This session is concerned with the investigation and parametrisation of small-scale physical processes in the ocean not explicitly resolved in today's ocean general circulation models (OGCMs), i.e. processes ranging from the sub-meso scale down to the dissipation scale. A special emphasis is put on small scale processes that, possibly, have a strong impact on the basin-scale circulation and/or the global energy balance. We encourage observational, laboratory, numerical and analytical investigations, in particular those focusing on frontal dynamics, internal wave mixing, ageostrophic instability, mixed-layer dynamics, gravity current entrainment, double diffusion, turbulent closures, ...