b. Bottom Circulation . A study of bottom circulation of waters 

 outside the Harbor was attempted by the SHL using current meters and bot- 

 tom drifters. Current measurements were made by the SHL for only three 

 stations A, B, C (Figure 9). 



At station A, 3.5 miles south of Atlantic Beach, bottom and mid-depth 

 observations were made in late June 1969. At station B, 2.5 miles south- 

 west of Ambrose Light, bottom measurements were taken in late February 

 1969. At station C, 3.5 miles east of Sandy Hook, bottom measurements 

 were taken in late May - early June 1969. The records are few, nonsynop- 

 tic and cover only short periods. It is difficult to generalize from 

 only three measurements the total bottom circulation of the Bight, or to 

 correlate with drifter studies as the SHL attempted to do. Although not 

 conclusive, the results of these current measurements taken by SHL are 

 illustrated in Figure 15. For each of the three stations A, B, C, in 

 this figure, the progressive vector diagram is presented for the valid 

 portion of the record. 



On the basis of these current measurements, the following conclusions 

 were reached by the SHL study. At station A, according to bottom-drifter 

 analysis, the bottom flow should be predominantly east. For the period 

 of the record (late June) local winds were variable but generally from 

 the south. The current-meter measurements (Figure 15) show such an init- 

 ial eastward movement of mid-depth and bottom water. One week later, 

 however, the mid-depth flow swings in a northeast direction, bottom drift 

 shifted to a southeast direction. The average net drift at point A was 

 3.3 miles per day for mid-depth water, and 1.9 miles per day for bottom 

 water. 



At station B, the station nearest the dumping grounds, bottom water 

 flow (February) was generally east, switching later toward the north 

 until the record became invalid. The average net drift for the entire 

 period was 3.9 miles per day. 



Finally, at station C (late May - early June) the path of the infer- 

 red bottom flow was northwest into the Bay. Figure 15 shows there was 

 substantial tidal oscillation, but net drift followed a heading of about 

 320° True. The average net drift over the period, according to the SHL 

 study, was 4.2 miles per day. 



In addition to the current measurements, bottom seabed drifters were 

 also released at stations shown in Figure 9. 



The total percent recovery of seabed drifters is shown in Figure 16. 

 Of 2,190 seabed drifters released in 1969, 710 (32 percent) were recover- 

 ed over a period of 6 months from beaches of Long Island. The origins of 

 seabed drifters recovered in the Hudson Estuary and the Long Island and 

 New Jersey coasts are shown in Figures 17, 18, 19. SHL data suggest a 

 strong flow at the bottom along the axis of the Hudson-Ambrose Channel 

 northward and towards Long Island and into the mouth of the Hudson Estuary. 

 Few drifters were recovered in the bay, but low drifter return was 



46 



