Open AccessA coastal current in winter: 2. Wind forcing and cooling of a coastal current east of Cape Cod
Author(s) -
Shcherbina Andrey Y.,
Gawarkiewicz Glen G.
Publication year - 2008
Publication title -
journal of geophysical research: oceans
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2008jc004750
Subject(s) - downwelling , geology , current (fluid) , oceanography , buoyancy , ekman transport , global wind patterns , upwelling , climatology , forcing (mathematics) , mechanics , physics
The combined effect of cooling and wind‐driven buoyancy flux (WDBF) on a buoyant coastal current east of Cape Cod is investigated using observations and process‐oriented numerical modeling. Theoretical considerations show that with the moderately strong surface density gradients observed in the Outer Cape Cod Coastal Current, WDBF can substantially exceed the buoyancy loss due to cooling, especially during intense winter storms. Evidence of deep convection associated with strong negative WDBF during downwelling‐favorable winds is clearly seen in the moored observations. A simplified two‐dimensional numerical model is used to illustrate the evolution of wind‐ and buoyancy‐driven cross‐shelf overturning circulation in response to surface cooling and episodic storm events. The simulation confirms that WDBF plays an important role in driving subduction of cold surface water at the offshore surface outcrop of the coastal current font. The presence of the coastal current is also shown to block onshore Ekman transport. As a result, the downwelling circulation in a cross‐shore plane is predicted to have a complex multicell structure, in which exchange between the inner shelf and midshelf is restricted. The downwelling circulation has a major impact on the cross‐shelf origin of cold, dense shelf waters contributing to intermediate layers of the Wilkinson Basin of the Gulf of Maine.