Massachusetts Bay is a semi-enclosed embayment in the western Gulf of Maine about 50 km wide and 100 km long and extends from Cape Ann southward along the eastern coast of Massachusetts (Figure 1). The Bay is open to the Gulf of Maine along the eastern boundary between Cape Ann and Cape Cod, but the opening is partly blocked by Stellwagen Bank, a shallow bank that rises to within 20 m of sea surface at its southern end. Stellwagen Basin, located to the west of Stellwagen Bank, is the deepest part of Massachusetts Bay with maximum water depth of 95 m. Cape Cod Bay is located between Cape Cod and the eastern coast of Massachusetts; the deepest water of Cape Cod Bay is 40 m at its center. Details of the mapping project are located at (http://woodshole.er.usgs.gov/project-pages/coastal_mass/).
Figure 1. Physical setting of Massachusetts Bay.
A set of simulations explored sediment-transport pathways caused by storms with winds from the northeast quadrant by simulating release of sediment at several locations in the Bay. Results from a simulated release of sediment in Boston Harbor are shown below in Figure 2. Storms with winds from the north cause transport southward along the western shore of Massachusetts Bay (left 2 panels), while storms with winds from the east (and southeast) drive northerly nearshore flow (right 2 panels). All simulations suggest Stellwagen Basin and Cape Cod Bay as long-term sediment sinks.
Figure 2. Animation showing trajectory of material originating from a point source in Boston Harbor for
Another experiment was performed to simulate the evolution of sediment grain distribution on the sea floor. The model was initialized with a spatially-uniform bed of seven mixed sediment classes. The model was subjected to a repeated Northeaster storm (December 1992) and the sediment distribution on the sea floor evolved to a pattern similar to the existing surficial sediment distribution.
|Figure 3. Animation showing bottom suspended sediment concentration, bottom stress, significant wave height,
bathymetric change, and mean grain size for a repeated storm (December 1992). The final panel of the animation
for the mean grain fraction is shown in Figure 4 and compared to observations
Figure 4. Results from model simulation of the evolution of a mixed sediment bed
Warner, J.C., Butman, B., and Alexander, P.S. (in press). “Storm-driven sediment transport in Massachusetts Bay.” Continental Shelf Research.
Poppe, L.J., Paskevich, V.F. , Williams, S.J. , Hastings, M.E. , Kelly, J.T. , Belknap, D.F., Ward, L.G. , FitzGerald, D.M. , and Larsen, P.F. (2003). Surficial Sediment Data from the Gulf of Maine, Georges Bank, and Vicinity: A GIS Compilation. U.S. Geological Survey Open-File Report 03-001, http://pubs.usgs.gov/of/2003/of03-001/index.htm.