CONCLUSIONS 



1. The depth of isotherms in the shallow summer thermocline fluctuates vir- 

 tually all the time. At Mission Beach, California, of the significant vertical oscil- 

 lations of a central isotherm in the thermocline, half were greater than 7.2 feet 

 and half had periods greater than 7.6 seconds. Because the internal waves were 

 refracted, they usually proceeded in a general shoreward direction at the meas- 

 urement site where they had an average speed of 0.31 knot. 



2. Every large internal wave of height greater than 14 feet had a sea surface 

 slick associated with it for the thermocline depths observed. 



3. In accordance with wave motion theory of simple internal waves, an active 

 convergence circulation occurs over the descending slope of an internal wave. In 

 85 cases out of 105, the slick occurred between the crest and the following trough. 

 The relationship was sufificiently reliable to provide an approximate prediction of 

 the subsurface thermal topography at the measurement site from a knowledge 

 of the distribution and movement of the sea surface slicks. 



RECOMMENDATIONS 



Continue the general study of the near-shore and near-surface environmental 

 characteristics which affect acoustic transmission. Give special emphasis to long 

 duration waves and to the geographical distribution of internal waves. Study 

 acoustical transmission through internal waves. 



REFERENCES 



1. Schuleikin, V. V., Fizika Moria, Moscow, Akademiia Nauk SSSR, 1941. 



2. Dietz, R. S. and LaFond, E. C, "Natural Slicks on the Ocean," Journal of 

 Marine Research, v. 9, p- 69-76, 1950. 



3. Woodcock, A. H. and Wyman, J., "Convective Motion in Air Over the Sea," 

 New York Academy of Sciences. Annals, v. 48, p. 749-776, 1947. 



4. Forbes, A., "Photogrammetry Applied to Aerology," Photo grammetric Engi- 

 neering, V. 11, p. 181-192, 1945. 



5. Ewing, G., "Relation Between Band Slicks at the Surface and Internal Waves 

 in the Sea," Science, v. Ill, p. 91-94, 17 January 1950. 



6. Ewing, G., "Slicks, Surface Films, and Internal Waves," Journal of Marine 

 Research, v. 9, p. 161-187, 1950. 



7. Navy Electronics Laboratory Report 828, Slicks and Related Physical Prop- 

 erties of Near-Shore Waters (an Investigation of the Possible Effects of the 

 Near-Shore Environment on Underwater Sottnd), by R. F. Dill and E. C. LaFond, 

 CONFIDENTIAL, 29 April 1959. 



8. Brown Instrument Co. Instruction Manual 15038G, Issue 4, Brown ElectroniK 

 Strip Chart Recorder, 1947. 



9. Lamb, H., Hydrodynamics, 6th ed., p. 372, Dover, 1945. 



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