Abstract
The decomposition of ocean dynamics into a superposition of waves is based on a linear approximation of the equations of fluid mechanics, which, in particular, neglects convective effects. For small-amplitude motions, these couplings can be regarded as corrections that induce only a slow evolution of the wave amplitudes. This interference-based approach is particularly well illustrated by the case of surface waves, where constructive or destructive interference can be observed, as well as non-resonant waves that essentially do not interact.
For wave propagators with a discrete spectrum, this interference mechanism is well understood: through filtering, one can characterize the resonances and describe the envelope equations of the waves. An important point to note is that the study of interference combines the spectral structure of the propagators (resonances) and the algebraic structure of the coupling terms (non-transparency conditions).
