If the salinity(含盐量)of ocean waters is analyzed, it is found to vary only slightly from place to place. Nevertheless, some of these small changes are important. There are three basic processes that cause a change in oceanic salinity. One of these is the subtraction of water from the ocean by means of evaporation-conversion of liquid water to water vapour. In this manner,the salinity is increased, since the salts stay behind. If this is carried to the extreme,of course, white crystals of salt would be left behind; this, by the way,is how much of the table salt we use is actually obtained
