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...
Main Authors: | , , , , , , , , , , |
---|---|
Format: | Article in Journal/Newspaper |
Language: | unknown |
Published: |
eScholarship, University of California
2016
|
Subjects: | |
Online Access: | https://escholarship.org/uc/item/5t357148 |
id |
ftcdlib:oai:escholarship.org/ark:/13030/qt5t357148 |
---|---|
record_format |
openpolar |
spelling |
ftcdlib:oai:escholarship.org/ark:/13030/qt5t357148 2023-05-15T14:43:16+02:00 Diverse origins of Arctic and Subarctic methane point source emissions identified with multiply-substituted isotopologues Douglas, PMJ Stolper, DA Smith, DA Walter Anthony, KM Paull, CK Dallimore, S Wik, M Crill, PM Winterdahl, M Eiler, JM Sessions, AL 2016-09-01 application/pdf https://escholarship.org/uc/item/5t357148 unknown eScholarship, University of California qt5t357148 https://escholarship.org/uc/item/5t357148 public Methane Clumped isotope geochemistry Arctic Carbon cycle Greenhouse gases Geochemistry Geology Physical Geography and Environmental Geoscience Geochemistry & Geophysics article 2016 ftcdlib 2021-06-28T17:07:28Z 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 δ18 values spanning a range of more than 5‰. Article in Journal/Newspaper Arctic Arctic Ocean Global warming Subarctic Alaska University of California: eScholarship Arctic Arctic Lake ENVELOPE(-130.826,-130.826,57.231,57.231) Arctic Ocean |
institution |
Open Polar |
collection |
University of California: eScholarship |
op_collection_id |
ftcdlib |
language |
unknown |
topic |
Methane Clumped isotope geochemistry Arctic Carbon cycle Greenhouse gases Geochemistry Geology Physical Geography and Environmental Geoscience Geochemistry & Geophysics |
spellingShingle |
Methane Clumped isotope geochemistry Arctic Carbon cycle Greenhouse gases Geochemistry Geology Physical Geography and Environmental Geoscience Geochemistry & Geophysics Douglas, PMJ Stolper, DA Smith, DA Walter Anthony, KM Paull, CK Dallimore, S Wik, M Crill, PM Winterdahl, M Eiler, JM Sessions, AL 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 Geochemistry Geology Physical Geography and Environmental Geoscience Geochemistry & Geophysics |
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 δ18 values spanning a range of more than 5‰. |
format |
Article in Journal/Newspaper |
author |
Douglas, PMJ Stolper, DA Smith, DA Walter Anthony, KM Paull, CK Dallimore, S Wik, M Crill, PM Winterdahl, M Eiler, JM Sessions, AL |
author_facet |
Douglas, PMJ Stolper, DA Smith, DA Walter Anthony, KM Paull, CK Dallimore, S Wik, M Crill, PM Winterdahl, M Eiler, JM Sessions, AL |
author_sort |
Douglas, PMJ |
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 |
eScholarship, University of California |
publishDate |
2016 |
url |
https://escholarship.org/uc/item/5t357148 |
long_lat |
ENVELOPE(-130.826,-130.826,57.231,57.231) |
geographic |
Arctic Arctic Lake Arctic Ocean |
geographic_facet |
Arctic Arctic Lake Arctic Ocean |
genre |
Arctic Arctic Ocean Global warming Subarctic Alaska |
genre_facet |
Arctic Arctic Ocean Global warming Subarctic Alaska |
op_relation |
qt5t357148 https://escholarship.org/uc/item/5t357148 |
op_rights |
public |
_version_ |
1766314955619958784 |