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Natural sources of atmospheric methane
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Any process that results in the production of methane and its release into the atmosphere can be considered a "source". Several main processes that are responsible for methane production include microorganisms anaerobically converting organic compounds into methane (methanogenesis), which are widespread in aquatic ecosystems and ruminant animals. Other natural sources include melting permafrost and methane clathrates.
Aquatic ecosystems
editNatural and anthropogenic methane emissions from aquatic ecosystems are estimated to contribute about half of total global emissions.[1] Urbanization and eutrophication are expected to lead to increased methane emissions from aquatic ecosystems.[1]
Permafrost
editPermafrost contains almost twice as much carbon as the atmosphere[2], with ~20 Gt of permafrost-associated methane trapped in methane clathrates.[3] Permafrost thaw results in the formation of thermokarst lakes in ice-rich yedoma deposits.[4] Methane frozen in permafrost is slowly released as permafrost melts.[5] Radiocarbon dating of trace methane in lake bubbles and soil organic carbon concluded that 0.2 to 2.5 Pg of permafrost carbon has been released as methane and carbon dioxide over the last 60 years.[6] The 2020 heat wave may have released significant methane from carbonate deposits in Siberian permafrost.[7]
Methane emissions by the 'permafrost carbon feedback' -- amplification of surface warming due to enhanced radiative forcing by carbon release from permafrost -- could contribute an estimated 205 Gt of carbon emissions, leading up to 0.5°C (0.9°F) of additional warming by the end of the 21st century.[8] However, recent research based on the carbon isotopic composition of atmospheric methane trapped in bubbles in Antarctic ice suggests that methane emissions from permafrost and methane hydrates were minor during the last deglaciation, suggesting that future permafrost methane emissions may be lower than previously estimated.[9]
References
edit- ^ a b Rosentreter, Judith A.; Borges, Alberto V.; Deemer, Bridget R.; Holgerson, Meredith A.; Liu, Shaoda; Song, Chunlin; Melack, John; Raymond, Peter A.; Duarte, Carlos M.; Allen, George H.; Olefeldt, David (2021). "Half of global methane emissions come from highly variable aquatic ecosystem sources". Nature Geoscience. 14 (4): 225–230. doi:10.1038/s41561-021-00715-2. ISSN 1752-0908.
- ^ Brouillette, Monique (2021). "How microbes in permafrost could trigger a massive carbon bomb". Nature. 591 (7850): 360–362. doi:10.1038/d41586-021-00659-y.
- ^ Ruppel, C. (2014). "Permafrost-Associated Gas Hydrate: Is It Really Approximately 1 % of the Global System?". Journal of Chemical & Engineering Data. 60 (2): 429–436. doi:10.1021/je500770m. ISSN 0021-9568.
- ^ in 't Zandt, Michiel H.; Liebner, Susanne; Welte, Cornelia U. (2020). "Roles of Thermokarst Lakes in a Warming World". Trends in Microbiology. 28 (9): 769–779. doi:10.1016/j.tim.2020.04.002. ISSN 0966-842X.
- ^ Intergovernmental Panel on Climate Change, "IPCC, 2021: Summary for Policymakers", Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, Cambridge: Cambridge University Press
- ^ Walter Anthony, Katey; Daanen, Ronald; Anthony, Peter; Schneider von Deimling, Thomas; Ping, Chien-Lu; Chanton, Jeffrey P.; Grosse, Guido (2016). "Methane emissions proportional to permafrost carbon thawed in Arctic lakes since the 1950s". Nature Geoscience. 9 (9): 679–682. doi:10.1038/ngeo2795. ISSN 1752-0908.
- ^ Froitzheim, Nikolaus; Majka, Jaroslaw; Zastrozhnov, Dmitry (2021). "Methane release from carbonate rock formations in the Siberian permafrost area during and after the 2020 heat wave". Proceedings of the National Academy of Sciences. 118 (32). doi:10.1073/pnas.2107632118. ISSN 0027-8424. PMID 34341110.
- ^ Schuur, E. a. G.; McGuire, A. D.; Schädel, C.; Grosse, G.; Harden, J. W.; Hayes, D. J.; Hugelius, G.; Koven, C. D.; Kuhry, P.; Lawrence, D. M.; Natali, S. M. (2015). "Climate change and the permafrost carbon feedback". Nature. 520 (7546): 171–179. doi:10.1038/nature14338. ISSN 1476-4687.
- ^ Dyonisius, M. N.; Petrenko, V. V.; Smith, A. M.; Hua, Q.; Yang, B.; Schmitt, J.; Beck, J.; Seth, B.; Bock, M.; Hmiel, B.; Vimont, I. (2020-02-21). "Old carbon reservoirs were not important in the deglacial methane budget". Science. 367 (6480): 907–910. doi:10.1126/science.aax0504. ISSN 0036-8075.