As a wave propagates from deeper to shallower waters, the behavior of its amplitude depends on the specific characteristics of the wave and the depth change. Generally, two key phenomena occur: wave shoaling and wave breaking. Let's discuss these phenomena and their impact on the wave amplitude:
- Wave Shoaling: When a wave enters shallower waters, the depth decreases, causing the wave to experience shoaling. In this process, the wave's speed decreases, while its wavelength decreases and its amplitude increases.
As the wave approaches shallow waters, its wavelength decreases due to the reduction in the distance over which the wave can spread out. According to the principle of conservation of energy, the decrease in wavelength is accompanied by an increase in wave amplitude to maintain the same total energy. Therefore, the amplitude of the wave tends to increase as it moves into shallower waters.
- Wave Breaking: In very shallow waters or near the shoreline, the wave may eventually reach a critical point where it breaks. Breaking occurs when the wave height becomes so steep that the crest topples over, leading to turbulent motion and dissipation of energy.
When a wave breaks, its amplitude can vary dramatically. Initially, the wave amplitude increases significantly during the breaking process, leading to a violent release of energy. However, once the wave breaks, the amplitude reduces as the wave transitions into turbulent water motion closer to the shoreline.
It's important to note that the exact behavior of wave amplitudes during shoaling and breaking can be influenced by factors such as wave characteristics (e.g., wave period, wave height, wave shape), bathymetry (variation in the water depth), and coastal features. Therefore, the specific changes in wave amplitude during the transition from deeper to shallower waters can vary in different scenarios.