for used line. To estimate effects of mooring motion, a finite element 

 model (Chhabra, 1973; Chhabra, Dahlen and Froidevaux, 1974) was used to 

 simulate array motion. The highest measured current speed profiles were 

 inputs to the finite element model. Time-dependent displacements of the 

 current meters were found to have a negligible effect on velocity measure- 

 ments. 



DESCRIPTION OF MEASURED CURRENTS 



Prior to detailed analysis, all 10-minute current speed and direction 

 values were resolved into east-west and north-south components. To obtain 

 an initial description of the current velocity field, individual components 

 were averaged vectorial ly to provide half -hour mean current vectors which 

 were plotted as a function of time. Figure 2 is an example of such a plot. 

 The plots indicate that the current speeds are very low and that the most 

 significant contributions to the time-dependent flow are clockwise motions 

 at the semidiurnal and local inertial frequencies. Although some current 

 vector records depict a slight velocity amplitude increase just above the 

 bottom, currents are generally characterized by a rapid decrease in velocity 

 amplitudes with increasing depth. In addition, currents at different depths 

 are not in phase. 



The probability distributions of current speeds are given in table 2 and 

 mean current speeds are given in table 3. For many of the deep current 

 records (below 1,000 m), current speeds are often below the threshold 

 speed (2.5 cm/sec) of the current meters. Although the meters appear to 

 operate satisfactorily below threshold speed, uncertainty about the meter 

 calibration and operation below threshold speed indicates that the inter- 

 pretation of the measured deeper current results should be primarily 

 qualitative, 



TIME SERIES ANALYSIS OF MEASURED CURRENTS 



1 . T heory 



Rotary energy spectra and cross-spectra were computed using techniques 

 described by Gonella (1972) and Hooers (1973). These techniques resolve 

 vector current records into clockwise and anticlockwise rotating components. 

 The east-west velocity component U^ (t) and the north-south velocity com- 

 ponent U2 (t), where t is time, can be represented by their Fourier 

 coefficients (a-., b-, ) and (a2, bg), respectively, as follows: 



U (t) = 1 I [a (a) cos(at) + b (a) sin(at)] da 



(1) 

 00 



U (t) = 1 ( [a (a) cos(at) + b (a) sin(at)] da 

 2 2^3 2 2 



