Internal Waves 



Internal waves are found between 

 density layers in the sea. They can be 

 caused by flow over an irregular bottom, 

 atmospheric disturbances, tidal forces, 

 and/or shear flow. They have amplitudes 

 considerably larger than ordinary surface 

 gravity waves and propagate at a much 

 slower velocity. The internal wave peri- 

 ods at the tower range from a few minutes 

 to long diurnal oscillations. 



At the relatively shallow tower 

 site, the vertical density structure may 

 normally be considered as a two-layer 

 system of warmer and colder water sepa- 

 rated by a thermocline. Under these con- 

 ditions, only one mode of oscillation can 

 exist. The internal waves at different 

 levels are usually in phase with each 

 other, and the greatest vertical displace- 

 ment of water particles takes place at the 

 thermocline. In rare cases a double 

 thermocline may resonate. 



and depressions. As the waves propaga 



over the continental shelf, they tend to form into 



long crests. 



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