Editing Methane clathrate (section)

{{short description|Methane-water lattice compound}}
{{Redirect|Fire ice|the book by Clive Cussler|Fire Ice}}
[[Image:Burning hydrate inlay US Office Naval Research.jpg|right|frame|"Burning ice". Methane, released by heating, burns; water drips.<br>
Inset: clathrate structure (University of Göttingen, GZG. Abt. Kristallographie).<br>
Source: [[United States Geological Survey]].]]

'''Methane clathrate''' (CH<sub>4</sub>·5.75H<sub>2</sub>O) or (4CH<sub>4</sub>·23H<sub>2</sub>O), also called '''methane hydrate''', '''hydromethane''', '''methane ice''', '''fire ice''', '''natural gas hydrate''', or '''gas hydrate''', is a solid [[clathrate compound]] (more specifically, a [[clathrate hydrate]]) in which a large amount of [[methane]] is trapped within a [[crystal]] structure of water, forming a solid similar to [[ice]].<ref>{{citation |publisher=U.S. Geological Survey |url=https://woodshole.er.usgs.gov/project-pages/hydrates/what.html |date=31 August 2009 |access-date=28 December 2014 |title=Gas Hydrate: What is it? |url-status=dead |archive-url=https://web.archive.org/web/20120614141539/http://woodshole.er.usgs.gov/project-pages/hydrates/what.html |archive-date=June 14, 2012}}</ref><ref name="Hassan 12305–12314">{{Cite journal |last=Hassan |first=Hussein |last2=Romanos |first2=Jimmy |date=2023-08-09 |title=Effects of Sea Salts on the Phase Behavior and Synthesis of Methane Hydrates + THF: An Experimental and Theoretical Study |url=https://pubs.acs.org/doi/10.1021/acs.iecr.3c00351 |journal=Industrial & Engineering Chemistry Research |language=en |volume=62 |issue=31 |pages=12305–12314 |doi=10.1021/acs.iecr.3c00351 |issn=0888-5885|url-access=subscription }}</ref><ref>{{Cite journal |title=Coupled Numerical Modeling of Gas Hydrate-BearingSediments: From Laboratory to Field-Scale Analyses |last1=Sánchez |first1=M. |last2=Santamarina |first2=C. |last3=Teymouri |first3=M. |last4=Gai |first4=X. |journal=Journal of Geophysical Research: Solid Earth |volume=123 |issue=12 |pages=10,326-10,348 |year=2018 |doi=10.1029/2018JB015966 |hdl=10754/630330 |url=https://repository.kaust.edu.sa/bitstream/10754/630330/1/S-nchez_et_al-2018-Journal_of_Geophysical_Research__Solid_Earth.pdf |bibcode=2018JGRB..12310326S|s2cid=134394736 |hdl-access=free }}</ref><ref>{{Cite journal |title=A pseudo-kinetic model to simulate phase changes in gas hydrate bearing sediments |last1=Teymouri |first1=M. |last2=Sánchez |first2=M. |last3=Santamarina |first3=C. |journal=Marine and Petroleum Geology |pages=104519 |year=2020 |volume=120 |doi=10.1016/j.marpetgeo.2020.104519 |bibcode=2020MarPG.12004519T |doi-access=free |hdl=10754/664452 |hdl-access=free }}</ref><ref>{{cite journal |last1=Chong |first1=Z. R. |last2=Yang |first2=S. H. B. |last3=Babu |first3=P. |last4=Linga |first4=P. |last5=Li |first5=X.-S. |date=2016 |title=Review of natural gas hydrates as an energy resource: Prospects and challenges |journal=Applied Energy |volume=162 |pages=1633–1652 |doi=10.1016/j.apenergy.2014.12.061}}</ref><ref>{{Cite journal|doi=10.1039/C8CS00989A|title=Gas hydrates in sustainable chemistry|year=2020|last1=Hassanpouryouzband|first1=Aliakbar|last2 = Joonaki|first2 = Edris|last3 = Vasheghani Farahani|first3 = Mehrdad|last4 = Takeya|first4 = Satoshi|last5 = Ruppel|first5 = Carolyn|last6 = Yang|first6 = Jinhai|last7 = J. English|first7 = Niall|last8 = M. Schicks|first8 = Judith|last9 = Edlmann|first9 = Katriona|last10 = Mehrabian|first10 = Hadi|last11 = M. Aman|first11 = Zachary|last12 = Tohidi|first12 = Bahman|journal=Chemical Society Reviews|volume=49|issue=15|pages=5225–5309|pmid=32567615|s2cid=219971360|doi-access = free|hdl = 1912/26136|hdl-access = free}}</ref> Originally thought to occur only in the outer regions of the [[Solar System]], where temperatures are low and water ice is common, significant deposits of methane clathrate have been found under [[sediment]]s on the [[ocean]] floors of the [[Earth]] (around 1100{{nbsp}}m below the sea level).<ref>{{Cite journal |title=Old Gas, New Gas |author=Roald Hoffmann |journal=[[American Scientist]] |volume=94 |issue=1 |pages=16–18 |year=2006 |doi=10.1511/2006.57.16 |url=https://www.americanscientist.org/article/old-gas-new-gas|url-access=subscription }}</ref> Methane hydrate is formed when hydrogen-bonded water and methane gas come into contact at high pressures and low temperatures in oceans.

Methane clathrates are common constituents of the shallow marine [[geosphere]] and they occur in deep [[Sedimentary rock|sedimentary]] structures and form [[outcrop]]s on the ocean floor. Methane hydrates are believed to form by the precipitation or crystallisation of methane migrating from deep along [[Fault (geology)|geological faults]]. Precipitation occurs when the methane comes in contact with water within the sea bed subject to temperature and pressure. In 2008, research on Antarctic [[Vostok Station]] and [[European Project for Ice Coring in Antarctica#Concordia Station at Dome C|EPICA Dome C]] ice cores revealed that methane clathrates were also present in deep [[Antarctica|Antarctic]] [[ice core]]s and record a history of [[atmospheric methane]] concentrations, dating to 800,000 years ago.<ref>{{Cite journal |title=High resolution carbon dioxide concentration record 650,000–800,000 years before present |journal=[[Nature (journal)|Nature]] |volume=453 |pages=379–382 |year=2008 |doi=10.1038/nature06949 |pmid=18480821 |last1=Lüthi |first1=D |last2=Le Floch |first2=M |last3=Bereiter |first3=B |last4=Blunier |first4=T |last5=Barnola |first5=JM |last6=Siegenthaler |first6=U |last7=Raynaud |first7=D |last8=Jouzel |first8=J |last9=Fischer |first9=H |display-authors=8 |issue=7193 |bibcode=2008Natur.453..379L |s2cid=1382081 |url=https://epic.awi.de/id/eprint/18281/1/Lth2008a.pdf|doi-access=free }}</ref> The ice-core methane clathrate record is a primary source of data for [[global warming]] research, along with oxygen and carbon dioxide.

Methane clathrates used to be considered as a potential source of [[abrupt climate change]], following the [[clathrate gun hypothesis]]. In this scenario, heating causes catastrophic melting and breakdown of primarily undersea hydrates, leading to a massive release of methane and accelerating warming. Current research shows that hydrates react very slowly to warming, and that it's very difficult for methane to reach the atmosphere after dissociation.<ref name="Wallmann2018">{{Cite journal|journal=Nature Communications|year=2018|author=Wallmann|display-authors=et al |title=Gas hydrate dissociation off Svalbard induced by isostatic rebound rather than global warming |volume=9 |issue=1 |pages=83 |doi=10.1038/s41467-017-02550-9 |pmid=29311564 |pmc=5758787 |bibcode=2018NatCo...9...83W}}</ref><ref>{{cite journal |last1=Mau |first1=S. |last2=Römer |first2=M. |last3=Torres |first3=M. E. |last4=Bussmann |first4=I. |last5=Pape |first5=T. |last6=Damm |first6=E. |last7=Geprägs |first7=P. |last8=Wintersteller |first8=P. |last9=Hsu |first9=C.-W. |last10=Loher |first10=M. |last11=Bohrmann |first11=G. |date=23 February 2017 |title=Widespread methane seepage along the continental margin off Svalbard - from Bjørnøya to Kongsfjorden |journal=Scientific Reports |volume=7 |page=42997 |doi=10.1038/srep42997 |pmid=28230189 |pmc=5322355 |bibcode=2017NatSR...742997M |s2cid=23568012 |doi-access=free }}</ref> Some active seeps instead act as a minor [[carbon sink]], because with the majority of methane dissolved underwater and encouraging [[methanotroph]] communities, the area around the seep also becomes more suitable for [[phytoplankton]].<ref>{{cite journal |last1=Pohlman |first1=John W. |last2=Greinert |first2=Jens |last3=Ruppel |first3=Carolyn |last4=Silyakova |first4=Anna |last5=Vielstädte |first5=Lisa |last6=Casso |first6=Michael |last7=Mienert |first7=Jürgen |last8=Bünz |first8=Stefan |date=1 February 2020 |title=Enhanced CO2 uptake at a shallow Arctic Ocean seep field overwhelms the positive warming potential of emitted methane |journal=Proceedings of the National Academy of Sciences |volume=114 |issue=21 |pages=5355–5360 |doi=10.1073/pnas.1618926114 |pmid=28484018 |pmc=5448205 |doi-access=free }}</ref> As the result, methane hydrates are no longer considered one of the [[tipping points in the climate system]], and according to the [[IPCC Sixth Assessment Report]], no "detectable" impact on the global temperatures will occur in this century through this mechanism.<ref name="IPCC AR6 WG1 Ch.5">{{Cite journal |last1=Fox-Kemper |first1=B. |last2=Hewitt |first2=H.T.|author2-link=Helene Hewitt |last3=Xiao |first3=C. |last4=Aðalgeirsdóttir |first4=G. |last5=Drijfhout |first5=S.S. |last6=Edwards |first6=T.L. |last7=Golledge |first7=N.R. |last8=Hemer |first8=M. |last9=Kopp |first9=R.E. |last10=Krinner |first10=G. |last11=Mix |first11=A. |date=2021 |editor-last=Masson-Delmotte |editor-first=V. |editor2-last=Zhai |editor2-first=P. |editor3-last=Pirani |editor3-first=A. |editor4-last=Connors |editor4-first=S.L. |editor5-last=Péan |editor5-first=C. |editor6-last=Berger |editor6-first=S. |editor7-last=Caud |editor7-first=N. |editor8-last=Chen |editor8-first=Y. |editor9-last=Goldfarb |editor9-first=L. |title=Chapter 5: Global Carbon and other Biogeochemical Cycles and Feedbacks |journal=Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change |url=https://www.ipcc.ch/report/ar6/wg1/downloads/report/IPCC_AR6_WGI_Full_Report.pdf |publisher=Cambridge University Press, Cambridge, UK and New York, NY, USA |page=5 |doi=10.1017/9781009157896.011}}</ref> Over several millennia, a more substantial {{convert|0.4-0.5|C-change|F-change}} response may still be seen.<ref name="Schellnhuber2018">{{Cite journal |last1=Schellnhuber |first1=Hans Joachim |last2=Winkelmann |first2=Ricarda |last3=Scheffer |first3=Marten |last4=Lade |first4=Steven J. |last5=Fetzer |first5=Ingo |last6=Donges |first6=Jonathan F. |last7=Crucifix |first7=Michel |last8=Cornell |first8=Sarah E. |last9=Barnosky |first9=Anthony D. |author-link9=Anthony David Barnosky |date=2018 |title=Trajectories of the Earth System in the Anthropocene |journal=[[Proceedings of the National Academy of Sciences]] |volume=115 |issue=33 |pages=8252–8259 |bibcode=2018PNAS..115.8252S |doi=10.1073/pnas.1810141115 |issn=0027-8424 |pmc=6099852 |pmid=30082409 |doi-access=free}}</ref>