Oxygen Depletion and Associated Benthic Mortalities 

 in New York Bight, 1976 



Chapter 8. Diagnostic Model of Water and 



Oxygen Transport 



G. Han, D. V. Hansen, and A. Cantillo^ 



' Physical Oceanography Laboratory, Atlantic 

 Oceanographic and Meteorological Laboratories, En- 

 vironmental Research Laboratories, NOAA, Miami, FL 

 33149 



INTRODUCTION 



To thoroughly analyze the 1976 oxygen depletion in 

 New York Bight, the transport of oxygen through the area 

 by currents must be carefully considered. Here the time- 

 averaged water and oxygen fluxes through certain seg- 

 ments of the Bight during the period of anoxia develop- 

 ment in May and June 1976 are calculated. Segment 

 boundaries and station locations are shown in figure 8-1. 



A simple mass transport model is employed to analyze 

 the oxygen balance, using observations of density, oxygen, 

 and current velocity fields to estimate the various terms. 

 Our major contribution here is an estimate of the water 

 fluxes, utilizing a vorticity balance diagnostic model of the 

 steady-state circulation field from May 18 to June 29, 1976. 

 This time interval was selected because suitable data were 

 available and because the dissolved oxygen (D.O.) con- 

 centration was decreasing rapidly, but anoxia had not yet 

 developed. Thus, the role of oxygen and water fluxes in 

 the development of the anoxic condition can be compared 

 to the observed changes of D.O. with time. This will result 

 in the estimate of the net oxygen utilization rates in each 

 segment and the evaluation of the role of water transports 

 on the net utilization rates. 



Segar and Berberian (1976) calculated oxygen utiliza- 

 tion rates in the Bight Apex. Studies have also been done 

 on the utilization of other dissolved constituents, such as 

 nutrients (Garside et al. 1976). 



Previous studies have been hampered by poor knowl- 

 edge ot water transports. Investigators have been forced 

 to resort to arbitrarily chosen and vaguely defined volumes 

 and flushing times to complete their analyses. Because 

 chemical reactions frequently depend on concentrations, 

 and most problems involve finding concentrations that 



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