Oceanic Methane Biogeochemistry

Reeburgh, William S.

doi:10.1021/cr050362v

Cited by 1,359 publications

(992 citation statements)

References 334 publications

(692 reference statements)

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“…6). However, the bottom layer [CH 4 ] was usually higher than that in the surface layer, indicating a rapid bottom-up transport mechanism (Reeburgh, 2007). At Stations 3 and 4 with the strongest water stratification, SST was 3.38°C and 2.38°C higher than the bottom temperature, respectively, while [CH 4 ] was relatively low and homogeneous, changing from 7.39 nmol kg À1 (Station 3) or 7.87 nmol kg À1 (Station 4) in the bottom layer to 6.14 nmol kg À1 (Station 3) or 5.11 nmol kg À1 (Station 4) in the surface layer (Fig.…”

Section: Bottom-up Transportation Of Chmentioning

confidence: 99%

“…Due to natural physical and biological processes and anthropogenic activities, sea surface concentrations of dissolved CH 4 ([CH 4 ] for short) usually exceed atmospheric equilibrium (e.g., Lamontagne et al, 1973;Conrad and Seiler, 1988;Plass-Dülmer et al, 1993, 1995Reeburgh, 2007). In open oceans, CH 4 sources in shallow water depths are provided by microbial subsurface CH 4 generation taking place in zooplankton guts, the oxygen-deficient interior of particles, or under phosphate-limiting conditions (Karl et al, 2008;Damm et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

“…In open oceans, CH 4 sources in shallow water depths are provided by microbial subsurface CH 4 generation taking place in zooplankton guts, the oxygen-deficient interior of particles, or under phosphate-limiting conditions (Karl et al, 2008;Damm et al, 2010). In waters overlying continental shelves, however, the organic-rich sediment serves as a major source of CH 4 in the water column compared to net production in the mixed layer (Martens and Berner, 1974;Martens and Klump, 1980;Reeburgh, 2007). The shallow-water [CH 4 ] can also be elevated due to gas seepages and/or oil spills (Bernard et al, 1976;Reed and Kaplan, 1977;Rehder et al, 1998Rehder et al, , 2002Kessler et al, 2011;Gülzow et al, 2013) and advection of CH 4 -rich freshwaters (Sackett and Brooks, 1975;Cline et al, 1986;Zhang et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

“…The shallow-water [CH 4 ] can also be elevated due to gas seepages and/or oil spills (Bernard et al, 1976;Reed and Kaplan, 1977;Rehder et al, 1998Rehder et al, , 2002Kessler et al, 2011;Gülzow et al, 2013) and advection of CH 4 -rich freshwaters (Sackett and Brooks, 1975;Cline et al, 1986;Zhang et al, 2008). Since CH 4 is oxidized to dissolved inorganic carbon via microbial oxidation processes (Sieburth et al, 1987;Jones, 1991;Reeburgh, 2007) and/or lost via sea-air gas exchange (Crutzen, 1991;Bange et al, 1994), determining [CH 4 ] in surface water with high spatiotemporal data coverage is critical in adding to our understanding of the marine CH 4 cycle and furthermore of the marine carbon cycle. Additionally, quantifying the leaked CH 4 dissolved in the water might be an effective approach to assess the size of an oil spill, which is essential to understand its environmental impacts (Valentine, 2010).…”

Section: Introductionmentioning

confidence: 99%

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Enhanced methane emissions from oil and gas exploration areas to the atmosphere – The central Bohai Sea

Zhang

Zhao

Zhai

et al. 2014

Marine Pollution Bulletin

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a b s t r a c tThe distributions of dissolved methane in the central Bohai Sea were investigated in November 2011, May 2012, July 2012, and August 2012. Methane concentration in surface seawater, determined using an underway measurement system combined with wavelength-scanned cavity ring-down spectroscopy, showed marked spatiotemporal variations with saturation ratio from 107% to 1193%. The central Bohai Sea was thus a source of atmospheric methane during the survey periods. Several episodic oil and gas spill events increased surface methane concentration by up to 4.7 times and raised the local methane outgassing rate by up to 14.6 times. This study demonstrated a method to detect seafloor CH 4 leakages at the sea surface, which may have applicability in many shallow sea areas with oil and gas exploration activities around the world.

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Section: Bottom-up Transportation Of Chmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Enhanced methane emissions from oil and gas exploration areas to the atmosphere – The central Bohai Sea

Zhang

Zhao

Zhai

et al. 2014

Marine Pollution Bulletin

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“…Gas seeps are defined by the source and composition of the gas feeding the seep, with biologically generated gas consisting almost entirely of methane, and thermally generated gas often consisting of methane with moderate levels of carbon dioxide, ethane, propane, and butane. Hydrocarbon seeps have been the subject of intense recent study, particularly on account of their interesting ecology, and their role in the marine methane and carbon cycle (Orphan et al 2002;Sahling et al 2002;Boetius and Suess 2004;Levin 2005;Reeburgh 2007). The amount of fossil, radiocarbon-free methane in the atmosphere suggests that natural emission from geological sources (seeps) is significant and possibly underestimated (Etiope et al 2008).…”

Section: Introductionmentioning

confidence: 99%

Gas flux and carbonate occurrence at a shallow seep of thermogenic natural gas

et al. 2010

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The Coal Oil Point seep field located offshore Santa Barbara, CA, consists of dozens of named seeps, including a peripheral ∼200 m 2 area known as Brian Seep, located in 10 m water depth. A single comprehensive survey of gas flux at Brian Seep yielded a methane release rate of ∼450 moles of CH 4 per day, originating from 68 persistent gas vents and 23 intermittent vents, with gas flux among persistent vents displaying a log normal frequency distribution. A subsequent series of 33 repeat surveys conducted over a period of 6 months tracked eight persistent vents, and revealed substantial temporal variability in gas venting, with flux from each individual vent varying by more than a factor of 4. During wintertime surveys sediment was largely absent from the site, and carbonate concretions were exposed at the seafloor. The presence of the carbonates was unexpected, as the thermogenic seep gas contains 6.7% CO 2 , which should act to dissolve carbonates. The average δ 13 C of the carbonates was −29.2±2.8‰ VPDB, compared to a range of −1.0 to +7.8‰ for CO 2 in the seep gas, indicating that CO 2 from the seep gas is quantitatively not as important as 13 Cdepleted bicarbonate derived from methane oxidation. Methane, with a δ 13 C of approximately −43‰, is oxidized and the resulting inorganic carbon precipitates as highmagnesium calcite and other carbonate minerals. This finding is supported by 13 C-depleted biomarkers typically associated with anaerobic methanotrophic archaea and their bacterial syntrophic partners in the carbonates (lipid biomarker δ 13 C ranged from −84 to −25‰). The inconsistency in δ 13 C between the carbonates and the seeping CO 2 was resolved by discovering pockets of gas trapped near the base of the sediment column with δ 13 C-CO 2 values ranging from −26.9 to −11.6‰. A mechanism of carbonate formation is proposed in which carbonates form near the sediment-bedrock interface during times of sufficient sediment coverage, in which anaerobic oxidation of methane is favored. Precipitation occurs at a sufficient distance from active venting for the molecular and isotopic composition of seep gas to be masked by the generation of carbonate alkalinity from anaerobic methane oxidation.

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Thermogenic methane injection via bubble transport into the upper Arctic Ocean from the hydrate‐charged Vestnesa Ridge, Svalbard

Smith

Mienert

Bünz

et al. 2014

Geochem Geophys Geosyst

169

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We use new gas-hydrate geochemistry analyses, echosounder data, and three-dimensional PCable seismic data to study a gas-hydrate and free-gas system in 1200 m water depth at the Vestnesa Ridge offshore NW Svalbard. Geochemical measurements of gas from hydrates collected at the ridge revealed a thermogenic source. The presence of thermogenic gas and temperatures of 3.3 C result in a shallow top of the hydrate stability zone (THSZ) at 340 m below sea level (mbsl). Therefore, hydrate-skinned gas bubbles, which inhibit gas-dissolution processes, are thermodynamically stable to this shallow water depth. This was confirmed by hydroacoustic observations of flares in 2010 and 2012 reaching water depths between 210 and 480 mbsl. At the seafloor, bubbles are released from acoustically transparent zones in the seismic data, which we interpret as regions where free gas is migrating through the hydrate stability zone (HSZ). These intrusions result in vertical variations in the base of the HSZ (BHSZ) of up to 150 m, possibly making the shallow hydrate reservoir more susceptible to warming. Such Arctic gas-hydrate and free-gas systems are important because of their potential role in climate change and in fueling marine life, but remain largely understudied due to limited data coverage in seasonally ice-covered Arctic environments.

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Oceanic Methane Biogeochemistry

Cited by 1,359 publications

References 334 publications

Enhanced methane emissions from oil and gas exploration areas to the atmosphere – The central Bohai Sea

Enhanced methane emissions from oil and gas exploration areas to the atmosphere – The central Bohai Sea

Gas flux and carbonate occurrence at a shallow seep of thermogenic natural gas

Thermogenic methane injection via bubble transport into the upper Arctic Ocean from the hydrate‐charged Vestnesa Ridge, Svalbard

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