Using ship-borne observations of methane isotopic ratio in the Arctic Ocean to understand methane sources in the Arctic
Characterizing methane sources in the Arctic remains challenging due to the remoteness, heterogeneity and variety of such emissions. In situ campaigns provide valuable datasets to reduce these uncertainties. Here we analyse data from the summer 2014 SWERUS-C3 campaign in the eastern Arctic Ocean, of...
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ftcopernicus:oai:publications.copernicus.org:acp77653 2023-05-15T14:43:21+02:00 Using ship-borne observations of methane isotopic ratio in the Arctic Ocean to understand methane sources in the Arctic Berchet, Antoine Pison, Isabelle Crill, Patrick M. Thornton, Brett Bousquet, Philippe Thonat, Thibaud Hocking, Thomas Thanwerdas, Joël Paris, Jean-Daniel Saunois, Marielle 2020-04-02 application/pdf https://doi.org/10.5194/acp-20-3987-2020 https://www.atmos-chem-phys.net/20/3987/2020/ eng eng doi:10.5194/acp-20-3987-2020 https://www.atmos-chem-phys.net/20/3987/2020/ eISSN: 1680-7324 Text 2020 ftcopernicus https://doi.org/10.5194/acp-20-3987-2020 2020-04-06T14:42:00Z Characterizing methane sources in the Arctic remains challenging due to the remoteness, heterogeneity and variety of such emissions. In situ campaigns provide valuable datasets to reduce these uncertainties. Here we analyse data from the summer 2014 SWERUS-C3 campaign in the eastern Arctic Ocean, off the shore of Siberia and Alaska. Total concentrations of methane, as well as relative concentrations of 12 CH 4 and 13 CH 4 , were measured continuously during this campaign for 35 d in July and August. Using a chemistry-transport model, we link observed concentrations and isotopic ratios to regional emissions and hemispheric transport structures. A simple inversion system helped constrain source signatures from wetlands in Siberia and Alaska, and oceanic sources, as well as the isotopic composition of lower-stratosphere air masses. The variation in the signature of lower-stratosphere air masses, due to strongly fractionating chemical reactions in the stratosphere, was suggested to explain a large share of the observed variability in isotopic ratios. These results point towards necessary efforts to better simulate large-scale transport and chemistry patterns to make relevant use of isotopic data in remote areas. It is also found that constant and homogeneous source signatures for each type of emission in a given region (mostly wetlands and oil and gas industry in our case at high latitudes) are not compatible with the strong synoptic isotopic signal observed in the Arctic. A regional gradient in source signatures is highlighted between Siberian and Alaskan wetlands, the latter having lighter signatures (more depleted in 13 C ). Finally, our results suggest that marine emissions of methane from Arctic continental-shelf sources are dominated by thermogenic-origin methane, with a secondary biogenic source as well. Text Arctic Arctic Ocean SWERUS-C3 Alaska Siberia Copernicus Publications: E-Journals Arctic Arctic Ocean Atmospheric Chemistry and Physics 20 6 3987 3998 |
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Open Polar |
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Copernicus Publications: E-Journals |
op_collection_id |
ftcopernicus |
language |
English |
description |
Characterizing methane sources in the Arctic remains challenging due to the remoteness, heterogeneity and variety of such emissions. In situ campaigns provide valuable datasets to reduce these uncertainties. Here we analyse data from the summer 2014 SWERUS-C3 campaign in the eastern Arctic Ocean, off the shore of Siberia and Alaska. Total concentrations of methane, as well as relative concentrations of 12 CH 4 and 13 CH 4 , were measured continuously during this campaign for 35 d in July and August. Using a chemistry-transport model, we link observed concentrations and isotopic ratios to regional emissions and hemispheric transport structures. A simple inversion system helped constrain source signatures from wetlands in Siberia and Alaska, and oceanic sources, as well as the isotopic composition of lower-stratosphere air masses. The variation in the signature of lower-stratosphere air masses, due to strongly fractionating chemical reactions in the stratosphere, was suggested to explain a large share of the observed variability in isotopic ratios. These results point towards necessary efforts to better simulate large-scale transport and chemistry patterns to make relevant use of isotopic data in remote areas. It is also found that constant and homogeneous source signatures for each type of emission in a given region (mostly wetlands and oil and gas industry in our case at high latitudes) are not compatible with the strong synoptic isotopic signal observed in the Arctic. A regional gradient in source signatures is highlighted between Siberian and Alaskan wetlands, the latter having lighter signatures (more depleted in 13 C ). Finally, our results suggest that marine emissions of methane from Arctic continental-shelf sources are dominated by thermogenic-origin methane, with a secondary biogenic source as well. |
format |
Text |
author |
Berchet, Antoine Pison, Isabelle Crill, Patrick M. Thornton, Brett Bousquet, Philippe Thonat, Thibaud Hocking, Thomas Thanwerdas, Joël Paris, Jean-Daniel Saunois, Marielle |
spellingShingle |
Berchet, Antoine Pison, Isabelle Crill, Patrick M. Thornton, Brett Bousquet, Philippe Thonat, Thibaud Hocking, Thomas Thanwerdas, Joël Paris, Jean-Daniel Saunois, Marielle Using ship-borne observations of methane isotopic ratio in the Arctic Ocean to understand methane sources in the Arctic |
author_facet |
Berchet, Antoine Pison, Isabelle Crill, Patrick M. Thornton, Brett Bousquet, Philippe Thonat, Thibaud Hocking, Thomas Thanwerdas, Joël Paris, Jean-Daniel Saunois, Marielle |
author_sort |
Berchet, Antoine |
title |
Using ship-borne observations of methane isotopic ratio in the Arctic Ocean to understand methane sources in the Arctic |
title_short |
Using ship-borne observations of methane isotopic ratio in the Arctic Ocean to understand methane sources in the Arctic |
title_full |
Using ship-borne observations of methane isotopic ratio in the Arctic Ocean to understand methane sources in the Arctic |
title_fullStr |
Using ship-borne observations of methane isotopic ratio in the Arctic Ocean to understand methane sources in the Arctic |
title_full_unstemmed |
Using ship-borne observations of methane isotopic ratio in the Arctic Ocean to understand methane sources in the Arctic |
title_sort |
using ship-borne observations of methane isotopic ratio in the arctic ocean to understand methane sources in the arctic |
publishDate |
2020 |
url |
https://doi.org/10.5194/acp-20-3987-2020 https://www.atmos-chem-phys.net/20/3987/2020/ |
geographic |
Arctic Arctic Ocean |
geographic_facet |
Arctic Arctic Ocean |
genre |
Arctic Arctic Ocean SWERUS-C3 Alaska Siberia |
genre_facet |
Arctic Arctic Ocean SWERUS-C3 Alaska Siberia |
op_source |
eISSN: 1680-7324 |
op_relation |
doi:10.5194/acp-20-3987-2020 https://www.atmos-chem-phys.net/20/3987/2020/ |
op_doi |
https://doi.org/10.5194/acp-20-3987-2020 |
container_title |
Atmospheric Chemistry and Physics |
container_volume |
20 |
container_issue |
6 |
container_start_page |
3987 |
op_container_end_page |
3998 |
_version_ |
1766315012577558528 |