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DISCOVERY REPORTS 



formed by the mixing of North Indian deep water with Antarctic intermediate and 

 bottom waters and North Atlantic deep water. 



In the Pacific Ocean the deep-water circulation differs very considerably from that 

 of the Atlantic and Indian Oceans. Except in the western part of the ocean and in the 

 extreme eastern part near the Drake Passage, the most saline water is found in the 

 southern part of the Antarctic zone, the salinity being greatest in about 65 S. The 

 temperature, salinity and oxygen content of this highly saline water are plainly very 

 similar to those of the deep water found south of Australia and very different from those 

 of the deep water found farther north in the Pacific Ocean itself, and they suggest that 

 the current has its origin chiefly in an eastward current from the Indian Ocean. Tracing 

 the history of the water farther back it must be regarded as North Indian deep water 

 and probably North Atlantic deep water, both waters having been considerably modified 

 during their progress towards the south and east by mixing with the Antarctic surface 

 and bottom waters. There are, however, indications that there may be a second though 

 smaller source of highly saline deep water in the western part of the ocean north of 

 New Zealand. 



The warm deep waters of the various oceans have considerable seasonal variations 

 of phosphate content. This must follow from the fact that there is a seasonal variation 

 in the density of plankton and phosphate content in the Antarctic surface water. Since the 

 phosphate content of the warm deep water is influenced by that of the Antarctic surface 

 water it must also show a seasonal variation in phosphate content. For this reason it 

 is not possible to draw charts of the distribution of phosphate content in any particular 

 stratum of the warm deep water, as for instance at the depth of maximum salinity, since 

 our observations are spread over several months in different years. When more data 

 become available it may be possible to estimate an average content for any given month 

 in various parts of the oceans and then construct charts giving the distribution of 

 phosphate in the deep waters. The following data, obtained in two cruises of January 

 and March 1934 show a great difference of phosphate content at the salinity maximum 

 of the warm deep water at two positions in the ice-edge region of the South Pacific 

 Ocean. 



Thus Sts. 1249 and 1257 were made in early January 1934 and had a phosphate 

 content at the salinity maximum of the order of 1 15-123 mg., whilst Sts. 1295 and 1303 

 had corresponding values of the order of 1 51-156 mg. about 6-8 weeks later. These 

 differences, which occur with corresponding differences in salinity and oxygen content, 

 must be related to seasonal variation. The phosphate content of the warm deep water 



