Isohaline

An isohaline is a line or surface of constant salinity on a section, map, or temperature-salinity diagram. Closely spaced isohalines mark a halocline, the vertical zone of strong salinity gradient that, with temperature, sets the density stratification. On a property section, isohalines trace the spreading of water masses such as low-salinity Antarctic Intermediate Water or the salty core of Mediterranean Outflow. They are the salinity analog of isotherms and isopycnals, and the surface 35 isohaline is a common reference for evaporation-dominated subtropical gyres.