TABLE VII. Power per band (bandwidth is 0.072 cpd = 2/month of Fy(w) + Fj'(w) for the first and second fortnight, and for the 

 combined record. 



broadened semidiurnal phase-peak is in line with the 

 known character of iyiteryial tides. (At Bermuda the 

 spectral peak occurs at one harmonic below M^ fre- 

 quency.) Internal tides have wavelengths short com- 

 pared to the acoustic paths, and one would expect them 

 to produce an incoherent phase modulation. An excep- 

 tion might be the terminal effects. Internal tides are 

 generated by conversion from surface to internal modes 

 in regions of prominent bottom topography, which is 

 just where the hydrophones are located. In such re- 

 gions the internal tides may dominate, whereas in the 

 open sea internal tides typically have 10% of the internal 

 wave energy. Take a large vertical tidal displacement 

 S = 10 m, corresponding to 6C/C = 10"* at 1-km depth; 

 then in a near zone of radius R = \/2-n, with X = 100 km 

 for the wavelength of the lowest internal tide mode, we 

 have 



A* = 27r(7(.R/C)(6C/C) = 2.6 cycles. 



This suggests that the location of the acoustic source 

 and receiver in the generating area of internal tides 

 may be a significant factor. 



TABLE VIII. il/2 component of tidal current and acoustic 

 phase. 



Tidal current, azimuth 55^ 



Midstation 1st fortnight 

 2nd fortnight 



Bennuda 1st fortnight 

 2nd fortnight 



Amplitude 



MODE measurements 0.3 cm/sec 



Parke— Hendershott model 0.5 



Acoustic phase *(() Amplitude 



0.3 

 1.3 



°G 



180 

 20 



180°■^°G 



1.8 cycles 78 



1.1 260 



105 

 179 



245 



