WATER MASSES AND CURRENTS OF THE OCEANS 209 



from the vertical sections in fig. 58, in which, between latitudes 45° and 

 63°S, the deep water seems to climb from a depth of about 3000 m to 

 within 200 m of the surface. The deep water does not appear to reach 

 the very surface, but within the entire antarctic region a considerable 

 amount of deep water of high salinity must be added to the surface layer, 

 because, otherwise, the salinity would be lowered by the excess of precipi- 

 tation and the addition of fresh water by the melting of antarctic icebergs. 

 A southward flow of deep water is also required for balancing the transport 

 to the north of the surface water by the prevailing winds. In the section 

 shown in fig. 58, sinking of water near the Antarctic Continent probably 

 does not take place, but in the Weddell Sea this sinking is of great impor- 

 tance, and a movement of the deep water toward the continent is there 

 necessary for the formation of the bottom water. Part of this bottom 

 water flows away from the Antarctic Continent, but part mixes with the 

 deep water and returns with this water to the antarctic regions (p. 214). 



At the Antarctic Convergence, water of relativel^y low salinity and low 

 temperature sinks. A small portion of the sinking water appears in some 

 areas to return toward the south at a depth of a few hundred meters, but 

 the greater part continues toward the north, forming the tongues of 

 Antarctic Intermediate Water that in all oceans can be traced to great 

 distances from the antarctic region. It is probable that this water 

 gradually mixes with the underlying deep water and returns to the 

 Antarctic with the deep water. Within the subantarctic regions the 

 upper water appears to flow toward the south, but the nature of this flow 

 is not fully understood. 



The Antarctic Water that sinks at the Antarctic Convergence has a 

 temperature of 2.2° and a salinity of 33.80°/oo. When sinking it is 

 rapidly mixed with surrounding waters, and a water mass, the Antarctic 

 Intermediate Water, is formed that spreads mainly toward the north, 

 being characterized at its core by a salinity minimum. Owing to con- 

 tinued mixing the characteristic temperature-salinity relation of the 

 intermediate water changes as the distance from the Convergence 

 increases, and, since layers of gradual transition are found both above and 

 below the water mass, no distinct boundaries can be introduced. 



On the basis of these considerations, one arrives at the schematic 

 picture of the transverse circulation that is shown in the block diagram 

 in fig. 59. In the diagram the formation of bottom water has been 

 taken into account, and, furthermore, it is indicated that the deep- 

 water flow toward the Antarctic Continent is strengthened by addition 

 of both intermediate and bottom water. The main features of the 

 transverse circulation are represented by the sinking of cold water near 

 the Antarctic Continent, the climb of the deep water toward the surface, 

 the northward flow of surface water, and the sinking of the Antarctic 

 Intermediate Water. 



