Surface salinity (SSS) is defined as the salt concentration in seawater. More precisely, it is the number of grams of salt per 1000 grams of water. One gram of salt per 1000 grams of water is defined as the Practical Salinity Unit (PSU) or as the Part Per Thousand (PPT) unit.
SSS is a very important variable as it impacts, with SST, the ocean circulation, the sea-ice formation and the seawater evaporation. Moreover, marine organisms regulate the salt content of their metabolism, hence SSS is an important determinant of biodiversity.
SSS can be measured through direct sampling. However, as the oceans cover 71% of the Earth, indirect methods have been developed, modelling and remote sensing.
Unit: PSU or PPT