On the Ocean

Except for tsunamis, which are the result of earthquakes, waves are born from wind blowing over the surface of the ocean. There is friction between the moving air and the surface of the ocean; the air pushes the water, causing it to build into crests. You may have seen small crests form when blowing on a bowl of soup. Waves begin small; the smallest waves are called capillary waves. These waves grow over time with consistent wind stress, and stronger winds will produce larger waves. The Drake Passage between Antarctica and South America is notorious for strong winds which produce massive seas.

Despite their appearance from the shore as a series of crests moving across the surface of the ocean, waves do not actually transport water from place to place. Waves are, instead, energy moving through the water. As waves pass by, a water particle drops into the trough of the wave, then is lifted to the crest, ultimately traveling in a circular motion. There are many different waves traveling across the surface of the ocean; these waves interact, neutralizing or enhancing the height of other interacting waves. If the wavelengths of waves are in phase, meaning their troughs and crests are matched, a larger wave will result from their interaction. If out of phase, they will cancel each other out and the resulting wave will be smaller. The propagation and interaction of multiple waves across the surface of the ocean is called the wave envelope. These waves will travel until they reach a coastline, where shallow water creates friction, slowing the wave and causing it to crash.

This has been On the Ocean, a program made possible by the Department of Oceanography and a production of KAMU-FM on the campus of Texas A&M University in College Station. For more information and links please go to ocean.tamu.edu and click “On the Ocean.”

Contributor: Dr. Henry Potter

Script Author: James M. Fiorendino