The temperature-salinity diagrams in figure 23 further 

 substantiate the conditions described above. The characteristic 

 temperature minimum is evident on all the T-S curves. This 

 minimum, which occurs very close to -1.0 degree C. and 

 between 34.1 and 34.2 o/oo, corresponds to the layer of winter- 

 cooled water. Surface heating and low salinity are indicated 

 by the sharp rise in the curves at the left of the temperature 

 minimum. At station C-l the elongation of the T-S curve on 

 the left shows the effect of dilution caused by the melting of 

 ice. The approximate T-S value of antarctic circumpolar 

 water at 600 meters for the region within which the stations 

 were occupied is plotted as a large dot labeled "A.C.P.W." 

 It can be seen that the increase of temperature and salinity 

 with depth below 100 meters tends to bring the T-S curves 

 toward this point. 



The density structure, as represented by the curves of 

 figure 24, indicates instability or indifferent equilibrium in 

 the upper 30 meters except at stations C-l and H-l. Station 

 H-l shows slight stability, while station C-l shows marked 

 stability, in this layer. There is generally a moderate in- 

 crease in density in the 30- to 60-meter layer, the increase 

 leading to moderate stability at these depths. Below 60 meters 

 there is only slight stability. 



The effect of this density structure on submarine diving 

 operations is indicated in figure 25. The amount of buoyancy 

 change required in diving from a depth of 50 feet to any depth 

 down to 300 feet has been computed for a 2400-ton submarine 

 using the diving rule of 1400 pounds per 100. feet. These 

 figures were computed on the basis of a 5400 pound change 

 in buoyancy for each unit change in«r.. At stations C-l and C-4, 

 the computed buoyancies indicate that flooding is necessary to 

 go from 50 feet to 150 feet. At station C-l, a submarine at 

 50 feet would be in the center of a sharp density layer. At 

 station C-4 there is a fairly sharp density layer, approximately 

 2000 pounds per 100 feet between 125 and 175 feet. At the other 

 four stations no appreciable density layer is indicated. These 

 data indicate that relatively little flooding or pumping is needed 

 for diving operations in the antarctic. 



44 



