  Turbulent mixing processes in deep alpine Lake Garda (I) have not extensively
been observed. Knowledge about drivers of turbulent fluxes are important for
insights in the transport of matter, nutrients and pollutants, in the lake and
in natural water bodies in general. In this paper, the occurrence of internal
wave induced turbulent convection is addressed as opposed to the more common
shear-induced turbulence in a density stratified environment. Observations are
analyzed from a dedicated yearlong mooring holding 100 high-resolution
temperature sensors at 1.5 m intervals under a single current meter in the
deeper half of the 344 m deep lake-center. Episodically, the weakly density
stratified waters in the lower 50 m above the lake floor show spectral slope
and coherence evidence of short-term (15 to 30 minutes) convective motions
under internal waves that are supported by the stronger stratified waters
above. The near-homogeneous conditions are not attributable to frictional Ekman
dynamics, but to large-scale internal wave crests.
