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  • 1
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    Atmospheric methane flux from bubbling seeps : spatially extrapolated quantification from a Black Sea shelf area (2010)
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    UID:
    gbv_625174259
    Format: 18 , Ill., graph. Darst
    ISSN: 2169-9291
    Content: Bubble transport of methane from shallow seep sites in the Black Sea west of the Crimea Peninsula between 70 and 112 m water depth has been studied by extrapolation of results gained through different hydroacoustic methods and direct sampling. Ship-based hydroacoustic echo sounders can locate bubble releasing seep sites very precisely and facilitate their correlation with geological or other features at the seafloor. Here, the backscatter strength of a multibeam system was integrated with single-beam data to estimate the amount of seeps/m2 for different backscatter intensities, resulting in 2709 vents in total. Direct flux measurements by submersible revealed methane fluxes from individual vents of 0.32-0.85 l/min or 14.5-37.8 mmol/min at ambient pressure and temperature conditions. A conservative estimate of 30 mmol/min per site was used to estimate the flux into the water to be 1219-1355 mmol/s. The flux to the atmosphere was calculated by applying a bubble dissolution model taking release depth, temperature, gas composition, and bubble size spectra into account. The flux into the atmosphere (3930-4533 mol/d) or into the mixed layer (6186-6899 mol/d) from the 21.8 km2 large study area is three times higher than independently measured fluxes of dissolved methane for the same area using geochemical methods (1030-2495 mol/d). The amount of methane dissolving in the mixed layer is 2256-2366 mol/d. This close match shows that the hydroacoustic approach for extrapolating the number of seeps/m2 and the applied bubble dissolution model are suitable to extrapolate methane fluxes over larger areas.
    In: Journal of geophysical research. C, Oceans, Hoboken, NJ : Wiley, 1978, 115(2010), 2169-9291
    In: volume:115
    In: year:2010
    In: extent:18
    Language: English
    DOI: 10.1029/2009JC005381
    URL: Volltext
    Author information: Linke, Peter 1959-
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  • 2
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    Methane emissions from a freshwater marsh in response to experimentally simulated global warming and nitrogen enrichment (2010)
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    UID:
    gbv_625809920
    Format: 9 , Ill., graph. Darst
    ISSN: 2169-8961
    Content: We determined methane (CH4) emissions in a field enclosure experiment in a littoral freshwater marsh under the influence of experimentally simulated warming and enhanced nitrogen deposition. Methane emissions by ebullition from the marsh composed of Phragmites australis were measured with funnel traps deployed in a series of enclosures for two 3 week periods. Diffusive fluxes were estimated on the basis of measured CH4 concentrations and application of Fick's law. Neither diffusive nor ebullitive fluxes of methane were significantly affected by warming or nitrate enrichment, possibly because variability both within and among replicate experimental enclosures was high. Average emission rates resulted primarily from ebullition (0.2-30.3 mmol CH4 m-2 d-1), which were 4 orders of magnitude higher than estimated diffusive fluxes and were of similar importance as the coarsely estimated advective methane transport through plants. Significant correlations between dissolved oxygen and dissolved methane and ebullition flux suggest that methane release from the sediment might feed back positively on methane production by reducing dissolved oxygen in the water column and oxygen flux into the sediment. Nitrate may have a similar effect. Extrapolation of our limited data indicates that total methane fluxes from vegetated littoral zones of temperate lakes may contribute 0.5%-7% of the global natural CH4 emissions. These results emphasize the importance of freshwater marshes as sources of methane emissions to the atmosphere, even when they occupy only relatively small littoral areas. More detailed investigations are clearly needed to assess whether global warming and nitrogen deposition can have climate feedbacks by altering methane fluxes from these wetlands.
    In: Journal of geophysical research. G, Biogeosciences, [Washington, DC] : [Verlag nicht ermittelbar], 2006, 115(2010), 2169-8961
    In: volume:115
    In: year:2010
    In: extent:9
    Language: English
    DOI: 10.1029/2009JG001079
    URL: Volltext
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  • 3
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    Methane seepage along the Hikurangi Margin of New Zealand : geochemical and physical data from the water column, sea surface and atmosphere (2010)
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    UID:
    gbv_625811658
    Format: graph. Darst
    ISSN: 1872-6151
    In: Marine geology, Amsterdam [u.a.] : Elsevier Science, 1964, 272(2010), Seite 170-188, 1872-6151
    In: volume:272
    In: year:2010
    In: pages:170-188
    Language: English
    DOI: 10.1016/j.margeo.2010.01.001
    Author information: Schneider von Deimling, Jens
    Author information: Linke, Peter 1959-
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  • 4
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    Variable sediment oxygen uptake in response to dynamic forcing (2010)
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    UID:
    gbv_625813316
    Format: graph. Darst
    ISSN: 1939-5590
    In: Limnology and oceanography, Oxford [u.a.] : Wiley-Blackwell, 1956, 55(2010), 2, Seite 950-964, 1939-5590
    In: volume:55
    In: year:2010
    In: number:2
    In: pages:950-964
    Language: English
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  • 5
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    Extreme methane emissions from a Swiss hydropower reservoir : contribution from bubbling sediments (2010)
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    UID:
    gbv_640196810
    Format: graph. Darst
    ISSN: 1520-5851
    In: Environmental science & technology, Columbus, Ohio : American Chemical Society, 1967, 44(2010), 7, Seite 24192425, 1520-5851
    In: volume:44
    In: year:2010
    In: number:7
    In: pages:24192425
    Language: English
    DOI: 10.1021/es9031369
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  • 6
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    Physical limitations of dissolved methane fluxes : the role of bottom-boundary layer processes (2010)
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    UID:
    gbv_687914922
    Format: Ill., graph. Darst
    ISSN: 1872-6151
    Content: In situ methane emission measurements from sediments are combined with water column backscatter anomalies recorded with an Acoustic Doppler Current Profiler (ADCP) integrated on a benthic observatory. During cruise SO191 to the Hikurangi Margin (New Zealand), the Fluid Flux Observatory (FLUFO) was deployed at a cold seep site at Omakere Ridge. The sediments incubated in the two benthic chambers of FLUFO contained seep-associated fauna, including small and larger tubeworms, juvenile bivalves of the genus Acharax and some juvenile clams. The first 26 h of in situ incubation revealed low to moderate methane fluxes of 0.01 to 0.4 mmol m- 2 d- 1 into the overlying water of the backup and flux chamber, respectively. In the following sampling sequence, however, the methane concentration in the flux chamber reached 3-fold higher concentrations whereas the methane concentration in the backup chamber remained low and unchanged. Simultaneous to the sudden methane increase, a significant backscatter anomaly was recorded and persisted for 30 min and covered the entire depth range (100 m) of the upward looking ADCP. Data analyses revealed that a single-phase plume (no bubbles) outburst likely occurred during this time. While bubbles appeared to be present during some periods, plume simulations revealed that the volume of gas required (rate of 8 ton/day) does not support a bubble plume. A second data set was obtained during lander deployments at Rock Garden where visual observations by ROV confirmed the transient pattern of free gas injection into the water column. Acoustic flares and methane concentration increase in the bottom water hint towards a pressure (tidal) induced discharge mechanism. The presented data demonstrate the temporal and spatial variability of seabed methane emission, and very short methane signal lifetime in the water column (hours to a few days) due to turbulent diffusion. Both have to be considered when methane budgets are extrapolated from single methane emission rates.
    In: Marine geology, Amsterdam [u.a.] : Elsevier Science, 1964, 272(2010), Seite 170-188, 1872-6151
    In: volume:272
    In: year:2010
    In: pages:170-188
    Language: English
    DOI: 10.1016/j.margeo.2009.03.020
    Author information: Linke, Peter 1959-
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  • 7
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    Single bubble dissolution model : the graphical user interface SiBu-GUI (2009)
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    UID:
    gbv_62580127X
    ISSN: 1873-6726
    Content: The presented software application allows GUI-based access to the bubble dissolution model presented by McGinnis et al. [McGinnis, D.F., Greinert, J., Artemov, Y., Beaubien, S.E., Wüest, A., 2006. The fate of rising methane bubbles in stratified waters: what fraction reaches the atmosphere? Journal of Geophysical Research 111, C09007. doi:10.1029/2005JC003183]. It quantifies the dissolution of gas bubbles (containing any combination of CH4, CO2, O2, N2, and Ar) in marine or lacustrine environments based on the initial bubble size, free gas composition and environmental parameters (temperature, salinity, and dissolved gas concentrations). The software enables scientists and engineers to evaluate bubble dynamics in a simple way on Windows® PCs.
    In: Environmental modelling & software, Amsterdam [u.a.] : Elsevier Science, 1997, 24(2009), 8, Seite 1012-1013, 1873-6726
    In: volume:24
    In: year:2009
    In: number:8
    In: pages:1012-1013
    Language: English
    DOI: 10.1016/j.envsoft.2008.12.011
    URL: Volltext
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