The equation above the 1902 year will provide salinity price of 0.03 o / oo if klorinitas equal to zero and this is very interesting and indicate a problem with the water samples used for laboratory measurement. Therefore, in 1969 UNESCO decided to repeat the determination of the relationship between salinity and klorinitas and introduce a new definition, known as absolute salinity using the formula:
S (o / oo) = 1.80655 Cl (o / oo) (1969)
However, from the repetition of this definition was obtained similar results with the previous definition.
Definition of salinity reviewed when techniques to determine salinity from measurements of conductivity, temperature and pressure developed. Since the year 1978, defined a new unit that is Practical Salinity Scale (Practical Salinity Scale) with the symbol S, as the ratio of the conductivity.
"Practical salinity of a seawater sample defined as the ratio of electrical conductivity (K) samples of sea water at a temperature of 15oC and atmospheric pressure for a standard solution of potassium chloride (KCl), where the mass of KCl is 0.0324356 at temperatures and pressures similar . The formula of this definition are:
S = 0.0080 - 0.1692 K1 / 2 + 25.3853 K + 14.0941 K3 / 2 - 7.0261 Y2 + 2.7081 K5 / 2
As a note: the use of this new definition, where the salinity is expressed as a ratio, the unit o / oo is no longer valid, 35o/oo value associated with the value in units of 35 practical. Some use the unit Oceanographer "PSU" in writing the price of salinity, which is an abbreviation of "practical Salinity units". Because the practical salinity is a ratio, then he really has no units, so the use of force "PSU" actually do not contain any meaning and is not required. In most of the equipment currently available, measuring salinity price is based on the results of conductivity measurements.
Salinity in the subpolar regions (ie the area above the subtropical regions closer to the poles) on the surface and lower increases in fixed (monotonic) with depth. In temperate regions (or semi-tropical, the area between 23.5 o - 23.5 o 40oLU or - 40oLS) salinity at the surface is greater than the amount of depth due to evaporation (evaporation). At a depth of about 500 to 1000 meters lower price and return salinitasnya a monotonic increase with depth. Meanwhile, in the tropics on the surface salinity is lower than in the depths of the high consequence of precipitation (rainfall)