Title

On The Modeling Of The Summer Circulation In The South Atlantic Bight By A Two-Layer Finite Element Model

Date of Award

1985

Availability

Article

Degree Name

Doctor of Philosophy (Ph.D.)

Department

Meteorology and Physical Oceanography

Abstract

The summer circulation in the South Atlantic Bight (SAB) was investigated using a two-layer finite element model. An impulsive wind experiment was done indicating that the frictional adjustment time on the shelf varies between 12 and 24 hours. The momentum balance study of this experiment indicated that for inner and mid-shelf regions a geostrophic balance dominates the dynamics for the cross-shelf direction. In the along-shore direction the coriolis acceleration of the cross-shore flow, the pressure gradient, the wind and the bottom stresses are all significant in the momentum balance. Both findings agree with results of data analysis of Lee and Pietrafesa (1985).The results of a real wind event experiment showed that modeled coastal sea level and currents compared reasonably well to observed coastal sea level and current velocities observed at mid-shelf at the 30 and 40 m isobaths. Shelf break currents could not be modeled since their main forcing are the Gulf Stream mean and transient components, which are not accounted for by the model. The results of this experiment together with the momentum balance study referred to above and the data analysis indicate that the inner and mid-shelf response of the SAB during the summer of 1981 was in the form of wind forced continental shelf waves. The short adjustment time on the shelf compared to the time scale of the forcing results in a quasi-steady state dynamic balance, giving these waves properties similar to the 'arrested topographic waves' of Csanady (1978).The summer upwelling present north of Cape Canaveral and off Daytona was represented very well in the model results both for upwelling favorable winds and by forcing the model at the shelf break by a negative along-shelf slope of -1.6 x 10('-7) as suggested by previous studies. These results indicate that the summer upwelling in that region is not produced by a single mechanism, but is the result of the joint effect of northward winds and onshore migrations of the Florida Current over the shelf.The implementation of sponge layers along the south and north open boundaries of the numerical domain was found to be very efficient in attenuating the wave reflections along these boundaries.

Keywords

Physical Oceanography

Link to Full Text

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