Temperature anomalies beneath breaking waves and the decay of wave‐induced turbulence

Temperature observations in the near surface layer of the ocean reveal brief temperature fluctuations O(20 mK) coincident with air entrainment due to wave breaking. These temperature fluctuations, typically confined to the upper ∼0.2 m, are interpreted as consequences of mixing of a surface layer of anomalous temperature. The thickness of this surface layer is estimated at ∼30–50 mm. Only ∼30% of breaking waves exhibit temperature signals, implying strong variability of the heat content of this layer. The evolution of the temperature profile in the upper 0.2 m is calculated according to a time dependent diffusion process which incorporates decay of wave induced turbulence. Combining the modeled temperature profile evolution with a simple one-dimensional mixing model shows that our observations are consistent with the decay rate of the turbulent diffusivity kT∝t−1.85 inferred from laboratory measurements of stable stratified flows. Stratification in the oceanic near-surface layer may be provided by microbubbles, suggesting that these bubbles play an important role in the dynamics of the near-surface region.