Methane hydrate stability in seawater

Dickens, Gerald R.; Quinby-Hunt, Mary S.

doi:10.1029/94gl01858

Cited by 358 publications

(288 citation statements)

References 21 publications

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“…The seawater methane hydrate stability work of Dickens and Quinby-Hunt (1994) indicates that methane hydrates in the deep Black Sea (9 1C) should be stable below 750 m. While the marine gas hydrate stability zone creates an effective geochemical barrier to upward-migrating methane, an unknown quantity of methane is able to transit the barrier (Ginsburg, 1998). Although the top clathrate boundary lies within the hydrate P-T stability field, lower methane concentrations here render this surface unstable (i.e.…”

Section: Article In Pressmentioning

confidence: 99%

Stable carbon and hydrogen isotope measurements on Black Sea water-column methane

Reeburgh

Tyler

Carroll

2006

Deep Sea Research Part II: Topical Studies in Oceanography

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We report measurements of d 13 C-CH 4 and d 2 H-CH 4 at a central station in the Black Sea. We considered the Black Sea as a ''biogeochemical bucket'' and the single station as a basin-wide integrator of processes affecting methane. Considering the rapid (3.6-18 yr) turnover of methane and the similarity of these stable isotope distributions to the methane concentration and oxidation rate profiles [Reeburgh, Ward, Whalen, Sandbeck, Kilpatrick, Kerkhof, 1991. Black Sea methane geochemistry. Deep-Sea Research 38, S1189-S1210], it appears that methane is being added approximately as fast as it is being oxidized. Methane can be thought of as ''running in place'' in the Black Sea water column.Recent reports of extensive vents on the northern side of the Black Sea suggest that they might be a methane source capable of effectively balancing the Black Sea methane budget. Unfortunately, we have limited information on basin-wide seep fluxes and cannot identify them with stable isotope measurements. Methane oxidation (and accompanying isotope fractionation) is so extensive that the water-column stable isotope measurements provide little information on methane sources. Future measurements of 14 C-CH 4 should permit partitioning Black Sea methane sources into fossil and recent components. r

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Section: Article In Pressmentioning

confidence: 99%

Stable carbon and hydrogen isotope measurements on Black Sea water-column methane

Reeburgh

Tyler

Carroll

2006

Deep Sea Research Part II: Topical Studies in Oceanography

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“…with six different methane hydrate phase boundaries: (1) and (2) Dickens and Quinby-Hunt (1994;, (3) Distribution Coefficient Method or K vsi -Method (Sloan and Koh, 2008), (4) Moridis et al (2008), (5) Tischenko et al (2005) and (6) Lu and Sultan (2008). Water depth was converted to hydrostatic pressure assuming a constant water density of 1046 kg m 3 (Giustiniani et al, 2013).…”

Section: Volume Of the Ghszmentioning

confidence: 99%

The challenges of quantifying the carbon stored in Arctic marine gas hydrate

Marín‐Moreno

Giustiniani

Tinivella

et al. 2016

Marine and Petroleum Geology

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Highlights• The amount of carbon stored in hydrate below the Arctic Ocean remains uncertain• A function for the fluid flow that gives observed hydrate saturations is proposed• Arctic marine gas hydrates likely form by upwards-advection of carbon-rich fluids• Equivalent fluid flows of 0.02-0.04 cm yr -1 result in hydrate saturations of 5-10%The quantification of the carbon stored in gas hydrate (GH) bearing marine sediments still remains a challenge. Despite recent efforts to develop approaches to better estimate the GH inventory globally, these estimates are still highly unconstrained due to insufficient field data and poor understanding of the mechanisms fuelling the GH stability zone (GHSZ). Here we use geophysically-derived GH saturations to constraint estimates of model-derived Arctic marine GH inventory at present. We also estimate the potential carbon released from GH dissociation under a seabed warming of 2°C over 100 yr. We estimate an inventory ranging between 0.28-541 Gt of C, which upper bound results in average GH saturations of 0.25%. Our upper bound is mainly controlled by our imposed upwards carbon-rich fluid flow of 0.01 cm yr -1 and it is five times greater than the most recent estimate that only considers in-situ degradation of particulate organic carbon (POC). To obtain the seismically-inferred GH saturations of 5-10% offshore west of Svalbard and in the Beaufort Sea, an upwards advection of carbon-rich fluids equivalent to 0.02 to 0.04 cm yr -1 is required. This mechanism may be the most important source of carbon reaching the GHSZ in Arctic marine sediments. A 2°C seabed temperature increase over 100 yr may reduce the GH inventory by about 88.44% (0.7 Gt C) if POC is the only source, and by about 5.4% (29.7 Gt C) if the main source of carbon is the upwards advection of carbon-rich fluids.

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“…Therefore, rather than extrapolating this empirical fit, we use phase boundaries based on a theoretical model tuned to experimental data up to~40 MPa [14]. These curves match the data of [13], but diverge from their empirical fits by 2-3 8C in the at the temperatures and pressures of interest here (Fig. 4).…”

Section: Heat Flowmentioning

confidence: 99%

“…The empirical fit to experimental data of Dickens and Quinby-Hunt [13] is based entirely on data below 15 MPa, whereas our data come entirely from hydrostatic pressures greater than 15 MPa. Therefore, rather than extrapolating this empirical fit, we use phase boundaries based on a theoretical model tuned to experimental data up to~40 MPa [14].…”

Section: Heat Flowmentioning

confidence: 99%

Low heat flow from young oceanic lithosphere at the Middle America Trench off Mexico

Minshull

Bartolomé

Byrne

et al. 2005

Earth and Planetary Science Letters

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Seismic reflection profiles across the Middle America Trench at 208N show a high amplitude bottom simulating reflector interpreted as marking a phase transition between methane hydrate and free gas in the pore space of both accreted and trench sediments. We determine the depth of the hydrate-gas phase boundary in order to estimate the geothermal gradient and hence the heat flow beneath the trench and the frontal part of the accretionary wedge which overlies the downgoing plate. After correction for sedimentation, heat flow values in the trench and through the accretionary wedge are only about half of the values predicted by plate cooling models for the 10 Ma subducting lithosphere. There is no systematic correlation between heat flow in the accretionary wedge and distance from the trench. A comparison with heat flow predicted by a simple analytical model suggests that there is little shear heating from within or beneath the wedge, despite the high basal friction suggested by the large taper angle of the wedge. The geothermal gradient varies systematically along the margin and is negatively correlated with the frontal slope of the wedge. Some local peaks may be attributed to channelised fluid expulsion. D

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Methane hydrate stability in seawater

Cited by 358 publications

References 21 publications

Stable carbon and hydrogen isotope measurements on Black Sea water-column methane

Stable carbon and hydrogen isotope measurements on Black Sea water-column methane

The challenges of quantifying the carbon stored in Arctic marine gas hydrate

Low heat flow from young oceanic lithosphere at the Middle America Trench off Mexico

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