Wave-coherent air-sea 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 momentum transfer from the atmosphere to the ocean, but the role of the waves in heat transfer has been ambiguous and poorly understood.

We present results of several field experiments and show evidence that there are surface-wave-coherent components of both the sensible and latent heat fluxes. Indeed, we show modulations of temperature and humidity at the surface and at 10 - 14 m above the surface, that are coherent with the surface wave field. We show that the phase relationship between temperature and surface displacement is a function of wind speed. At 10-14 m elevation we found wave-coherent heat transfer of O(1)W/m² dominated by the latent heat transfer, and wave-coherent fractional contributions to the total heat flux of up to 7%. Since, by analogy with momentum transfer, we expect the wave-coherent heat transfer to decay with height over scales of the order of k^-1, where k is the characteristic surface wavenumber, we expect that measurements at O(10) m elevation may underestimate the contribution of the wave-induced heat flux to the atmosphere. In addition, the wave coherent heat flux scales with the surface wave slope parameters. For the wind speeds and wave conditions of these experiments, which encompass the range of global averages, this wave contribution to total heat flux is comparable in magnitude to the atmospheric heat fluxes commonly attributed to the effects of greenhouse gases or aerosols.