From the UNH CCOM/JHC Seminar Series 2012-2013, UNH CCOM graduate student Christina Fandel defends her Master's thesis, "Observations of Pockmark Flow Structure in Belfast Bay, Maine". Christina spoke on Tuesday, April 16th, 2013 at UNH's Chase Ocean Engineering Laboratory.
Vertical current and hydrographic profiles were acquired over a spherical, northerly-located pockmark and a more elongated, southerly-located pockmark in Belfast Bay, Maine in July 2011. These observations show evidence for mixing within the pockmarks, a rotational pattern that resembles open cavity flow, and incipient motion along the rims. Over the center of each pockmark, observations of uniform temperature properties below 12 m are indicative of mixing within the pockmark. The observed complex rotational structure over each pockmark shows significant rotation with depth and a greater degree of rotation during ebbing tide. These observations are qualitatively consistent with circulation patterns predicted by cavity flow models. Critical Shields parameters for cohesive sediment were estimated at the rim and center of each pockmark and were only exceeded along the rim. During the infrequently observed upwelling events, and in the absence of flocculation, suspended sediment would be unable to settle through the water column. This presentation will focus on the methodology employed to characterize periods of incipient motion and sediment suspension over the rim and center of each pockmark and the influence of near-bed sediment transport on post-formation pockmark evolution during the observed average, benign conditions in Belfast Bay.
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