?2 DISCOVERY REPORTS 



and North Cape, New Zealand (Sts. 912-928), it may be seen that the phosphate 

 content at the salinity minimum of the intermediate current is greater than south of 

 Australia and varies between the narrow limits of n8mg. and 125 mg. 



In September 1932 the depth of the intermediate current south of Wellington in the 

 direction of the pack-ice north of the Ross Sea varied considerably. Plate XVII shows 

 the phosphate content along section 12 (Sts. 942-956). The variation in the depth of the 

 nucleus of the intermediate current has a corresponding variation in the phosphate 

 content at this depth. The variation of phosphate content at the salinity minimum was 

 between 88 mg. and 127 mg., the greatest value being towards the south. A somewhat 

 similar section (13) was made in January 1934 (Sts. 1267-1281), the vertical section of 

 which is shown in Plate XIX. Again there was a large variation in depth of the salinity 

 minimum, and the phosphate values at this depth varied correspondingly between 79 mg. 

 and 128 mg. The section differed from that of September 1932 in that the greatest 

 phosphate content of the intermediate water was found near New Zealand, whereas 

 in September 1932 the greatest values were found towards the south. 



During September 1932 in the central part of the South Pacific Ocean the phosphate 

 content at the nucleus of the intermediate current was greater than it was east of New 

 Zealand and was of the order 100-125 mg. Maximum phosphate was not found in the 

 intermediate water but in the highly saline deep layer. 



In 8o° W our observations did not extend north of 55 S, and the mixed water 

 forming the intermediate current had not sunk to depths greater than 400-600 m. The 

 phosphate content at the salinity minimum of the intermediate water fell from south 

 to north and exhibited seasonal variation. Thus in 1934 it varied as follows: March 

 1 15-130 mg., September 80-95 mg., and October 88-109 mg. Maximum phosphate 

 was found at greater depths, usually between 1000 and 1500 m., in the warm deep water. 



In summarizing the phosphate data of the Antarctic intermediate current, attention 

 must first be drawn to the importance of seasonal variation in nutrient salt content of 

 the constituent waters of this current. As a consequence of this seasonal variation the 

 phosphate content at a particular level in the current such as the depth of minimum 

 salinity, does not fall off smoothly towards the north. When the phosphate content at 

 this depth is plotted against latitude a series of maxima and minima are seen in the curve. 

 These maxima and minima are considered to have a real significance and may be the 

 basis for an approximate estimation of the speed of this current in a northerly direction. 



In the western part of the South Atlantic Ocean north of the Rio Grande ridge the 

 intermediate current contains more phosphate content than the warm deep water. 

 Maximum phosphate appears to exist in the region 3 8°-43 ° S which is considered to be the 

 position of maximum decomposition of the plankton which was originally in the Antarctic 

 surface water. In the eastern part of the South Atlantic Ocean maximum phosphate in 

 the intermediate current is found in 41 ° S, a position comparable with that in the western 

 part of the ocean. 



In the western part of the South Atlantic Ocean the phosphate content at the depth 

 of minimum salinity of the intermediate current north of the Rio Grande ridge varied 



