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'''Thwaites Glacier''' is an unusually broad and vast [[Antarctic]] [[glacier]] located east of [[Mount Murphy]], on the [[Walgreen Coast]] of [[Marie Byrd Land]]. It was initially sighted by polar researchers in 1940, mapped in 1959–1966 and officially named in 1967, after the late American [[glaciologist]] Fredrik T. Thwaites.<ref name="ThwaitesFacts" /><ref name="gnisThwaitesGlacier" /> This glacier flows into [[Pine Island Bay]], part of the [[Amundsen Sea]], at surface speeds which exceed {{convert|2|km}} per year near its [[grounding line]]. Its fastest-flowing grounded ice is centered between {{convert|50 and 100|km}} east of Mount Murphy.<ref name="ThwaitesFacts" />
Thwaites Glacier is closely monitored for its potential to [[Sea level rise|elevate sea levels]].<ref>{{cite magazine|url=https://www.wired.com/story/antarctica-thwaites-glacier-breaking-point |title=The Race to Understand Antarctica's Most Terrifying Glacier |author=Jon Gertner |date=10 December 2018 |magazine=Wired |access-date=15 December 2018}}</ref> Since the 1980s, Thwaites and [[Pine Island Glacier]] have been described as part of the "weak underbelly" of the [[West Antarctic Ice Sheet]], in part because they seem vulnerable to irreversible retreat and collapse even under relatively little warming, yet also because if they go, the entire ice sheet is likely to eventually follow.<ref name="VoosenSciMag" /><ref name="Hughes1981" /><ref name="Feldmann2015" /> This hypothesis is based on both theoretical studies of the stability of marine ice sheets and observations of large changes on these two glaciers. In recent years, the flow of both of these glaciers has accelerated, their surfaces have lowered, and their grounding lines have retreated.<ref name="NASAUnderbelly" /> They are believed very likely to eventually collapse even without any further warming.<ref name="Joughin2014" /><ref name="Wolovick2018" /><ref name="Holland2023" /> The outsized danger Thwaites poses has led to some reporters nicknaming it the '''Doomsday Glacier''',<ref name="GoodellRS" /><ref name="RowlattBBC" /><ref name="PappasLiveSci" /><ref name="BakerSciAm" /><ref name="FritzCNN" /> although this nickname is controversial among scientists.<ref name="RyanCNET" />
The [[Thwaites Ice Shelf]], a floating ice shelf which braces and restrains the eastern portion of Thwaites Glacier, is likely to collapse within a decade from 2021.<ref name="VoosenSciMag" /><ref name="CIRES" /><ref name="AmosBBC">{{Cite news|last=Amos|first=Jonathan|date=13 December 2021 |title=Thwaites: Antarctic glacier heading for dramatic change|language=en-GB|work=BBC News|url=https://www.bbc.com/news/science-environment-59644494|access-date=16 December 2021}}</ref><ref name="KaplanWaPo" /> The glacier's outflow is likely to accelerate substantially after the shelf's disappearance; while the outflow currently accounts for 4% of global [[sea level rise]], it would become equivalent to 5% in the short term, before accelerating further. The amount of ice from Thwaites likely to be lost in this century will only amount to several cm of sea level rise,<ref name="ThwaitesFacts" /><ref name="Yu2018" /> but its breakdown will rapidly accelerate in the 22nd and 23rd centuries,<ref name="Wolovick2018" /> and the volume of ice contained in the entire glacier
==Location and features==
[[File:Thwaites_Ice_Tongue_from_Sentinel-2_pillars.jpg|thumb|Photo taken in 2019 by the [[Sentinel-2]] satellite of the [[European Space Agency]]. It shows the glacier, the ice shelf on its eastern side, and the remains of the ice tongue in the west, now reduced to a "mélange" of icebergs which is much less effective at supporting the glacier and preventing calving events.<ref name="ESA2023" />]]
Thwaites Glacier is located at the northern edge of the [[West Antarctic Ice Sheet]], next to [[Pine Island Glacier]]. Both glaciers continually shed ice from their [[grounding line]] into Pine Island Bay, which is part of the [[Amundsen Sea]]. The fastest flows of ice occur between {{convert|50 and 100|km}} east of Mount Murphy, where they can exceed {{convert|2|km}} per year.<ref name="ThwaitesFacts" /> At {{cvt|120|km}} in width,<ref name="Gramling" /> Thwaites Glacier is the single widest glacier in the world, and it has an area of {{cvt|192,000|sqkm|sqmi|abbr=off}}. This makes it larger than the American state of [[Florida]] ({{cvt|170,000|sqkm|sqmi|abbr=off}}), and a little smaller than the entire island of [[Great Britain]] ({{convert|209,000|sqkm|sqmi|abbr=off}}). It is also very tall, with ice thickness from bedrock to surface measuring between {{convert|800|m|ft|frac=2}} and {{convert|1200|m|ft|frac=2}}.<ref name="ThwaitesFacts">{{cite web |title=Thwaites Glacier Facts |publisher=The International Thwaites Glacier Collaboration |url=https://thwaitesglacier.org/about/facts |access-date=8 July 2023 }}</ref> Due to this immense size, enormous mass is shed when the repeated [[ice calving]] events occur at the glacier's marine terminus – the point where grounding line is in contact with water. The largest events, on the glacier's more vulnerable western side, are [[seismology|seismically detectable]] at ranges up to {{cvt|1,600|km}}.<ref>{{cite journal | last1= Winberry | first1=J. P. | first2=A. D. | last2=Huerta | first3=S.| last3= Anandakrishnan| first4= R. | last4=Aster | first5=A. | last5=Nyblade | first6= D. A. | last6= Wiens |display-authors= 3| year= 2020 | title= Glacial Earthquakes and Precursory Seismicity Associated with Thwaites‐Glacier Calving | journal= Geophysical Research Letters | volume=47 | issue=3 |doi=10.1029/2019gl086178| bibcode=2020GeoRL..4786178W | s2cid=212851050 | doi-access=free }}</ref>
The third Antarctic expedition of [[Richard E. Byrd]] in 1940 is believed to be first official sighting of the coastline of Thwaites. Detailed mapping of the glacier's surface took place between 1959 and 1966.<ref name="ThwaitesFacts" /> In 1967, it was officially named by the [[Advisory Committee on Antarctic Names]] after Fredrik T. Thwaites (1883–1961), who had never personally visited the glacier, but was a renowned [[Glaciology|glacial geologist]], [[Geomorphology|geomorphologist]] and [[professor emeritus]] at the [[University of Wisconsin–Madison]].<ref name="gnisThwaitesGlacier">{{cite web |title = Thwaites Glacier |work=[[Geographic Names Information System]] |publisher=[[United States Geological Survey]] |url={{gnis3|type=antarid|15283}} |access-date = 23 October 2011
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Between 1992 and 2017, Thwaites Glacier retreated at between {{cvt|0.3|km}} and {{cvt|0.8|km}} annually, depending on the sector,<ref name="Milillo2019">{{Cite journal|last1=Milillo |first1=P.|last2=Rignot |first2=E. |last3=Rizzoli |first3=P. |last4=Scheuchl |first4=B.|last5=Mouginot |first5=J. |last6=Bueso-Bello |first6=J. |last7=Prats-Iraola |first7=P. |date=30 January 2019 |title=Heterogeneous retreat and ice melt of Thwaites Glacier, West Antarctica | url=https://www.science.org/doi/10.1126/science.abj3266| journal=Science Advances |volume=5 |issue=1 |pages=eaau3433 |doi=10.1126/sciadv.aau3433 |pmid=30729155 |pmc=6353628 |bibcode=2019SciA....5.3433M |s2cid=59607481 }}</ref> and experienced a net loss of over 600 billion tons of ice as the result.<ref>{{cite news |last1=Patel |first1=Jugal K. |title=In Antarctica, Two Crucial Glaciers Accelerate Toward the Sea |url=https://www.nytimes.com/interactive/2017/10/26/climate/antarctica-glaciers-melt.html |access-date=4 February 2019 |work=The New York Times |date=26 October 2017}}</ref> This loss had caused about 4% of the global [[sea level rise]] over that period.<ref name="CIRES" /><ref name="JacobsNYT" /> If all of the ice contained within Thwaites Glacier melted (which is expected to take place over multiple centuries),<ref name="VoosenSciMag" /><ref name="Joughin2014" /><ref name="Schwans2023" /> it would be sufficient to raise the global sea level by {{cvt|65|cm|frac=2}}.<ref name="ITGCDrill" /> This is more than twice as large as all of the sea level rise which occurred between 1901 and 2018 (estimated at {{cvt|15|–|25|cm|in|frac=2}}),<ref name="IPCC_2021_WGI" />{{rp|5}} though only a fraction of the total sea level rise which would be seen in the future, particularly under high warming.<ref name="IPCC_2021_WGI">IPCC, 2021: [https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_SPM.pdf Summary for Policymakers]. In: [https://www.ipcc.ch/report/ar6/wg1/ Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change] [Masson-Delmotte, V., P. Zhai, A. Pirani, S.L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M.I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T.K. Maycock, T. Waterfield, O. Yelekçi, R. Yu, and B. Zhou (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, US, pp. 3−32, doi:10.1017/9781009157896.001.</ref>{{rp|21}}
[[File:Dotto_2022_PIB_meltwater.png|thumb|left|Distribution of meltwater hotspots caused by ice losses in [[Pine Island Bay]], the location of both Thwaites (TEIS refers to Thwaites Eastern Ice Shelf) and Pine Island Glaciers.<ref name="Dotto2022" />]]
Fears of the entire [[West Antarctic Ice Sheet]] (WAIS) being prone to geologically rapid (centuries or even decades) collapse in response to accelerated warming from [[greenhouse gas emissions]] have been present since the seminal 1968 paper by [[glaciologist]] J.H. Mercer.<ref name="Mercer1968">{{cite web |last1=Mercer |first1=J. H. |title=ANTARCTIC ICE AND SANGAMON SEA LEVEL |url=https://iahs.info/uploads/dms/079020.pdf |publisher=International Association Of Hydrological Sciences |access-date=8 July 2023 }}</ref><ref name="NASAUnderbelly" /> These concerns were reiterated by Mercer's 1978 follow-up study and by another study in 1973.<ref>{{cite journal |last1=Mercer |first1=J. H. |date=1 January 1978 |title=West Antarctic ice sheet and CO2 greenhouse effect: a threat of disaster |journal=Nature |volume=271 |issue=5643 |pages=321–325 |bibcode=1978Natur.271..321M |doi=10.1038/271321a0 |s2cid=4149290}}</ref><ref name="NASAUnderbelly" /> In 1981, scientists also advanced the theory that "the weak underbelly" of the WAIS lay in the [[Amundsen Sea]] region, with the collapse of Thwaites and [[Pine Island Glacier]]s serving as the trigger for the subsequent collapse of the entire ice sheet.<ref name="Hughes1981">{{cite journal | doi-access=free |doi=10.3189/S002214300001159X |title=The weak underbelly of the West Antarctic ice sheet |year=1981 |last1=Hughes |first1=T. J. |journal=Journal of Glaciology |volume=27 |issue=97 |pages=518–525 }}</ref><ref name="NASAUnderbelly">{{cite web |title=The "Unstable" West Antarctic Ice Sheet: A Primer |date=12 May 2014 |publisher=[[NASA]] |url=https://www.nasa.gov/jpl/news/antarctic-ice-sheet-20140512/ |access-date = 8 July 2023 }}</ref> This theory was informed by radar measurement data from research flights over West Antarctica in the 1960s and 1970s, which had revealed that in [[Pine Island Bay]], the glacier bed slopes downwards at an angle, and lies well below the [[sea level]]. This [[topography]], in addition to proximity to powerful [[ocean current]]s, makes both glaciers particularly vulnerable to increases in [[ocean heat content]].<ref name="NASAUnderbelly" /><ref name="Dotto2022">{{Cite journal|last1=Dotto |first1=Tiago S. |last2=Heywood |first2=Karen J. |last3=Hall |first3=Rob A. |last4=Scambos |first4=Ted A. |last5=Zheng |first5=Yixi |last6=Nakayama |first6=Yoshihiro |last7=Hyogo |first7=Shuntaro |last8=Snow |first8=Tasha |last9=Wåhlin |first9=Anna K. |last10=Wild |first10=Christian |last11=Truffer |first11=Martin |last12=Muto |first12=Atsuhiro |last13=Alley |first13=Karen E. |last14=Boehme |first14=Lars |last15=Bortolotto |first15=Guilherme A. |last16=Tyler |first16=Scott W. |last17=Pettit |first17=Erin |date=21 December 2022 |title=Ocean variability beneath Thwaites Eastern Ice Shelf driven by the Pine Island Bay Gyre strength| display-authors= 3 |journal=Nature Communications|language=en |volume=13 |issue=1 |page=7840 |doi=10.1038/s41467-022-35499-5 |pmid=36543787 |pmc=9772408 |bibcode=2022NatCo..13.7840D }}</ref> Subsequent research reinforced the hypothesis that Thwaites is the single part of the [[cryosphere]] that would have the largest near-term impact on the sea levels, and that it is likely to disappear even in response to [[climate change]] which had already occurred.<ref>{{cite news|title=This Antarctic glacier is the biggest threat for rising sea levels. The race is on to understand it|url=https://www.washingtonpost.com/news/energy-environment/wp/2016/10/20/u-s-and-u-k-announce-major-research-mission-to-enormous-melting-antarctic-glacier|newspaper=[[The Washington Post]]|date=20 October 2016}}</ref><ref name="Joughin2014" /> Similarly, there is now widespread agreement that its loss is likely to pave the way for the loss of the entire West Antarctic Ice Sheet,<ref name="VoosenSciMag" /><ref name="NASAUnderbelly" /><ref name="Feldmann2015" /> which would raise the sea levels by around {{convert|3.3
Once the potential contribution of Thwaites to future sea level rise became better known, some stories have started to refer to it as the "Doomsday Glacier". The first known usage of that nickname was in a May 2017 [[Rolling Stone]] magazine article by Jeff Goodell,<ref name="GoodellRS">{{cite magazine |first=Jeff |last=Goodell |title=The Doomsday Glacier |date=9 May 2017 |url=https://www.rollingstone.com/politics/politics-features/the-doomsday-glacier-113792/ | magazine=[[Rolling Stone]] |access-date=8 July 2023 }}</ref> and it has subsequently been used more widely.<ref name="RowlattBBC">{{cite web |first=Justin |last=Rowlatt |url=https://www.bbc.com/news/science-environment-51097309 |title=Antarctica melting: Climate change and the journey to the 'doomsday glacier' |publisher=BBC News |date=28 January 2020 }}</ref><ref name="PappasLiveSci" /><ref name="BakerSciAm" /><ref name="FritzCNN" /> While some scientists have embraced the name,<ref>{{Cite journal |last1=Mackintosh |first1=Andrew |date=5 September 2022 |title=Thwaites Glacier and the bed beneath |journal=Nature Geoscience |volume=15 |issue=9 |language=en |pages=687–688 |doi=10.1038/s41561-022-01020-2 |bibcode=2022NatGe..15..687M |s2cid=252081115 }}</ref> many others, including leading researchers like Ted Scambos, [[Eric Rignot]], [[Helen Fricker]] and Robert Larter have criticized it as alarmist and inaccurate.<ref name="RyanCNET">{{cite web |first=Jackson |last=Ryan |url=https://www.cnet.com/science/climate/please-stop-calling-it-the-doomsday-glacier/ |title=Please Stop Calling It the 'Doomsday Glacier' |publisher=[[CNET]] |date=6 September 2022 }}</ref>
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Some engineering interventions have been proposed for Thwaites Glacier and the nearby [[Pine Island Glacier]] to stabilize its ice physically, or to preserve it by blocking the flow of warm ocean water, which currently renders the collapse of these two glaciers practically inevitable even without further warming.<ref name="Joughin2014" /><ref name="MIT2022" /> A proposal from 2018 included building sills at the Thwaites' [[grounding line]] to either physically reinforce it, or to block some fraction of warm water flow. The former would be the simplest intervention, yet still equivalent to "the largest civil engineering projects that humanity has ever attempted": it is also only 30% likely to work. Constructions blocking even 50% of the warm water flow are expected to be far more effective, yet far more difficult as well.<ref name="Wolovick2018">{{Cite journal |last1=Wolovick |first1=Michael J. |last2=Moore |first2=John C. |date=20 September 2018 |title=Stopping the flood: could we use targeted geoengineering to mitigate sea level rise? |url=https://tc.copernicus.org/articles/16/397/2022/ |journal=The Cryosphere |volume=12 |issue=9 |pages=2955–2967 |language=en |doi=10.5194/tc-12-2955-2018 |bibcode=2018TCry...12.2955W |s2cid=52969664 }}</ref> Further, some researchers dissented, arguing that this proposal could be ineffective, or even accelerate sea level rise.<ref name="Moon2018">{{Cite journal |last1=Moon |first1=Twila A. |title=Geoengineering might speed glacier melt |date=25 April 2018 |journal=Nature |volume=556 |issue=7702 |language=en |pages=436 |doi=10.1038/d41586-018-04897-5 |pmid=29695853 |bibcode=2018Natur.556R.436M |doi-access=free }}</ref> The original authors have suggested attempting this intervention on smaller sites, like the [[Jakobshavn Glacier]] in [[Greenland]], as a test run,<ref name="Wolovick2018" /><ref name="MIT2022" /> as well as acknowledging that this intervention cannot prevent [[sea level rise]] from the increased [[ocean heat content]], and would be ineffective in the long run without [[greenhouse gas emission]] reductions.<ref name="Wolovick2018" />
In 2023, a modified proposal was tabled: it was proposed that an installation of underwater "curtains", made out of a flexible material and anchored to [[Amundsen Sea]] floor would be able to interrupt warm water flow while reducing costs and increasing their longevity (conservatively estimated at 25 years for curtain elements and up to 100 years for the foundations) relative to more rigid structures. With them in place, Thwaites Ice Shelf and Pine Island Ice Shelf would presumably be able to regrow to a state
[[File:Wolovick2023_Thwaites_curtain.jpeg|thumb|Diagram of a proposed "curtain".<ref name="Wolovick2023a" />]]
The authors estimated that this project would take a decade to construct, at $40–80 billion initial cost, while the ongoing maintenance would cost $1–2 billion a year.<ref name="Wolovick2023a" /><ref name="Wolovick2023b" /> Yet, a single [[seawall]] capable of protecting the entire [[New York City]] may cost twice as much on its own,<ref name="MIT2022" /> and the global costs of [[climate change adaptation|adaptation]] to [[sea level rise]] caused by the glaciers' collapse are estimated to reach $40 billion annually:<ref name="Wolovick2023a" /><ref name="Wolovick2023b" /> The authors also suggested that their proposal would be competitive with the other "[[climate engineering]]" proposals like [[stratospheric aerosol injection]] (SAI) or [[carbon dioxide removal]] (CDR), as while those would stop a much larger spectrum of climate change impacts, their estimated annual costs range from $7–70 billion for SAI to $160–4500 billion for CDR powerful enough to help meet the {{convert|1.5|C-change|F-change}} [[Paris Agreement]] target.<ref name="Wolovick2023a">{{Cite journal |last1=Wolovick |first1=Michael |last2=Moore |first2=John |last3=Keefer |first3=Bowie |date=27 March 2023 |title=Feasibility of ice sheet conservation using seabed anchored curtains |url=https://academic.oup.com/pnasnexus/article/2/4/pgad103/7087219 |journal=PNAS Nexus |volume=2 |issue=3 |pages=pgad053 |language=en |doi=10.1093/pnasnexus/pgad053 |pmid=37007716 |pmc=10062297 }}</ref><ref name="Wolovick2023b">{{Cite journal |last1=Wolovick |first1=Michael |last2=Moore |first2=John |last3=Keefer |first3=Bowie |date=27 March 2023 |title=The potential for stabilizing Amundsen Sea glaciers via underwater curtains |url=https://academic.oup.com/pnasnexus/article/2/4/pgad103/7087219 |journal=PNAS Nexus |volume=2 |issue=4 |pages=pgad103 |language=en |doi=10.1093/pnasnexus/pgad103 |pmid=37091546 |pmc=10118300 }}</ref>
== See also ==
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