Salinity of water or soil. Represents the amount of dissolved salt in water.
Salinity is presented in Practical Salinity Units (PSUs). Since 1978, the “Practical Salinity Scale” (PSS78) has been used. Compared to the previously used (chemical) equations, the PSS78 definition has the advantage a) that it does not depend on knowing seawater’s precise ionic composition, b) that far more precise density values form the basis for calculation, and d) that it can be determined using CTD devices (CTD = conductivity, temperature, depth) for in-situ measurements. PSS78 is based on a seawater sample that, compared to 32.4356 g of potassium chloride (KCl) in one kilogramme of solution, has a ratio of conductivity of 1. Water from the North Atlantic was selected as the standard water; it has a chlorinity of 19.3740 ‰ and defines the 35.00 ‰ point on the scale. Learn more about desalination processes in the formation of sea ice here.