Salinity from space

Although ocean salinity is a key parameter for determining the ocean circulation on local and global scales, measuring salinity from space has only been possible since the launch of the European Space Agency’s Soil Moisture and Ocean Salinity (SMOS) mission in November 2009. This is in contrast to the other key oceanographic parameter temperature, which has been measured from space using satellite sensors since the 1970s. Traditionally, oceanographers have used ship-based measurements to observe ocean temperature and salinity. Here the rationale for measuring salinity from space is explained and the technical advances that have made this possible are described. Some examples are given of how the recently available sea surface salinity measurements from space have provided new insights into oceanographic phenomena.