OBSERVED DISTRIBUTION OF TEMPERATURE AND SALINITY 161 



At a depth of 20 m. the same general characteristics of the surface distribution are to be found, but 

 by 50 m. a change is evident. The disposition of the isotherms and isohalines at these depths repre- 

 sents a transition in varying stages between the surface distribution and that at greater depths. The 

 isotherms and isohalines at 100 m. (Fig. 10) exhibit some more considerable changes which are 

 worthy of note. It will be seen that little change is evident in the Luderitz Bay-Orange river region, 

 (27 to 30 S.) but the cooler coastal water can now be traced more continuously along the coast, and 

 extends to the north in a tongue leaving the coast in the vicinity of Walvis Bay. On the landward 

 flank of this extension warmer water is present, apparently intruding southwards along the coast as far 

 as Concepcion Bay (24 S.). The eddy in 25 S. at stations WS 986 and 987 is still present, and from 

 the north of it another area of low temperatures extends offshore through WS 977, with a markedly 

 lower salinity (35 - o6% ) than the surrounding water at WS 976 and 978 (35-23 % and 3 5 • 1 6 % 

 respectively). 



The smaller number of observations made below this depth make it impossible to construct any 

 detailed picture. It is evident, however, that at a depth of 200 m. (Fig. 11) there was an extensive 

 area of cooler water extending N.N.W. from the area between Orange river and Luderitz Bay, the 

 axis of this belt running through WS 986 and 977. Between this tongue and the coast the water was 

 warmer and more saline and suggests a flow from the north along the edge of the continental shelf as 

 far south as Luderitz Bay. 



Vertical distribution of temperature and salinity 



At most stations there is a layer of almost homogeneous water at the surface, within which the 

 density remains almost constant with depth. This is generally referred to as the convection layer. 

 Throughout the region it is present to a greater or lesser extent, and as a rule it is underlain by a 



Table 5. Depth of the convection layer 



Survey I 



Survey II 



Survey I 



Survey II 



Station 



WS982 

 WS983 

 WS984 

 WS985 



WS986 

 WS987 

 WS988 

 WS989 



WS990 

 WS991 

 WS 992 

 WS 993 

 WS994 

 WS995 



WS966 

 WS997 

 WS998 

 WS 999 

 WS 1000 

 WS 1001 

 WS 1002 



Depth 

 (m.) 



4 

 o 

 o 



o 

 o 

 o 

 o 



10 



o 



9 



3° 



40 



5 



10 

 10 

 20 

 10 

 20 

 o 

 o 



Station 



WS 1074 

 WS 1073 

 WS 1072 

 WS 1071 



WS 1070 

 WS 1069 

 WS 1064 

 WS 1063 



WS 1062 

 WS 1061 

 WS 1060 

 WS 1059 



WS 1058 

 WS 1057 



WS 1056 

 WS 1055 

 WS 1054 

 WS 1053 

 WS 1052 

 WS 1051 

 WS 1050 



Depth 



(M.) 



10 

 30 



3° 



3° 

 o 

 o 

 o 



o 

 10 



10 



50 



100 



100 



50 



5° 

 3° 

 10 

 20 

 10 

 o 



i less than 10 m. in thickness. 



