ANTARCTIC INTERMEDIATE WATER 73 



between 98 mg. and 136 mg., being, in general, greatest to the north. In the eastern side 

 of the same ocean the content at the corresponding depth ranged from 76 mg. to 1 56 mg. 

 between 46!° S and 3!° N, the high value of 156 mg. being exceptional. In general 

 there is slightly more phosphate in the intermediate current in the west than in the 

 eastern part of the South Atlantic Ocean. 



In the western part of the South Indian Ocean, south of Durban (30 S), maximum 

 phosphate appears to lie in or close to the depth of the salinity minimum of the 

 intermediate layer. North of this latitude, the influence of the North Indian deep water 

 with its very high phosphate content causes the maximum to lie at greater depths. In 

 this respect the intermediate current in the western part of the South Indian Ocean 

 differs from that in the South Atlantic, where phosphate is maximal in the intermediate 

 current north of 35 S, in the west and north of 46 S in the east. 



In the western part of the South Indian Ocean the phosphate content at the nucleus of 

 the intermediate current between 42^° S and 7 N varied between 95 mg. and 147 mg., 

 the greater amounts being found when the salinity minimum was depressed by the 

 immense volume of water in the Agulhas current system. 



A diagonal section across the South Indian Ocean in a south-west to north-east 

 direction showed that in this part of the ocean the intermediate current was not the seat 

 of maximum phosphate which on the contrary was found in the warm deep water. At 

 the depth of minimum salinity of the intermediate water the phosphate ranged from 

 108 mg. to 147 mg. but was usually of the order of 120-125 mg. 



South of Australia the phosphate content of the intermediate current was less than 

 that of the western part of the South Indian Ocean. South of Tasmania less phosphate 

 was present in the intermediate current, and values of the order of 84-121 mg. were 

 recorded at the salinity minimum, but south of the eastern part of the Tasman Sea 

 there was more phosphate in the layer, and the corresponding values were from 118 mg. 

 to 125 mg. 



South-east of New Zealand the depth of the intermediate current varied considerably 

 with corresponding variations in the phosphate content at the depth of minimum 

 salinity. Two sections differed as to the direction in which the phosphate content of 

 the intermediate current increased. 



In the western part of the South Pacific Ocean the phosphate content at the salinity 

 minimum of the intermediate current varied between about 80 mg. and 128 mg. in the 

 two years in which we have observations. In the central part of the same ocean slightly 

 more phosphate was recorded, the variation being between 100 mg. and 125 mg., but 

 these figures are only for the southern part of the sub-Antarctic zone. In 8o° W seasonal 

 variation was indicated, the content being highest in March and lowest in September. 



As we have seen above when phosphate leaves the Antarctic zone either free in the 

 surface layer or in combination with the plankton, it does so by sinking with the 

 Antarctic surface layer into sub-Antarctic water at the Antarctic convergence ; it is later 

 found as a high content in the Antarctic intermediate current. Phosphate is also lost 

 to the Antarctic zone in the bottom water but to a lesser degree. 



