UNCLASSIFIED 



Security Classification 



DOCUMENT CONTROL DATA -R&D 



3f title, body of abstract anil indexing annotation must be entered when tin 



3/1 report is classified) 



I. ORIGINA TING ACTI 



(Corporate author) 



U. S. NAVAL OCEANOGRAPHIC OFFICE 



2a. REPORT SECURITY C L A SSI F I C A TIC^ 



UNCLASSIFIED 



3. REPORT TITLE 



OCEANOGRAPHY IN THE CHANNEL ISLANDS AREA OFF SOUTHERN CALIFORNIA - SEPTEMBER 

 AND OCTOBER 1965 



DESCRIPTIVE NOTES (Type of report and inclusive dates) 



Technical Report 16 September to 15 October 1965 



5- AUTHORIS) (-First I 



iddle initial, las 



SAMUEL G. TOOMA, JR. 

 HARRY IREDALE, III 



6- REPORT DATE 



June 1968 



TOTAL NO. OF PAGES 



50 



'6. NO. OF REFS 



22 



8a. CONTRACT OR GRANT NO. 



9a. ORIGINATOR'S REPORT 



b. PROJEC T NO. 



202 



TR 203 



10. DISTRIBUTION STATEMENT 



Distribution of this document is unlimited, 



11. SUPPLEMENTARY NOTES 



12. SPONSORING MILITARY ACTIVITN 



U. S. Naval Oceanographic Office 



ABSTRACT 



The Naval Oceanographic Office conducted an oceanographic survey in the Channel Islands 

 area aboard USNS DAVIS (T-AGOR 5) during September and October 1965. The survey was a 

 detailed environmental study with major emphasis on currents, sound velocity structure, 

 and bottom composition. Physical, chemical, geological, and biological data were collected. 



Seaward decreases in surface temperature and salinity depicted the Influence of the cold, 

 low salinity California Current on the survey area. The sound channel was bottom bounded 

 due to the shallow depths, and the sound velocity axis occurred at a depth of 850 meters 

 (2800 feet). Surface duct development was weak and usually restricted to the upper 10 

 meters (30 feet) . 



Data from repeated Nansen casts ac anchor stations revealed temperature, salinity, and 

 sound velocity to oscillate in a sinusoidal manner throughout a day. This oscillation is 

 attributed to a combination of internal waves, tidal forces, and the earth's rotational 

 forces. 



Current data from parachute current drogues, current meters, and computed dynamics 

 showed the San Nicolas Basin to be the center of a counterclockwise gyre. Maximum 

 current speeds of about 25 cm/sec occurred around the basin periphery. Lesser speeds 

 existed towards the center of the basin and with increasing depth. Current meters, planted 

 2 miles northeast of San Nicolas Island, indicated a clockwise rotational water movement 

 produced by the tides. 



Both bottom sediment analyses and bottom photographs showed the survey area to have the 

 same general characteristics as have been observed in previous studies. Fine-grained, 

 green-gray muds of high organic content were found in depressions, and somewhat coarser 

 materials were found on elevations. 



From one plankton collection in September and several in October, a study of the abun- 

 dance of various planktera suggested that the autumnal decline occurred between 23 September 

 and the second week of October. 



DD 



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