Methane release from gas hydrates in the Rock Garden of the Hikurangi margin, New Zealand
Dissolved methane and high resolution bathymetry surveys were conducted over the Rock Garden region of Ritchie Ridge, along the Hikurangi margin, eastern New Zealand. Multibeam bathymetry reveals two prominent, northeast trending ridges, parallel to subduction along the margin, that are steep sided...
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Royal Society of New Zealand
2006
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ftoceanrep:oai:oceanrep.geomar.de:21397 2023-05-15T17:12:10+02:00 Methane release from gas hydrates in the Rock Garden of the Hikurangi margin, New Zealand Faure, K. Greinert, Jens Pecher, I. Graham, I. J. Massoth, G. J. deRonde, C. E. J. Wright, I. C. Baker, E. T. Olson, E.J. 2006 text https://oceanrep.geomar.de/id/eprint/21397/ https://oceanrep.geomar.de/id/eprint/21397/1/Faure.pdf en eng Royal Society of New Zealand https://oceanrep.geomar.de/id/eprint/21397/1/Faure.pdf Faure, K., Greinert, J. , Pecher, I., Graham, I. J., Massoth, G. J., deRonde, C. E. J., Wright, I. C., Baker, E. T. and Olson, E. J. (2006) Methane release from gas hydrates in the Rock Garden of the Hikurangi margin, New Zealand. New Zealand Journal of Geology and Geophysics, 49 . pp. 503-516. Article PeerReviewed 2006 ftoceanrep 2023-04-07T15:09:36Z Dissolved methane and high resolution bathymetry surveys were conducted over the Rock Garden region of Ritchie Ridge, along the Hikurangi margin, eastern New Zealand. Multibeam bathymetry reveals two prominent, northeast trending ridges, parallel to subduction along the margin, that are steep sided and extensively slumped. Elevated concentrations of methane (up to 10 nM, 10× background) within the water column are associated with a slump structure at the southern end of Eastern Rock Garden. The anomalous methane concentrations were detected by a methane sensor (METS) attached to a conductivity‐temperature‐depth‐optical backscatter device (CTDO) and are associated with elevated light scattering and flare‐shaped backscatter signals revealed by the ship's echo sounder. Increased particulate matter in the water column, possibly related to the seepage and/or higher rates of erosion near slump structures, is considered to be the cause of the increased light scattering, rather than bubbles in the water column. Methane concentrations calculated from the METS are in good agreement with concentrations measured by gas chromatography in water samples collected at the same time. However, there is a c. 20 min (c. 900 m) delay in the METS signal reaching maximum CH4 concentrations. The maximum methane concentration occurs near the plateau of Eastern Rock Garden close to the edge of a slump, at 610 m below sea level (mbsl). This is close to the depth (c. 630 mbsl) where a bottom simulating reflector (BSR) pinches out at the seafloor. Fluctuating water temperatures observed in previous studies indicate that the stability zone for pure methane hydrate in the ocean varies between 630 and 710 mbsl. However, based on calculations of the geothermal gradients from BSRs, we suggest gas hydrate in the study area to be more stable than hydrate from pure methane in sea water, moving the phase boundary in the ocean upward. Small fractions of additional higher order hydrocarbon gases are the most likely cause for increased hydrate ... Article in Journal/Newspaper Methane hydrate OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) Eastern Rock ENVELOPE(-55.715,-55.715,53.317,53.317) New Zealand |
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Open Polar |
collection |
OceanRep (GEOMAR Helmholtz Centre für Ocean Research Kiel) |
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ftoceanrep |
language |
English |
description |
Dissolved methane and high resolution bathymetry surveys were conducted over the Rock Garden region of Ritchie Ridge, along the Hikurangi margin, eastern New Zealand. Multibeam bathymetry reveals two prominent, northeast trending ridges, parallel to subduction along the margin, that are steep sided and extensively slumped. Elevated concentrations of methane (up to 10 nM, 10× background) within the water column are associated with a slump structure at the southern end of Eastern Rock Garden. The anomalous methane concentrations were detected by a methane sensor (METS) attached to a conductivity‐temperature‐depth‐optical backscatter device (CTDO) and are associated with elevated light scattering and flare‐shaped backscatter signals revealed by the ship's echo sounder. Increased particulate matter in the water column, possibly related to the seepage and/or higher rates of erosion near slump structures, is considered to be the cause of the increased light scattering, rather than bubbles in the water column. Methane concentrations calculated from the METS are in good agreement with concentrations measured by gas chromatography in water samples collected at the same time. However, there is a c. 20 min (c. 900 m) delay in the METS signal reaching maximum CH4 concentrations. The maximum methane concentration occurs near the plateau of Eastern Rock Garden close to the edge of a slump, at 610 m below sea level (mbsl). This is close to the depth (c. 630 mbsl) where a bottom simulating reflector (BSR) pinches out at the seafloor. Fluctuating water temperatures observed in previous studies indicate that the stability zone for pure methane hydrate in the ocean varies between 630 and 710 mbsl. However, based on calculations of the geothermal gradients from BSRs, we suggest gas hydrate in the study area to be more stable than hydrate from pure methane in sea water, moving the phase boundary in the ocean upward. Small fractions of additional higher order hydrocarbon gases are the most likely cause for increased hydrate ... |
format |
Article in Journal/Newspaper |
author |
Faure, K. Greinert, Jens Pecher, I. Graham, I. J. Massoth, G. J. deRonde, C. E. J. Wright, I. C. Baker, E. T. Olson, E.J. |
spellingShingle |
Faure, K. Greinert, Jens Pecher, I. Graham, I. J. Massoth, G. J. deRonde, C. E. J. Wright, I. C. Baker, E. T. Olson, E.J. Methane release from gas hydrates in the Rock Garden of the Hikurangi margin, New Zealand |
author_facet |
Faure, K. Greinert, Jens Pecher, I. Graham, I. J. Massoth, G. J. deRonde, C. E. J. Wright, I. C. Baker, E. T. Olson, E.J. |
author_sort |
Faure, K. |
title |
Methane release from gas hydrates in the Rock Garden of the Hikurangi margin, New Zealand |
title_short |
Methane release from gas hydrates in the Rock Garden of the Hikurangi margin, New Zealand |
title_full |
Methane release from gas hydrates in the Rock Garden of the Hikurangi margin, New Zealand |
title_fullStr |
Methane release from gas hydrates in the Rock Garden of the Hikurangi margin, New Zealand |
title_full_unstemmed |
Methane release from gas hydrates in the Rock Garden of the Hikurangi margin, New Zealand |
title_sort |
methane release from gas hydrates in the rock garden of the hikurangi margin, new zealand |
publisher |
Royal Society of New Zealand |
publishDate |
2006 |
url |
https://oceanrep.geomar.de/id/eprint/21397/ https://oceanrep.geomar.de/id/eprint/21397/1/Faure.pdf |
long_lat |
ENVELOPE(-55.715,-55.715,53.317,53.317) |
geographic |
Eastern Rock New Zealand |
geographic_facet |
Eastern Rock New Zealand |
genre |
Methane hydrate |
genre_facet |
Methane hydrate |
op_relation |
https://oceanrep.geomar.de/id/eprint/21397/1/Faure.pdf Faure, K., Greinert, J. , Pecher, I., Graham, I. J., Massoth, G. J., deRonde, C. E. J., Wright, I. C., Baker, E. T. and Olson, E. J. (2006) Methane release from gas hydrates in the Rock Garden of the Hikurangi margin, New Zealand. New Zealand Journal of Geology and Geophysics, 49 . pp. 503-516. |
_version_ |
1766068954355204096 |