Gas bubble emissions from submarine hydrocarbon seeps at the Makran continental margin (offshore Pakistan)
Fuente:
PANGAEA
Saved in:
| Main Authors: | , , , , |
|---|---|
| Format: | Dataset Open Access |
| Language: | en |
| Published: |
PANGAEA
2012
|
| Subjects: | |
| Online Access: | |
| Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
| _version_ | 1867170464263045120 |
|---|---|
| author | Römer, Miriam Sahling, Heiko Pape, Thomas Spieß, Volkhard Bohrmann, Gerhard |
| author_facet | Römer, Miriam Sahling, Heiko Pape, Thomas Spieß, Volkhard Bohrmann, Gerhard |
| collection | Datos científicos de ciencias marinas y ambientales |
| contents | Evidence for twelve sites with gas bubble emissions causing hydroacoustic anomalies in 18 kHz echosounder records ('flares') was obtained at the convergent Makran continental margin. The hydroacoustic anomalies originating from hydrocarbon seeps at water depths between 575 and 2870 m disappeared after rising up to 2000 m in the water column. Dives with the remotely operated vehicle 'Quest 4000 m' revealed that several individual bubble vents contributed to one hydroacoustic anomaly. Analyzed gas samples suggest that bubbles were mainly composed of methane of microbial origin. Bubble size distributions and rise velocities were determined and the volume flux was estimated by counting the emitted bubbles and using their average volume. We found that a low volume flux (Flare 1 at 575 mbsl: 90 ml/min) caused a weak hydroacoustic signal in echograms whereas high volume fluxes (Flare 2 at 1027 mbsl: 1590 ml/min; Flare 5 C at 2870 mbsl: 760 ml/min) caused strong anomalies. The total methane bubble flux in the study area was estimated by multiplying the average methane flux causing a strong hydroacoustic anomaly in the echosounder record with the total number of equivalent anomalies. An order-of-magnitude estimate further considers the temporal variability of some of the flares, assuming a constant flux over time, and allows a large range of uncertainty inherent to the method. Our results on the fate of bubbles and the order-of-magnitude estimate suggest that all of the ?40 ± 32 ? 106 mol methane emitted per year within the gas hydrate stability zone remain in the deep ocean. |
| format | Dataset Open Access |
| id | pangaea_https___doi_org_10_1594_PANGAEA_802141 |
| institution | PANGAEA |
| language | en |
| publishDate | 2012 |
| publisher | PANGAEA |
| record_format | pangaea |
| spellingShingle | Gas bubble emissions from submarine hydrocarbon seeps at the Makran continental margin (offshore Pakistan) Römer, Miriam Sahling, Heiko Pape, Thomas Spieß, Volkhard Bohrmann, Gerhard Center for Marine Environmental Sciences; MARUM Evidence for twelve sites with gas bubble emissions causing hydroacoustic anomalies in 18 kHz echosounder records ('flares') was obtained at the convergent Makran continental margin. The hydroacoustic anomalies originating from hydrocarbon seeps at water depths between 575 and 2870 m disappeared after rising up to 2000 m in the water column. Dives with the remotely operated vehicle 'Quest 4000 m' revealed that several individual bubble vents contributed to one hydroacoustic anomaly. Analyzed gas samples suggest that bubbles were mainly composed of methane of microbial origin. Bubble size distributions and rise velocities were determined and the volume flux was estimated by counting the emitted bubbles and using their average volume. We found that a low volume flux (Flare 1 at 575 mbsl: 90 ml/min) caused a weak hydroacoustic signal in echograms whereas high volume fluxes (Flare 2 at 1027 mbsl: 1590 ml/min; Flare 5 C at 2870 mbsl: 760 ml/min) caused strong anomalies. The total methane bubble flux in the study area was estimated by multiplying the average methane flux causing a strong hydroacoustic anomaly in the echosounder record with the total number of equivalent anomalies. An order-of-magnitude estimate further considers the temporal variability of some of the flares, assuming a constant flux over time, and allows a large range of uncertainty inherent to the method. Our results on the fate of bubbles and the order-of-magnitude estimate suggest that all of the ?40 ± 32 ? 106 mol methane emitted per year within the gas hydrate stability zone remain in the deep ocean. |
| title | Gas bubble emissions from submarine hydrocarbon seeps at the Makran continental margin (offshore Pakistan) |
| topic | Center for Marine Environmental Sciences; MARUM |
| url | https://doi.org/10.1594/PANGAEA.802141 |