  The energy pathways from propagating internal waves to the scales of
irreversible mixing in the ocean are not fully described. In the ocean
interior, the triadic resonant instability is an intrinsic destabilization
process that may enhance the energy cascade away from topographies. The present
study focuses on the integrated impact of mixing processes induced by a
propagative normal mode-1 over long term experiments in an idealised setup. The
internal wave dynamics and the evolution of the density profile are followed
using the light attenuation technique. Diagnostics of the turbulent diffusivity
$K_{T}$ and background potential energy $BPE$ are provided. Mixing effects
result in a partially mixed layer colocated with the region of maximum shear
induced by the forcing normal mode. The maximum measured turbulent diffusivity
is 250 times larger than the molecular value, showing that diapycnal mixing is
largely enhanced by small scale turbulent processes. Intermittency and
reversible energy transfers are discussed to bridge the gap between the present
diagnostic and the larger values measured in Dossmann et al, Experiments in
Fluids, 57(8), 132 (2016). The mixing efficiency $\eta$ is assessed by relating
the $BPE$ growth to the linearized $KE$ input. One finds a value of
$\Gamma=12-19\%$ larger than the mixing efficiency in the case of breaking
interfacial wave. After several hours of forcing, the development of staircases
in the density profile is observed. This mechanism has been previously observed
in experiments with weak homogeneous turbulence and explained by argument. The
present experiments suggest that internal wave forcing could also induce the
formation of density interfaces in the ocean.
