Fluxes and fate of dissolved methane released at the seafloor at the landward limit of the gas hydrate stability zone offshore western Svalbard
Widespread seepage of methane from seafloor sediments offshore Svalbard close to the landward limit of the gas hydrate stability zone (GHSZ) may, in part, be driven by hydrate destabilization due to bottom water warming. To assess whether this methane reaches the atmosphere where it may contribute t...
Published in: | Journal of Geophysical Research: Oceans |
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Online Access: | https://oceanrep.geomar.de/id/eprint/29852/ https://oceanrep.geomar.de/id/eprint/29852/1/Graves.pdf https://doi.org/10.1002/2015JC011084 |
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ftoceanrep:oai:oceanrep.geomar.de:29852 2023-05-15T15:10:55+02:00 Fluxes and fate of dissolved methane released at the seafloor at the landward limit of the gas hydrate stability zone offshore western Svalbard Graves, Carolyn A. Steinle, Lea Rehder, Gregor Niemann, Helge Connelly, Douglas P. Lowry, David Fisher, Rebecca E. Stott, Andrew W. Sahling, Heiko James, Rachael H. 2015-09 text https://oceanrep.geomar.de/id/eprint/29852/ https://oceanrep.geomar.de/id/eprint/29852/1/Graves.pdf https://doi.org/10.1002/2015JC011084 en eng AGU (American Geophysical Union) Wiley https://oceanrep.geomar.de/id/eprint/29852/1/Graves.pdf Graves, C. A., Steinle, L., Rehder, G., Niemann, H., Connelly, D. P., Lowry, D., Fisher, R. E., Stott, A. W., Sahling, H. and James, R. H. (2015) Fluxes and fate of dissolved methane released at the seafloor at the landward limit of the gas hydrate stability zone offshore western Svalbard. Open Access Journal of Geophysical Research: Oceans, 120 (9). pp. 6185-6201. DOI 10.1002/2015JC011084 <https://doi.org/10.1002/2015JC011084>. doi:10.1002/2015JC011084 info:eu-repo/semantics/openAccess Article PeerReviewed 2015 ftoceanrep https://doi.org/10.1002/2015JC011084 2023-04-07T15:21:05Z Widespread seepage of methane from seafloor sediments offshore Svalbard close to the landward limit of the gas hydrate stability zone (GHSZ) may, in part, be driven by hydrate destabilization due to bottom water warming. To assess whether this methane reaches the atmosphere where it may contribute to further warming, we have undertaken comprehensive surveys of methane in seawater and air on the upper slope and shelf region. Near the GHSZ limit at ∼400 m water depth, methane concentrations are highest close to the seabed, reaching 825 nM. A simple box model of dissolved methane removal from bottom waters by horizontal and vertical mixing and microbially mediated oxidation indicates that ∼60% of methane released at the seafloor is oxidized at depth before it mixes with overlying surface waters. Deep waters are therefore not a significant source of methane to intermediate and surface waters; rather, relatively high methane concentrations in these waters (up to 50 nM) are attributed to isopycnal turbulent mixing with shelf waters. On the shelf, extensive seafloor seepage at <100 m water depth produces methane concentrations of up to 615 nM. The diffusive flux of methane from sea to air in the vicinity of the landward limit of the GHSZ is ∼4-20 μmol m-2 d-1, which is small relative to other Arctic sources. In support of this, analyses of mole fractions and the carbon isotope signature of atmospheric methane above the seeps do not indicate a significant local contribution from the seafloor source. Article in Journal/Newspaper Arctic Svalbard OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) Arctic Svalbard Journal of Geophysical Research: Oceans 120 9 6185 6201 |
institution |
Open Polar |
collection |
OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) |
op_collection_id |
ftoceanrep |
language |
English |
description |
Widespread seepage of methane from seafloor sediments offshore Svalbard close to the landward limit of the gas hydrate stability zone (GHSZ) may, in part, be driven by hydrate destabilization due to bottom water warming. To assess whether this methane reaches the atmosphere where it may contribute to further warming, we have undertaken comprehensive surveys of methane in seawater and air on the upper slope and shelf region. Near the GHSZ limit at ∼400 m water depth, methane concentrations are highest close to the seabed, reaching 825 nM. A simple box model of dissolved methane removal from bottom waters by horizontal and vertical mixing and microbially mediated oxidation indicates that ∼60% of methane released at the seafloor is oxidized at depth before it mixes with overlying surface waters. Deep waters are therefore not a significant source of methane to intermediate and surface waters; rather, relatively high methane concentrations in these waters (up to 50 nM) are attributed to isopycnal turbulent mixing with shelf waters. On the shelf, extensive seafloor seepage at <100 m water depth produces methane concentrations of up to 615 nM. The diffusive flux of methane from sea to air in the vicinity of the landward limit of the GHSZ is ∼4-20 μmol m-2 d-1, which is small relative to other Arctic sources. In support of this, analyses of mole fractions and the carbon isotope signature of atmospheric methane above the seeps do not indicate a significant local contribution from the seafloor source. |
format |
Article in Journal/Newspaper |
author |
Graves, Carolyn A. Steinle, Lea Rehder, Gregor Niemann, Helge Connelly, Douglas P. Lowry, David Fisher, Rebecca E. Stott, Andrew W. Sahling, Heiko James, Rachael H. |
spellingShingle |
Graves, Carolyn A. Steinle, Lea Rehder, Gregor Niemann, Helge Connelly, Douglas P. Lowry, David Fisher, Rebecca E. Stott, Andrew W. Sahling, Heiko James, Rachael H. Fluxes and fate of dissolved methane released at the seafloor at the landward limit of the gas hydrate stability zone offshore western Svalbard |
author_facet |
Graves, Carolyn A. Steinle, Lea Rehder, Gregor Niemann, Helge Connelly, Douglas P. Lowry, David Fisher, Rebecca E. Stott, Andrew W. Sahling, Heiko James, Rachael H. |
author_sort |
Graves, Carolyn A. |
title |
Fluxes and fate of dissolved methane released at the seafloor at the landward limit of the gas hydrate stability zone offshore western Svalbard |
title_short |
Fluxes and fate of dissolved methane released at the seafloor at the landward limit of the gas hydrate stability zone offshore western Svalbard |
title_full |
Fluxes and fate of dissolved methane released at the seafloor at the landward limit of the gas hydrate stability zone offshore western Svalbard |
title_fullStr |
Fluxes and fate of dissolved methane released at the seafloor at the landward limit of the gas hydrate stability zone offshore western Svalbard |
title_full_unstemmed |
Fluxes and fate of dissolved methane released at the seafloor at the landward limit of the gas hydrate stability zone offshore western Svalbard |
title_sort |
fluxes and fate of dissolved methane released at the seafloor at the landward limit of the gas hydrate stability zone offshore western svalbard |
publisher |
AGU (American Geophysical Union) |
publishDate |
2015 |
url |
https://oceanrep.geomar.de/id/eprint/29852/ https://oceanrep.geomar.de/id/eprint/29852/1/Graves.pdf https://doi.org/10.1002/2015JC011084 |
geographic |
Arctic Svalbard |
geographic_facet |
Arctic Svalbard |
genre |
Arctic Svalbard |
genre_facet |
Arctic Svalbard |
op_relation |
https://oceanrep.geomar.de/id/eprint/29852/1/Graves.pdf Graves, C. A., Steinle, L., Rehder, G., Niemann, H., Connelly, D. P., Lowry, D., Fisher, R. E., Stott, A. W., Sahling, H. and James, R. H. (2015) Fluxes and fate of dissolved methane released at the seafloor at the landward limit of the gas hydrate stability zone offshore western Svalbard. Open Access Journal of Geophysical Research: Oceans, 120 (9). pp. 6185-6201. DOI 10.1002/2015JC011084 <https://doi.org/10.1002/2015JC011084>. doi:10.1002/2015JC011084 |
op_rights |
info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.1002/2015JC011084 |
container_title |
Journal of Geophysical Research: Oceans |
container_volume |
120 |
container_issue |
9 |
container_start_page |
6185 |
op_container_end_page |
6201 |
_version_ |
1766341851420295168 |