From the CCOM/JHC 2011-2012 Seminar Series, Dr. Laura Brothers of the USGS Coastal & Marine Science Center at Woods Hole presents, "The Thawing Arctic: Mapping U.S. Beaufort Sea Offshore Permafrost / Gas Hydrates (?)." The talk was given on Friday, March 11, 2011 at UNH's Chase Ocean Engineering Laboratory.
Pockmarks are one the largest, most ubiquitous types of marine landforms in world. Common in areas with gas hydrates or underlying thermogenic fluids, pockmarks are not well understood in nearshore settings lacking such extensive subsurface fluid sources. Questions persist regarding their origins, activity, how pockmark fields evolve overtime and their potential role as geohazards. To address these uncertainties we conducted repeat-swath bathymetry surveys, seismic, sedimentological, spatial, geotechnical, numerical and analog investigations of the Belfast Bay, Maine pockmark field. The pockmarks are non-randomly clustered and correspond to irregular underlying topography, which likely created the fluid-focusing gradients necessary for sea floor alteration. This finding coupled with a review of global pockmark field distribution suggests that irregular underlying topography may ultimately control nearshore pockmark field occurrence. Over 100 years of bathymetric observations and shallow sediment characterization indicate that pockmark initiation is an episodic, potentially catastrophic, event. Numerical simulations and flume tank experiments suggest roughness-induced turbulence creates a feedback loop responsible for pockmark maintenance and evolution.
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