Dissolution rates of pure methane hydrate and carbon-dioxide hydrate in undersaturated seawater at 1000-m depth

Rehder, Gregor; Kirby, Stephen H.; Durham, W. B.; Stern, Laura A.; Peltzer, Edward T.; Pinkston, John; Brewer, Peter G.

doi:10.1016/j.gca.2003.07.001

Cited by 140 publications

(135 citation statements)

References 30 publications

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“…Substantial microbial oxidation in adjacent sediments and overlying waters precludes the use of stable isotopes of CH 4 to identify the fraction of CH 4 dissolved in the water column or sediment that is released from clathrates. Rehder et al [19] measured the rate of dissolution of synthetic CH 4 clathrate in the clathrate stability zone (P, T) in an advecting field of seawater that was undersaturated with respect to CH 4 concentration. Since natural clathrates are usually located within a sediment matrix surrounded by CH 4 -rich or CH 4 -saturated fluids, the Rehder et al rates place an upper bound on the decomposing clathrate contribution (11670 ± 950 mol CH 4 m − 2 yr − 1 ).…”

Section: Discussionmentioning

confidence: 99%

“…Methane clathrate hydrates (clathrates), an important global CH 4 reservoir estimated to contain over 10 3 times more CH 4 than the atmosphere [15], are also present in deep Black Sea sediments [11,12], and represent an unknown CH 4 source. The stability of clathrates is governed by pressure, temperature, and CH 4 concentration [16][17][18][19]. Even in a pressure-temperature zone where clathrates are stable, a clathrate will decompose if the water surrounding it contains a CH 4 concentration below what is necessary to form clathrates.…”

Section: Introductionmentioning

confidence: 99%

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Basin-wide estimates of the input of methane from seeps and clathrates to the Black Sea

Kessler

Reeburgh

Southon

et al. 2006

Earth and Planetary Science Letters

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Numerous methane-emitting bottom features, such as seeps, methane clathrate hydrates (clathrates), and mud volcanoes, have been identified recently in the Black Sea. The fluxes of methane from these sources averaged over large spatial scales are unknown. Here we take advantage of the fact that the Black Sea is a semi-enclosed basin with restricted deep water circulation to establish firstorder estimates of basin-wide fluxes of methane from these sources to the water column and atmosphere. First, we measured the natural radiocarbon content of methane ( 14 C-CH 4 ) dissolved in the water column and emitted from seeps. The 14 C-CH 4 results showed that the dominant source of methane to the water column is emitted from seeps and a smaller source is diagenetically produced in relatively modern sediments. The 14 C-CH 4 results were then used to partition a basin-wide total methane budget; this analysis estimated the basin-wide flux of methane from seeps and clathrates to the water column to be 3.60 to 4.28 Tg yr − 1 . Second, a geochemical box model was used to calculate possible distributions of methane inputs from seeps and clathrates as well as provide additional estimates of the basin-wide flux of methane from seeps and clathrates to the water column (4.95 to 5.65 Tg yr − 1 ).

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Basin-wide estimates of the input of methane from seeps and clathrates to the Black Sea

Kessler

Reeburgh

Southon

et al. 2006

Earth and Planetary Science Letters

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“…The net r esult is a gas ex change rate for CO 2 ≅10 x slower than for typical atmospheri c gases, inclu ding nitro gen. However, th e approximatel y 10x greater solubility of CO 2 in seawat er (Aya et al, 1997;Haugan an d Drang e, 1992;Rehder et al, 2004) until the hydr ate phase boundary i s reach ed, result s in far faster dissolutio n rates.…”

Section: Air-sea Gas Exchangementioning

confidence: 99%

Determination of gas bubble fractionation rates in the deep ocean by laser Raman spectroscopy

2006

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A new d eep-sea l aser Ram an spectrom eter (DORISS -Deep Ocean Raman In Situ Spectromet er) is used to ob serv e the preferenti al dissoluti on of CO 2 into seawater from a 50%-50% CO 2 -N 2 gas mi xture in a set of experimen ts that test a proposed met hod of CO 2 sequestrati on i n the deep ocean. In a fir st set of experiments performed at 300 m depth, an open-bott omed 1000 cm 3 cube was used to contai n the gas mixture; and in a second set of experiment s a 2.5 cm 3 funnel was used t o hold a bubbl e of t he gas mixtur e in front of the sampli ng optic. By ob servi ng th e ch anging ratios of the CO 2 and N 2 Raman bands we were abl e to determi ne the g as flux and the mass tran sfer co efficient at 300 m depth and com pare th em to t heoreti cal calcul ations for air-sea gas ex change. Although each exp eriment had a differ ent config uration, comparable result s were obt ained. As expected, th e ratio of CO 2 to N 2 drops off at an expon ential rate as CO 2 i s preferen tially di ssolved i n seawater. In fitting th e dat a with theoretical gas flux calculation s, the boundary layer thick ness was det ermined t o be ~42 µm for the gas cube, and ~165 µm for the gas funnel reflecting different boundary l ayer t urbulence. The mass tran sfer co efficient s for CO 2 are k L = 2.82 x 10 -5 m/s for the gas cube experiment, and k L = 7.98 x 10 -6 m/s for the gas funnel experim ent.

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“…The North Sea is an important petroleum production basin with estimated reserves in 2001 of 19.5 and 17 billion barrels for the UK and Norwegian sectors, respectively (Sem and Ellerman, 1999), providing 5.7% of global supply in 2005 (Nakhle, 2008). At the 22/4b site, a bubble megaplume (> 10 6 L d -1 ) is associated with a gas blowout in 1990 in the central North Sea ~200 km from the Scottish mainland at 1.63°E, 57.92°N (Leifer and Judd, 2015), and has been the subject of studies for many years (Rehder et al, 1998;Rehder et al, 2004;Schneider von Deimling et al, 2007;Schneider von Deimling et al, 2015). This megaplume is by far the strongest bubble plume quantified to date , emitting an estimated 90 L s -1 at 12 bar from a seabed crater with maximum depth of 120 m, while exhibiting strong upwelling flows.…”

Section: Geologic Marine Methane Importancementioning

confidence: 99%

Bubble momentum plume as a possible mechanism for an early breakdown of the seasonal stratification in the northern North Sea

Nauw

Линке

Leifer

2015

Marine and Petroleum Geology

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The presence of a seasonal thermocline likely plays a key role in restraining methane released from a seabed source in the deeper water column, thereby inhibiting exchange to the atmosphere. The bubble plume itself, however, generates an upward motion of fluid, e.g. upwelling and may thereby be partially responsible for an early breakdown of the seasonal thermocline. Measurements at site 22/4b, located at (57 o 55'N, 1 o 38'E) in the UK Central North Sea, 200 km east of the Scottish mainland, where gas is still being released since a blow out in 1990, have been used to identify the generation of the seasonal thermocline, and thus, the depth of the upper mixed layer and its breakdown in autumn. Data derived from two landers, containing an Acoustic Doppler Current Profiler and a Conductivity Temperature Depth recorder, were used to determine the mixed layer depth and the breakdown of the thermocline. Mixing of upper layer fluid into the lower layer has been inferred from large amplitude variations in the near-bottom temperature. The ADCPs estimate velocity profiles in four beam directions using Doppler shifted frequency from acoustic pings sent out and received by four different transducers in a specific configuration. Besides that, the intensity of the backscattered sound per transducer is also recorded. Bubbles from the nearby plume contaminate the signal during part of the tidal cycle, but in bubble free periods, the mixed layer depth can be estimated using the acoustic backscatter signal as local maxima. Results show that the thermocline broke down between mid-October and early November, several weeks earlier than the breakdown of the thermocline in nearby/comparable areas, likely caused by bubble-induced downwelling at the site. The early breakdown of the thermocline was accompanied by multiple occurrence of a strong jet-like structure, associated with the seasonal tidal mixing front. 2

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Dissolution rates of pure methane hydrate and carbon-dioxide hydrate in undersaturated seawater at 1000-m depth

Cited by 140 publications

References 30 publications

Basin-wide estimates of the input of methane from seeps and clathrates to the Black Sea

Basin-wide estimates of the input of methane from seeps and clathrates to the Black Sea

Determination of gas bubble fractionation rates in the deep ocean by laser Raman spectroscopy

Bubble momentum plume as a possible mechanism for an early breakdown of the seasonal stratification in the northern North Sea

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