Salinity

The amount of dissolved salts in seawater or other water.

Ocean salinity varies with evaporation, precipitation, river input, ice formation and melting, and mixing between water masses. It influences seawater density, buoyancy, sound speed, freezing point and large-scale circulation.

Modern oceanography commonly reports practical salinity as a dimensionless value derived from conductivity, while absolute salinity is expressed as mass fraction, usually grams per kilogram. “Parts per thousand” and PSU remain common informal descriptions but should not be treated as interchangeable with every modern salinity definition.