High turbulent dissipation rates are observed in the ocean interior over mid-ocean ridges and are most likely attributed to breaking internal waves generated by tidal flows over the topography. The turbulence created by the rubbing of tidal currents over the rough topography may be an additional internal wave source, and may contribute to the high dissipation rates. We report on laboratory experiments that examine the properties of the internal wave field excited from an overlying oscillating grid-generated turbulent region.

In the first of two non-intrusive visualization methods, dye lines are used to mark the vertical motions of isopycnal layers. The dye lines highlight large tank-scale wave modes which are generated from a large-scale circulation that develops in the turbulent region. The amplitudes of the isopycnal lines, A, vary with buoyancy frequency, N, as A ~ N^(-1.5).

The second visualization method, ``synthetic schlieren,'' measures the entire wave field and allows us to isolate the properties of the strongest eddy-scale waves that propagate from the base of the turbulent layer. These waves have a narrow range of frequencies and vertical wavenumbers. The angles of wave propagation from the vertical for the eddy-scale waves lie between 42 and 55 degrees. These waves are of large amplitude with vertical displacements from 2 to 4 percent of their horizontal wavelength and follow the relation A ~ N^(-1.68).

We discuss a continuation of this investigation into wave-turbulence interaction through numerical simulations.