Influence of internal wave induced vertical mixing on ice algal production in a highly stratified sound

Field observations of tidally forced flow over a sill in a constricted region of the highly stratified Manitounuk Sound (Hudson Bay, Canada) are examined during the winter period under a complete landfast ice cover. Necessary conditions for high frequency internal wave generation over the semi-diurnal tidal cycle for both spring and neap tides are considered. Internal wave activity is found to occur more often on the downstream side of the constriction during flood. A fortnightly variation in upper layer salinity and nutrients is attributed to a similar periodicity in internal wave activity and upward salt transport across the pycnocline. The variation in nutrient levels within the upper layer and at the ice-water interface is thought to have a controlling effect on underice microalgal biomass downstream of the sill.