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.
2. one of the things, propositions, or courses of action that can be chosen: The alternative to riding is walking. 3. a possible or remaining course or choice: There was no alternative but to walk. adjective. 4. affording a choice of two or more things, propositions, or courses of action.