UNCLASSIFIED 



Security Classification 



DOCUMENT CONTROL DATA -R&D 



ol lille, body of abstract and indexiiit; annotation must be entered when the 



all report is classilied) 



ORIGINATING ACTIVITY (Corporate author) 



U.S. NAVAL OCEANOGRAPHIC OFFICE 

 WASHINGTON, D.C. 20390 



2a. REPORT SECURITY CLASSIF 



UNCLASSIFIED 



N.A. 



3- REPORT TITLE 



THE SOUND VELOCITY STRUCTURE OF THE NORTH INDIAN OCEAN 



4. DESCF 



1 VE NOTES (Type of report and inclusive dates) 



Technical Report 



Don F. Fenner and Paul J. Bucca 



6- REPORT DATE 



December 1972 



OF PAGES 



98 



7b. NO. OF REFS 



39 



CONTRACT OR GRANT NO. 



714-GT-HKE 



9a. ORIGINATOR'S REPOF 



TR-231 



b. PROJEC T NO. 



10. DISTRIBUTION STATEMEN 



Approved for public release; distribution unlimited. 



U.S. NAVAL OCEANOGRAPHIC OFFICE 

 WASHINGTON, D. C. 20390 



All available sound velocity data in the North Indian Ocean (north of 10°S latitude) 

 have been analyzed in terms of annual areal extent and depth of perturbations above deep axial 

 depth, annual average depth and velocity of the deep sound channel and critical depth for the 

 northeast and southwest monsoons. The vertical extent of these and other sound velocity features 

 is shown on six north -south and six east-west cross-sections that extend to a maximum depth of 

 5000 meters. These analyses indicate that highly saline Red Sea Intermediate Water (RSIW) is the 

 major factor controlling sound velocity structures in the North Indian Ocean. Mixing of RSIW 

 with low salinity water masses causes either sporadic perturbations or an essentially isovelocity 

 layer above deep axial depth. In relatively high concentrations, RSIW causes an anomalously 

 deep (greater than 1700 meters) and narrow sound channel with velocities greater than 1493 meters/ 

 second (Gulf of Aden, Arabian Sea, and Arabian Basin). In relatively low concentrations, RSIW 

 causes a somewhat shoaler (1200-1600 meters) and broader sound channel at velocities between 

 1490 and 1493 meters/second. The deep sound channel along the southern boundary of the area 

 (less than 1100 meters at velocities less than 1490 meters/second) is controlled by low salinity 

 Banda Intermediate Water. Critical depths show the effects of reversing monsoon circulation 

 north of about 10°N latitude, in the western Somali Basin, and south of Java. In the remainder 

 of the area, critical depths are similar during both monsoons. In addition, sound velocity/ 

 temperature-salinity comparisons for 36 locations and circulation diagrams for the surface 

 (both monsoons) and for subsurface and intermediate water masses are presented. 



UNCLASSIFIED 



