Diverse origins of Arctic and Subarctic methane point source emissions identified with multiply-substituted isotopologues
Methane is a potent greenhouse gas, and there are concerns that its natural emissions from the Arctic could act as a substantial positive feedback to anthropogenic global warming. Determining the sources of methane emissions and the biogeochemical processes controlling them is important for understa...
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ftcaltechauth:oai:authors.library.caltech.edu:b4c3m-gmt65 2024-09-15T17:54:14+00:00 Diverse origins of Arctic and Subarctic methane point source emissions identified with multiply-substituted isotopologues Douglas, P. M. J. Stolper, D. A. Smith, D. A. Anthony, K. M. Walter Paull, C. K. Dallimore, S. Wik, M. Crill, P. M. Winterdahl, M. Eiler, J. M. Sessions, A. L. 2016-09-01 https://doi.org/10.1016/j.gca.2016.05.031 unknown Elsevier https://doi.org/10.1016/j.gca.2016.05.031 oai:authors.library.caltech.edu:b4c3m-gmt65 eprintid:67826 resolverid:CaltechAUTHORS:20160610-103423261 info:eu-repo/semantics/closedAccess Other Geochimica et Cosmochimica Acta, 188, 163-188, (2016-09-01) Methane Clumped isotope geochemistry Arctic Carbon cycle Greenhouse gases info:eu-repo/semantics/article 2016 ftcaltechauth https://doi.org/10.1016/j.gca.2016.05.031 2024-08-06T15:35:03Z Methane is a potent greenhouse gas, and there are concerns that its natural emissions from the Arctic could act as a substantial positive feedback to anthropogenic global warming. Determining the sources of methane emissions and the biogeochemical processes controlling them is important for understanding present and future Arctic contributions to atmospheric methane budgets. Here we apply measurements of multiply-substituted isotopologues, or clumped isotopes, of methane as a new tool to identify the origins of ebullitive fluxes in Alaska, Sweden and the Arctic Ocean. When methane forms in isotopic equilibrium, clumped isotope measurements indicate the formation temperature. In some microbial methane, however, non-equilibrium isotope effects, probably related to the kinetics of methanogenesis, lead to low clumped isotope values. We identify four categories of emissions in the studied samples: thermogenic methane, deep subsurface or marine microbial methane formed in isotopic equilibrium, freshwater microbial methane with non-equilibrium clumped isotope values, and mixtures of deep and shallow methane (i.e., combinations of the first three end members). Mixing between deep and shallow methane sources produces a non-linear variation in clumped isotope values with mixing proportion that provides new constraints for the formation environment of the mixing end-members. Analyses of microbial methane emitted from lakes, as well as a methanol-consuming methanogen pure culture, support the hypothesis that non-equilibrium clumped isotope values are controlled, in part, by kinetic isotope effects induced during enzymatic reactions involved in methanogenesis. Our results indicate that these kinetic isotope effects vary widely in microbial methane produced in Arctic lake sediments, with non-equilibrium Δ_18 values spanning a range of more than 5‰. © 2016 Elsevier Ltd. Received 9 November 2015, Accepted 18 May 2016, Available online 25 May 2016. Thanks to Nami Kitchen and Yanhua Shuai for help with clumped isotope ... Article in Journal/Newspaper Arctic Ocean Global warming Subarctic Alaska Caltech Authors (California Institute of Technology) Geochimica et Cosmochimica Acta 188 163 188 |
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Open Polar |
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Caltech Authors (California Institute of Technology) |
op_collection_id |
ftcaltechauth |
language |
unknown |
topic |
Methane Clumped isotope geochemistry Arctic Carbon cycle Greenhouse gases |
spellingShingle |
Methane Clumped isotope geochemistry Arctic Carbon cycle Greenhouse gases Douglas, P. M. J. Stolper, D. A. Smith, D. A. Anthony, K. M. Walter Paull, C. K. Dallimore, S. Wik, M. Crill, P. M. Winterdahl, M. Eiler, J. M. Sessions, A. L. Diverse origins of Arctic and Subarctic methane point source emissions identified with multiply-substituted isotopologues |
topic_facet |
Methane Clumped isotope geochemistry Arctic Carbon cycle Greenhouse gases |
description |
Methane is a potent greenhouse gas, and there are concerns that its natural emissions from the Arctic could act as a substantial positive feedback to anthropogenic global warming. Determining the sources of methane emissions and the biogeochemical processes controlling them is important for understanding present and future Arctic contributions to atmospheric methane budgets. Here we apply measurements of multiply-substituted isotopologues, or clumped isotopes, of methane as a new tool to identify the origins of ebullitive fluxes in Alaska, Sweden and the Arctic Ocean. When methane forms in isotopic equilibrium, clumped isotope measurements indicate the formation temperature. In some microbial methane, however, non-equilibrium isotope effects, probably related to the kinetics of methanogenesis, lead to low clumped isotope values. We identify four categories of emissions in the studied samples: thermogenic methane, deep subsurface or marine microbial methane formed in isotopic equilibrium, freshwater microbial methane with non-equilibrium clumped isotope values, and mixtures of deep and shallow methane (i.e., combinations of the first three end members). Mixing between deep and shallow methane sources produces a non-linear variation in clumped isotope values with mixing proportion that provides new constraints for the formation environment of the mixing end-members. Analyses of microbial methane emitted from lakes, as well as a methanol-consuming methanogen pure culture, support the hypothesis that non-equilibrium clumped isotope values are controlled, in part, by kinetic isotope effects induced during enzymatic reactions involved in methanogenesis. Our results indicate that these kinetic isotope effects vary widely in microbial methane produced in Arctic lake sediments, with non-equilibrium Δ_18 values spanning a range of more than 5‰. © 2016 Elsevier Ltd. Received 9 November 2015, Accepted 18 May 2016, Available online 25 May 2016. Thanks to Nami Kitchen and Yanhua Shuai for help with clumped isotope ... |
format |
Article in Journal/Newspaper |
author |
Douglas, P. M. J. Stolper, D. A. Smith, D. A. Anthony, K. M. Walter Paull, C. K. Dallimore, S. Wik, M. Crill, P. M. Winterdahl, M. Eiler, J. M. Sessions, A. L. |
author_facet |
Douglas, P. M. J. Stolper, D. A. Smith, D. A. Anthony, K. M. Walter Paull, C. K. Dallimore, S. Wik, M. Crill, P. M. Winterdahl, M. Eiler, J. M. Sessions, A. L. |
author_sort |
Douglas, P. M. J. |
title |
Diverse origins of Arctic and Subarctic methane point source emissions identified with multiply-substituted isotopologues |
title_short |
Diverse origins of Arctic and Subarctic methane point source emissions identified with multiply-substituted isotopologues |
title_full |
Diverse origins of Arctic and Subarctic methane point source emissions identified with multiply-substituted isotopologues |
title_fullStr |
Diverse origins of Arctic and Subarctic methane point source emissions identified with multiply-substituted isotopologues |
title_full_unstemmed |
Diverse origins of Arctic and Subarctic methane point source emissions identified with multiply-substituted isotopologues |
title_sort |
diverse origins of arctic and subarctic methane point source emissions identified with multiply-substituted isotopologues |
publisher |
Elsevier |
publishDate |
2016 |
url |
https://doi.org/10.1016/j.gca.2016.05.031 |
genre |
Arctic Ocean Global warming Subarctic Alaska |
genre_facet |
Arctic Ocean Global warming Subarctic Alaska |
op_source |
Geochimica et Cosmochimica Acta, 188, 163-188, (2016-09-01) |
op_relation |
https://doi.org/10.1016/j.gca.2016.05.031 oai:authors.library.caltech.edu:b4c3m-gmt65 eprintid:67826 resolverid:CaltechAUTHORS:20160610-103423261 |
op_rights |
info:eu-repo/semantics/closedAccess Other |
op_doi |
https://doi.org/10.1016/j.gca.2016.05.031 |
container_title |
Geochimica et Cosmochimica Acta |
container_volume |
188 |
container_start_page |
163 |
op_container_end_page |
188 |
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1810430488313069568 |