Spatial and Temporal Variation in San Juan Channel during Fall 2013

Abstract

The San Juan Channel links the Strait of Georgia and the Strait of Juan de Fuca, and is dominated by an estuarine flow regime. For fall 2013, Pelagic Ecosystem Function Research Apprenticeship sampled a 5-station transect along the San Juan Channel. A CTD was deployed and temperature, salinity, and density data were collected. From these data, channel structure could be deduced, and contour plots were created to help extrapolate out the trends. Water and air temperature decreased throughout autumn. Short-term channel salinity and density structure was modulated by tides and winds. Density stratification was highest at South Station and North Station stratification was greatest when the freshwater signal was strongest. The depth of the pycnocline at South Station was not correlated to tidal height. However, when data points were separated by tidal cycle, there was a correlation between neap tide’s pycnocline depth and tidal height. Also, finer temporal resolution analysis of the northern channel salinity structure revealed that there is extensive within channel variation, and that salinity is regulated by tidal phase and cycle, as well as winds. The temperature, salinity and density structure patterns presented within this study, strengthens our understanding of their physical drivers within the San Juan Channel.