Air-sea turbulent heat fluxes in climate models and observational analyses: what drives their variability?

AbstractA traditional view is that the ocean outside of the Tropics responds passively to atmosphere forcing, which implies that air-sea heat fluxes are mainly driven by atmosphere variability. This paper tests this viewpoint using state-of-the-art air-sea turbulent heat flux observational analyses and a climate model run at different resolutions. It is found that in midlatitude ocean frontal zones variability of air-sea heat fluxes is not predominantly driven by the atmosphere variations, instead being forced by sea surface temperature (SST) variations arising from intrinsic oceanic variability. Meanwhile in most of the Tropics and subtropics wind is the dominant driver of heat flux variability, and atmosphere humidity is mainly important in higher latitudes. The predominance of ocean forcing of heat fluxes found in frontal regions occurs on scales of around 700 km or less. Spatially smoothing the data to larger scales results in the traditional atmosphere-driving case, whilst filtering to retain only sm...