A NUMERICAL-ANALYSIS OF SHIPBOARD AND COASTAL ZONE COLOR SCANNER TIME-SERIES OF NEW PRODUCTION WITHIN GULF-STREAM CYCLONIC EDDIES IN THE SOUTH-ATLANTIC BIGHT

Eddy-induced upwelling occurs along the western edge of the Gulf Strea m between Cape Canaveral, Florida, and Cape Hatteras, North Carolina, in the South Atlantic Bight (SAB). Coastal zone color scanner images o f 1-km resolution spanning the period April 13-21, 1979, were processe d to examine these eddy features in relation to concurrent shipboard a nd current/temperature measurements at moored arrays. A quasi-one-dime nsional (z), time-dependent biological model, using only nitrate as a nutrient source, has been combined with a three-dimensional physical m odel in an attempt to replicate the observed phytoplankton field at th e northward edge of an eddy. The model is applicable only to the SAB s outh of the Charleston Bump, at approximately 31.5-degrees-N, since no feature analogous to the bump exists in the model bathymetry. The mod eled chlorophyll, nitrate, and primary production fields of the euphot ic zone are very similar to those obtained from the satellite and ship board data at the leading edges of the observed eddies south of the Ch arleston Bump. The horizontal and vertical simulated fluxes of nitrate and chlorophyll show that only approximately 10% of the upwelled nitr ate is utilized by the phytoplankton of the modeled grid box on the no rthern edge of the cyclone, while approximately 75% is lost horizontal ly, with the remainder still in the euphotic zone after the 10-day per iod of the model. Loss of chlorophyll due-to sinking is very small in this strong upwelling region of the cyclone. The model is relatively i nsensitive to variations in the sinking parameterization and the exter nal nitrate and chlorophyll fields but is very sensitive to a reductio n of the maximum potential growth rate to half that measured. Given th e success of this model in simulating the new production of the select ed upwelling region, other upwelling regions for which measurements or successful models of physical and biological quantities and rates exi st could be modeled similarly.