and return transit in February is illustrated in Figure 11, In addi- 

 tion, six representative BT toaces have been presented on the chart. 

 The irregularity of some of the traces and the complexity of isotherms 

 in the cross sections is a result of the characteristic sinuosity of 

 the convergence. The letter "A" is used on the chart to show the 

 Antarctic Surface Water with its seasonally heated upper layer while 

 "B" indicates the deep warm water. Despite temperatures warmer than 

 the water immediately above, this mass is of high enough salinity to 

 make it denser than "A", 



C« Pacific Ocean Section 



In November the GLACIER crossed the Antarctic Convergence at 

 approximately 62°S, 173°E. The BT observations taken during this 

 transit have been used in preparation of Figure 12, This shows clearly 

 the cold Antarctic Surface Water to the south (relatively unaffected by 

 seasonal warming at the early date). Surface salinity samples collected 

 during the BT observations have also been plotted, and from these and 

 teirperature values the surface density is also shown. 



The thermal profile section presented in Figure 13 was derived from 

 BT's obtained by the ATKA during the southward transit in December, The 

 position of the Convergence was approximately the same as recorded by 

 the GLACIER during its November crossing. Figure Ih illustrates the 

 thermal structure of the s^xrface layers extrapolated from BT's taken 

 during the ATKA's return transit in late February, The position of the 

 Convergence zone was almost the same as in the December crossing; how- 

 ever, seasonal warming raised the surface temperatures considerably, A 

 seasonal thermocline is prominent. As in Figure 13 the shaded zone 

 marks the remains of winter water in the Antarctic Surface Water mass. 



D, Indian Ocean Section 



Figure 15 shows a cross section through the Convergence taken by 

 the GLACIER during a transit from the Knox Coast to Australia in late 

 February. Here the zone was observed much farther northward then in 

 the Pacific Sector to the east. The illustration portrays well the 

 characteristic horizontal temperature gradient of the surface and the 

 spreading of the colder Antarctic Surface Water northward below the 

 warmer surface water at lower latitudes. 



25 



