Published on: 11/27/2020 2:49:26 AM

T-S Diagram is also called sigma T (σ - t) diagram. It was proposed by Helland-Hansen (1916) with a purpose to show the relationship between temperature and salinity on the basis of density the water masses are identified. Thus, this diagram specifically helps in the identification of water masses. Water masses is defined as the large body of masses with more or less homogeneous physical property, a 3D water column where density variations are sleek.

  • The T-S curve helps in the scientific preparation of oceanographic data and is used to detect errors and to make it homogenous. Incorrect observations can be detected since they fall outside the normal T-S curve for that oceanic Area.
  • The T-S curve is also helpful in the investigation of the problem of the origin and the mixing of characteristic water masses in oceanic areas.
  • An accurate analysis of the T-S relationship in different parts of the oceans goes a long way in the closer classification of the water types of which ocean is made up.
  • This also helps in a clarification of the formation, spreading and mixing of the individual water types, and thus facilitates a quantitative description of the oceanic circulation of the deep and bottom layers.
  • Temperature and salinity combine to determine the potential density of seawater, contours of constant potential density are often shown in T-S diagram.

On the given graph, the sigma values are plotted to show the location of air masses.

On the X-axis, salinity and on the Y-axis temperature and depth are plotted. Halocline (salinity with depth) and thermocline (temperature with depth) are pointed on the graph. These 2 lines always remain parallel showing that the temperature and salinity the physical properties are directly proportional to each other. The freshwater density is taken as 1.0 and the sea water density may vary from 1.028 to 1.032, To find the value of sigma, 1 is extracted from the density of sea water and the received value is multiplied with 1000, the sigma is equal to 32 which denotes the density conditions in comparison to the freshwater and normal water. Once the water masses are identified as OTEC (Ocean Thermal Energy Conversion) are established. If the water masses have thermal contrast of 22°, harnessing energy from the ocean by inserting physio-electrical sheet which convert physical pressure into electrical currents. Thus T-S diagram is useful for the OTEC Plants and also identifying the water masses and moreover it shows the thermo-haline condition with depth and can establish the circulatory pattern.