upward as internal waves are destroyed near shore until 

 other processes set in to maintain dynamic equilibrium. 

 Scalar surfaces tend to parallel the bottom near 

 shore, and uplifted density surfaces near shore can be 

 observed in cross-sectional plots of density such as those 

 found in various atlases of oceanographic data. Horizontal 

 gradients, in addition to vertical gradients, would be ex- 

 pected to be more important in coastal waters than in the 

 deep, open sea. The importance of these horizontal gra- 

 dients has not been investigated, and they are ignored in 

 acoustic models assumed for the ocean. 



Other Effects 



In addition to fluctuation in sound speed and thus 

 sound refraction, numerous other changes in the sea 

 caused by internal waves are applicable to naval operations, 

 These include buoyancy changes, water motions, water 

 mixing, and displacement of water properties. Mathemat- 

 ical analyses have been conducted on the generation of 

 internal waves by idealized bodies moving in stratified 

 water. This has its obvious application to submarine 

 detection, provided small signals can be discerned from a 

 high background of natural internal waves. 



STAGES OF INTERNAL WAVES 



The studies of internal waves listed in the bibliog- 

 raphy can be placed under three general subject headings 

 origin, existence, and destruction. Most of the reports 

 have treated one of these phases without regard for the 

 other two. 



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