  The dynamic and thermal regimes of climate are regulated by an exchange of
energy and momentum between the atmosphere and the ocean. The role exerted by
surface waves on this interchange is particularly enigmatic. Waves induce
turbulence in the upper ocean by breaking and through Langmuir circulations.
However, waves can directly inject energy into subsurface layers. This relates
to waves not being truly irrotational and therefore the induced orbital motion
being turbulent. The existence, extent and properties of this turbulent
oscillatory flow still remain uncertain. Here we present measurements of the
velocity field of oscillatory flows, which are induced by mechanically
generated random wave fields in a large scale experimental facility. Velocities
were recorded at a depth sufficiently far from the water surface to rule out
effects of wave breaking. We demonstrate that the spectral tail of the velocity
field follows a power-law scaling close to $\omega^{-5/3}$. The turbulent
behaviour is investigated via rigorous statistical analysis of the structure
functions to highlight the emergence of intermittency in oscillatory flows. The
results show that wave motion is turbulent and can contribute to ocean mixing.
By deepening of the mixed layer, wave induced motion affects cyclogenesis and
sediment resuspension.

Atmospheric and Oceanic Physics;Fluid Dynamics