A concept of wave-amplitude-based Reynolds number is suggested which is hypothesised to indicate a transition from laminarity to turbulence for the wave-induced motion. If the hypothesis is correct, the wave-induced motion can be turbulent and the depth of upper ocean mixing due to such wave-generated turbulence can be predicted based on knowledge of the wave climate. Estimates of the critical wave Reynolds number provide an approximate value of Re _cr = 3000. This number was tested on mechanically-generated laboratory waves and was confirmed. Once this number is used for ocean conditions when mixing due to heating and cooling is less important than that due to the waves, quantitative and qualitative characteristics of the ocean's Mixed Layer Depth (MLD) are shown to be predicted with a satisfactory degree of agreement with observations. Testing the hypothesis against other known results in turbulence generation and wave attenuation is also conducted.