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  • 1
    Electronic Resource
    Electronic Resource
    The Multiple Sources and Patterns of Methane inNorth Sea Waters (1998)
    Springer
    Aquatic geochemistry 4 (1998), S. 403-427 
    Details
    ISSN: 1573-1421
    Keywords: methane ; trace gases ; North Sea ; air-sea exchange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The methane concentration in the atmosphere andsurface water was surveyed along 58° N acrossthe North Sea. In addition, the vertical methanedistribution in the water column was determined at sixstations along the transect. The methane contents ofthe surface water as well as in the water column wereextremely inhomogeneous. Input by freshwater fromriver discharge and injection of methane from thesediment were both observed. The survey continued fromthe western side of the North Sea to the Elbe Riverestuary. The Elbe River appears to have low methaneconcentrations compared to other European rivers, itsaverage input into the North Sea is estimated to be70 nmol s-1 of methane. Near 58° N,1°40' E, an abandoned drill site releases about 25 % ofthe North Sea's emission of methane to the atmosphere.The advective methane transport induced by watercirculation was assessed for May 16, 1994, using a 3-DNorth Sea circulation model. For the period of thissurvey, the North Sea's source strength foratmospheric methane is estimated using in situwind velocities. In comparison to the advectivetransport by the water circulation, the gas flux tothe atmosphere appears to be the dominant sink ofNorth Sea methane. This flux is estimated to bebetween 1500 · 106 mol a-1 and 3100 ·106mol a-1, depending on the relationbetween wind speed and gas transfer velocity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009644600833
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    Paper (German National Licenses)
    Fulltext
  • 2
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    Hydrothermal activity at Hook Ridge in the Central Bransfield Basin, Antarctica (1999)
    Springer
    In:  Geo-Marine Letters, 18 (4). pp. 277-284.
    Details
    Publication Date: 2017-06-29
    Description: Hydrothermal activity in the Central Bransfield Basin revealed an active low-temperature vent field on top of a submarine volcanic structure. A temperature anomaly was detected and the sea floor showed various patches of white silica (opal-A) precipitate exposures and some yellow–brown Fe-oxyhydroxide crusts. Enriched dissolved methane concentrations were encountered. Sediment was near 24°C just after the grab came on deck. No dense population of chemosynthetically based macrofauna known from other hydrothermal venting areas was present, except for pogonophora. The observations suggest that the sedimented hydrothermal field at Hook Ridge is a low-temperature end-member branch from a deeper hydrothermal source.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s003670050080
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 3
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    An experiment demonstrating that marine slumping is a mechanism to transfer methane from seafloor gas-hydrate deposits into the upper ocean and atmosphere (2003)
    Springer
    In:  Geo-Marine Letters, 22 (4). pp. 198-203.
    Details
    Publication Date: 2017-05-24
    Description: The scientific community is engaged in a lively debate over whether and how venting from the gas-hydrate reservoir and the Earth’s climate is connected. The various scenarios which have been proposed are based on the following assumptions: the inventory of methane gas-hydrate deposits is locally enormous, the stability of marine gas-hydrate deposits can easily be perturbed by temperature and pressure changes, enough methane can be released from these deposits to contribute adequate volumes of this isotopically distinct greenhouse gas to alter the composition of oceanic or atmospheric methane reservoirs, and the mechanisms exist for the transfer of methane from deeper geologic reservoirs to the ocean and/or atmosphere. However, some potential transfer mechanisms have been difficult to evaluate. Here, we consider the possibility of marine slumping as a mechanism to transfer methane carbon from gas hydrates within the seafloor into the ocean and atmosphere. Our analyses and field experiments indicate that large slumps could release volumetrically significant quantities of solid gas hydrates which would float upwards in the water column. Large pieces of gas hydrate would reach the upper layers of the ocean before decomposing, and some of the methane would be directly injected into the atmosphere.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00367-002-0113-y
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    OceanRep: Article in a Scientific Journal - peer-reviewed
  • 4
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    Seepage of methane at Jaco Scar, a slide caused by seamount subduction offshore Costa Rica (2014)
    Springer
    In:  International Journal of Earth Sciences, 103 (7). pp. 1801-1815.
    Details
    Publication Date: 2019-09-23
    Description: Methane (CH4) concentrations and CH4 stable carbon isotopic composition (d13CCH4 ) were investigated in the water column within Jaco Scar. It is one of several scars formed by massive slides resulting from the subduction of seamounts offshore Costa Rica, a process that can open up structural and stratigraphical pathways for migrating CH4. The release of large amounts of CH4 into the adjacent water column was discovered at the outcropping lowermost sedimentary sequence of the hanging wall in the northwest corner of Jaco Scar, where concentrations reached up to 1,500 nmol L-1. There CH4-rich fluids seeping from the sedimentary sequence stimulate both growth and activity of a dense chemosynthetic community. Additional point sources supplying CH4 at lower concentrations were identified in density layers above and below the main plume from light carbon isotope ratios. The injected CH4 is most likely a mixture of microbial and thermogenic CH4 as suggested by d13CCH4 values between -50 and -62 % Vienna Pee Dee Belemnite. This CH4 spreads along isopycnal surfaces throughout the whole area of the scar, and the concentrations decrease due to mixing with ocean water and microbial oxidation. The supply of CH4 appears to be persistent as repeatedly high CH4 concentrations were found within the scar over 6 years. The maximum CH4 concentration and average excess CH4 concentration at Jaco Scar indicate that CH4 seepage from scars might be as significant as seepage from other tectonic structures in the marine realm. Hence, taking into account the global abundance of scars, such structures might constitute a substantial, hitherto unconsidered contribution to natural CH4 sources at the seafloor.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1007/s00531-012-0822-z
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    OceanRep: Article in a Scientific Journal - peer-reviewed
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