Adjustment of the Surface Heat Balance over the Tropical and Subtropical Oceans

Trends in the surface heat budget over tropical and subtropical oceans for 1979 – 2014 are investigated to understand how the surface heat balance is adjusting as global temperatures increase. Three atmospheric and four ocean reanalyses are used; confidence in the reanalysis heat budget terms is evaluated by comparison among the reanalyses, statistical significance testing, and a consideration of physical processes.

The atmospheric reanalyses are used to calculate trends in the total net heat flux from the atmosphere into the ocean, and its components. The ocean reanalyses are used to calculate trends in ocean heat storage, horizontal and vertical temperature advection, and the diffusion of heat. Enhanced transport of heat from the warming ocean is accomplished primarily by increases in the latent heat flux, with secondary support from a reduced solar flux in some regions. The latent heat flux is decomposed into thermal (Claussius-Clapeyron), dynamical (wind speed) and hydrological (vapor pressure depression) components. Dynamically-driven changes in the latent heat flux are similar in magnitude to the thermally-driven changes, and even dominate in some regions.