Salinity of Ocean Waters

Tropical seas have a higher salinity when compared with polar seas. This is because evaporation causes the salt content to increase with the dissolved salts being redeposited in sea spray when winds blow from land towards the sea.

Cooler oceans have a lower salinity due to the increasing amount of ice melting in them which reduces their salinity.

Salinity is the term used to define the total content of dissolved salts in sea. It is calculated as the amount of salt (in gm) dissolved in 1,000 gm (1 kg) of seawater.

Salinity of 24.7 %has been considered as the upper limit to demarcate ‘brackish water’.

Factors affecting ocean salinity

Evaporation of ocean water and formation of sea ice both increase the salinity of the ocean. However, these “salinity raising” factors are continually counterbalanced by processes that decrease salinity such as the continuous input of fresh water from rivers, precipitation of rain and snow, and melting of ice.

(i) The salinity of water in the surface layer of oceans depend mainly on evaporation and precipitation.

(ii) Surface salinity is greatly influenced in coastal regions by the fresh water flow from rivers, and in polar regions by the processes of freezing and thawing of ice.

Wind, also influences salinity of an area by transferring water to other areas.

The ocean currents contribute to the salinity variations. Salinity, temperature and density of water are interrelated. Hence, any change in the temperature or density influences the salinity of water in an area: Spatial pattern of surface temperature (°C) of the oceans. Highest salinity in water bodies Lake, Van in Turkey.