There is growing evidence that a significant fraction of the diapycnal mixing in the oceans is caused by internal hydraulic processes (e.g., internal wave breaking, internal hydraulic jumps etc.). Fjords are convenient as ocean process laboratories since they exhibit many of the physical phenomena, and are relatively easily accessible. In this project, we propose a case study in Van Mijenfjorden in Svalbard to investigate the physical pathways whereby the energy provided by surface tide is transformed at the sill into internal waves, and how the internal waves and internal hydraulic processes lead to mixing. These processes have implications for the efficacy of vertical mixing, transport of pollutants, heat and nutrients in the fjord, thereby influencing the ice cover and the ecosystem. Attempts will be made to scale, parameterize and extrapolate the results to deeper ocean and relate to bathymetric features in the Arctic (e.g., Lomonosov Ridge). Two experiments will be conducted: In summer 2010 from a re search vessel, including mooring deployments and in early April 2011 from ice over the ice covered. Moorings will be recovered in summer 2011. Observations will include year-long time series from moored instruments at selected positions and one week durat ion microstructure profiling each in summer 2010 and April 2011. The collaborator Sergey Pisarev (Shirshov Institute of Oceanology, Russian Academy of Sciences, Moscow) has long standing experience in Arctic field work and internal waves related studies. The project contributes to network building between high-latitude ocean physics process study groups in Bergen and in Moscow.