The influence of waves and turbulence on the oceanic heat flux

Air-sea fluxes of heat and momentum play a crucial role in weather, climate and the coupled general circulation of the oceans and atmosphere. Much progress has been made to quantify momentum transfer from the atmosphere to the ocean for a wide range of wind and wave conditions. Yet, despite the fact that global heat budgets are now at the forefront of current research in atmospheric, oceanographic and climate problems, and despite the good progress in recent years, much remains to be done to better understand and quantify air-sea heat transfers. It is well-known that ocean surface waves may support much of the momentum transfer from the atmosphere to the ocean, but the role of the waves and the small scale surface turbulence in heat transfer has been ambiguous and poorly understood. We present results of several field experiments on the kinematics of small-scale surface turbulence and surface waves, their influence on the surface skin layer, and the resulting transfers of heat across the diffusive layer at the surface of the ocean. A variety of optical and electro-mechanical instruments are used to measure the evolution of the surface and sub-surface velocity, and temperature fields. These include visible and infrared imaging of the surface, thermal/IR surface velocimetry, and fast-response thermometry. Additional instruments include an eddy covariance system and a long-wave short-wave net radiometer. We show that at low wind speed, it is the small-scale turbulence at the surface of the ocean, rather than breaking waves that most influence and disrupt the surface skin layer. We find that the surface turbulence correlates with the surface heat flux and that the total heat flux increase approximately linearly with increasing surface vorticity and divergence. At moderate wind speed, we find that the surface wave field modulates the surface temperature and that the phase relationship between temperature and surface elevation is a function of wind speed. This suggests that a fraction of the total heat flux is coherent with the surface wave field.