of dissolved oxygen. It will be noted that in general the isopleths follow very 

 closely those for actual dissolved oxygen values (Figs. 5, 12, and 17). In 

 Figure 6, percentages along the 32° S. parallel are shown. Saturation or slight 

 supersaturation can be observed at the surface and in the zone of turbulence 

 where the water was well mixed by wind and waves, and where the water was in 

 contact with the air. Below the zone of turbulence, percentages of saturation 

 decreased; the lowest values occurred below the level of the Antarctic Intermed- 

 iate water. Here, at between 1200 and 2000 meters depth there was only 50% 

 saturation. Saturation percentages increased below these depths as far as the 

 bottom of the cast . 



As shown in Figure 12, dissolved oxygen saturation percentages at and near 

 the surface, which commenced at 32° S. latitude at saturation point, declined 

 somewhat as observations reached areas farther to the north. The 100% isopleth 

 remains well within the zone of turbulence as far north as about 16 ° S . Here it 

 terminates at the surface, and beyond this point complete saturation was never 

 regained. The advancing season with higher air temperatures and water temper- 

 atures, plus low oxygen water from the Arabian Sea accounted for the decrease 

 In saturation as one progresses northward. The large mass of low saturation water 

 coming in from the Arabian Sea and pushing under the upper waters is clearly 

 shown in Figure 12. Dissolved oxygen saturation reached a low at 800 meters 

 depth at station 27 (10%). The 10% isopleth continues at a depth of 800 meters 

 westward (as shown in Fig. 18) past station 29. At station 30, however, it rises 

 sharply to the 200 meter level . Surface waters attained 100% saturation only at 

 station 28, and there was a noticeable decrease westward . Red Sea water account- 

 ed for the low saturation percentages found at station 30 where, below 150 meters, 

 saturation was less than 10% . The lowest saturation percentages (6%) were found 

 at station 28 at 240 meters depth and at station 30 between 400 and 600 meters. 

 Although dissolved oxygen saturation percentages increased toward the bottom 

 of the cast east of station 30, a high saturation value was never attained. Mix- 

 ing of the low oxygen water originating in the Red Sea accounted for this. 



G . Sound Velocity 



Figure 7 shows vertical distribution of sound velocity between station 1 and 

 5. At and near the surface, sound velocity Is greatest at the western or mid- 

 Indian Ocean end of the profile. The actual value reached slightly more than 

 5000 feet/second. A sound channel where the velocity has decreased to 4851 to 

 4866 feet/second, is located at a depth of 800 meters at station 2 but drops to 

 1200 meters at the next station and continues at this level to the end of the pro- 

 file at 78° E. longitude. 



Vertical distribution of sound velocity between station 5 and 27 Is shown in 

 Figure 13. Sound velocity at the surface Increases toward the north because of 



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