Variations of atmospheric methane supply from the Sea of Okhotsk induced by the seasonal ice cover

Lammers, Stefan; Suess, Erwin; Mansurov, M. N.; Anikiev, V. V.

doi:10.1029/95gb01144

Cited by 17 publications

(16 citation statements)

References 19 publications

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“…As shown in Figures 2–4 anomalously high concentrations of methane were observed in waters near the bottom of the eastern shelfbreak at a depth of approximately 200 m in every year (1998, 1999, and 2000), due to methane seepage from an underlying oil field [ Ginsburg et al , 1993; Lammers et al , 1995]. The methane concentration in the near‐bottom water along line E was relatively low compared to those of lines B and C at the south, clearly showing that thermogenic methane sources are not uniformly distributed geographically over the shelf northeast of Sakhalin.…”

Section: Resultsmentioning

confidence: 99%

“…The average emission rate in the western part of the Sea of Okhotsk (0.73 × 10 6 km 2 , ∼51% of the total) was estimated to be 11 Gg CH 4 yr −1 . On the basis of methane data observed in the northeastern shelf off Sakhalin in March 1991 and July 1992 along with a constant wind speed of 7 m s −1 , Lammers et al [1995] gave a sea‐air flux of 130 Gg CH 4 yr −1 in the entire Sea of Okhotsk, which was about 32% of the global flux (405 Gg CH 4 yr −1 ) given by Bates et al [1996]. They reported a remarkably high sea‐air methane flux (150 mol CH 4 km −2 d −1 in July 1992) as compared with that of this work (Table 1).…”

Section: Resultsmentioning

confidence: 99%

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Methane in the western part of the Sea of Okhotsk in 1998–2000

et al. 2004

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We measured oceanic methane in the western part of the Sea of Okhotsk in 1998, 1999, and 2000. An anomalously high methane concentration was found in near‐bottom water above the shelfbreak (∼200 m) off northeast Sakhalin every year: up to 488 nmol kg−1 in 1998, 981 nmol kg−1 in 1999, and 556 nmol kg−1 in 2000. This anomalously high concentration can be used to trace the water with density range 26.6 to 26.8 σθ in the upper Dense Shelf Water. In the shelf off east Sakhalin, a strong stratification caused by freshwater from Amur River controlled the upward transport of methane through the suppression of vertical convection. The calculated methane flux was largest in the northeastern shelf region of Sakhalin (88 mol CH4 km−2 d−1). In the western part of the Sea of Okhotsk (0.73 × 106 km2, 51% of total Sea of Okhotsk area), the emission rate of methane was 11 Gg CH4 yr−1.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Methane in the western part of the Sea of Okhotsk in 1998–2000

et al. 2004

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“…Lammers et al, 1995;Gaedicke et al, 1997;Obzhirov et al, 2004 Bering Sea <200 m Siliciclastic, polar, convergent margin.…”

Section: Australian Offshore Marginsmentioning

confidence: 99%

Australian offshore natural hydrocarbon seepage studies, a review and re-evaluation

Logan

Jones

Kennard

et al. 2010

Marine and Petroleum Geology

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“…Thus, we suggest that the decomposition of the recent primary production of organic matter supplies the methane in Storfjorden. In comparison, release of fossil methane from seepages would cause a much higher concentration like that detected in the ice-covered Sea of Okhotsk where methane is accumulated in concentrations 4300 nM under the ice (Lammers et al, 1995).…”

Section: Sediment Resuspension and Discharge Of Submarine Methanementioning

confidence: 99%

“…Water samples for methane measurements were taken immediately from the Niskin bottles and, within a few hours, the dissolved gas was extracted from the water by vacuum-ultrasonic treatment. Methane concentrations were measured with a gas chromatograph Chrompack 9003 (GC) with flame ionization detector (FID) (Lammers et al, 1995). For GC separation, we used a packed column (Porapac Q 80/100 mesh).…”

Section: Methodsmentioning

confidence: 99%

Excess of bottom-released methane in an Arctic shelf sea polynya in winter

Damm

Schauer

Rudels³

et al. 2007

Continental Shelf Research

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Latent heat polynyas are regions generating strong ice formation, convection and extensive water mass formation. Here we report on the effects of these processes on resuspension of sediments and subsequent methane release from the seafloor and on the resulting excess methane concentration in surface water on a polar shelf during winter. The study is based on measurements of concentration and d 13C values of methane, water temperature, salinity, light transmission and sea ice data collected in March 2003 in Storfjorden, southern Svalbard. In winter, strong and persistent northeasterly winds create polynyas in eastern Storfjorden and cause ice formation. The resulting brine-enriched water cascades from the Storfjordbanken into the central depression thereby enhancing the turbulence near the seafloor. A distinct benthic nepheloid layer was observed reflecting the resuspension of sediments by the cascading dense bottom water. High concentrations of 13 C-depleted methane suggest submarine discharge of methane with the resuspended sediments. As the source of the submarine methane, we propose recent bacterial methanogenesis near the sediment surface because of extremely high accumulation rates of organic carbon in Storfjorden. Convective mixing transports newly released methane from the bottom to the sea surface. This eventually results in an excess concentration in surface water with respect to the atmospheric equilibrium, and a sea-air flux of methane during periods of open water. When a new ice cover is formed, methane becomes trapped in the water column and subsequently oxidized. Thus, the residual methane is strongly enriched in 13 C in relation to the d 13 C CH 4 signature of atmospheric methane. Our results show that latent heat polynyas may induce a direct pathway for biogases like methane from sediments to the atmosphere through coupling of biogeochemical and oceanographic processes. Extrapolating these processes to all Arctic ocean polynyas, we estimate a transfer of CH 4 between 0.005 and 0.02 Tg yr À1 . This is not a large contribution but the fluxes from the polynyas are 20-200 times larger than the ocean average and the methane evasion process in polynyas is certainly one that can be altered under climate change. r

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Variations of atmospheric methane supply from the Sea of Okhotsk induced by the seasonal ice cover

Cited by 17 publications

References 19 publications

Methane in the western part of the Sea of Okhotsk in 1998–2000

Methane in the western part of the Sea of Okhotsk in 1998–2000

Australian offshore natural hydrocarbon seepage studies, a review and re-evaluation

Excess of bottom-released methane in an Arctic shelf sea polynya in winter

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