 2010, Sea level fears as Greenland darkens,weblink BBC News,weblink 30 July 2023, In 2018, it was found that the regions covered in dust, soot, and living microbes and algae altogether grew by 12% between 2000 and 2012.NEWS, Berwyn, Bob, 19 April 2018, What's Eating Away at the Greenland Ice Sheet?,weblink Inside Climate News, 13 January 2023, 25 April 2020,weblink live, In 2020, it was demonstrated that the presence of algae, which is not accounted for by ice sheet models unlike soot and dust, had already been increasing annual melting by 10–13%.JOURNAL, Cook, Joseph M., Tedstone, Andrew J., Williamson, Christopher, McCutcheon, Jenine, Hodson, Andrew J., Dayal, Archana, Skiles, McKenzie, Hofer, Stefan, Bryant, Robert, McAree, Owen, McGonigle, Andrew, Ryan, Jonathan, Anesio, Alexandre M., Irvine-Fynn, Tristram D. L., Hubbard, Alun, Hanna, Edward, Flanner, Mark, Mayanna, Sathish, Benning, Liane G., van As, Dirk, Yallop, Marian, McQuaid, James B., Gribbin, Thomas, Tranter, Martyn, 29 January 2020, Glacier algae accelerate melt rates on the south-western Greenland Ice Sheet, The Cryosphere, en, 14, 1, 309–330, 10.5194/tc-14-309-2020, 2020TCry...14..309C, free, Additionally, as the ice sheet slowly gets lower due to melting, surface temperatures begin to increase and it becomes harder for snow to accumulate and turn to ice, in what is known as surface-elevation feedback.JOURNAL, Roe, Gerard H., 2002, Modelling Precipitation over ice sheets: an assessment using Greenland, Journal of Glaciology, en, 48, 160, 70–80, 10.3189/172756502781831593, 2002JGlac..48...70R, (File:Hopwood_2018_runoff_patterns.png|thumb|upright=0.9|Meltwater runoff has the greatest positive effect on phytoplankton when it can force nitrate-rich waters to the surface (b), which will become more difficult as the glaciers retreat (d).)Geophysical and biochemical role of Greenland's meltwater
{{See also|Marine primary production|Atlantic meridional overturning circulation}}Even in 1993, Greenland's melt resulted in 300 cubic kilometers of fresh meltwater entering the seas annually, which was substantially larger than the liquid meltwater input from the Antarctic ice sheet, and equivalent to 0.7% of freshwater entering the oceans from all of the world's rivers.JOURNAL, Peter J., Statham, Mark, Skidmore, Martyn, Tranter, 1 September 2008, Inputs of glacially derived dissolved and colloidal iron to the coastal ocean and implications for primary productivity, Global Biogeochemical Cycles, 22, 3, GB3013, 10.1029/2007GB003106, en, 2008GBioC..22.3013S, 1944-9224, free, This meltwater is not pure, and contains a range of elements - most notably iron, about half of which (around 0.3 million tons every year) is bioavailable as a nutrient for phytoplankton.JOURNAL, Bhatia, Maya P., Kujawinski, Elizabeth B., Elizabeth Kujawinski, Das, Sarah B., Breier, Crystaline F., Henderson, Paul B., Charette, Matthew A., 2013, Greenland meltwater as a significant and potentially bioavailable source of iron to the ocean, Nature Geoscience, en, 6, 4, 274–278, 10.1038/ngeo1746, 2013NatGe...6..274B, 1752-0894, Thus, meltwater from Greenland enhances ocean primary production, both in the local fjords,JOURNAL, Arendt, Kristine Engel, Nielsen, Torkel Gissel, Rysgaard, Sren, Tnnesson, Kajsa, 22 February 2010, Differences in plankton community structure along the GodthÃ¥bsfjord, from the Greenland Ice Sheet to offshore waters, Marine Ecology Progress Series, 401, 49–62, 10.3354/meps08368, 2010MEPS..401...49E, free, and further out in the Labrador Sea, where 40% of the total primary production had been attributed to nutrients from meltwater.JOURNAL, Arrigo, Kevin R., van Dijken, Gert L., Castelao, Renato M., Luo, Hao, Rennermalm, Ã…sa K., Tedesco, Marco, Mote, Thomas L., Oliver, Hilde, Yager, Patricia L., 31 May 2017, Melting glaciers stimulate large summer phytoplankton blooms in southwest Greenland waters, Geophysical Research Letters, 44, 12, 6278–6285, 10.1002/2017GL073583, 2017GeoRL..44.6278A, Since the 1950s, the acceleration of Greenland melt caused by climate change has already been increasing productivity in waters off the North Icelandic Shelf,JOURNAL, Simon, Margit H., Muschitiello, Francesco, Tisserand, Amandine A., Olsen, Are, Moros, Matthias, Perner, Kerstin, BÃ¥rdsnes, Siv Tone, Dokken, Trond M., Jansen, Eystein, 29 September 2020, A multi-decadal record of oceanographic changes of the past ~165 years (1850-2015 AD) from Northwest of Iceland, PLOS ONE, 15, 9, e0239373, 10.1371/journal.pone.0239373, 32991577, 7523958, 2020PLoSO..1539373S, free, while productivity in Greenland's fjords is also higher than it had been at any point in the historical record, which spans from late 19th century to present.JOURNAL, Oksman, Mimmi, Kvorning, Anna Bang, Larsen, Signe Hillerup, Kjeldsen, Kristian Kjellerup, Mankoff, Kenneth David, Colgan, William, Andersen, Thorbjørn Joest, Nørgaard-Pedersen, Niels, Seidenkrantz, Marit-Solveig, Mikkelsen, Naja, Ribeiro, Sofia, 24 June 2022, Impact of freshwater runoff from the southwest Greenland Ice Sheet on fjord productivity since the late 19th century, The Cryosphere, 16, 6, 2471–2491, 10.5194/tc-16-2471-2022, 2022TCry...16.2471O, free, Some research suggests that Greenland's meltwater mainly benefits marine productivity not by adding carbon and iron, but through stirring up lower water layers that are rich in nitrates and thus bringing more of those nutrients to phytoplankton on the surface. As the outlet glaciers retreat inland, the meltwater will be less able to impact the lower layers, which implies that benefit from the meltwater will diminish even as its volume grows.JOURNAL, Hopwood, M. J., Carroll, D., Browning, T. J., Meire, L., Mortensen, J., Krisch, S., Achterberg, E. P., 14 August 2018, Non-linear response of summertime marine productivity to increased meltwater discharge around Greenland, Nature Communications, 9, 1, 3256, 10.1038/s41467-018-05488-8, 30108210, 6092443, 2018NatCo...9.3256H, (File:Christiansen_2018_GrIS_meltwater_flow.png|thumb|left|A photo of a meltwater flow at Russell Glacier. Water emerging through the small crack comes from the melting of underground ice and is particularly rich in carbon.)The impact of meltwater from Greenland goes beyond nutrient transport. For instance, meltwater also contains dissolved organic carbon, which comes from the microbial activity on the ice sheet's surface, and, to a lesser extent, from the remnants of ancient soil and vegetation beneath the ice.JOURNAL, Bhatia, Maya P., Das, Sarah B., Longnecker, Krista, Charette, Matthew A., Kujawinski, Elizabeth B., Elizabeth Kujawinski, 1 July 2010, Molecular characterization of dissolved organic matter associated with the Greenland ice sheet, Geochimica et Cosmochimica Acta, en, 74, 13, 3768–3784, 10.1016/j.gca.2010.03.035, 2010GeCoA..74.3768B, 1912/3729, 0016-7037, free, There is about 0.5-27 billion tonnes of pure carbon underneath the entire ice sheet, and much less within it.JOURNAL, Wadham, J. L., Hawkings, J. R., Tarasov, L., Gregoire, L. J., Spencer, R. G. M., Gutjahr, M., Ridgwell, A., Kohfeld, K. E., Ice sheets matter for the global carbon cycle, Nature Communications, 15 August 2019, 10, 3567, 10.1038/s41467-019-11394-4, 31417076, 2019NatCo..10.3567W, This is much less than the 1400–1650 billion tonnes contained within the Arctic permafrost,JOURNAL, Tarnocai, C., Canadell, J.G., Schuur, E.A.G., Kuhry, P., Mazhitova, G., Zimov, S., June 2009, Soil organic carbon pools in the northern circumpolar permafrost region, Global Biogeochemical Cycles, 23, 2, GB2023, 2009GBioC..23.2023T, 10.1029/2008gb003327, free, or the annual anthropogenic emissions of around 40 billion tonnes of {{CO2}}.{{rp|1237}}) Yet, the release of this carbon through meltwater can still act as a climate change feedback if it increases overall carbon dioxide emissions.JOURNAL, Ryu, Jong-Sik, Jacobson, Andrew D., 6 August 2012, CO2 evasion from the Greenland Ice Sheet: A new carbon-climate feedback, Chemical Geology, en, 320, 13, 80–95, 10.1016/j.chemgeo.2012.05.024, 2012ChGeo.320...80R, There is one known area, at Russell Glacier, where meltwater carbon is released into the atmosphere as methane, which has a much larger global warming potential than carbon dioxide:JOURNAL, Christiansen, Jesper Riis, Jørgensen, Christian Juncher, 9 November 2018, First observation of direct methane emission to the atmosphere from the subglacial domain of the Greenland Ice Sheet, Scientific Reports, 8, 1, 16623, 10.1038/s41598-018-35054-7, 30413774, 6226494, 2018NatSR...816623C, however, it also harbours large numbers of methanotrophic bacteria, which limit those emissions.JOURNAL, Dieser, Markus, Broemsen, Erik L J E, Cameron, Karen A, King, Gary M, Achberger, Amanda, Choquette, Kyla, Hagedorn, Birgit, Sletten, Ron, Junge, Karen, Christner, Brent C, 17 April 2014, Molecular and biogeochemical evidence for methane cycling beneath the western margin of the Greenland Ice Sheet, The ISME Journal, 8, 11, 2305–2316, 10.1038/ismej.2014.59, 24739624, 4992074, 2014ISMEJ...8.2305D, JOURNAL, ZnamÃnko, MatÄ›j, Falteisek, Lukáš, Vrbická, Kristýna, KlÃmová, Petra, Christiansen, Jesper R., Jørgensen, Christian J., Stibal, Marek, Methylotrophic Communities Associated with a Greenland Ice Sheet Methane Release Hotspot, Microbial Ecology, 16 October 2023, 86, 4, 3057–3067, 10.1007/s00248-023-02302-x, 37843656, 10640400, 2023MicEc..86.3057Z, In 2021, research claimed that there must be mineral deposits of mercury (a highly toxic heavy metal) beneath the southwestern ice sheet, because of the exceptional concentrations in meltwater entering the local fjords. If confirmed, these concentrations would have equalled up to 10% of mercury in all of the world's rivers.JOURNAL, Hawkings, Jon R., Linhoff, Benjamin S., Wadham, Jemma L., Stibal, Marek, Lamborg, Carl H., Carling, Gregory T., Lamarche-Gagnon, Guillaume, Kohler, Tyler J., Ward, Rachael, Hendry, Katharine R., Falteisek, Lukáš, Kellerman, Anne M., Cameron, Karen A., Hatton, Jade E., Tingey, Sarah, Holt, Amy D., VinÅ¡ová, Petra, Hofer, Stefan, BulÃnová, Marie, VÄ›trovský, Tomáš, Meire, Lorenz, Spencer, Robert G. M., 24 May 2021, Large subglacial source of mercury from the southwestern margin of the Greenland Ice Sheet, Nature Geoscience, 14, 5, 496–502, 10.1038/s41561-021-00753-w, 2021NatGe..14..496H, WEB, Walther, Kelcie, As the Greenland Ice Sheet Retreats, Mercury is Being Released From the Bedrock Below, 15 July 2021,weblink Columbia Climate School, 23 December 2023, 23 December 2023,weblink live, In 2024, a follow-up study found only "very low" concentrations in meltwater from 21 locations. It concluded that the 2021 findings were best explained by accidental sample contamination with mercury(II) chloride, used by the first team of researchers as a reagent.JOURNAL, Jørgensen, Christian Juncher, Søndergaard, Jens, Larsen, Martin Mørk, Kjeldsen, Kristian Kjellerup, Rosa, Diogo, Sapper, Sarah Elise, Heimbürger-Boavida, Lars-Eric, Kohler, Stephen G., Wang, Feiyue, Gao, Zhiyuan, Armstrong, Debbie, Albers, Christian Nyrop, 26 January 2024, Large mercury release from the Greenland Ice Sheet invalidated, Science Advances, 10, 4, EN, 10.1126/sciadv.adi7760, However, there is still a risk of toxic waste being released from Camp Century, formerly a United States military site built to carry nuclear weapons for the Project Iceworm. The project was cancelled, but the site was never cleaned up, and it now threatens to pollute the meltwater with nuclear waste, 20,000 liters of chemical waste and 24 million liters of untreated sewage as the melt progresses.JOURNAL, Colgan, William, Machguth, Horst, MacFerrin, Mike, Colgan, Jeff D., van As, Dirk, MacGregor, Joseph A., 4 August 2016, The abandoned ice sheet base at Camp Century, Greenland, in a warming climate, Geophysical Research Letters, 43, 15, 8091–8096, 10.1002/2016GL069688, 2016GeoRL..43.8091C, WEB, Rosen, Julia, 4 August 2016, Mysterious, ice-buried Cold War military base may be unearthed by climate change,weblink Science Magazine, 23 December 2023, 15 January 2024,weblink live, File:16-008-NASA-2015RecordWarmGlobalYearSince1880-20160120.png|thumb|upright=1.25|The cold blob visible on NASA's global mean temperatures for 2015, the warmest year on record up to 2015 (since 1880). Colors indicate temperature evolution (NASA/NOAA; 20 January 2016).WEB, Brown, Dwayne, Cabbage, Michael, McCarthy, Leslie, Norton, Karen, NASA, NOAA Analyses Reveal Record-Shattering Global Warm Temperatures in 2015,weblink 20 January 2016, NASANASAFinally, increased quantities of fresh meltwater can affect ocean circulation. Some scientists have connected this increased discharge from Greenland with the so-called cold blob in the North Atlantic, which is in turn connected to Atlantic meridional overturning circulation, or AMOC, and its apparent slowdown.JOURNAL, Nature, Exceptional twentieth-century slowdown in Atlantic Ocean overturning circulation, Stefan Rahmstorf, Jason E. Box, Georg Feulner, Michael E. Mann, Alexander Robinson, Scott Rutherford, Erik J. Schaffernicht, 10.1038/nclimate2554, 5, 5, 475–480, 2015NatCC...5..475R, May 2015,weblink 23 September 2019, 9 September 2016,weblink" title="web.archive.org/web/20160909080138weblink">weblink live, WEB, 22 January 2016, Melting Greenland ice sheet may affect global ocean circulation, future climate,weblink Phys.org, 25 January 2016, 19 August 2023,weblink live, JOURNAL, Yang, Qian, Dixon, Timothy H., Myers, Paul G., Bonin, Jennifer, Chambers, Don, van den Broeke, M. R., Ribergaard, Mads H., Mortensen, John, Recent increases in Arctic freshwater flux affects Labrador Sea convection and Atlantic overturning circulation, Nature Communications, 22 January 2016, 7, 10525, 10.1038/ncomms10525, 26796579, 4736158, 2016NatCo...710525Y, JOURNAL, Greene, Chad A., Gardner, Alex S., Wood, Michael, Cuzzone, Joshua K., 2024-01-18, Ubiquitous acceleration in Greenland Ice Sheet calving from 1985 to 2022,weblink Nature, en, 625, 7995, 523–528, 10.1038/s41586-023-06863-2, 0028-0836, 18 January 2024, 18 January 2024,weblink live, In 2016, a study attempted to improve forecasts of future AMOC changes by incorporating better simulation of Greenland trends into projections from eight state-of-the-art climate models. That research found that by 2090–2100, the AMOC would weaken by around 18% (with a range of potential weakening between 3% and 34%) under Representative Concentration Pathway 4.5, which is most akin to the current trajectory, while it would weaken by 37% (with a range between 15% and 65%) under Representative Concentration Pathway 8.5, which assumes continually increasing emissions. If the two scenarios are extended past 2100, then the AMOC ultimately stabilizes under RCP 4.5, but it continues to decline under RCP 8.5: the average decline by 2290–2300 is 74%, and there is 44% likelihood of an outright collapse in that scenario, with a wide range of adverse effects.JOURNAL, Bakker, P, Schmittner, A, Lenaerts, JT, Abe-Ouchi, A, Bi, D, van den Broeke, MR, Chan, WL, Hu, A, Beadling, RL, Marsland, SJ, Mernild, SH, Saenko, OA, Swingedouw, D, Sullivan, A, Yin, J, 11 November 2016, Fate of the Atlantic Meridional Overturning Circulation: Strong decline under continued warming and Greenland melting, Geophysical Research Letters, 43, 23, 12,252–12,260, 10.1002/2016GL070457, 2016GeoRL..4312252B, 10150/622754, 133069692, free,Future ice loss
Near-term
{{multiple image| total_width = 450| width1 =| footer =| image1 = Beckmann 2023 Greenland 2300 RCP85.png| alt1 = Greenland ice sheet's impact on sea level rise under the worst-case warming scenario, by 2300.Long-term
(File:Mean regional trends in ice thickness and front position.webp|thumb|These graphs indicate the switch of peripheral glaciers to a dynamic state of sustained mass loss after the widespread retreat in 2000–2005, making their disappearance inevitable.)(File:Beckmann 2023 Greenland 2300 RCP85 extent.png|thumb|2023 projections of how much the Greenland ice sheet may shrink from its present extent by the year 2300 under the worst possible climate change scenario (upper half) and of how much faster its remaining ice will be flowing in that case (lower half)JOURNAL, Beckmann, Johanna, Winkelmann, Ricarda, 27 July 2023, Effects of extreme melt events on ice flow and sea level rise of the Greenland Ice Sheet, The Cryosphere, en, 17, 7, 3083–3099, 10.5194/tc-17-3083-2023, 2023TCry...17.3083B, free, )Notably, the ice sheet's massive size simultaneously makes it insensitive to temperature changes in the short run, yet also commits it to enormous changes down the line, as demonstrated by paleoclimate evidence. Polar amplification causes the Arctic, including Greenland, to warm three to four times more than the global average:WEB, 2021-05-20, Arctic warming three times faster than the planet, report warns,weblink Phys.org, en, 6 October 2022, 26 July 2023,weblink live, JOURNAL, Rantanen, Mika, Karpechko, Alexey Yu, Lipponen, Antti, Nordling, Kalle, Hyvärinen, Otto, Ruosteenoja, Kimmo, Vihma, Timo, Laaksonen, Ari, 11 August 2022, The Arctic has warmed nearly four times faster than the globe since 1979, Communications Earth & Environment, en, 3, 1, 168, 10.1038/s43247-022-00498-3, 2022ComEE...3..168R, 251498876, 2662-4435, free, WEB, 2021-12-14, The Arctic is warming four times faster than the rest of the world,weblink en, 6 October 2022, 8 November 2023,weblink live, thus, while a period like the Eemian interglacial 130,000–115,000 years ago was not much warmer than today globally, the ice sheet was {{convert|8|C-change|F-change}} warmer, and its northwest part was 130 ± 300 meters lower than it is at present.JOURNAL, Eemian interglacial reconstructed from a Greenland folded ice core, Nature, 493, 7433, 489–494, 24 January 2013, 10.1038/nature11789, 23344358, 2013Natur.493..489N, NEEM community members, Dahl-Jensen, D., Albert, M. R., Aldahan, A., Azuma, N., Balslev-Clausen, D., Baumgartner, M., Berggren, A. -M., Bigler, M., Binder, T., Blunier, T., Bourgeois, J. C., Brook, E. J., Buchardt, S. L., Buizert, C., Capron, E., Chappellaz, J., Chung, J., Clausen, H. B., Cvijanovic, I., Davies, S. M., Ditlevsen, P., Eicher, O., Fischer, H., Fisher, D. A., Fleet, L. G., Gfeller, G., Gkinis, V., Gogineni, S., Goto-Azuma, K., 4420908, 29,weblink 25 September 2019, 29 September 2019,weblink" title="web.archive.org/web/20190929001352weblink">weblink live, JOURNAL, Landais, Amaelle, Masson-Delmotte, Valérie, Capron, Emilie, Langebroek, Petra M., Bakker, Pepijn, Stone, Emma J., Merz, Niklaus, Raible, Christoph C., Fischer, Hubertus, Orsi, Anaïs, Prié, Frédéric, Vinther, Bo, Dahl-Jensen, Dorthe, How warm was Greenland during the last interglacial period?, 29 September 2016, Climate of the Past, 12, 3, 369–381, 10.5194/cp-12-1933-2016, 2016CliPa..12.1933L, free, Some estimates suggest that the most vulnerable and fastest-receding parts of the ice sheet have already passed "a point of no return" around 1997, and will be committed to disappearance even if the temperature stops rising.NEWS, 13 August 2020, Warming Greenland ice sheet passes point of no return,weblink 15 August 2020, Ohio State University, 5 September 2023,weblink live, JOURNAL, King, Michalea D., Howat, Ian M., Candela, Salvatore G., Noh, Myoung J., Jeong, Seongsu, Noël, Brice P. Y., van den Broeke, Michiel R., Wouters, Bert, Negrete, Adelaide, 13 August 2020, Dynamic ice loss from the Greenland Ice Sheet driven by sustained glacier retreat, Communications Earth & Environment, en, 1, 1, 1–7, 10.1038/s43247-020-0001-2, 2020ComEE...1....1K, 2662-4435, free, (File:CC-BY_icon.svg|50x50px) Text and images are available under a (creativecommons:by/4.0/|Creative Commons Attribution 4.0 International License).JOURNAL, Noël, B., van de Berg, W. J, Lhermitte, S., Wouters, B., Machguth, H., Howat, I., Citterio, M., Moholdt, G., Lenaerts, J. T. M., van den Broeke, M. R., 31 March 2017, A tipping point in refreezing accelerates mass loss of Greenland's glaciers and ice caps, Nature Communications, 8, 1, 14730, 10.1038/ncomms14730, 28361871, 5380968, 2017NatCo...814730N, A 2022 paper found that the 2000–2019 climate would already result in the loss of ~3.3% volume of the entire ice sheet in the future, committing it to an eventual {{cvt|27|cm|in|frac=2}} of SLR, independent of any future temperature change. They have additionally estimated that if the then-record melting seen on the ice sheet in 2012 were to become its new normal, then the ice sheet would be committed to around {{cvt|78|cm|in|frac=2}} SLR.JOURNAL, Box, Jason E., Hubbard, Alun, Bahr, David B., Colgan, William T., Fettweis, Xavier, Mankoff, Kenneth D., Wehrlé, Adrien, Noël, Brice, van den Broeke, Michiel R., Wouters, Bert, Bjørk, Anders A., Fausto, Robert S., Greenland ice sheet climate disequilibrium and committed sea-level rise, Nature Climate Change, 29 August 2022, 12, 9, 808–813, 10.1038/s41558-022-01441-2, 2022NatCC..12..808B, 251912711, free, Another paper suggested that paleoclimate evidence from 400,000 years ago is consistent with ice losses from Greenland equivalent to at least {{cvt|1.4|m|ft|frac=2}} of sea level rise in a climate with temperatures close to {{convert|1.5|C-change|F-change}}, which are now inevitable at least in the near future.JOURNAL, Christ, Andrew J., Rittenour, Tammy M., Bierman, Paul R., Keisling, Benjamin A., Knutz, Paul C., Thomsen, Tonny B., Keulen, Nynke, Fosdick, Julie C., Hemming, Sidney R., Tison, Jean-Louis, Blard, Pierre-Henri, Steffensen, Jørgen P., Caffee, Marc W., Corbett, Lee B., Dahl-Jensen, Dorthe, Dethier, David P., Hidy, Alan J., Perdrial, Nicolas, Peteet, Dorothy M., Steig, Eric J., Thomas, Elizabeth K., 20 July 2023, Deglaciation of northwestern Greenland during Marine Isotope Stage 11, Science, 381, 6655, 330–335, 10.1126/science.ade4248, 37471537, 2023Sci...381..330C, 259985096, It is also known that at a certain level of global warming, effectively the entirety of the Greenland Ice Sheet will eventually melt. Its volume was initially estimated to amount to ~{{convert|2850000|km3|cumi|-3|abbr=on}}, which would increase the global sea levels by {{convert|7.2|m|ft|0|abbr=on}}, but later estimates increased its size to ~{{convert|2900000|km3|cumi|-3|abbr=on}}, leading to ~{{convert|7.4|m|ft|0|abbr=on}} of sea level rise.Thresholds for total ice sheet loss
In 2006, it was estimated that the ice sheet is most likely to be committed to disappearance at {{convert|3.1|C-change|F-change}}, with a plausible range between {{convert|1.9|C-change|F-change}} and {{convert|5.1|C-change|F-change}}.JOURNAL, Gregory, J. M, Huybrechts, P, 25 May 2006, Ice-sheet contributions to future sea-level change, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences., en, 364, 1844, 1709–1732, 10.1098/rsta.2006.1796, 16782607, 2006RSPTA.364.1709G, 447843,weblink 13 December 2023, 10 December 2023,weblink live, However, these estimates were drastically reduced in 2012, with the suggestion that the threshold may lie anywhere between {{convert|0.8|C-change|F-change}} and {{convert|3.2|C-change|F-change}}, with {{convert|1.6|C-change|F-change}} the most plausible global temperature for the ice sheet's disappearance.JOURNAL, Robinson, Alexander, Calov, Reinhard, Ganopolski, Andrey, 11 March 2012, Multistability and critical thresholds of the Greenland ice sheet, Nature Climate Change, en, 2, 6, 429–432, 10.1038/nclimate1449, 2012NatCC...2..429R, That lowered temperature range had been widely used in the subsequent literature,JOURNAL, Nordhaus, William, 4 June 2019, Economics of the disintegration of the Greenland ice sheet, Proceedings of the National Academy of Sciences, en, 116, 25, 12261–12269, 10.1073/pnas.1814990116, 31164425, 7056935, 2019PNAS..11612261N, free, and in the year 2015, prominent NASA glaciologist Eric Rignot claimed that "even the most conservative people in our community" will agree that "Greenland’s ice is gone" after {{convert|2|C-change|F-change}} or {{convert|3|C-change|F-change}} of global warming.WEB, Gertner, Jon, 12 November 2015, The Secrets in Greenland's Ice Sheet,weblink The New York Times,weblink 30 July 2023, In 2022, a major review of scientific literature on tipping points in the climate system barely modified these values: it suggested that the threshold would be most likely be at {{convert|1.5|C-change|F-change}}, with the upper level at {{convert|3|C-change|F-change}} and the worst-case threshold of {{convert|0.8|C-change|F-change}} remained unchanged.JOURNAL, Armstrong McKay, David, Abrams, Jesse, Winkelmann, Ricarda, Sakschewski, Boris, Loriani, Sina, Fetzer, Ingo, Cornell, Sarah, Rockström, Johan, Staal, Arie, Lenton, Timothy, 9 September 2022, Exceeding 1.5°C global warming could trigger multiple climate tipping points,weblink Science, en, 377, 6611, eabn7950, 10.1126/science.abn7950, 36074831, 10871/131584, 252161375, 0036-8075, free, 22 October 2022, 14 November 2022,weblink live, WEB, Armstrong McKay, David, 9 September 2022, Exceeding 1.5°C global warming could trigger multiple climate tipping points – paper explainer,weblink 2 October 2022, climatetippingpoints.info, en, 18 July 2023,weblink live, At the same time, it noted that the fastest plausible timeline for the ice sheet disintegration is 1000 years, which is based on research assuming the worst-case scenario of global temperatures exceeding {{convert|10|C-change|F-change}} by 2500, while its ice loss otherwise takes place over around 10,000 years after the threshold is crossed; the longest possible estimate is 15,000 years.File:Höning 2023 GIS thresholds.jpg|thumb|Potential equilibrium states of the ice sheet in response to different equilibrium carbon dioxide concentrations in 1.8|m|ft|0|abbr=on}} and {{convert|2.4|m|ft|0|abbr=on}} of sea level rise, while the fourth state is equivalent to {{convert|6.9|m|ft|0|abbr=on}}.Model-based projections published in the year 2023 had indicated that the Greenland ice sheet could be a little more stable than suggested by the earlier estimates. One paper found that the threshold for ice sheet disintegration is more likely to lie between {{convert|1.7|C-change|F-change}} and {{convert|2.3|C-change|F-change}}. It also indicated that the ice sheet could still be saved, and its sustained collapse averted, if the warming were reduced to below {{convert|1.5|C-change|F-change}}, up to a few centuries after the threshold was first breached. However, while that would avert the loss of the entire ice sheet, it would increase the overall sea level rise by up to several meters, as opposed to a scenario where the warming threshold was not breached in the first place.Another paper using a more complex ice sheet model has found that since the warming passed {{convert|0.6|C-change|F-change}} degrees, ~{{cvt|26|cm|in|frac=2}} of sea level rise became inevitable, closely matching the estimate derived from direct observation in 2022. However, it had also found that {{convert|1.6|C-change|F-change}} would likely only commit the ice sheet to {{convert|2.4|m|ft|0|abbr=on}} of long-term sea level rise, while near-complete melting of {{convert|6.9|m|ft|0|abbr=on}} worth of sea level rise would occur if the temperatures consistently stay above {{convert|2|C-change|F-change}}. The paper also suggested that ice losses from Greenland may be reversed by reducing temperature to {{convert|0.6|C-change|F-change}} or lower, up until the entirety of South Greenland ice melts, which would cause {{convert|1.8|m|ft|0|abbr=on}} of sea level rise and prevent any regrowth unless {{CO2}} concentrations is reduced to 300 ppm. If the entire ice sheet were to melt, it would not begin to regrow until temperatures fall to below the preindustrial levels.(File:Greenland-ice sheet hg.jpg|thumb|upright=0.7|Aerial view of the ice sheet's eastern coast.)See also
- List of glaciers in Greenland
- Glaciation
- Climate change in the Arctic
- Sea level rise
- Arctic sea ice decline
- Isostatic depression – induced by Greenland ice sheet
References
{{reflist|3}}External links
{{Commons category}}- Geological Survey of Denmark and Greenland (GEUS) {{Webarchive|url=https://web.archive.org/web/20090926071239weblink |date=26 September 2009 }}
- Greenland Ice Cap, 1942–1944 Report at Dartmouth College Library
- Greenland Ice Cap literary Survey/Bibliography 1953 at Dartmouth College Library
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