Project Team Member

LT Catherine M McDougall, USN

Major Findings

Shelfbreak fronts are the result of differences in hydrographic properties between the coastal ocean and the open sea. They separate shelf water from the slope water. The shelf water can be significantly fresher, saltier, colder or warmer than the water of the adjacent deep ocean. Generally the shelfbreak front coincides with the sharp change in bottom slope at the shelfbreak. A shelfbreak front will persist in the presence of strong external forces such as the surface wind stress and deep ocean eddies. These forces temporarily disrupt the fronts, but they reform after the forcing ceases. Shelfbreak fronts are more or less stationary and their mean position is controlled entirely by the location of the shelfbreak.

A prominent shelfbreak front is found on the shelf along the Atlantic coast of the United States. The linear stability models developed by Gawarkiewicz give an idea of the different structure of the shelfbreak front observed throughout the year. In the winter, the shelf waters are vertically uniform and a surface to bottom front is present at the shelfbreak. By the summer, increased surface heating has produced a strong, seasonal thermocline of about 25 m depth overlying the shelf, front, and slope regions that confines the strongest horizontal gradient to the subsurface waters.

References

- Linder, C.A. and Gawarkiewicz, G., 1998: "A climatology of the shelfbreak front in the Middle Atlantic Bight." J. Geophysical Research, Vol 103, 18,405-18,423.

- Gawarkiewicz, G., 1991: "Linear Stability Models of Shelfbreak Fronts." J. Phys. Oceanogr., Vol 21, 471-488.

- Garvine, R.W., Wong, K.C., Gawarkiewicz, G., and McCarthy R.W., 1988: "The Morphology of Shelfbreak Eddies." J. Geophys. Research, Vol 93, 15,593-15,607.

- Gawarkiewicz, G. and Chapman, D.C., 1991: "Formation and Maintenance of Shelfbreak Fronts in Unstratified Flow." J. Phys. Oceanogr., Vol 21, 1225-1239.

- Pickard, R.S., Torres, D. J., McKee, T.K., Caruso, M. J. and Przystup, J.E., 1999: "Diagnosing a meander of the shelf break current in the Middle Atlantic Bight." J. Geophys.Research, Vol 104, 3121-3132.
 

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