Wave Breaking Energy in Coastal Region

Huang (2006) suggested that wave breaking in the coastal region is a major energy source for the ocean circulation based on the observational data. Because the area of a coastal region is generally 5 % or less of the ocean, the energy loss from wave breaking in the coastal region must be significantly greater than in the open ocean. Two major discoveries in the past have supported Huang’s suggestion. In 1980, Herterich and Hasselmann indicated that rapid nonlinear wave-wave interactions could occur and increase as water depth decreased based on the Boltzmann integral method. In 1998, Resio and Tracy, also Lin and Perrie, proved the phenomenon using their numerical models (first using Boltzmann method and later using the Hamiltonian variation principle) as presented at the International Base Enhancement Wave Prediction Conference, Vicksburg, Mississippi. Lin and Perrie (1997) further showed that three wave interactions cannot satisfy the resonant condition in shallow water. Instead, four-wave interactions consisting of three local wind waves interacting with one long wave are required for the resonant in shallow water. Based on these two discoveries, higher frequency and smaller wave amplitude waves no longer dominate in the coastal region. The long wave propagating from the ocean to the coastal region can absorb the wave energy from local wind waves and grow faster than in the deep ocean. This fast nonlinear interaction i