Lateral stratification and dynamic balance at the Matane transect in the lower Saint Lawrence estuary

The lateral stratification and momentum balance in the lower Saint Lawrence estuary (LSLE) were investigated over a period of six days from current, temperature, and salinity measurements taken in 1979 at the Matane transect. Asymptotic singular decomposition analysis was used to show that the spatial variability of hydrodynamic parameters at that cross-section was more pronounced than their temporal or tidal variability. Classification of the section in the lateral circulation/stratification diagram revealed that the LSLE is one of the most laterally-stratified estuaries examined in the world. Estimates of various acceleration terms in the lateral dynamic balance equation showed that, when averaged over many tidal cycles, the motion can be considered as being quasigeostrophic to a first approximation, with contributions of the same order of magnitude from the baroclinic and the barotropic pressure gradients. Convection accelerations were found to be important only near the north shore, where strong cross-channel currents were recorded, whilst local and centrifugal accelerations were found to be of secondary importance.