Investigation of the sensitivity to wave breaking and the Prandtl number in the ocean mixed layer model under surface heating reveals an interesting latitude-dependent feature in the dynamical process of the ocean mixed layer. The effect of Prandtl number variation with stratification plays an important role in the equatorial ocean, whereas, in the extratropical ocean, the effect of strong near-surface turbulence caused by wave breaking is dominant. The contrasting responses to parameterization is attributed to the fact that turbulence production in the ocean mixed layer is dominated by turbulent kinetic energy flux from the sea surface in the extratropical ocean, and by shear production in the equatorial ocean. Comparisons were also made between the sensitivity tests from different ocean mixed layer models.