DEEP CURRENTS: PACIFIC OCEAN 101 



rejects a possibility of its being formed in the Antarctic regions because its temperature 

 (presumably for water whose salinity had been raised to 34-64 °/ 00 by freezing processes) 

 is too high, and concludes that it belongs to an eastward current from the Atlantic and 

 Indian Antarctic Oceans, especially the latter, which enters the Pacific Ocean south of 

 Australia. The existence of an eastward movement had previously been suggested by 

 Defant (1928, p. 491), Wiist (1929, p. 48) and Moller (1929, pp. 37-8), but it assumed a 

 new significance when Sverdrup had shown that there was no sinking of surface water 

 in the equatorial regions. 



Our data, collected during the circumpolar cruise, have been used in the construction 

 of sections 14-18 (Plates XXXI-XLII) and the charts in Figs. 19-22, the latter are also 

 based on the preliminary examination of observations made during cruises across the 

 ocean south of 65 S in 1934 (see Mackintosh, 1935, p. 629). A few of these observa- 

 tions have also been used to continue sections 14, 16 and 18 towards the south. 



Except in the western part of the ocean and in the extreme eastern part near the 

 western end of the Drake Passage, the most saline deep water is found in the southern 

 part of the Antarctic Zone, the salinity being actually 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 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. 



In spite of the fact that the greater part of the most saline deep water appears 

 to belong to the eastward current from the Indian Ocean there are some 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 observations made during 

 the circumpolar cruise suggest that the deep water east of New Zealand has a slightly 

 higher salinity than the eastward movement which enters the ocean south of New 

 Zealand. The water actually had a salinity of not more than 3475 °/ 00 , which, together 

 with its temperature and oxygen content, suggests that it belongs to the same current 

 as the deep water south of Australia ; but the observations south of the Tasman Sea 

 indicate that the two waters, east of New Zealand and south of Australia, are separated 

 by an extensive area in which the deep water has a slightly lesser salinity. Between New 

 Zealand and 6i° S in section 13 the salinity of the deep water is not more than 3474 7oo. 

 and between Tasmania and the same latitude, in section 12, it is for the most part less 

 than 3475 % . A close examination of the hydrological conditions in this region sup- 

 ports the conclusion that the salinity of the water found south of Australia should be 

 reduced as it flows towards the east. The bottom topography south of New Zealand is 

 so irregular that the eastward current must be interrupted by numerous eddy move- 

 ments which will cause the salinity to be lowered by turbulent mixing with the less 



