The generation and scattering of a low mode internal tide

The flux of energy into, and the eventual dissipation of, the low-mode internal tide is believed to play an important role in ocean dynamics. While reasonable bounds are being established for the amount of energy in the low-mode internal tide, the ultimate fate of this energy is still a source of debate. Using a novel internal wave generator, it is now possible to generate arbitrary combinations of vertical modes in linear and nonlinear stratifications in laboratory experiments. Furthermore, modal decomposition techniques are being refined to track the linear and nonlinear evolution of these modes in high-resolution experimental data sets. Here we present laboratory experimental results demonstrating this approach, which have provided the first experimental data on internal tide scattering by finite-amplitude bathymetry. The transition from a long vertical wavelength, low-mode structure to high-mode wave beams is clearly observed, and the efficiency of scattering is calculated. The results provide insight into field observations of internal tide scattering at the Line Islands Ridge, Hawaii.