A Description of Summer Physical Oceanographic Conditions in Rupert Bay (James Bay, Canada)

Abstract

Measurements of current velocity, temperature, salinity, and water level were made over a period of two months in Rupert Bay, James Bay (Canada). From an analysis of the current meter time series, the circulation and distribution of physical properties were found to be dominated by the tides, with the semi-diurnal component being the predominant component. An analysis of variance revealed that 77% of the salinity variations were related to the tides. Vertically homogeneous conditions prevailed in many areas because of a large tidal amplitude/depth ratio of 0.625, causing intense mixing in two-thirds of the estuary. Non-tidal velocity components were found to be 0(1) less than tidal currents, with the long-term mean circulation directed out of the bay. Non-tidal water level variations were well correlated with the wind. The maximum cross-correlation coefficient was calculated to be 0.77 for a 7 hour lag. The centrifugal force, Coriolis force, and baroclinic pressure gradient were dominant forces driving the secondary flows of the bay. Tidal fronts were found to be either aligned parallel to the main axes of principal channels or around small downstream islands with the arrangement influenced by bottom topography.Key words: estuary, circulation, tides, salinity, mixing, secondary flow, front