The heat budget of the equatorial western Pacific surface mixed layer

The turbulent heat flux through the equatorial western Pacific surface mixed layer is estimated, using conductivity-temperature-depth and Doppler profiler data obtained in January 1986 and the assumption that a useful approximation to the heat flux can be obtained with the Pacanowski-Philander eddy diffusivity. Fluxes appeared to be an order of magnitude less along the equator than in the central Pacific because the only layer of very low Richardson number (and hence large eddy diffusivity) lay in the isothermal but salt-stratified “barrier layer.” The top of the thermocline, just below the barrier layer, coincided with the core of the (subsurface) South Equatorial Current; hence current shears, eddy diffusivities, and heat fluxes were small in this region. Away from the equator, heat flux estimates were of the order of 3 W m−2. Use of the recent Peters et al. diffusivities reduces these estimates still further. In combination with previous analyses of heat advection in the equatorial western Pacific heat pool, our results indicate that the net surface heat flux entering the region is near zero. There must therefore be systematic errors in several recent estimates of this net heat flux in the equatorial western Pacific, which range between 20 and 80 W m−2.