Oceanography (2+1)

T.S. Diagaram

T-S Diagram

            Water masses can be classified on the basis of their temperature-salinity characteristics, but density cannot be used for classification, because two water masses of different temperatures and salinities may have the same density. For the study of the water masses it is convenient to make use of the temperature-salinity diagram, which was introduced by Helland-Hansen (1916). Helland- Hansen points out that when in a given area the temperatures and corresponding salinities of the 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.

            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 curves, which then will also give information on variation of temperature and salinity with depth.

            Since the density of the water at atmospheric pressure, which is expressed by means of  depends only on temperature and salinity, curves of equal values of  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 curves gives immediately an idea of the stability of the stratification.

A T-S diagram is shown in figure. In that the temperature and salinity values between 277 and 461m at stations 1638 agree with those between 590 to 790m at station 1640, indicating that at the two stations waters of similar characteristics was present, but at different depths.