Salinity of the Ocean, its Variation in Oceanic Space and in Time 179 



Aden and from here extends southwards beneath the Antarctic intermediate water 

 at a depth of 1500-2000 m as a tongue of highly saline water. This salinity maxi- 

 mum shows very clearly throughout the western and central parts of the Indian 

 Ocean. 



In the Pacific the few observations that have been made below 1 500 m show a 

 remarkably uniform vertical and horizontal salinity distribution at all latitudes. Its 

 average value is about 34-65-34-68%o, but it is nowhere connected with the equally 

 high values in salinity of the surface layers. There is no tropical or subtropical ad- 

 jacent sea acting as a source for saline water for the Pacific stratosphere like the 

 Mediterranean does for the Atlantic one or the Red Sea for the Indian Ocean strato- 

 sphere. It must therefore be supposed as pointed out by Sverdrup (1931), that the 

 Pacific deep water below about 1 500 m depth for which there is no area of formation 

 in the Pacific itself must be formed in the Indian Ocean or even in the Atlantic. 

 Water masses from these two oceans must be carried to the east by the Antarctic 

 ciicumpolar ocean current and then spread northward in form of current branches 

 to fill the deep basins of the Pacific. 



(8) The salinity of the bottom layers. The salinity of the deepest layers shows also the 

 same characteristic distribution already known from the bottom temperatures. In 

 the Atlantic Ocean (Wust, 1936) it varies between 34-62 and 34-92%o in the most 

 northern parts; this is explicable from conditions of formation of the bottom water. 

 The deepest parts of the Antarctic regions are filled with Antarctic bottom water with 

 a salinity of 34-67-34-69%o, formed at the continental slope of the Weddell Sea 

 (see p. 14?). Above this the Antarctic deep water is found at 5000-4000 m with 34-62- 

 34-66%o that feeds the Antarctic bottom currents of the Eastern and Western Troughs. 

 The isohalines of meridional sections demonstrate a clear conformity with the 

 bottom profile and show the penetration of the water across the Equator in the Western 

 Trough and the Eastern Trough as far as the Whalefish ridge. Figure 82 gives meri- 

 dional salinity sections through the Western and Eastern Troughs of the Atlantic which 

 show how the spreading of the bottom water is reflected in the distribution of the 

 salinity in the same way as in the distribution of potential temperature (see p. 152) 

 deduced previously. 



A typical Arctic bottom water cannot be recognized from the salinity distribution 

 though traces of it can be detected in the Labrador Basin north of the Newfoundland 

 Rise (WiJST, 1943). Our knowledge of the salinity of the bottom water of the other two 

 oceans is still pure due to a lack of systematic salinity data. 



4. The Horizontal Distribution of Salinity at Particular Depths 



Horizontal charts of salinity distribution are so far available only for the Atlantic: 

 they are given for instance in the ''Meteor'" Report for depths of 200-800 m at 200m 

 intervals, for depths of 1000-2000 m at 250 m intervals and for depths of 2000-4000m 

 at 500 m intervals. Plate 6 shows charts for 400 m and 1000 m depths. It is clear that 

 these charts do not give other information than the longitudinal and transverse sec- 

 tions. The charts down to 800 m, of which the 400 m chart is given as an example, 

 all show essentially the surface salinity distribution; only the horizontal differences 

 become smaller with increasing depth. Of the two extensive regions with salinity 

 maxima in the subtropics the northern is the larger. The highest values appear, 



