70 DISCOVERY REPORTS 



40 and 20 S it is only 0-03 °j OQ compared with 0-18 °/ 00 in the Atlantic Ocean. The slow 

 rate of increase suggests that the ratio between the movements of poorly saline water 

 towards the north and highly saline water towards the south is more in favour of the 

 northward movement in the Pacific Ocean than it is in the Atlantic. 



A preliminary examination of the observations made in the coastal region in the 

 eastern part of the Pacific Ocean suggests that the intermediate current is even stronger. 

 The 34-30 °/ 00 isohaline reaches as far as 30 S as against 40-45 S in the central part of 

 the Ocean. The salinity distribution in the layer is on the whole in keeping with the 

 conclusion that the intermediate water has a movement towards the east and is deflected 

 northwards in the eastern part of the ocean. 



None of our series of observations made south of 41 ° S in the Pacific Ocean showed 

 the existence of a temperature inversion between the intermediate current and the more 

 saline deep water, but between the 2-5 and 2-25° C. isotherms the temperature depth 

 gradient was only very small, whilst there was a large increase of salinity, and it is very 

 likely that the isotherms mark the boundary region between the intermediate layer and 

 the highly saline deep current. This agrees with the conclusions made by Wiist (1929, 

 p. 30) who found that the observations of H.M.S. 'Challenger' north of 40 S in the 

 central part of the ocean frequently point to the existence of a temperature inversion in 

 the neighbourhood of the 2-25° C. isotherm. 



The observations made just north of the Antarctic convergence show that there is 

 generally a secondary temperature minimum at the level of minimum salinity, probably 

 because the sub-Antarctic water contains the greatest percentage of Antarctic water at 

 that level. Below this stratum the temperature increases to a secondary maximum at a 

 depth of about 600 m. According to Sverdrup this warm water flows southwards as a 

 return current into the Antarctic Zone ; it has, however, a low salinity compared with the 

 deep water in the Antarctic regions, whose properties suggest that it is chiefly composed 

 of water which climbs from a deeper southward current (see pp. 49, 50, 94, 95). The ob- 

 servations used in making sections 14-18 showed that the temperature at the secondary 

 maximum, just north of the convergence, varied from about 2-8 to 4-2° C, whilst the 

 salinity varied from 34-20 to 34-27 °/ 00 ; most of this water probably mixes with the 

 descending Antarctic water and is returned towards the north with the intermediate 



current. 



In the Drake Passage there is generally neither a level of minimum salinity nor one of 

 minimum temperature in the sub-Antarctic water. Their absence suggests that there is 

 only a relatively small volume of Antarctic water sinking at the convergence ; and it is 

 reasonable to suppose that the lateral movements, including the sinking of Antarctic 

 water towards the north, are restricted by the narrowness of the passage. 



TEMPERATURE AND SALINITY 



Observations made in the Falkland Sector at a point about 100 miles north of the 

 Antarctic convergence (Deacon, 1933, pp. 212-14) show that the temperature of the 

 surface water in the southern part of the zone varies between 3-0-3-5° C. in winter 



