Because salinity (in concert with temperature) affects the density of seawater, it can play a role in its vertical stratification. Essentially, lower salinity water (= lower density) floats on top of higher salinity water (= higher density).
Alternative definition, a choice limited to one of two or more possibilities, as of things, propositions, or courses of action, the selection of which precludes any other possibility: You have the alternative of riding or walking. See more.
The fundamental reasons for something; the basis: the rationale for dropping the atomic bomb. Origin of rationale. Late Latin rati&omacron;nale, from neuter of Latin rati&omacron;nalis, rational; see rational.