Observations of Overturning in the Thermocline: The Context of Ocean Mixing

The time sequence of events that lead to internal wave breaking and ocean turbulence is investigated. Data are obtained from depths 100–400 m with a repeat profiling CTD and a coded-pulse Doppler sonar. The instruments were deployed from RP FLIPduring February–March 1995 while stationed 30 km west of Point Argüello, California, as an aspect of the Marine Boundary Layer Experiment. Although the water depth at the site is 1500 m, both rms shear and diapycnal diffusivity, as inferred from the average rate and size of overturning events, increase with depth below 250 m. A deep source of wave energy is implied.