VERTICAL CIRCULATION IN THE OCEAN 



159 



containing 140-150 mg. PgOs/m.^, but it contains relatively small amounts of oxygen. 

 The lowest oxygen values, 3-8 c.c. /litre, are found directly below the return current. 



The deep water below the return current again appears to have a component towards 

 the south and shows an ascending motion, while the cold bottom water from the 

 Weddell Sea sinks and pushes to the north. 



In the northern part of the section, features are met with which were not present in 

 the Pacific and in the Drake Passage. Below the sub-tropical convergence Atlantic deep 

 water with salinities above 34-8 °j^^ pushes to the south at depths between 2500 and 



Fig. 13. Section IV. Distribution of oxygen (0^ c.c. /litre). 



3000 m. This southward flow of deep water is also indicated by the bends of the iso- 

 therms at depths between 1500 and 2500 m. From the temperature and salinity sections 

 it appears as if the water of high temperature and relatively high salinity at 500 m. in 

 56° S represents the last traces of the Atlantic deep water, but it must, as pointed out 

 by Clowes (1933), be borne in mind that the general direction of the current in this 

 region is from west and that, therefore, the water in 56° S does not come from the Atlantic 

 but from the Pacific. A section farther to the east in the Atlantic might, on the other 

 hand, show traces of Atlantic water in high latitudes. Near Bouvet Island salinities of 

 3475 °/oo were observed below 600 m. (Discovery St. 453 in 54° 06' S and 04° E), 

 and this water probably represents water from the Pacific which has been mixed with 

 deep water from the Atlantic. 



