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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2014
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Online Access: | https://doi.org/10.5194/bg-11-6029-2014 https://doaj.org/article/da6e2b90b06946d1be92254d698e193c |
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ftdoajarticles:oai:doaj.org/article:da6e2b90b06946d1be92254d698e193c 2023-05-15T17:58:21+02:00 Gas emissions at the continental margin west of Svalbard: mapping, sampling, and quantification H. Sahling M. Römer T. Pape B. Bergès C. dos Santos Fereirra J. Boelmann P. Geprägs M. Tomczyk N. Nowald W. Dimmler L. Schroedter M. Glockzin G. Bohrmann 2014-11-01T00:00:00Z https://doi.org/10.5194/bg-11-6029-2014 https://doaj.org/article/da6e2b90b06946d1be92254d698e193c EN eng Copernicus Publications http://www.biogeosciences.net/11/6029/2014/bg-11-6029-2014.pdf https://doaj.org/toc/1726-4170 https://doaj.org/toc/1726-4189 1726-4170 1726-4189 doi:10.5194/bg-11-6029-2014 https://doaj.org/article/da6e2b90b06946d1be92254d698e193c Biogeosciences, Vol 11, Iss 21, Pp 6029-6046 (2014) Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 article 2014 ftdoajarticles https://doi.org/10.5194/bg-11-6029-2014 2022-12-31T02:22:52Z 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 δ 13 C = −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 × 10 6 mol methane were annually emitted at the two areas and allow for a large range of uncertainty due to our method (9 to 118 × 10 6 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 ... Article in Journal/Newspaper permafrost Svalbard Directory of Open Access Journals: DOAJ Articles Svalbard Forlandet ENVELOPE(19.647,19.647,68.976,68.976) Biogeosciences 11 21 6029 6046 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 |
spellingShingle |
Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 H. Sahling M. Römer T. Pape B. Bergès C. dos Santos Fereirra J. Boelmann P. Geprägs M. Tomczyk N. Nowald W. Dimmler L. Schroedter M. Glockzin G. Bohrmann Gas emissions at the continental margin west of Svalbard: mapping, sampling, and quantification |
topic_facet |
Ecology QH540-549.5 Life QH501-531 Geology QE1-996.5 |
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 δ 13 C = −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 × 10 6 mol methane were annually emitted at the two areas and allow for a large range of uncertainty due to our method (9 to 118 × 10 6 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 ... |
format |
Article in Journal/Newspaper |
author |
H. Sahling M. Römer T. Pape B. Bergès C. dos Santos Fereirra J. Boelmann P. Geprägs M. Tomczyk N. Nowald W. Dimmler L. Schroedter M. Glockzin G. Bohrmann |
author_facet |
H. Sahling M. Römer T. Pape B. Bergès C. dos Santos Fereirra J. Boelmann P. Geprägs M. Tomczyk N. Nowald W. Dimmler L. Schroedter M. Glockzin G. Bohrmann |
author_sort |
H. Sahling |
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://doaj.org/article/da6e2b90b06946d1be92254d698e193c |
long_lat |
ENVELOPE(19.647,19.647,68.976,68.976) |
geographic |
Svalbard Forlandet |
geographic_facet |
Svalbard Forlandet |
genre |
permafrost Svalbard |
genre_facet |
permafrost Svalbard |
op_source |
Biogeosciences, Vol 11, Iss 21, Pp 6029-6046 (2014) |
op_relation |
http://www.biogeosciences.net/11/6029/2014/bg-11-6029-2014.pdf https://doaj.org/toc/1726-4170 https://doaj.org/toc/1726-4189 1726-4170 1726-4189 doi:10.5194/bg-11-6029-2014 https://doaj.org/article/da6e2b90b06946d1be92254d698e193c |
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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1766166950406258688 |