WARM DEEP WATER 



95 



water which has made the circuit of the Weddell Sea has a very high content. Ob- 

 servations south of 6o° S in the Atlantic sector of the Southern Ocean showed that the 

 content decreased towards the east and north. 



In the eastern part of the South Atlantic Ocean between 69^° S and 3f° N the content 

 in the current increased from the ice-edge (3700-3900 mg. in the upper part and 

 4000 mg. at the depth of maximum salinity) to 4950 mg. and 5000 mg. in the eastward- 

 flowing Weddell Sea deep water. North of this latter current the content decreased 

 until at i2|° S the content at the salinity maximum was 2250 mg. 



South of Cape Town the content increased southwards, and in the upper part of the 

 current values of 1 200-1 700 mg. were recorded at the Antarctic convergence, with 

 4450 mg. at the ice-edge. At the deeper position of the salinity maximum the increase 

 southwards was from 2850 mg. to 4850 mg. at the ice-edge. Higher values were, how- 

 ever, found in 1932 in this area. 



In the western part of the South Indian Ocean the upper part of the current had a 

 content of 4250-5050 mg. in the south and 3250 mg. at the Antarctic convergence, the 



LATITUDE 68°5 

 I 





64° 





nj«fr 



sa° 



56* S 



1 5CQ* 



V 



• DECEMBER 1933 X SEPTEMBER 1934 



G MARCH 1934 AOCTOBER 1934 



■ NOVEMBER 1934 



Fig. 27. Graph showing the variation of the silicate content from south to north at the depth of maximum 



salinity of the warm deep water in 8o° W. 



content falling northwards across the sub-Antarctic zone from 2900 mg. to 1 100 mg. At 

 the deeper position in the current the decrease northwards from the ice-edge to the 

 subtropical convergence was from 5200-61 00 mg. to 350omg. In the subtropical zone 

 the warm deep water is mainly of North Atlantic origin, and the content at the salinity 

 maximum was 3150-3300 mg. North of 20 S in the tropical zone the warm deep 

 water is of North Indian Ocean origin, and although a decrease was observed north- 

 wards, the actual content of North Indian deep water was shown to be greater than of 

 North Atlantic deep water at the same latitude ; this higher silicate content of the North 

 Indian deep water may be correlated with the fact that the phosphate content of Indian 

 deep water is higher. 



At the ice-edge south of Australia the content in the upper part of the deep layer was 

 4300 mg., a value which decreased towards the north across the Antarctic zone to 3150 

 mg. At the depth of maximum salinity an ice-edge value was 5055 mg. , the content falling 

 towards the north. In the deep channel near Cape Leeuwin a higher content was noted. 



South-east of New Zealand the content of the warm deep water was shown to be 



