By David E. Boruchowitz
NASA’s Aquarius instrument has mapped the oceans of the planet from orbit, providing an accurate representation of salinity across the globe. You can read about it here:
And you can view or download the map from NASA at:
In viewing the map, keep in mind that the entire scale runs only from a salinity of 30 to one of 40, so although the differences depicted are significant, it is still the case that the chemical makeup of seawater is much the same everywhere, in sharp contrast to the chemistry of different freshwater environments.
It is especially fascinating to see the visual representation of the dilution effects well out to sea of large rivers like the Amazon, the Orinoco, and the Ganges, as well as the influence of heavy terrestrial rainfall in the Northern Pacific.