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UBC Theses and Dissertations

Pacific sources of biologically significant constituents in the Salish Sea using Lagrangian particle tracking Beutel, Rebecca


The Salish Sea is a semi-enclosed coastal sea between Vancouver Island and the coast of British Columbia and Washington State, invaluable from both an economic and ecologic perspective. Pacific inflow to the Sea is the main contributor of many biologically important constituents. The contribution of Pacific water masses to the flow through Juan de Fuca Strait (JdF), the Salish Sea’s primary connection to the Pacific Ocean, is explored. Quantitative Lagrangian particle tracking within Ariane, an offline Lagrangian tool capable of volume transport calculations, was applied to two numerical ocean models to track the paths and properties of water parcels before entering JdF and within the Salish Sea. The Coastal Ice Ocean Prediction System (CIOPS) for the west coast was used to track water parcels from JdF backwards in time to analyse their paths on the shelf and offshore before entering the Salish Sea, while SalishSeaCast was used to track water parcels forwards in time to assess the success of the water masses identified in the CIOPS analysis at reaching the Sea’s inner basins as opposed to being advected back out to the shelf region. During summer upwelling, intermediate flow from the north shelf and offshore dominate inflow, while during winter downwelling, intermediate flow from the south shelf and surface flow from the Columbia River plume are the dominant sources. A weaker and less consistent estuarine flow regime in the winter leads to less Pacific inflow overall and a smaller percentage of said inflow reaching the Salish Sea's inner basins than in the summer. Nevertheless, it was found that winter dynamics are the main driver of interannual variability, in part due to the strongly anti-correlated behaviour and distinct properties of the two dominant winter sources. This analysis extends the knowledge on the dynamics of Pacific inflow to the Salish Sea and highlights the importance of winter inflow to the interannual variability in biogeochemical conditions in the region.

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