Chapter VI 



The [TS] -relationship and its 

 Connection with Mixing Processes and 

 Large Water Masses 



1. Temperature as a Function of Salinity and Large Water Masses 



Temperature and salinity vary with the depth h or the pressure p, and an investiga- 

 tion of the vertical distribution of these factors is based mainly on a graphical repre- 

 sentation of the variation of these quantities with depth h. In this way it is almost 

 unconsciously assumed that these factors (temperature and salinity) are independent 

 of each other. This is, however, not the case. Assuming salinity as a function of tem- 

 perature or plotting it against temperature in a system of co-ordinates (tempera- 

 ture as ordinate, the salinity as abscissa) the points for each depth are not distributed 

 at random over the diagram but fall on a definite, more or less smooth curve. It is 

 found that for oceanic regions with uniform oceanographic and special climatic, as 

 well as undisturbed flow conditions, the [r^J-relationship is quite characteristic. A 

 given temperature corresponds to a given salinity regardless of the depth. The prac- 

 tical significance of this [r^J-relationship was first pointed out by Helland-Hansen 

 (1918) and since then it has become increasingly important. Any given water type, a 

 water mass, formed continuously in a particular oceanic area for any kind of condi- 

 tions is characterized by a definite temperature and a definite salinity. If this water 

 mass is homogeneous then the oceanographic factors in it are constant and it can be 

 represented on a [r5]-diagiam by a single point. If this water mass is moved in any 

 direction without altering its physical-chemical structure the point does not change its 

 position on the diagram. However, under influence of certain processes, for instance 

 mixing, radiation or evaporation, the water mass loses its homogeneity and the 

 position of the point in the co-ordinate system is changed. Such changes occur espe- 

 cially in the top layer (down to 200 m), where climatic conditions are able to pro- 

 duce continuous "disturbances" in the normal state. Beneath the top layer with dis- 

 turbances, however, conditions in the ocean are qudL^i-stationary and thus every station 

 has its characteristic [r5']-curve which for that special station remains largely in- 

 variable. This constancy is, however, not only true for each individual station but 

 applies also in a somewhat wider sense to more or less larger oceanic spaces. Standard 

 curves can thus be constructed for diff"erent regions and conclusions can be drawn 

 about the origin and spreading of a water mass from the deviations of the values at a 

 particular station from those of the standard curves. 



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