Temperature anomalies beneath breaking waves and the decay of wave-inducedturbulence

Temperature observations in the near surface layer of the ocean reveal brie f temperature fluctuations O(20 mK) coincident with air entrainment due to wave breaking. These temperature fluctuations, typically confined to the up per similar to 0.2 m, are interpreted as consequences of mixing of a surfac e layer of anomalous temperature. The thickness of this surface layer is es timated at similar to 30 - 50 mm. Only similar to 30% of breaking waves exh ibit temperature signals, implying strong variability of the heat content o f this layer. The evolution of the temperature profile in the upper 0.2 m i s calculated according to a time dependent diffusion process which incorpor ates decay of wave induced turbulence. Combining the modeled temperature pr ofile evolution with a simple one-dimensional mixing model shows that our o bservations are consistent with the decay rate of the turbulent diffusivity k(T)proportional to t(-1.85) inferred from laboratory measurements of stab le stratified flows. Stratification in the oceanic near-surface layer may b e provided by microbubbles, suggesting that these bubbles play an important role in the dynamics of the near-surface region.