Why are there waves

Question:

Where do the waves in the sea come from?

The most common waves to be observed on the sea surface are wind waves, which usually arise far out in the sea and then run towards the coasts and can be observed on the beach in Warnemünde, for example. To understand the birth of these waves, one must first consider the air flow over the water surface. The air does not move evenly across the sea, but in turbulent air eddies, which are always present and which we perceive, for example, as "gusts of wind".

Such air eddies "press" a little more strongly in some places, a little weaker in other places, on the water and cause small "valleys" or "mountains" in the surface - the wave is born. And it is also the wind that raises these "wave babies" in the truest sense of the word. Just as the airstream sweeps over the curved surface of an aircraft wing and lifts it upwards along with the aircraft, so the wind also sweeps over the curved surface of the young wave crests and thereby pulls them up a bit: the young wave grows. Incidentally, this phenomenon, regardless of whether it is a wing or a wave, is called the "Bernoulli effect". It creates ever stronger waves, which can then influence each other and, through a complicated mechanism, also create longer waves.

But be careful, not all waves that we see on the beach in Warnemünde were created this way. Especially when the weather is calm, most of the waves are caused by the incoming ferries, and that's a completely different story.

The question was posed by PD Dr. Lars Umlauf, IOW, answered.