210 \TS]-relationship and Connection with Mixing Processes and Large Water Masses 



T^ 



Fig. 97. [rSJ-relationship in a water column at successive times. 



4. Further Examples of the [J'S'] -Relationship 



Extensive use has been made of the [rS'] -relationship in oceanographic investiga- 

 tions of different oceanic regions. A detailed discussion of these investigations belongs 

 to the individual sections on special oceanography and would be out of place here. 

 The attention of the reader will therefore at present be directed more to the method 

 used rather than to the phenomena characteristic for different parts of the ocean. 



A most intensive analysis of the [TlSj-curves for a single ocean was first made by 

 Jacobsen (1929) on the data collected by the "Dana" Expedition. He divided the 

 North Atlantic into twenty-four areas with approximately uniform conditions, and 

 he derived mean characteristic [r^SJ-curves for these areas, using then these curves 

 to give an interpretation of the formation of the stratification by mixing of the five 

 principal water types. A homogeneous set of data for the preparation of [T^J-curves 

 for the South Atlantic as far as 10° N. has been provided by the "Meteor" Expedition. 

 Figure 98 presents [rSj-curves for the West Atlantic Trough as an example for meri- 

 dional changes. In this region extending over more than 44° of latitude (almost 

 5000 km) the thermo-haline structure follows the same law almost without exceptions. 

 It is in principle fixed by five water masses U, Z, T, Bn and Bg and corresponding 

 mixing curves. Basic values are given in Table 82. 



Five points on the diagram characterize each of these water masses together with 

 straight lines joining them, on which the mixed water masses must lie. The variations 

 of the actual [r^j-curves from these ideal curves of pure mixing are surprisingly small, 

 especially when there is a sufficient mass of water in the cores. This is usually the case, 

 though for the subantarctic intermediate water as it progresses from south to north 

 the [7'6']-curve moves farther and farther into the angle between VZ and ZT, as is 

 required by theory, showing that in this comparatively thin layer of water the core is 

 also involved in the mixing process. This case can be used to calculate the ratio 

 Ajpu for the spreading of the sub-antarctic intermediate water by applying the 

 Jacobsen method (Defant, 1954). Figure 99 shows [r-SJ-curves at four successive 

 oceanographic stations from south to north in the Western Trough of the South 



