Net Heat Flux

Net heat flux is the sum of the four surface energy-budget terms at the sea surface: net shortwave (solar) radiation, net longwave (infrared) radiation, sensible heat flux, and latent heat flux. Written Q_net = Q_sw - Q_lw - Q_s - Q_L with heat into the ocean positive, it sets whether the upper ocean gains or loses heat. The shortwave term is the only large heat gain; latent heat is usually the dominant loss. Global annual-mean Q_net is near zero over the open ocean but strongly positive in upwelling and equatorial regions and strongly negative over western boundary currents in winter. It drives sea surface temperature and mixed-layer heat content.