Observations and linear analysis of sill-generated internal tides and estuarine flow in Haro Strait

Abstract

Current meter records from two sets of observations 20 years apart in Haro Strait, British Columbia, Canada, are analyzed. Haro Strait is a deep channel separated from larger bodies of water on either side by relatively shallow sills. The estuarine flow in this region is in approximate geostrophic balance and is apparently unaffected by the tidally driven spring/neap cycle in vertical stratification. Strong baroclinic variability with an amplitude 1 m s-1 (close to the amplitude of the barotropic tide) is present. A linear theory for internal tides in silled basins is developed using no-bottom-flow boundary conditions to represent sill effects. By comparison with observations it is concluded that an internal tide is generated at the seaward sill and propagates inshore. Although local damping appears to be weak, no return signal is found from the inshore sill, suggesting that either dissipation is strong in that area or that the internal tide is transmitted across that sill.