Near-surface turbulence and thermal structure in a wind-driven sea

Ocean surface turbulence at high sea states is evaluated using heat as a na turally occurring passive tracer. A freely drifting instrument with a mecha nically driven temperature profiler, fined depth thermistors, and conductiv ity cells was used to monitor breaking wave activity and fine-scale tempera ture structure within the upper 2 m of the water column. The combination of temperature profiles and independent heat flux measurements demonstrate th e presence of wave-enhanced turbulence and the effects of subsurface advect ion due to Langmuir circulation. The turbulence length scale, extracted fro m the temperature profile fine structure, suggests a surface value signific antly smaller than previously reported. A Prandtl-type mixing length model matched with a surface energy flux due to wave breaking and the observed tu rbulent length scale is consistent with the authors' observations. Both adv ection and enhanced diffusion are reconciled in a two-dimensional model of the upper-ocean boundary layer, providing a framework for studying Langmuir circulation and upper-ocean turbulence in terms of the measured temperatur e structure.