Pockmark Flow Structure in Belfast Bay, Maine
Pockmarks are large, circular or elongate depressions in the seafloor that are globally distributed in a wide range of geologic settings including shallow, estuarine environments like Belfast Bay, Maine. The primary mechanism of pockmark formation in Belfast Bay is attributed to episodic methane venting of shallow, natural gas in the area. Recent models suggest pockmarks may be further maintained by the reduction or prevention of fine-grained sediment deposition due to inner-pockmark upwelling events induced by near-bed current flow and flow separation over the depressions. A four day current study was conducted in July of 2011 to examine the flow structure in and around two pockmarks within the Belfast Bay pockmark field. Sub-surface current meter moorings deployed at the rim and center of each pockmark and conductivity, temperature, and depth (CTD) casts were used to characterize the flow field and examine the water column properties within and around each pockmark. CTD results suggest active mixing between the rim and center of the pockmark and a well-mixed water column below 15 m. Similarities and differences in flow structure between the two pockmarks will be discussed as well as how hourly-averaged current flow data suggest pockmark flow circulation may resemble cavity flow.
Christy Fandel is pursuing a Masters of Science in Earth Science with a focus in Ocean Mapping. Christy graduated from the College of Charleston in 2010 with a Bachelors of Science in Geology and Environmental Geosciences. She completed her senior thesis on “Seabed Characterization of the Transect Meanders using Multibeam Sonar, Backscatter, and Sedimentology.”