  Deep water circulation and mixing processes in deep lakes are largely
unknown, although they are responsible for the transport of matter, nutrients
and pollutants. Such a lack of knowledge cannot be reliably provided by
numerical hydrodynamic modelling studies because detailed observations are
typically not available to validate them. To overcome some of these
deficiencies, a dedicated yearlong mooring comprising 100 high-resolution
temperature sensors and a single current meter were located in the deeper half
of the 344 m deepest point of the subalpine Lake Garda (Italy). The
observations show peaks and calms of turbulent exchange, besides ubiquitous
internal wave activity. In late winter, northerly winds activate episodic deep
convective overturning, the dense water being subsequently advected along the
lake-floor. Besides deep convection, such winds also set-up seiches and
inertial waves that are associated with about 100 times larger turbulence
dissipation rates than that by semidiurnal internal wave breaking observed in
summer. In the lower 60 m above the lake-floor however, the average turbulence
dissipation rate is approximately constant in value year-around, being about 10
times larger than open-ocean values, except during deep convection episodes.
