Recent years have seen significant developments in satellites for oceanographers. The European Space Agency launched the Soil Moisture and Ocean Salinity (SMOS) mission and NASA launched the Aquarius instrument on the Argentine SAC-D mission.
Salinity has always been a challenging but critically important measurement for oceanographers. The small changes in salinity that we sea in the ocean are important in determining the density of seawater and density differences are partly responsible for ocean circulation (direct forcing by the wind being another big factor). It’s a challenging measurement because we estimate salinity by simultaneously measuring the temperature and conductivity of seawater and using a well-established formula to calculate salt concentration. The salinity of the open ocean ranges from about 33 to 38 parts per thousand and the target accuracy of satellites is to measure differences of 0.2 parts per thousand. That is like measuring the change in salinity from adding a pinch of salt to a gallon of waters. I challenge you to taste the difference!