because the low-speed currents result in a low signal-to-noise ratio and 

 because of bottom influences. 



Garrett and Munk (1972) developed an internal wave model which assumes 

 that the internal wave field is horizontally isotropic. For isotropy, the 

 coherence between horizontal velocity components has the same form as 

 equation 14. That is. 



where y is the coherence between the east-west and north-south velocity 

 components. For the current records above 1,000 m, the coherences between 

 these components are nearly identical to the rotary coefficients in figure 

 12. 



Rotary cross-spectra were computed for simultaneous current records at 

 the same depths less than or equal to 1,000 m at adjacent arrays and for 

 simultaneous records at different depths on the same array. At the 1,000 m 

 depth for arrays E and F which were 1,500 m apart, all frequency bands 

 with significant energy (0.053 to 0.082 cph) have coherence values between 

 clockwise rotating components greater than 0.95 and phase differences less 

 than 31 degrees. These values for these close arrays place confidence in 

 the measurement techniques. Except for cross-spectra between arrays E and 

 F, no other coherence values exceed the 90-percent confidence level. Low 

 horizontal coherences are expected because the experiment was designed with 

 large horizontal spacings between arrays and because the most important 

 current contributions are from inertial currents and internal waves which 

 have horizontal scales smaller than the array spacings except for arrays E 

 and F. 



CONCLUSIONS 



This description and analysis of measured intermediate and deep currents 

 in the northeast Pacific provides the following general characteristics of 

 the current velocity field; 



1. The measured currents, particularly the mean- and low-frequency 

 currents, have ^ery low speeds. Low speeds are expected, because the 

 measurements were made near the center of the eastern gyre of the North 

 Pacific. 



2. Inertial currents, which are concentrated near the surface and are 

 incoherent over vertical distances, are a major contributor to the current 

 structure. 



3. Semidiurnal tidal frequency currents are significant. Time series 

 analysis indicates that the oscillatory motion of semidiurnal tidal 

 frequency is due to baroclinic internal tides rather than to barotropic 

 surface tides. Semidiurnal tidal frequency currents are also concentrated 

 near the surface, where the Brunt-Vaisala frequency is largest. 



