Phase equilibrium of gas hydrate: Implications for the formation of hydrate in the deep sea floor

Zatsepina, Olga Ye.; Buffett, B. A.

doi:10.1029/97gl01599

Cited by 157 publications

(104 citation statements)

References 17 publications

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“…This mismatch arises as local pathways for fluid and gas flow are not considered in our approach. Both fluid and gas flow have a strong effect on the accumulation of gas hydrates in marine sediments and could enhance the hydrate inventory [Zatsepina and Buffett, 1997;Xu and Ruppel, 1999;Buffett and Archer, 2004;Piñero et al, 2013]. Therefore, the value of 1146 Gt C should be considered as a minimum estimate based on the in situ microbial degradation of POC.…”

Section: Discussionmentioning

confidence: 99%

Modeling the fate of methane hydrates under global warming

Kretschmer

Biastoch

Rüpke

et al. 2015

Global Biogeochemical Cycles

127

146

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Large amounts of methane hydrate locked up within marine sediments are vulnerable to climate change. Changes in bottom water temperatures may lead to their destabilization and the release of methane into the water column or even the atmosphere. In a multimodel approach, the possible impact of destabilizing methane hydrates onto global climate within the next century is evaluated. The focus is set on changing bottom water temperatures to infer the response of the global methane hydrate inventory to future climate change. Present and future bottom water temperatures are evaluated by the combined use of hindcast high‐resolution ocean circulation simulations and climate modeling for the next century. The changing global hydrate inventory is computed using the parameterized transfer function recently proposed by Wallmann et al. (2012). We find that the present‐day world's total marine methane hydrate inventory is estimated to be 1146 Gt of methane carbon. Within the next 100 years this global inventory may be reduced by ∼0.03% (releasing ∼473 Mt methane from the seafloor). Compared to the present‐day annual emissions of anthropogenic methane, the amount of methane released from melting hydrates by 2100 is small and will not have a major impact on the global climate. On a regional scale, ocean bottom warming over the next 100 years will result in a relatively large decrease in the methane hydrate deposits, with the Arctic and Blake Ridge region, offshore South Carolina, being most affected.

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Section: Discussionmentioning

confidence: 99%

Modeling the fate of methane hydrates under global warming

Kretschmer

Biastoch

Rüpke

et al. 2015

Global Biogeochemical Cycles

127

146

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show abstract

“…Modeling of hydrate formation has shown that free gas is not required for the formation of hydrate in seafloor sediments [Rempel and Buffett, 1997;Zatsepina and Buffett, 1997;Xu and Ruppel, 1999]. When fluids with a high concentration of dissolved methane are advected into the hydrate stability zone, a decrease in methane solubility can result in hydrate formation without the presence of free gas.…”

Section: Is Hydrate Required?mentioning

confidence: 99%

Seismic and seafloor evidence for free gas, gas hydrates, and fluid seeps on the transform margin offshore Cape Mendocino

et al. 2003

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[1] Seismic data and seafloor samples indicate the presence of free gas, gas hydrate, and fluid seeps south of the Gorda Escarpment, a topographic feature that marks the eastern end of the Gorda/Pacific transform plate boundary southwest of Cape Mendocino, California. In spite of high sedimentation rates and high biological productivity, direct or indirect indicators of gas hydrate presence had not previously been recognized in this region, or along transform margins in general. Gas is indicated by a bottom simulating reflection (BSR) observed near the Gorda Escarpment, by ''bright spots'' and ''gas curtains'' scattered throughout the sedimentary basin to the south, and by d C and d18 O isotopes of carbonates, which are similar to those recovered from other hydrate-bearing regions. The BSR reflection coefficient of À0.13 ± 0.04 and interval velocities as low as 1.38 km/s indicate that free gas is present beneath the BSR. Local shallowing of the BSR toward the north facing Gorda Escarpment and beneath a channel near the crest suggests fluid flow toward the seafloor. Integrating these various observations, we suggest a scenario in which methane is formed in thick Miocene and Pliocene deposits of organicrich sediments that fill the marginal basin south of the transform fault. Dissolved and free gas migrates toward the escarpment along stratigraphic horizons, resulting in hydrate formation and in channels, slumps and chemosynthetic communities on the face of the escarpment. We conclude that the BSR appears where hydrate-bearing sediments are uplifted because of current triple junction tectonics.

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“…The pressure and temperature conditions used for the MGH stability curve were calculated using Multiflash (InfoChem Computer Services, Ltd., London, UK) assuming a gas composition of pure methane and a euxinic pore water salinity of 33.5k. Methane solubility was calculated using the methods outlined by Zatsepina and Buffett [1997] and Rempel and Buffett [1998]. In particular, for a given pressure P the methane solubility along the stability curve Ceq(T3) is first determined as a function of the stability temperature •.…”

Section: Introductionmentioning

confidence: 99%

Effect of seafloor temperature and pressure variations on methane flux from a gas hydrate layer: Comparison between current and late Paleocene climate conditions

Xu¹,

Lowell²,

Peltzer³

2001

J. Geophys. Res.

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Abstract. We investigate the response of a methane hydrate layer in marine sediments to cyclic seafloor perturbations of temperature and pressure in order to determine the change in seafloor methane flux resulting from gas hydrate dissociation or accumulation. By using a one-dimensional model describing mass, energy, and methane transport through porous sediments we show that seafloor pressure changes have negligible effect on methane transport to the seafloor. The effect of seafloor temperature perturbations is more pronounced than that of pressure. With an initial seafloor temperature of 3øC, which corresponds to current conditions on Earth, a + 4øC seafloor temperature perturbation occurring over 104 years does The principal point is that strong coupling between methane transport and seafloor temperature occurs because significant hydrate accumulation and dissociation take place near the seafloor only when the seafloor temperature is relatively high. This was the case during the late Paleocene, but it is not the case at present.

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Phase equilibrium of gas hydrate: Implications for the formation of hydrate in the deep sea floor

Cited by 157 publications

References 17 publications

Modeling the fate of methane hydrates under global warming

Modeling the fate of methane hydrates under global warming

Seismic and seafloor evidence for free gas, gas hydrates, and fluid seeps on the transform margin offshore Cape Mendocino

Effect of seafloor temperature and pressure variations on methane flux from a gas hydrate layer: Comparison between current and late Paleocene climate conditions

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