In that layer are "internal" waves. If one could pull off the top layer of ocean, the internal waves would look a lot like ordinary surface waves, except they would probably be longer (lower frequency) and taller (higher amplitude) than the ones on the surface. They happen because the waves on the surface are transmitting energy to the sea floor. Just as the energy from wind makes waves on the surface, the energy is transferred to the thermocline, where it make the internal waves.
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Meanwhile, the seafloor isn't perfectly smooth. The shape of it can affect the motion of deep water as it flows over it and some of that energy can get transferred all the way back to surface waves.
Alam found that if he used a rippled sheet of material, one that had a specific set of heights and lengths, and put it on the oceanfloor, the energy from deep water would make the internal waves in the thermocline more energentic, but cancel out surface waves. That makes for calm water on the surface.
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Alam told Discovery News that if one were building a working version - something several years away at least - it would only need to face in one direction, since you only need to cancel the waves out when they are approaching. Waves also tend to come from one side - they don't often go from shore to sea, for instance.
He added that there is a lot of interest in this kind of work for another reason: underwater acoustics. Understanding how sound transmits through water is crucial for designing better sonar. The interface between warm and cold water can affect what a sonar system "sees" and better understanding that layer could improve sonar systems.
Beyond building something to protect floating structures, this kind of work could also help engineers decide where to put them. The "cloaking" effect sometimes occurs because the seafloor isn't level;
there are areas of calm water as a result. Putting an oil drilling platform in a place where big waves are less likely to happen at all would make the whole operation safer.
Credit: Mick Roessler/Corbis