Salinity

Synonyms

Brininess; Salinity; Salt; Saltiness

Definition

Concentration of dissolved salts found in a sample of water. It is measured as the total amount of dissolved salts in parts per 1,000. Seawater has an average salinity of about 35 parts/1,000.

Nearly all water contains dissolved chemicals, even rainwater. These dissolved chemicals are called salts. The salinity of normal ocean water is about 35 parts per 1,000, total dissolved solids. This is written as 35‰ or 35 ppth. A salinity of 35‰ is the same as 3.5%. The symbol resembles a percentage sign (%), but percent means per 100. But the symbol with two zeros on the bottom of the fraction (‰) means per 1,000.

Salinity varies slightly from place to place around the world, and also varies somewhat with the seasons (affected by temperature and precipitation). The salinity of seawater ranges from about 30‰ to 40‰. Warm temperatures and high evaporation rates (particularly in shallow seas) raise the salinity. Warmer waters will tend to...