A primitive equation ocean general circulation model (OGCM) of the Atlanic is coupled with an explicit mixed layer model (MLM). The coupled model is used to investigate the impact and possible improvement achieved by an MLM on the representation of temperature and heat flux. The MLM improves model performance in regions where mixed layer (ML) formation is governed by wind stirring, which is identified as a major missing process in the OGCM. It is shown that the widely used parameterization of Pacanowski and Philander for the vertical exchange coefficients is not able to properly represent this process. The deepening of the ML by wind stirring leads of temperature and heat flux being in closer agreement with climatology than is the case without MLM.

Integrations with a coupled ocean-atmosphere model are needed to show whether this improvement leads to a reduced climate drift in such models. Furthermore, momentum mixing improves the vertical profiles of velocity. The Ekman transport now occurs over the whole depth of the ML instead of just within the upper model layer. Convective adjustment as incorporated in the OGCM already tends to overestimate the depth of the mixed layer in buoyancy-driven situtations. Adding the MLM cannot remedy this failure. Thus under these circumstances there are only slight improvements of some model aspects while others become even worse. We conclude that the parameterization of convection has to be improved. ¿ American Geophysical Union 1994