Methane and methane carbon isotope ratios in the Northeast Atlantic including the Mid-Atlantic Ridge (50°N)

Keir, Robin S.; Greinert, Jens; Rhein, Monika; Petrick, Gert; Sültenfuß, Jürgen; Fürhaupter, K.

doi:10.1016/j.dsr.2004.12.006

Cited by 24 publications

(30 citation statements)

References 56 publications

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“…153 Unfortunately, no fluid fluxes are available, so the amount of methane supplied by these structures cannot be estimated at this time. Keir et al 154 observed water column methane anomalies in the rift valley of the Mid-Atlantic Ridge with δ 13 C values from -15‰ to -10‰. Model calculations indicate that 10 9 mol of CH 4 year -1 are released from the Mid-Atlantic Ridge to the open ocean.…”

Section: Hydrothermal Systems and The Serpentinization Reactionmentioning

confidence: 99%

Oceanic Methane Biogeochemistry

2007

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from 1968 until 1993, when he joined the University of California Irvine as one of the founding faculty of the Program in Geosciences, now the Department of Earth System Science. He was editor of Global Biogeochemical Cycles from 1998 to 2004 and was elected AGU Fellow in 2001. His research focus has been on methane geochemistry, particularly documenting the occurrence and extent of anaerobic oxidation of methane, and recent measurements of natural stable isotopes ( 2 H-CH 4 , 13 C-CH 4 ) and radiocarbon ( 14 C-CH 4 ) in methane from anoxic marine sediments and waters.

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Section: Hydrothermal Systems and The Serpentinization Reactionmentioning

confidence: 99%

Oceanic Methane Biogeochemistry

2007

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“…Schmitt et al (1991) introduced another discrete sampling technique using vacuum to extract the amount of dissolved methane from a water sample. Further improved methods (Lammers and Suess 1994;Rehder 1996;Keir et al 2005) offer additional subsamples for stable isotope analysis. Butler et al (1989) were the first to design an equilibration system (equilibrator developed by R.F.…”

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confidence: 99%

A new method for continuous measurement of methane and carbon dioxide in surface waters using off‐axis integrated cavity output spectroscopy (ICOS): An example from the Baltic Sea

Gülzow

Rehder

Schneider

et al. 2011

Limnology & Ocean Methods

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A new system is presented that allows the continuous measurement of methane and carbon dioxide concentrations in surface waters autonomously using ships of opportunity. The analytical setup consists of a methane carbon dioxide-Analyzer (MCA, Los Gatos Research) joined to an established equilibrator setup. The analyzer uses off-axis integrated cavity output spectroscopy (ICOS) and combines a highly specific infrared band laser with a set of strongly reflective mirrors to obtain an effective laser path length of several kilometers. This allows detecting methane and carbon dioxide in the equilibrated gas phase with high precision (less than 0.1%) and frequency. The system was installed on the cargo ship Finnmaid (Finnlines) in November 2009, which commutes regularly in the Baltic Sea between Travemünde (Germany), Gdynia (Poland), and Helsinki (Finland). Methane concentrations of the equilibrated gas phase measured by gas chromatography and by the MCA during lab tests are in excellent agreement. The comparison of carbon dioxide data measured by the MCA system to CO 2 values gathered from the same type of equilibrator in combination with a LICOR CO 2 detector (Schneider et al. 1992) during onboard operation show concordant results. The time constant for the system in freshwater at room temperature was determined to be 676 s for CH 4 and 226 s for CO 2 . Additional performance tests are presented. First field results show large regional differences with remarkable features, especially in shallow regions, demonstrating the need for the high spatiotemporal data coverage provided by the instrument.

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“…Recently, a limited set of helium isotope measurements on three stations provided evidence of a plume of 3 He that lies deeper than a methane plume in the MAR rift valley south of the Gibbs Fracture Zone (Keir et al, 2005). Here, we report additional evidence for this helium plume as well as a separation of methane and helium signals at 5.4°N on the MAR.…”

Section: Introductionmentioning

confidence: 64%

Separation of 3He and CH4 signals on the Mid-Atlantic Ridge at 5°N and 51°N

Keir

Sültenfuß

Rhein

et al. 2006

Geochimica et Cosmochimica Acta

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Abiogenic methane may be produced in submarine hydrothermal systems by degassing of basalts or serpentinization of ultramafic outcrops. The latter process presumably releases little primordial helium and is therefore implicated by high CH 4 / 3 He ratios in vent fluids from the ultramafic-hosted Rainbow field and in methane plumes near ultramafic outcrops. We report the existence of depth-separated CH 4 and 3 He plumes in two segments of the Mid-Atlantic Ridge, at 5.4˚N and 51˚N. In both cases, the helium plume was deeper, near the valley floor, and the methane carbon isotope ratio was heavy (δ 13 C ≈ -14%¸). The plumes may issue from separate vents, where the helium is discharged near the volcanic axis and the methane is generated by serpentinization higher on the valley wall. However, at the present time the locations of the vents that produce these plumes are not known. Using a one-pass model, we investigated whether separate venting could arise from heat conduction from a primary, helium-carrying, hydrothermal circulation to a second, shallower fracture loop intersecting ultramafic rock. The model results indicate that the flow rate through the secondary loop would have to be relatively low in order for it to stay warm enough for serpentinization to proceed. In this case, some of the exothermic heat production is lost by conduction, and the temperature increase in the circulating fluid is only a fraction of that expected from a water/rock ratio of 1:1.

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Methane and methane carbon isotope ratios in the Northeast Atlantic including the Mid-Atlantic Ridge (50°N)

Cited by 24 publications

References 56 publications

Oceanic Methane Biogeochemistry

Oceanic Methane Biogeochemistry

A new method for continuous measurement of methane and carbon dioxide in surface waters using off‐axis integrated cavity output spectroscopy (ICOS): An example from the Baltic Sea

Separation of 3He and CH4 signals on the Mid-Atlantic Ridge at 5°N and 51°N

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