| Vertical current and CTD profiles were acquired over a small, spherical pockmark and a larger, more elongated pockmark in Belfast Bay, Maine in July 2011. These observations showed 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. |
