DISTRIBUTION OF SALINITY, TEMPERATURE, DENSITY 



87 



subsurface water are plotted against each other, the points generally fall 

 on a well-defined curve, the T-S curve, showing the temperature-salinity 

 relationship of the subsurface water of that region. Surface data have 

 to be omitted, because annual variations and local modifications lead to 

 discrepancies. 



The corresponding temperature and salinity values in a water column 

 are found to arrange themselves according to depth. The depths of the 

 observed values can be entered along the T-S curve, which then will also 

 give information as to variation of temperature and salinity with depth. 



The density of the water at atmospheric pressure, which is expressed 

 by means of at (p. 11), depends only on temperature and salinity, and 



-200 



400 1 



SAL. 35.0 35.5 36.0 36.5 %o 



5 T EMP 10 15 20 25 °C ^30 



1 [ 



SAL. 35.0 



35.5 



36.0 



36.5 %o 



600 



800 



1200' 



Fig. 19. Left: Temperature and salinity at Atlantis stations 1638 and 1640 in the 

 Gulf Stream off Onslow Bay, plotted against depth. Right: The same data plotted 

 in a T-S diagram in which at curves have been entered. 



therefore curves of equal values of at can be plotted in the T-S diagram. 

 If a sufficiently large scale is used, the exact at value corresponding to any 

 combination of temperature and salinity can be read off, and, if a small 

 scale is used, as is commonly the case, approximate values can be obtained. 

 The slope of the observed T-S curve relative to the at curves gives 

 immediately an idea of the stability of the stratification (p. 100). 



A T-S diagram is shown on the right in fig. 19. On the left in the 

 same figure the observed temperatures and salinities at Atlantis stations 

 1638 and 1640 in the Gulf Stream off Onslow Bay are plotted against 

 depth, and on the right the same values are entered in a T-S diagram. 

 The depths of a few of the observations are indicated. In this case, the 

 temperature-salinity values between 277 and 461 m at station 1638 agree 

 with those between 690 and 790 m at station 1640, indicating that at the 

 two stations water of similar characteristics was present but at different 

 depths. 



