Picture the ocean shore, but underground, there’s a line where the freshwater and the seawater meet, called the salt line. This salt line moves with the tides. But rising sea levels and an increase of people living by the shore tapping into freshwater underground can also pull more saltwater from the ocean toward the land. … [P]laces all around the U.S. and the world are now starting to study this problem. … California is going through drought conditions. Aridification refers to the climate getting drier in the long term, not just in seasonal drought cycles.