Séminaire

Ubiquitous in geophysical systems, internal gravity waves have significant impact on both fundamental processes and engineering applications. In the ocean, for example, internal waves are a significant means of tidal dissipation, eventually affecting abyssal mixing and the global energy budget. In the atmosphere, internal waves affect momentum and energy transport processes. While the generation of internal waves in both the ocean and the atmosphere is beginning to be well understood, what is now of great interest is the life of internal waves after their generation. More specifically, how are they dissipated, and what fundamental phenomena occur along the way? To investigate these issues, this talk presents the results of internal wave studies using a combination of experimental and analytical modeling, with a focus on internal wave scattering in the ocean.

In the first part of the talk, an analogy between internal wave transmission in nonuniform stratifications and light transmission in optical interferometry is established. Constructing an internal wave interferometer in the lab using a novel internal wave generator, selective transmission of wavelengths by nonuniform stratifications is demonstrated. In the second part of the talk, an investigation of internal wave scattering by ocean-floor topography is presented. An existing Green function method for internal tide generation is advanced to account for arbitrary two-dimensional topography in arbitrary nonuniform stratifications. The analytical model is then utilized to study the scattering of a mode-1 internal tide by idealized topographic shapes in uniform and nonuniform stratifications. The talk concludes with a case study of the scattering of mode-1 internal tide at the Line Islands Ridge at Hawaii, the location of an upcoming NSF field study, the EXperiment on Internal Tide Scattering (EXITS).

Riwal Plougonven, Laboratoire de Météorologie Dynamique, Ecole Normale Supérieure, 24 rue Lhomond, 75005 Paris

01 44 32 27 31