In winter, intense cooling results in a virtually homo- 

 geneous layer of water about 100 meters (300 feet) thick. Or 

 the basis of winter observations in this region, this layer has 

 a temperature that is near freezing. Below this mixed layer, 

 increasing salinity allows for an increase in temperature 

 without resulting in instability. According to Sverdrup, 

 Johnson, and Fleming, antarctic circumpolar water, which 

 occurs a short distance below the surface water, is charac- 

 terized by a temperature maximum at a depth of 500 to 600 

 meters . 



In summer, the radiation surplus is first used to melt 

 the ice and next to increase the temperature of the surface 

 layers. Station C-l, which was occupied in the Ross Sea 

 fairly close to the ice pack, shows a temperature minimum 

 at a depth of only 35 meters, compared to approximately 

 75 meters for the other stations. The increase of temperature 

 above 35 meters is much less than in the other cases, indi- 

 cating that in this region the radiation surplus had apparently 

 been used mainly for melting the ice. 



The relatively high temperature of the surface layer 

 above 45 meters (150 feet) in the five hydrographic stations 

 other than C-l must be largely the result of actual heating of 

 the surface layers. There is some indication that stations 

 C-2, C-3, and C-4 were taken near the Antarctic Convergence, 

 hence the high temperatures found on the surface at these 

 stations may be partly due to the southward intrusion of a 

 thin surface layer of warm water from north of the conver- 

 gence. The stability which is associated with the strong 

 negative gradients thus developed aids in restricting this 

 warm layer to the upper 150 feet. 



The minimum temperatures found at all stations from 

 60 to 100 meters (200 to 300 feet) must therefore be the re- 

 mainder of the winter-cooled surface layer mentioned above. 

 The increase in temperature that occurs below 100 meters 

 at the different stations evidently corresponds to the transition 

 layer between surface water and antarctic circumpolar water, 

 which has a maximum temperature of between 2.0 and 2.5 de- 

 grees C. at depths from 500 to 600 meters. 



Figure 22 gives the salinity-depth curves for all stations. 

 These curves also show certain characteristics which tend 

 to support the conclusions gained from the thermal structures. 

 The melting of ice results in lowered salinities very near the 

 surface. This low salinity layer is shown best at station C-l, 



42 



