TM No. 327 



data sheets in appendix A.) One probable source of error is that the 

 receivers were used 110 nautical miles from the transmitting sites, resulting 

 in a loss of signal strength (reference l). In addition^ a storm from the 

 northeast with winds of 30 miles per hour interrupted tracking. (See appendix 

 B for wind data- ) The drag on the surface float due to the wind was probably 

 sufficient to bias the drogue data. 



Some current data (6 days) were obtained kO nautical miles east of Abaco 

 (26°06'W and 76°19'W) during late October I962 with a Richard son- type array 

 (by J, Hirshman^ Alpine Geophysical Associates^ Norwood^ N.J„)« Data were 

 taken at depths of 550^ 61O, 915;, 1220;, and 27il-0 meters. Briefly, these data 

 indicated that currents at 550 and 61O meters were tidal in nature;, with speeds 

 ranging from 2„5 cm/sec to 20 cm/see. The net direction was toward the south- 

 west. At 915 and 1220 meters the currents were still indicative of tidal 

 motion, but this was not as definitive as at 550 and 61O meters „ Current speeds 

 were generally greater at 915 meters with a flow of from 10 to 30 cm/sec 

 toward the south and southeast. At 1220 meters the current was steady between 

 15 and 20 cm/sec toward the south and southwest. At 27^0 meters the current 

 was steady at 15 cm/sec. No directions were reported at this depth. 



If a steady state current regime exists east of Abaco (there is little 

 data to support this one way or another), then it is reasonable to assume that 

 currents in this area can affect water motion in the Northeast Providence 

 Channel and thus in the Tongue itself. 



Vertical current gradients were computed from data presented in table 2, 

 This was accomplished' by computing a velocity component parallel to the long 

 axis of the Northeast Providence Channel from the average current velocity 

 presented in table 2. The bearing of the long axis of the channel isC50°T- 

 239 °T. 



The velocity components for the northern and southern halves of the 

 channel are plotted against depth in figure 6. The values for the vertical 

 current gradient are shown on the figure . 



The vertical current gradients were generally greater in the northern 

 half (drogues 2, 8, and X-ray) than in the southern half (drogues 3} ^ and 

 Zebra) of the channel. It is important to note that at nearly all depths 

 sampled, there was a definite JCHihannel (in TOTO) flow of water. The one 

 exception was the out-channel flow at I5OO meters in the southern part of 

 the channel. Negative gradients were shown from 200 to 15OO meters over the 

 southern part of the channel and from 200 to 15OO meters over the northern 

 portion, with a maximum of -6,6 cm/sec per 100 meters. 



Transect 2 



Eight drogues were set at various depths and tracked along transect 2 

 (T2 in figure l). The drogue history and data sheets are included in 



