Source Biogeochemistry

The Salish Sea’s biogeochemistry is tightly linked to the Pacific Ocean waters that flow in through Juan de Fuca Strait. These inflows vary from year to year in both volume and chemical makeup, with important consequences for temperature, oxygen, nutrients, and the carbon system. In this project, we used a decade of high-resolution model output from LiveOcean combined with Lagrangian particle tracking to determine which Pacific source waters contribute to Salish Sea inflow, how their contributions and properties vary over time, and what that means for the inflow of key biogeochemical constituents. We paired model results with observations of tracers not included in the model, such as dissolved phosphate, dissolved silica, and a suite of trace metals, to characterise the distinct properties of each source water mass. 

Combinning Lagrangian volume transport results with biogeochemical properties allowed us to determine the drivers of interannual variability in Salish Sea inflow: the volume transport or tracer variability in each of the source waters. The attribution method developped may be useful for studying other coastal regions influenced by large scale circulation. Our results show that deep source waters control nutrient supply through volume changes, while shelf waters—particularly from the southern shelf—drive interannual variability in oxygen and carbonate chemistry due to both property and volume changes. Understanding how Pacific source waters drive variability in coastal systems is essential for anticipating and managing future risks as the properties and dynamics of those sources change. 

Beutel, B; Allen, S.E. , Xiong, J., Cullen, J.T., Anderlini, T. (2025). Water property variability into a semi-enclosed sea dominated by dynamics, modulated by properties. Biogeosciences. 22, 7309-7336. https://bg.copernicus.org/articles/22/7309/2025/