[TS]-relationship and Connection with Mixing Processes and Large Water Masses 203 



Figure 93 shows an example of such a [rS']-curvefor "Meteor" station 171 in the cen- 

 tral part of the South Atlantic. Its shape is characteristic for the entire South Atlantic 

 from 40° S. to beyond 10° N. Its constancy over such a large area expresses well the 

 strong conservatism of vertical stratification which is of course necessary under sta- 

 tionary conditions. If, in addition, lines of equal density Cf (isopycnals) are also included 

 in the same diagram, as was done in Fig. 93, a rather instructive although not com- 

 pletely correct representation of the stability of vertical stratification is obtained. If 



34-2 



350 



360 



370 



Fig. 93. [75] -curve for "Meteor" St. 171 (22° 1-5' S. 23° 470'W.) in the central part of the 

 South Atlantic (the thin dashed curves are the isopycnals Of). 



the [TS]-cmyQ of a certain layer runs approximately parallel to the isopycnals the 

 stability in the layer is only small but if the [rSJ-curve cuts the isopycnals at a wide 

 angle the stability is larger. For greater accuracy the [J'5']-curve must be constructed 

 by using potential temperatures, but the differences in most cases remain small. 



As with temperature, so can any other property of sea-water be combined with the 

 salinity in exactly the same way. Such a combination was made in particular with the 

 oxygen content in order to see how changes in the oxygen content affect the temperature 

 and salinity conditions, which determine the water mass. 



2. Practical Significance of the [T^S"] -curve 



The [rS'l-curve offers advantages in the scientific preparation of oceanographic data 

 and is used to detect errors and to make it homogeneous. If the value for a particular 

 depth at an oceanographic station does not fall on the simple, regular and usually 

 smooth [rSJ-curve it can be confidently assumed that there is an observational error 

 or a fault in calculation (for examples see Merz, 1925). The [r5']-curve is thus a 

 reliable criterion of the accuracy and homogeneity of a set of data. Since curves for 

 neighbouring stations are similar all values can be checked immediately, but a faulty 



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