TURBULENCE INTENSITY MEASUREMENTS IN A WIND-DRIVEN MIXED-LAYER

Neutrally buoyant, high-drag floats were used to measure vertical velo city in the upper-ocean mixed layer during a period of rapid mixed lay er deepening resulting from a storm. Salinity and temperature profiles , air-sea fluxes, and surface wave spectra were also measured. The loc ation, Georgia Strait, British Columbia, is coastal with strong horizo ntal variability and may not be representative of the open ocean. The floats moved freely within the deepening mixed layer; the envelope of their motion corresponded closely to the extent of the mixed layer. Th e maximum vertical velocity was 0.12 m s(-1); the rms vertical velocit y was about (0.02 m s(-1))(2). The mean square vertical velocity, excl uding surface waves, was 1.5-3.0 mu(2), clearly higher than the upper bound of US found in solid wall turbulent boundary layers. The author s speculate that these anomalously high vertical velocities were due t o Langmuir circulations generated by surface waves. These cannot occur in solid-wall boundary layers.