Turbulence and Mixing in the Surface Wave Layer

The aim of this work is to measure turbulence and mixing in the upper mixed layer, or surface wave zone and correlate it with wind and wave parameters, breaking and Langmuir circulations, and with air entrainment and acoustic events due to breaking. We will test scaling and models of the turbulence, especially the dissipation rate, proposed by Craig & Banner (1994), Craig (1996), Melville (1994), Terray et al. (1995), and Drennan et al. (1996). We will also compare our measurements with recent large eddy simulations (LSE’s) of Skyllingstad & Denbo (1995) and McWilliams et al. (1996). Sufficiently far below the surface we anticipate that the length scales imposed by the surface waves will no longer apply and the only relevant length scale will again become the distance from the surface. If this is the case then we anticipate that wall-layer scaling will apply at depth. We will examine the transition from wave-zone scaling to wall-layer scaling of the dissipation.

The measurements will employ instrumentation and techniques developed under previous NSF funding (OCE 95-05628 “Measurements of Dissipation by Breaking Waves”) which provided the capability of measuring dissipation with a pulse-to-pulse coherent Doppler profiler. A second capability is that of measuring air entrainment and bubble-size distributions in the upper ocean (OCE 95-29808 “Instrumentation for Measuring Bubble Size Distributions in the Ocean Surface Layer”) by inverting sound speed and attenuation measurements.