Topographic Waves and Topographically Induced Motions in the St. Lawrence Estuary

The St. Lawrence Estuary exhibits an estuarine character between Quebec City and the Saguenay Fjord (Upper estuary) and a maritime character between the Saguenay Fjord and the Gulf of St. Lawrence (Lower estuary). Topographically modified motions are mostly suprainertial in the former section and sub-inertial in the latter. The shallow Upper estuary is dominated by high-frequency motions such as internal waves and tides, which are generated by interaction of the tidal flow with sills, banks and especially the shoaling region at the head of the Laurentian Trough. The deeper Lower estuary exhibits a variety of strong low-frequency motions including topographic waves and unstable shear waves.