Sure, the ocean is salty. For most people it’s just a nasty inconvenience if they get a mouthful when swimming/ surfing/snorkelling. For those people studying the ocean’s currents, or in fact the global climate, it’s critical. Colder, saltier water is more dense that warmer, ‘fresher’ water and so will sink. This helps drive ocean currents and transports heat around the globe.
Salinity varies; in areas where there is lots of rainfall (the equator) it’s lower and it’s higher where there’s more evaporation (the subtropics, which is also where we find the ‘desert belts’ on land).
NASA’s new satellite instrument, Aquarius, became operational on 25th August and just two weeks later the Aquarius team have produced their first global map of ocean salinity by calibrating the satellite image with known surface salinity measurements. The map not only shows the large-scale features but also shows finer detail such as reduced salinity where the Amazon river meets the sea. It’s a preliminary plot, but they hope to use further data to monitor changes in salinity and any links this may have to variations in short-term weather or long-term climate.