D . Density 



In Figure 4, the profile of density distribution with depth between stations 

 1 and 5 shows no startling features. In the zone of turbulence density decreased 

 from east to west about one unit of sigma-t. At 50 meters depth, however, density 

 remained nearly constant at around 26.00, and,as normally occurs, density In- 

 creased with depth. The 27.00 Isopleth was between 700 and 900 meters between 

 these stations . 



The profile of density distribution with depth, between stations 5 and 27 

 (Figure 10), shows a decided drop In density at the surface and In the zone of 

 turbulence from south to north . Rising water temperatures are responsible for the 

 lower densities. Commencing at about 50 meters depth, the 26.00 Isopleth drops 

 to 90 meters at station 8 and to 270 meters at station 1 1 . North of this point, 

 this Isopleth Is pushed upward by the tongue of water of lower salinity (Antarctic 

 Intermediate water). By station 18, it has reached 150 meters depth,and from 

 this point (5° S .) north,it remains at only a few meters below this level . The 

 27.00 Isopleth shows considerably more of the effects of the tongue of Antarctic 

 Intermediate water than the others. Starting at a depth of 850 meters at station 

 5, It is pushed up to a little under 500 meters at station 13 (16° S .) With minor 

 up and down variations, it follows approximately this depth to the northern end 

 of the section . 



Between stations 28 and 30 (Fig. 16), there was a slight Increase at the 

 surface. This was caused by increasing salinity as the Red Sea was approached. 

 The 26.00 Isopleth almost constantly remains at a depth of about 175 meters, 

 while the 27.00 isopleth only varies from 430 to 465 meters depth. 



E . Dissolved Oxygen 



The distribution of dissolved oxygen with depth between stations 1 and 5 is 

 shown In Figure 5. Vertical distribution at selected stations along the 32° S. 

 parallel is shown In Figure 20, A, B, and C. There was no apparent trend in the 

 upper waters, but from around 1200 to 2000 meters a tongue of water with low 

 oxygen extended from the east and became mixed as mid-Indian Ocean areas 

 were reached at station 5. This Is the characteristic low oxygen layer underlying 

 Antarctic Intermediate water, which is comparatively high In oxygen. There was 

 also water containing more oxygen below the low oxygen tongue that extended 

 to the bottom of the casts . 



In Figure 20, A. B. and C, vertical distribution curves for dissolved oxygen 

 at stations 1, 3, and 5 are similar,and roughly follow the temperature curve below 

 the zone of turbulence. The layer of low oxygen from the surface to 50 meters 

 depth was apparently a result of the western coastal current of Australia. 



38 



