What does the term "salinity" refer to in ocean water?

Salinity in ocean water specifically refers to the concentration of dissolved salts, primarily sodium chloride, within the water. It is measured in parts per thousand (ppt) and indicates how much salt is present relative to the total volume of water. Understanding salinity is crucial in oceanography because it affects water density, marine life, and ocean circulation. Variations in salinity can result from factors such as freshwater input from rivers, evaporation, and precipitation, significantly influencing ocean chemistry and ecosystems. The other options, while related to ocean characteristics, do not pertain to the salt concentration that defines salinity.