CHAPTER 8 



Table 8-1. — Surface area, volume, and average dissolved oxygen concenlralions in New York Bight, 1976 



XWCC-10 (June 28 to July 



Segment numbers and boundary designators refer to figure 8-1. 



averaged over selected time intervals such as shown in 

 figure 8-8 . These patterns are consistent with the current 

 velocities shown in figure 8-5 and are based upon both 

 these current data and the density data described more 

 extensively in chapters 2 and 7. The diagnosed currents 

 are evaluated at much greater spatial resolution than can 

 be obtained from current meters only. However, it is dif- 

 ficult to demonstrate the veracity of the model in as much 

 detail as it portrays. Because of the nature of the available 

 oxygen data, as discussed previously, transports are in fact 

 more useful than detailed velocity structure in application 

 to the anoxia problem. Thus, the major results from the 

 circulation model are presented instead as transports in 

 the lower layer through the various boundaries of the 

 several segments of New York Bight. These are shown in 

 figure 8-10. 



Transport below the thermocline during the interval 

 diagnosed is consistently to the southwest, into the Bight, 

 all across the shelf off eastern Long Island. Off southern 

 New Jersey, transport is predominantly southward, out 

 of the Bight, over the outer shelf, and is directed weakly 

 southward over the inner shelf on the average, but the 

 transport undergoes large reversals over the interval. 



The lower layer flow in the Hudson Shelf Valley is 

 predominantly shoreward into the Apex. In the Apex seg- 

 ment, the diagnosed horizontal transport from all adjacent 

 segments is into the Apex, causing the mass balance to 

 be maintained by an estuarine-like upward flow through 

 the pycnocline. Exchange with the estuary has been ig- 

 nored because the required upwelling flux is more than 

 30 times the Hudson River discharge. A small but perhaps 

 significant fraction of this upwelling probably occurs by 

 horizontal transport into, and upwelling within, the es- 

 tuary. Neglect of this detail does not invalidate the model 

 for the present analysis. The implied vertical flow rate 

 across the thermocline in the Apex segment is about 1.3 

 m/d, and the outer shelf segment has upwelling across the 

 pycnocline of the order of 0.1 m/d. Diaz (chap. 3) used 

 monthly mean wind values to compute the mean vertical 

 motion in New York Bight during May and June as upward 

 at about 0.04 and 0.02 m/d. respectively. The upwelling 

 velocity, as determined with the diagnostic model but av- 

 eraged over all the Bight as defined for the model, is 

 upward at about 0.06 m/d. The discrepancy between these 

 results can probably be attributed to the limit of accuracy 

 in the diagnositc model and to the fact that Diaz's com- 



187 



