Cross-shelf circulation and momentum and heat balances over the inner continental shelf near Martha's Vineyard, Massachusetts
Citable URI
https://hdl.handle.net/1912/2121Location
Martha's Vineyard, MADOI
10.1575/1912/2121Abstract
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.
Description
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.
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Suggested Citation
Thesis: Fewings, Melanie R., "Cross-shelf circulation and momentum and heat balances over the inner continental shelf near Martha's Vineyard, Massachusetts", 2007-09, DOI:10.1575/1912/2121, https://hdl.handle.net/1912/2121Related items
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