values were computed from STD (salinify,„tgmperature, depth) measurements 

 made during August 1973. The Brunt-Vaisala frequency decreases nearly 

 exponentially with increasing depth. The kinetic energy spectrum for ,, ,, ,, 

 baroclinic internal waves is theoretically proportional to the Brunt-Vaisala 

 frequency. The observed depth decrease of the Brunt-VaisSla frequency 

 closely resembles the observed depth decrease of the semidiurnal energy 

 densities. Similar comparisons have been made in the eastern North Atlantic 

 near the Continental Shelf (e.g.. Regal and Wunsch, 1973). At several 

 locations, the semidiurnal tidal energy density increases as the bottom is 

 approached. This may indicate that the internal tide interacts with local 

 bottom bathymetry or that internal waves are beinq generated near the bottom 

 by bottom roughness or the bottom boundary layer. Examination of the 

 topography near the array locations showed no clear correlations between 

 semidiurnal energy density variations near the bottom and topographic features 

 or changes in bottom roughness. At locations where the diurnal energy is 

 separated from the local inertial energy, the diurnal energy density is more 

 nearly uniform with depth. 



Further insight into the current structure is gained from rotary co- 

 efficients. Figure 12 provides the coefficients for current records at 

 depths less than or equal to 1,000 m. Figure 13 provides the coefficients 

 for current records at greater depths. The rotary coefficient is a measure 

 of the strength of rotary motion. For currents which rotate in a perfect 

 circle, the magnitude of the rotary coefficient is unity. The sign of the 

 rotary coefficient is positive for clockwise rotating currents and negative 

 for anticlockwise rotating currents. Because the current measurements were 

 made far from continental boundaries and in the Northern Hemisphere, currents 

 due to inertial and internal wave motion should rotate clockwise. Figures 

 12 and 13 show that clockwise motion is nearly always observed for 

 frequencies at and above the local inertial frequency. At these frequencies 

 internal waves may occur. For the records at 1,000 m which contain con- 

 siderable inertial and semidiurnal energy, currents at these frequencies 

 rotate clockwise in nearly perfect circular orbits. 



For internal waves, Fofonoff (1969) has shown that the rotary coefficient 

 is given by: 



where f is the local Coriolis parameter. Values of Rq from equation 14 

 are indicated on figures 12 and 13 for latitudes bracketing all of the 

 measurements. Below the inertial frequency, values from equation 14 are 

 shown by a broken line to indicate that internal waves cannot occur. 

 Observed values of the rotary coefficient compare well with equation 14 

 for the upper current records (fig. 12). Agreement is especially good 

 at the local inertial and semidiurnal frequencies where energy is concen- 

 trated. Poorer agreement (fig. 13) is expected for the deeper currents. 



