Contrasting internal tide turbulence in a tributary of the Whittard Canyon

Submarine canyons that incise continental slopes are considered an important conduit for transport of suspended matter between shelf seas and deep-ocean. However, the exact mechanisms influencing deposition still largely unknown. We present moored observations current flows, acoustic echo intensity and, in high-resolution, temperature variation from two contrasting mooring sites 6.5 km apart horizontally 790 1130 m water depth one tributaries incising flank easternmost branch Whittard Canyon, North-East Atlantic Ocean. The shallow site is situated on a steep thalweg slope which supercritical semidiurnal internal tides have >100 amplitudes turbulent overturning evenly distributed over 240 range observations, with no particular intensification near seafloor. In contrast, deep located along-canyon approximately critical tides, steeper up-canyon to sidewalls. tide amplitude at about 75 m. lower 100 m, flow intensifies becomes more rectilinear along canyon axis, together intensifying mean turbulence dissipation rate tidally-averaged down-canyon flow. Over tidal period three episodes relatively large observed. Turbulence largest when upslope moving bore passes. Smaller but associated secondary strong convective during downslope phase. convection clearly distinguished variance spectra buoyancy Ozmidov frequencies, anisotropic stratified expected. Averaged entire depth-time series, kinetic energy amounts 4.4 ± 2 × 10 -7 s -3 , equal both sites. tributary, first will affect sediment resuspension most. • 240-m 2-day averaged above seafloor found similar Canyon tributary. Larger than waves where tides. Flow Per primary occur phase Primary reach potential effects resuspension.