When a deep water wave encounters the ocean floor as it moves into shallower areas, its energy interacts with the bottom, causing significant changes to the wave's structure and the movement of the water particles within it.
Interaction with the Ocean Floor
As waves transition from deep water into shallow regions, the depth becomes a significant factor influencing their behavior. In deep water, the wave's energy does not reach the bottom, and water particles move in roughly circular orbits. However, when the water becomes shallow enough for the wave's energy to touch the ocean floor, this dynamic changes.
According to the provided reference, "When the energy of the waves touches the ocean floor, the water particles drag along the bottom and flatten their orbit." This crucial interaction fundamentally alters the wave.
Key Effects of Bottom Interaction
The energy of the wave making contact with the seabed has several important consequences:
- Particle Orbit Flattening: The circular motion of water particles characteristic of deep water waves is inhibited by the bottom. Particles closer to the seabed are forced into more elliptical, flattened orbits.
- Bottom Drag: The interaction causes friction between the moving water particles and the ocean floor. This drag slows the wave down.
- Wavelength Shortening: As the wave speed decreases due to bottom drag, the wavelength (the distance between wave crests) also shortens.
- Wave Height Increase: While the wavelength shortens and speed decreases, the wave's energy is compressed into a smaller area, causing the wave height to increase.
- Transformation to Breaking Waves: The combination of increasing height, decreasing speed, and shortening wavelength leads to the wave becoming unstable. Ultimately, as described in the reference, these waves change into breaking waves, which are the surf we see near the shore.
This transformation from a deep-water wave to a shallow-water wave culminating in breaking is a fundamental process in coastal dynamics and explains why waves change dramatically as they approach the shore.
