Cross-shelf circulation and momentum and heat balances over the inner continental shelf near Martha's Vineyard, Massachusetts
Fewings, Melanie R.
MetadataShow full item record
LocationMartha's Vineyard, MA
The water circulation and evolution of water temperature over the inner continental shelf are investigated using observations of water velocity, temperature, density, and bottom pressure; surface gravity waves; wind stress; and heat flux between the ocean and atmosphere during 2001-2007. When waves are small, cross-shelf wind stress is the dominant mechanism driving cross-shelf circulation. The along-shelf wind stress does not drive a substantial cross-shelf circulation. The response to a given wind stress is stronger in summer than winter. The cross-shelf transport in the surface layer during winter agrees with a two-dimensional, unstratified model. During large waves and onshore winds the cross-shelf velocity is nearly vertically uniform, because the wind- and wave-driven shears cancel. During large waves and offshore winds the velocity is strongly vertically sheared because the wind- and wave-driven shears have the same sign. The subtidal, depth-average cross-shelf momentum balance is a combination of geostrophic balance and a coastal set-up and set-down balance driven by the cross-shelf wind stress. The estimated wave radiation stress gradient is also large. The dominant along-shelf momentum balance is between the wind stress and pressure gradient, but the bottom stress, acceleration, Coriolis, Hasselmann wave stress, and nonlinear advection are not negligible. The fluctuating along-shelf pressure gradient is a local sea level response to wind forcing, not a remotely generated pressure gradient. In summer, the water is persistently cooled due to a mean upwelling circulation. The cross-shelf heat flux nearly balances the strong surface heating throughout midsummer, so the water temperature is almost constant. The along-shelf heat flux divergence is apparently small. In winter, the change in water temperature is closer to that expected due to the surface cooling. Heat transport due to surface gravity waves is substantial.
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution September 2007.
Showing items related by title, author, creator and subject.
Slope/shelf circulation and cross-slope/shelf transport out of a bay driven by eddies from the open ocean Zhang, Yu (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2009-09)Interaction between the Antarctic Circumpolar Current and the continental slope/shelf in the Marguerite Bay and west Antarctic Peninsula is examined as interaction between a wind-driven channel flow and a zonally uniform ...
Ice shelf-ocean interactions in a general circulation model : melt-rate modulation due to mean flow and tidal currents Dansereau, Veronique (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2012-09)Interactions between the ocean circulation in sub-ice shelf cavities and the overlying ice shelf have received considerable attention in the context of observed changes in flow speeds of marine ice sheets around Antarctica. ...
Moffat Varas, Carlos F. (Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 2007-09)Observations of current velocity, temperature, salinity and pressure from a 2-year moored array deployment and four hydrographic cruises conducted by the United States Southern Ocean GLOBEC program on the western Antarctic ...