40 



30 



20 



10 



j 















TOTAL: : 



26 







1 

























I 

























vl 



i 



th 



A/ 



Jlrli 



Aw\ i 



\ 



/ 





A 



CNJ •—! 



Figure 1. Distribution of papers on internal 

 waves by year . 



U. S. help this problem somewhat, but interpretation of 

 the data is difficult. For example, towing of thermistors 

 introduces a Doppler shift into any periodic phenomenon 

 that is in motion, and the magnitude of the shift is unknown 

 because the directionality of internal waves is also unknown. 



A large number of temperature observations in the 

 ocean have been made for purposes other than the study of 

 internal waves. Some of the features of these observations 

 have been explained on the basis of internal waves, for 

 example, the variability in dynamic heights, from which 

 dynamic currents are computed. Changes in the relative 

 topography of the sea surface of ±1 centimeter have been 

 estimated for the region off Southern California. 



Limitations on Measurement 



The ability to measure internal waves is presently 

 confined to the ability to measure temperature in the 

 ocean. It is not yet possible to measure density in situ 

 continuously. Internal waves are measured by assuming 



