The majority of the profiles in our sample (60 percent) were less than 75 m in 

 depth while only 19 percent were greater than 100 m deep. Profiles greater than 300 m 

 were edited out of our data sample. Table 3.16 summarizes the sound speed profiles 

 found in this area. A large majority (>85 percent) were positive gradient profiles. All 

 profiles from January-March and 76 percent of the July-December profiles were positive 

 gradient profiles. The few deep profiles had large negative gradients from 100 to 300 m. 



Season 



Total 



Positive 

 Gradient, # 



Positive 

 Gradient, % 



January-March 

 August-Decembe r 



20 

 42 



20 

 32 



100. 

 76. 



Table 3.16. Coast of Brazil sound speed profiles. 



No profiles were found in the months of April-July. No propagation loss calcula- 

 tions were made for this area. 



3.10 Summary 



Table 3.17 summarizes the positive gradient profile data. The winter profiles from 

 each site were predominately of the positive gradient type; eight of the nine sites had 

 90-100 percent positive gradients. The ninth site, East of Singapore, a low latitude site, 

 showed 82 percent positive gradients in the winter and 71 percent overall. Numbers of 

 positive gradient profiles are low in summer at mid and high (58°) latitudes. The exception 

 is the Bass Strait, 40° S latitude, where 60 percent positive gradients were found in the 

 summer. This may be an isolated case. The small number of sites does not allow any strong 

 statements on the dependence upon latitude. No sites at latitudes above 60° or between 

 10° and 30° were sampled. The large number of positive gradient profiles found at all 

 sites may be in part due to our definitions. The seasonal dependence at low latitudes 

 (where seasonal effects should be minimal) is somewhat surprising. In general, we sensed 

 that seasonal and latitudinal dependencies in shallow water may be overshadowed by land- 

 mass effects. 







Positive Gradient Profiles, % 



Site 



Latitude 



Summer 



Winter 



North Sea 



58°N 



24 



94 



Shallow Bering Sea 



58°N 



13 



100 



Lands End 



50°N 



27 



100 



Strait of Juan de Fuca 



49°N 







98 



Bass Strait 



40°?^ S 



60 



96 



Straits of Sicily 



37°N 



15 



100 



Korea Strait 



33°N 



26 



90 



North Coast of Brazil 



2°N 



76 



100 



East of Singapore 



1°N 



60 



82 



Table 3.17. Summary of positive gradient profiles. 



38 



