This instrument contains well-calibrated electronics with highly accurate sensors, and enables oceanographers to get detailed data on the vertical distribution of temperature and salinity by lowering and raising the instrument. Other instruments may also be attached to measure other properties of interest such as light transmittance or scattering, chlorophyll concentration, or dissolved oxygen. The average salinity of the ocean is about 35 psu. Open ocean salinities usually range from about 32 to about 37 psu, a variation that has a big effect on ocean circulation. These extreme ranges limit the kinds and abundance of organisms that can survive in these locations.
Salinity is high in marginal seas surrounded by arid land, such as the Mediterranean and Red Sea.
Otherwise, salinity is low along the equator and at high latitudes, both of which are areas of relatively high precipitation. The intermediate latitudes have warm surface temperature and relatively strong wind, promoting evaporation and minimizing precipitation. Variation in solubility depends on the degree to which the ions are attracted to each other. All of the ions in this list made up the major constituents of sea salt. All other constituents are considered trace elements, and each of them is The major constituents make up a constant proportion of the total salt, so the concentration of each can easily be calculated from the salinity and the percentage of each constituent by weight.