University of Victoria
Victoria, British Columbia, Canada
The mean flow in Juan de Fuca Strait is primarily estuarine: relatively fresh water in the upper layer flows seaward while saltier Pacific water is forced into the strait at depth. The landward along-channel sea surface pressure gradient due primarily to river runoff is reversed in the lower layer due to internal mixing within the strait which causes isopycnals to shallow towards the Pacific. A momentum balance using historical sea level, atmospheric pressure and current data suggests that these mixing levels may be significantly higher than expected and larger than presently used in numerical models. Unfortunately, historical current data are of insufficient vertical resolution to reveal any patterns in the secondary flows which would be expected from strong internal mixing. Acoustic doppler data collected in 1996 can, for the first time in Juan de Fuca Strait, resolve the current well enough vertically and temporally to examine shears and Reynolds stresses and to compare them to microstructure and hydrographic data to better understand the role of friction in estuarine dynamics.