| Work described in this thesis has increased our understanding of high latitude river/estuarine air-water carbon dioxide (CO2) exchange through examination of the Churchill River and estuary system of southwestern Hudson Bay, which was studied throughout the 2007 open-water season. An automated monitoring instrument was used to measure the concentrations of CO2 in air and water of the Churchill River and estuary. River and estuarine waters were sampled and analyzed to determine differences in CO2 flux with respect to season, space, and source (river or marine). Riverine CO 2 flux ranged from -51.4 to +30.8 mmol m-2 day -1 (mean flux of -5.8 mmol m-2day-1), while estuarine flux ranged from -11.04 to +22.76 mmol m-2day -1 (mean fluxes of -1.07 at low tide, +0.06 at high tide, and -0.37 mmol m-2day-1 overall). These results indicate that the Churchill River and estuary are net CO2 sinks throughout the 2007 open-water season. Analyses of water samples collected from the Churchill River (surface waters) and estuary (surface and bottom waters) indicate that the river is a source of chlorophyll a, dissolved organic carbon, coloured dissolved organic matter, and particulate organic carbon and nitrogen to the estuary basin, while marine waters are a source of dissolved inorganic carbon, salinity, and alkalinity. A multi-sensor probe was used to determine estuarine stratification and seasonal mixing patterns. The Churchill River estuary was stratified by water source, with fresh river water flowing over brackish marine water. The nature of the stratification varied seasonally with temperature and changing river discharge and tidal amplitude. |
