SHELF-SLOPE WATER FRONTAL STRUCTURE, MOTION AND EDDY HEAT-FLUX IN THESOUTHERN MIDDLE ATLANTIC BIGHT

Results of an analysis of SEEP-II temperature and velocity data to inv estigate the shelf-slope frontal structure, motion and eddy heat flux in the southern Middle Atlantic Bight are presented. In the winter and spring the inclination of the frontal boundary and the vertical veloc ity shear, when averaged over periods greater than a week, approximate ly satisfy the Margules' equation. Associated with the locally wind dr iven cross-shelf excursions (similar to 20 km) of the foot of the fron t are vertical displacements of the frontal boundary due to vorticity constraints imposed by the bottom topography. Some of the smaller-scal e frontal motions suggest wave-like disturbances propagating southward along the continental margin. In April 1988 the most severe wind even t recorded during SEEP-II displaced the foot of the front into the upp er slope region and injected shelf water into the interior of the slop e water column. On the mid-shelf cross-shelf eddy heat fluxes are negl igible, as temperature variations and cross-shelf velocities are in qu adrature. At the shelfbreak, however, depth-averaged heat fluxes, appr oximately 4 x 10(6) W m(-1) onshore, are significantly different from zero and comparable to the exchange estimated by Fairbanks using O-18 tracer data. In the winter and spring the eddy flux is greatest near t he frontal boundary in the lower water column and is dominated by a fe w large exchange events. In the summer the subtidal eddy flux is great est just below the seasonal pycnocline in the upper water column, with a peak in the 5-11 day band that may be a contribution from frontal i nstabilities. Bottom Eulerian mean velocities are 1-2 x 10(-2) m s(-1) offshore over the shelf and slope. Measured eddy fluxes are adequate to achieve the advective-diffusive balance required to maintain the fr ontal position in steady state.