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.
1. used as a noun. An excuse is a reason that you give in order to explain why something has been done, has not been done, or will not be done. They are trying to find excuses for their failures. There is no excuse for this happening in a new building. You say that someone makes an excuse. I made an excuse and left the meeting early.