Gas emissions at the continental margin west of Svalbard: mapping, sampling, and quantification
We mapped, sampled, and quantified gas emissions at the continental margin west of Svalbard during R/V Heincke cruise He-387 in late summer 2012. Hydroacoustic mapping revealed that gas emissions were not limited to a zone just above 396 m water depth. Flares from this depth have gained significant...
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Language: | English |
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Copernicus Publications
2014
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ftnonlinearchiv:oai:noa.gwlb.de:cop_mods_00018620 2023-05-15T17:58:22+02:00 Gas emissions at the continental margin west of Svalbard: mapping, sampling, and quantification Sahling, H. Römer, M. Pape, T. Bergès, B. dos Santos Fereirra, C. Boelmann, J. Geprägs, P. Tomczyk, M. Nowald, N. Dimmler, W. Schroedter, L. Glockzin, M. Bohrmann, G. 2014-11 electronic https://doi.org/10.5194/bg-11-6029-2014 https://noa.gwlb.de/receive/cop_mods_00018620 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00018575/bg-11-6029-2014.pdf https://bg.copernicus.org/articles/11/6029/2014/bg-11-6029-2014.pdf eng eng Copernicus Publications Biogeosciences -- http://www.bibliothek.uni-regensburg.de/ezeit/?2158181 -- http://www.copernicus.org/EGU/bg/bg.html -- 1726-4189 https://doi.org/10.5194/bg-11-6029-2014 https://noa.gwlb.de/receive/cop_mods_00018620 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00018575/bg-11-6029-2014.pdf https://bg.copernicus.org/articles/11/6029/2014/bg-11-6029-2014.pdf uneingeschränkt info:eu-repo/semantics/openAccess article Verlagsveröffentlichung article Text doc-type:article 2014 ftnonlinearchiv https://doi.org/10.5194/bg-11-6029-2014 2022-02-08T22:53:04Z We mapped, sampled, and quantified gas emissions at the continental margin west of Svalbard during R/V Heincke cruise He-387 in late summer 2012. Hydroacoustic mapping revealed that gas emissions were not limited to a zone just above 396 m water depth. Flares from this depth have gained significant attention in the scientific community in recent years because they may be caused by bottom-water warming-induced hydrate dissolution in the course of global warming and/or by recurring seasonal hydrate formation and decay. We found that gas emissions occurred widespread between about 80 and 415 m water depth, which indicates that hydrate dissolution might only be one of several triggers for active hydrocarbon seepage in that area. Gas emissions were remarkably intensive at the main ridge of the Forlandet moraine complex in 80 to 90 m water depths, and may be related to thawing permafrost. Focused seafloor investigations were performed with the remotely operated vehicle (ROV) "Cherokee". Geochemical analyses of gas bubbles sampled at about 240 m water depth as well as at the 396 m gas emission sites revealed that the vent gas is primarily composed of methane (> 99.70%) of microbial origin (average δ13C = −55.7‰ V-PDB). Estimates of the regional gas bubble flux from the seafloor to the water column in the area of possible hydrate decomposition were achieved by combining flare mapping using multibeam and single-beam echosounder data, bubble stream mapping using a ROV-mounted horizontally looking sonar, and quantification of individual bubble streams using ROV imagery and bubble counting. We estimated that about 53 × 106 mol methane were annually emitted at the two areas and allow for a large range of uncertainty due to our method (9 to 118 × 106 mol yr−1). First, these amounts show that gas emissions at the continental margin west of Svalbard were on the same order of magnitude as bubble emissions at other geological settings; second, they may be used to calibrate models predicting hydrate dissolution at present and in the future; and third, they may serve as a baseline (year 2012) estimate of the bubble flux that will potentially increase in the future due to ever-increasing global-warming-induced bottom water warming and hydrate dissociation. Article in Journal/Newspaper permafrost Svalbard Niedersächsisches Online-Archiv NOA Forlandet ENVELOPE(19.647,19.647,68.976,68.976) Svalbard Biogeosciences 11 21 6029 6046 |
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Open Polar |
collection |
Niedersächsisches Online-Archiv NOA |
op_collection_id |
ftnonlinearchiv |
language |
English |
topic |
article Verlagsveröffentlichung |
spellingShingle |
article Verlagsveröffentlichung Sahling, H. Römer, M. Pape, T. Bergès, B. dos Santos Fereirra, C. Boelmann, J. Geprägs, P. Tomczyk, M. Nowald, N. Dimmler, W. Schroedter, L. Glockzin, M. Bohrmann, G. Gas emissions at the continental margin west of Svalbard: mapping, sampling, and quantification |
topic_facet |
article Verlagsveröffentlichung |
description |
We mapped, sampled, and quantified gas emissions at the continental margin west of Svalbard during R/V Heincke cruise He-387 in late summer 2012. Hydroacoustic mapping revealed that gas emissions were not limited to a zone just above 396 m water depth. Flares from this depth have gained significant attention in the scientific community in recent years because they may be caused by bottom-water warming-induced hydrate dissolution in the course of global warming and/or by recurring seasonal hydrate formation and decay. We found that gas emissions occurred widespread between about 80 and 415 m water depth, which indicates that hydrate dissolution might only be one of several triggers for active hydrocarbon seepage in that area. Gas emissions were remarkably intensive at the main ridge of the Forlandet moraine complex in 80 to 90 m water depths, and may be related to thawing permafrost. Focused seafloor investigations were performed with the remotely operated vehicle (ROV) "Cherokee". Geochemical analyses of gas bubbles sampled at about 240 m water depth as well as at the 396 m gas emission sites revealed that the vent gas is primarily composed of methane (> 99.70%) of microbial origin (average δ13C = −55.7‰ V-PDB). Estimates of the regional gas bubble flux from the seafloor to the water column in the area of possible hydrate decomposition were achieved by combining flare mapping using multibeam and single-beam echosounder data, bubble stream mapping using a ROV-mounted horizontally looking sonar, and quantification of individual bubble streams using ROV imagery and bubble counting. We estimated that about 53 × 106 mol methane were annually emitted at the two areas and allow for a large range of uncertainty due to our method (9 to 118 × 106 mol yr−1). First, these amounts show that gas emissions at the continental margin west of Svalbard were on the same order of magnitude as bubble emissions at other geological settings; second, they may be used to calibrate models predicting hydrate dissolution at present and in the future; and third, they may serve as a baseline (year 2012) estimate of the bubble flux that will potentially increase in the future due to ever-increasing global-warming-induced bottom water warming and hydrate dissociation. |
format |
Article in Journal/Newspaper |
author |
Sahling, H. Römer, M. Pape, T. Bergès, B. dos Santos Fereirra, C. Boelmann, J. Geprägs, P. Tomczyk, M. Nowald, N. Dimmler, W. Schroedter, L. Glockzin, M. Bohrmann, G. |
author_facet |
Sahling, H. Römer, M. Pape, T. Bergès, B. dos Santos Fereirra, C. Boelmann, J. Geprägs, P. Tomczyk, M. Nowald, N. Dimmler, W. Schroedter, L. Glockzin, M. Bohrmann, G. |
author_sort |
Sahling, H. |
title |
Gas emissions at the continental margin west of Svalbard: mapping, sampling, and quantification |
title_short |
Gas emissions at the continental margin west of Svalbard: mapping, sampling, and quantification |
title_full |
Gas emissions at the continental margin west of Svalbard: mapping, sampling, and quantification |
title_fullStr |
Gas emissions at the continental margin west of Svalbard: mapping, sampling, and quantification |
title_full_unstemmed |
Gas emissions at the continental margin west of Svalbard: mapping, sampling, and quantification |
title_sort |
gas emissions at the continental margin west of svalbard: mapping, sampling, and quantification |
publisher |
Copernicus Publications |
publishDate |
2014 |
url |
https://doi.org/10.5194/bg-11-6029-2014 https://noa.gwlb.de/receive/cop_mods_00018620 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00018575/bg-11-6029-2014.pdf https://bg.copernicus.org/articles/11/6029/2014/bg-11-6029-2014.pdf |
long_lat |
ENVELOPE(19.647,19.647,68.976,68.976) |
geographic |
Forlandet Svalbard |
geographic_facet |
Forlandet Svalbard |
genre |
permafrost Svalbard |
genre_facet |
permafrost Svalbard |
op_relation |
Biogeosciences -- http://www.bibliothek.uni-regensburg.de/ezeit/?2158181 -- http://www.copernicus.org/EGU/bg/bg.html -- 1726-4189 https://doi.org/10.5194/bg-11-6029-2014 https://noa.gwlb.de/receive/cop_mods_00018620 https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00018575/bg-11-6029-2014.pdf https://bg.copernicus.org/articles/11/6029/2014/bg-11-6029-2014.pdf |
op_rights |
uneingeschränkt info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.5194/bg-11-6029-2014 |
container_title |
Biogeosciences |
container_volume |
11 |
container_issue |
21 |
container_start_page |
6029 |
op_container_end_page |
6046 |
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1766166965426061312 |