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    Active methane venting observed at giant pockmarks along the U.S. mid-Atlantic shelf break

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    Date
    2007-11
    Author
    Newman, Kori R.  Concept link
    Cormier, Marie-Helene  Concept link
    Weissel, Jeffrey K.  Concept link
    Driscoll, Neal W.  Concept link
    Kastner, Miriam  Concept link
    Solomon, Evan A.  Concept link
    Robertson, Gretchen  Concept link
    Hill, Jenna C.  Concept link
    Singh, Hanumant  Concept link
    Camilli, Richard  Concept link
    Eustice, Ryan M.  Concept link
    Metadata
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    Citable URI
    https://hdl.handle.net/1912/2234
    As published
    https://doi.org/10.1016/j.epsl.2007.11.053
    Keyword
     Pockmarks; Seafloor venting; Methane; AUV 
    Abstract
    Detailed near-bottom investigation of a series of giant, kilometer scale, elongate pockmarks along the edge of the mid-Atlantic continental shelf confirms that methane is actively venting at the site. Dissolved methane concentrations, which were measured with a commercially available methane sensor (METS) designed by Franatech GmbH mounted on an autonomous underwater vehicle (AUV), are as high as 100 nM. These values are well above expected background levels (1-4 nM) for the open ocean. Sediment pore water geochemistry gives further evidence of methane advection through the seafloor. Isotopically light carbon in the dissolved methane samples indicates a primarily biogenic source. The spatial distribution of the near-bottom methane anomalies (concentrations above open ocean background), combined with water column salinity and temperature vertical profiles, indicate that methane-rich water is not present across the entire width of the pockmarks, but is laterally restricted to their edges. We suggest that venting is primarily along the top of the pockmark walls with some advection and dispersion due to local currents. The highest methane concentrations observed with the METS sensor occur at a small, circular pockmark at the southern end of the study area. This observation is compatible with a scenario where the larger, elongate pockmarks evolve through coalescing smaller pockmarks.
    Description
    Author Posting. © Elsevier B.V., 2007. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Earth and Planetary Science Letters 267 (2008): 341-352, doi:10.1016/j.epsl.2007.11.053.
    Collections
    • Applied Ocean Physics and Engineering (AOP&E)
    Suggested Citation
    Preprint: Newman, Kori R., Cormier, Marie-Helene, Weissel, Jeffrey K., Driscoll, Neal W., Kastner, Miriam, Solomon, Evan A., Robertson, Gretchen, Hill, Jenna C., Singh, Hanumant, Camilli, Richard, Eustice, Ryan M., "Active methane venting observed at giant pockmarks along the U.S. mid-Atlantic shelf break", 2007-11, https://doi.org/10.1016/j.epsl.2007.11.053, https://hdl.handle.net/1912/2234
     

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