Why do ocean waves break?
As waves move toward shore and into shallow water they begin to feel the ocean bottom. And in turn the ocean bottom causes friction; it slows the wave down from the speed the wave was moving in deep water. It turns out that the greatest wave slow down is in that part of the wave closest to the ocean bottom where bottom friction is greatest. The least slow down is at the air-water interface at the wave crest, farthest from the seafloor. The result is that the wave crest begins to move faster at its top than at the wave’s base. Eventually this speed difference causes the wave to tip forward and the wave breaks.
