Progress toward a sea-floor observatory at a carbonate/hydrate mound in the northern Gulf of Mexico

McGee, Thomas M.; Woolsey, J. Robert; Macelloni, Leonardo; Battista, B.; Caruso, Simona; Lapham, L.; Goebel, Vaughn; Carrol, J.

doi:10.1109/baltic.2008.4625508

Cited by 9 publications

(8 citation statements)

References 10 publications

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“…The site overlies a salt diapir (Ryan et al, 2009). Weak coupling of methane and sulfur cycling ($500 m subbottom), and a complex fault networks connect deep subsurface and surficial habitats (McGee et al, 2008). Sediments from the northwest seep at MC118 (hereafter gassy seep) were gas-charged and overlain by Beggiatoa mats.…”

Section: Study Sitementioning

confidence: 99%

Weak coupling between sulfate reduction and the anaerobic oxidation of methane in methane-rich seafloor sediments during ex situ incubation

Bowles

Samarkin

Bowles

et al. 2011

Geochimica et Cosmochimica Acta

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Section: Study Sitementioning

confidence: 99%

Weak coupling between sulfate reduction and the anaerobic oxidation of methane in methane-rich seafloor sediments during ex situ incubation

Bowles

Samarkin

Bowles

et al. 2011

Geochimica et Cosmochimica Acta

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“…Water depth at the site is approximately 900 m and the bottom water temperature is typically around 6°C. The geologic setting of this site has been described in detail by Sassen et al (2006) and McGee et al (2008McGee et al ( , 2009a. Briefly, hydrocarbon gases and oil seep to the seafloor via fault migration-conduits derived from an isolated salt body some hundreds of meters beneath the seafloor.…”

Section: Site Characteristicsmentioning

confidence: 99%

Time integrated variation of sources of fluids and seepage dynamics archived in authigenic carbonates from Gulf of Mexico Gas Hydrate Seafloor Observatory

et al. 2014

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“…The swath bathymetry at MC 118 (Figure 4.3A) shows that the seafloor is smooth and featureless except for a submarine canyon crossing its northeastern portion and an area of irregular relief in its southwest portion [Lutken et al, 2006;McGee et al, 2008]. The area of irregular topography to the southeast is the focus of this study, and is a 1 km 2 mound that contains three crater complexes (Figure 4.3A).…”

Section: Site Descriptionmentioning

confidence: 97%

“…Fluid and gas venting at the mound is associated with fractures that originate from an underlying salt diapir that is estimated to be greater than 350 m deep [McGee et al, 2008]. There are large Structure II gas hydrate outcrops associated with the region of high methane flux.…”

Section: Hyflux Final Reportmentioning

confidence: 99%

Remote Sensing and Sea-Truth Measurements of Methane Flux to the Atmosphere (HYFLUX project)

MacDonald¹

2011

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A multi-disciplinary investigation of distribution and magnitude of methane fluxes from seafloor gas hydrate deposits in the Gulf of Mexico was conducted based on results obtained from satellite synthetic aperture radar (SAR) remote sensing and from sampling conducted during a research expedition to three sites where gas hydrate occurs (MC118, GC600, and GC185). Samples of sediments, water, and air were collected from the ship and from an ROV submersible using sediments cores, niskin bottles attached to the ROV and to a rosette, and an automated sea-air interface collector.The SAR images were used to quantify the magnitude and distribution of natural oil and gas seeps that produced perennial oil slicks on the ocean surface. A total of 176 SAR images were processed using a texture classifying neural network algorithm, which segmented the ocean surface into oil-free and oilcovered water. Geostatistical analysis indicates that there are a total of 1081 seep formations distributed over the entire Gulf of Mexico basin. Oil-covered water comprised an average of 780.0 sq. km (sd 86.03) distributed with an area of 147,370 sq. km. Persistent oil and gas seeps were also detected with SAR sampling on other ocean margins located in the Black Sea, western coast of Africa, and offshore Pakistan.Analysis of sediment cores from all three sites show profiles of sulfate, sulfide, calcium and alkalinity that indicated anaerobic oxidation of methane with precipitation of authigenic carbonates. Difference among the three sampling sites may reflect the relative magnitude of methane flux.Methane concentrations in water column samples collected by ROV and rosette deployments from MC118 ranged from ~33,000 nM at the seafloor to ~12 nM in the mixed layer with isolated peaks up to ~13,670 nM coincident with the top of the gas hydrate stability field. Average plume methane, ethane, and propane concentrations in the mixed layer are 7, 630, and 9,540 times saturation, respectively. Based on the contemporaneous wind speeds at this site, contemporary estimates of the diffusive fluxes from the mixed layer to the atmosphere for methane, ethane, and propane are 26.5, 2.10, and 2.78 µmol/m 2 d, respectively.Continuous measurements of air and sea surface concentrations of methane were made to obtain high spatial and temporal resolution of the diffusive net sea-to-air fluxes. The atmospheric methane fluctuated between 1.70 ppm and 2.40 ppm during the entire cruise except for high concentrations (up to 4.01 ppm) sampled during the end of the occupation of GC600 and the transit between GC600 and GC185. Results from interpolations within the survey areas show the daily methane fluxes to the atmosphere at the three sites range from 0.744 to 300 mol d-1.Considering that the majority of seeps in the GOM are deep (>500 m), elevated CH 4 concentrations in near-surface waters resulting from bubble-mediated CH 4 transport in the water column are expected to be widespread in the Gulf of Mexico. HYFLUX Final Report iiTexas A&M University -Corpus Christi...

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Progress toward a sea-floor observatory at a carbonate/hydrate mound in the northern Gulf of Mexico

Cited by 9 publications

References 10 publications

Weak coupling between sulfate reduction and the anaerobic oxidation of methane in methane-rich seafloor sediments during ex situ incubation

Weak coupling between sulfate reduction and the anaerobic oxidation of methane in methane-rich seafloor sediments during ex situ incubation

Time integrated variation of sources of fluids and seepage dynamics archived in authigenic carbonates from Gulf of Mexico Gas Hydrate Seafloor Observatory

Remote Sensing and Sea-Truth Measurements of Methane Flux to the Atmosphere (HYFLUX project)

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