672 



The Stratospheric Circulation 



and animal organisms. Dead organisms sink downwards and decompose and therefore 

 the water of the returning intermediate current is also rich in phosphate. The lower 

 oxygen content in and just beneath the returning current indicates strong oxidation of 

 organic matter. Since only a part of the water transported in the uppermost layers 

 returns to the south there must be a compensating poleward component in the deep 

 layers in order to replace the cold polar waters sinking down in the very southern 

 latitudes along the Antarctic continental slope. Beneath the vertical circulation of the 

 upper layers there should therefore be a somewhat weaker one which rotates in a clock- 

 wise sense looking east. These vertical circulations are superimposed on a general 

 basic movement towards the east so that the resultant motion occurs in form of elon- 

 gated spirals. In these circulatory motions of the water the water properties are altered 

 in the upper layers by influences from the atmosphere above while in the lower layers 

 changes occur due to mixing. The water of the higher southern latitudes is thus made 

 up partly of water of the returning intermediate current and partly of deep water from 

 lower latitudes. The schematic block diagram presented by Sverdrup that is shown in 

 Fig. 318a shows the meridional components of motion in the Antarctic Circumpolar 

 Ocean. 



A.C. 



/ 



Fig. 31 8o. Schematic representation of the meridional circulation inside the Antarctic 

 Circumpolar Current (according to Sverdrup). 



This concept of the circulation character occurring in these higher latitudes of the 

 Southern Hemisphere differs somewhat from the ideas expressed in elder investigations. 

 Merz and Wust (1928), for instance, interpreted the warm and highly saline water of 

 the intermediate layer of the higher southern latitudes only as the last traces of Atlantic 

 Deep Water reaching the sea surface in this region. According to Clowes (1933), this 

 water should be of Pacific origin and should reach the Atlantic only by way of the zonal 

 circulation. Both suppositions are only partly tenable. Sverdrup attempted to estimate 

 also the magnitude of the meridional velocity components, on the one hand, from the 

 shearing stresses of the wind leading to an estimate of the resultant total water trans- 

 port, and on the other hand, from the steady-state condition in the temperature field 

 of the returning intermediate current. For the upper layers a mean value was about 



