C. Density 



Since densities expressed as Sigma-t are derived from salinities, 

 the graph showing their seasonal variation at various depths (Figure 

 7) is almost identical with the salinity distribution graph (Figure 6). 

 Table 4 presents seasonal variations of density values. The approxi- 

 mate value of 2800 follows a rising curve, with some fluctuations, 

 until it reached the surface on 7 November 1960. This value then fol- 

 lows a descending curve fluctuating from the surface early in December 

 and continues to follow the general path of the salinity curve there- 

 after. Vertical distribution of Sigma-t in summer and winter in 

 Figures 3 and 4, follows the salinity curve. 



D. Sound Velocity 



Table 5 presents seasonal variations of sound velocities at dif- 

 ferent depth throughout the period of observation. The range is from 

 4710 to 4747ft/sec. A.t each level, there is very little change through- 

 out the year; such microchanges as there are, are found in the upper 

 waters. At each station, sound velocity shows a gradual and regular 

 increase from surface to the bottom. There is no sound channel unless 

 it is from the surface down to about 100 meters. The absence of a 

 deep sound channel in the polar regions has been noted before. A 

 review of sound velocities determined on some Hydrographic Office 

 antarctic cruises (US Navy H. 0. TR-48, 1956, TR-29, 1957, TR-33, 

 1956, and TR-82, 1961) shows comparable figures for the McMurdo Sound 

 area. A slight sound channel was believed to exist at 10 meters at 

 one station taken in McMurdo Sound in 1956. In other stations taken 

 during DEEP FREEZE 60 in McMurdo Sound, there was some indication of 

 a sound channel existing at depths of from 30 to 150 meters but the 

 gradients were very slight. Further to the east, not too clearly 

 marked sound channels were noted off the Bay of Whales at 100 meters 

 depth and off Kainan Bay at between 50 and 100 meters. On DEEP FREEZE 

 I, a section from Kainan Bay to Sulzberger Bay showed a sound channel 

 between 50 and 200 meters depth. The 200 meters depth occurred at 

 two deep stations off Kainan Bay where there was a minimum temperature 

 layer. No sound channel was observed at stations taken off Cape Adare 

 nor in Vincennes Bay in East Antarctica. 



KUWAHARA, SUSUMU. Velocity of sound in sea water and calculation 

 of the velocity for use in sonic soundings, Hydro Rev., vol. 16, 

 no. 2, pp. 123-140, 1939. 



2 



Authors Preference The Advisory Committee on Antarctic Names has 



under consideration the names, EAST ANTARCTICA and WEST ANTARCTICA. 



48 



