'9 



TM Wo, 377 



From the time of low water to the time of high water, the current flow 

 is fastest and steadiest. In general, the flow is westward at low water, 

 and slowly tends to rotate clockwise, attaining a northwest direction 4 to 

 4.5 hours after low water. At this point the swiftest current is found "be- 

 tween 20 and 40 cm sec" 1 ,, At low water plus 6,2 hours (i„e , at high water), 

 the flow has decelerated and tends more to the north. At a point generally 

 20-90 minutes after the time of high water, the current slows to the minimum 

 for the whole cycle, turns abraptly eastward, and continues to rotate anti- 

 cyclonically to the south. The change indirection from north to south at 

 the cycloid peaks usually occurs within a single 20-minute sampling interval. 

 Once this southern component is attained, the speed gradually increases, as 

 indicated by the spacing of the points in figure IV-?. As the time of low 

 water draws nearer the current flow tends to decrease in magnitude while 

 turning alowly to the west. At the time of low water the current is generally 

 tending westward. 



The anti -cyclonic current patterns in figure IV-T show the influence of 

 the coriolis deflection; indicating that the flow at BEEI£, although ti dally 

 driven, has strong inertial tendencies. The progressive vector diagram is 

 reminiscent of patterns obtained by Gustafson and Kullenberg during obser- 

 vations of suggested inertial motto currents in the Baltic Sea in 1933 (see 

 Sverdrup, Johnson, and Fleming, 1942). 



The current patterns must also be affected to some extent by the vari- 

 ations in wind conditions. During the period 29 April through 6 May, the 

 winds were from the HE. These winds were caused by an unusual stationary 

 high pressure system positioned off Nova Scotia. This resulted in HE winds 

 and a seven-day period of fair weather. (Normally HE winds are caused by 

 low pressure cyclones moving up the east coast, bringing rain and storm 

 conditions). ■This high moved on after 6 May, and the winds shifted to the 

 southwest on 6 and 8 May. Farther studies on the time variability of 

 various current vector components should reveal the effects of the wind. 



This nine-day series of measurements revealed the gross tidal character 

 at BBEI£, and provided some basis for predicting the relationship of tidal 

 amplitude with current speed and direction. 



There is evidence, from the frequent spikes oc curing in figure IV-6, 

 that motions exist which may occur at frequencies of O.p-1.0 cycle per 

 hour or less. This intermediate frequency range was further examined by 

 means of an auto-spectrum analysis (figure IV-8) of the equi-spaeed speed 

 data. 



For the analysis, the time increments 4& T was 20 minutes (1.2 ksec), 

 and the total lags m were 50. This gave a maximum lag of 60 ksec or a 

 little less than 10 percent of the total data record. The number of data, 

 points was 6k8 a Equation (III-9) gives the degrees of freedom DF as equal 

 to about 26, which gives reasonably narrow confidence bands of spectral 

 resolution. For DF - 26 (referring to figure III-3) the ratio is I.36 above 



82 



