The speed and direction of internal waves are also determined 

 visually and photographically by observing the movements of 

 sea-surface slicks. The long slick lines are found at the surface 

 above the convergence zone, which is behind the crest of the 

 internal waves. When the internal wave crests are near the sea 

 surface, the surface becomes rougher, thus identifying the 

 orientation and phase of the internal wave. 



AtyU 



i— o 



— 2 



— 3 



— 4 



— 5 

 6 



— 7 



— 8 



— 9 



— 10 



SEA SURFACE 



10 MIN 



i 10 



30 



A 



I \ A ^ i\ 



m v y V / Vb 



Isotherms outlining the shape of internal waves 

 change as the thermocline approaches either the sea 

 floor or the surface. These are three typical record- 

 ings of isotherm depths when the thermocline is: 

 (A) near the surface; (B) at mid-depth around 30 

 feet; and (C) near the sea floor. 



50 



A 



*■*" " 60'--,-,^ 



SEA FLOOR 



A 



37 



