Do tropical cells ventilate the Indo-Pacific equatorial thermocline?

Source waters of the Indo-Pacific equatorial thermocline are studied with a high-resolution ocean model. In the annual mean fields, tropical and subtr opical overturning cells are found that upwell at the equator and downwell at. 5 degrees and 20 degrees poleward of the equator respectively. Tropical cells are common in ocean models, but their role in ventilating the equato rial thermocline is obscure because the downwelled water is too warm to mat ch the subsurface equatorial waters. The tropical cells are much weaker whe n the overturning is considered in density coordinates. When high-frequency mass fluxes are included tropical cells are compensated by an eddy-induced overturning. Seasonal variations and tropical instability waves are respon sible for the compensation. It follows that only subtropical cells transfer surface water to the equatorial thermocline. Strong tropical cells are sho wn to be an artefact.