Season 



Total 



Positive 

 Gradient, # 



Positive 

 Gradient, % 



April-September 

 October-March 



194 

 13 



26 

 13 



13.4 

 100.0 



Table 3.14. Shallow Bering Sea sound speed profiles. 



No calculations were made for this area. However, propagation testing has been 

 done here (References 4 and 5) and sediment properties are obtainable. Thus, optimum 

 frequency studies and/or comparisons to propagation loss data will be included in future 

 reports. For this site, as well as the remaining two sites, no detailed bathymetry and sound 

 speed profiles will be included in this report. 



3.8 The Bass Strait 



The Bass Strait is between Australia and the Island of Tasmania. This is a southern 

 hemisphere site that has sufficient (year round) data in the NODC data banks. The site 

 location is 39°-4rS, 145°-I49°E (see Figure 2.2). Water depths varied between 30 and 

 90 m with an averaged recorded depth (in our data sample) of 66.2 m. There was a high 

 number of positive gradient profiles from each season as seen in Table 3.15. 







Positive 



Positive 



Season 



Total 



Gradient, # 



Gradient, % 



July-September 



28 



27 



96.4 



April-June 



27 



20 



74.1 



Totals 



55 



47 



85.5 



October-December 



50 



30 



60.0 



January-March 



47 



28 



59.6 



Totals 



97 



58 



60.0 



Table 3.15. Bass Strait sound speed profiles. 



Even in the spring and summer months (the seasons are reversed in the Southern 

 Latitudes) 60 percent of the sample profiles were of the positive gradient type. During 

 fall and winter, surface ducted propagation is expected about 86 percent of the time, 

 the average of 96 percent in winter and 74 percent in fall. 



No propagation loss calculations were made in this location due to the lack of sea 

 floor sediment information. 



3.9 North Coast of Brazil 



This site is located on the continental shelf off the coast of Brazil. The location is 

 shown in Figure 2.2 and is included within 0-1. 5°N, 46.5°-48.5°W; 1.5°-2°N, 47°-49°W; 

 2°-3°N, 47.5°-50°W and 3°-4°20'N, 48°-50°W. This area was enlarged in this manner to 

 include the shelf area between the mouth of the Amazon River and the Amazon Canyon 

 and tojncrease the number of sound speed profiles in the data sample. 



37 



