Making Waves

Ask anybody what they like about North Carolina’s beaches and you’ll likely hear responses like warm sun, warm sand, ocean breeze, and fresh seafood at the restaurants. The answers vary, of course, but I think one thing that everyone likes about the beach is the sound of the waves.

So the question is... What makes an ocean wave?

The answer is simple: wind.

The folks at the National Oceanic and Atmospheric Administration (NOAA) say winds from a storm either close to shore or far out at sea transfer their energy into the ocean, which creates ripples on the surf. If the wind continues, the ripples turn into chop and as the chop gathers speed it combines and turns into waves.

The longer and faster the wind blows the larger the waves will become. Spencer Rogers, a coastal specialist with North Carolina Sea Grant, says buoys off the North Carolina coast have measured waves higher than 40 feet during hurricanes.

Waves can come from different storms and directions. When different waves hit a point in the ocean at the same time they either add to or subtract from each other. When the wave trough (bottom) meets the crest (top), the waves seem to cancel each other out and you get a smaller wave. When the crests combine, you add the two heights and get a much larger wave.

Waves can travel thousands of miles in deep water. The speed at which they travel in deep water is determined by the wavelength, which is the distance between wave crests, as well as the wave period (the time between wave crests). The waves with the longest wavelength or wave period move the fastest.

But none of this makes for the crashing waves we all enjoy at the coast. Those waves are created as the swell moves closer to the coast and the water gets shallower. The energy of the swell drags along the ocean floor, which not only slows down the wave, it also pushes the energy up. Eventually the top of the wave becomes unstable and breaks.

Beachgoers love it.

— Frank Graff

Frank Graff is a producer/reporter with UNC-TV, focusing on North Carolina Science Now, a weekly science series that airs Wednesdays, beginning in August 2013, as part of North Carolina Now on UNC-TV. In addition to producing these special segments, Frank will provide additional information related to his stories through this North Carolina Science Now Reporter's Blog!

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