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Subsurface Ocean Waves Can Be More Than 500 Meters High
An anonymous reader writes: New field studies out of MIT found that "internal waves" — massive waves below the surface of the ocean — can reach enormous sizes. The most powerful internal waves known to science are in the South China Sea, and they can be over 500 meters high. These waves mix disparate layers of ocean water, and contribute to evening temperatures between various bodies of water (abstract). The waves grow larger as they propagate, and carry on all year. These waves have enough mass to affect the earth-moon system: "To cut a long story short, it's not unreasonable to say internal waves play a role in the moon moving away or receding from the Earth. They are big enough that they affect large-scale celestial motions."
I can tell you that undersurface waves are freaking awesome for those with a good sense of adventure :-) Best rides I have ever had.
The definition above is a visual description of what are generally caused by wind. You want definition 11 in your link.
No, definition 1 is correct. The "body" is not the ocean as a whole, it is the body of denser water within the ocean, and the "surface" is not that of the ocean, but the surface of the higher density water.
The full wave equations are the same, but at the surface there is a simplifying assumption that density of water is much greater than density of air and the density terms can be ignored. The density term is something like (d2-d1)/(d2+d1). If d1 (density of upper layer) is very small compared to d2 (density of lower layer) then that term is essentially d2/d2, or 1. That's not true for an internal wave at the boundary between water layers of different salinity or temperature.
This is an example of internal waves, although it is intended to evoke the calming effect of ocean surface waves. If you had just water and air in that box, the waves would be too small and fast, but by using two liquids of similar density the celerity and amplitude of the waves will be slower and larger, simulating the large scale behavior of ocean surface waves.
The turbulence as internal waves move is also not completely unknown. It is possible to see surface effects of internal waves created by ship wakes, for example.