Salinity

Salinity is a saltiness or amount of salt dissolved in the body of water, called saline water see also soil salinity. It is normally measured in g/L or g/kg grams of salt per liter/kilogram of water; the latter is dimensionless as well as equal to ‰.

Salinity is an important component in introducing many aspects of the chemistry of natural waters & of biological processes within it, and is a thermodynamic state variable that, along with temperature and pressure, governs physical characteristics like the density and heat capacity of the water.

A contour line of constant salinity is called an isohaline, or sometimes isohale.

Environmental considerations

Salinity is an ecological element of considerable importance, influencing the brand of organisms that exist in a body of water. As well, salinity influences the kinds of plants that will grow either in a water body, or on land fed by a water or by a groundwater. A plant adapted to saline conditions is called a halophyte. A halophyte which is tolerant to residual sodium carbonate salinity are called glasswort or saltwort or barilla plants. Organisms mostly bacteria that can exist in very salty conditions are classified as extremophiles, or halophiles specifically. An organism that can withstand a wide range of salinities is euryhaline.

Salt is expensive to remove from water, and salt content is an important factor in water usage such(a) as other salt de-icers in runoff.

The measure of salinity in oceans is a driver of the world's ocean circulation, where density recast due to both salinity reorientate and temperature changes at the surface of the ocean cause changes in buoyancy, which make the sinking and rising of water masses. Changes in the salinity of the oceans are thought to contribute to global changes in carbon dioxide as more saline waters are less soluble to carbon dioxide. In addition, during glacial periods, the hydrography is such that a possible cause of reduced circulation is the production of stratified oceans. In such(a) cases, this is the more unoriented to subduct water through the thermohaline circulation.

Not only is salinity a driver of ocean circulation, but changes in ocean circulation also affect salinity, particularly in the subpolar North Atlantic where from 1990 to 2010 increased contributions of Greenland meltwater were counteracted by increased northward transport of salty Atlantic waters. However, North Atlantic waters have become fresher since the mid-2010s due to increased Greenland meltwater flux.