Salish Sea model ecosystem - lower trophic: episodic nutrient supply in the northern Strait of Georgia

Salish Sea Model Ecosystem - Lower Trophic (SMELT) is a three-dimensional biogeochemical model coupled to a NEMO-based physical model of the Salish Sea, run operationally at UBC as part of the SalishSeaCast system. In this presentation, we will first establish the model's skill at reproducing nitrate concentrations by comparison with data from the Pacific Salmon Foundation’s citizen science program and Institute of Ocean Sciences repeat surveys. We will then discuss episodic nitrate supply to the surface waters of the northwest Strait of Georgia. This phenomenon is evident as a region of elevated mean (March-November) and standard deviation (April-September) of surface nitrate stretching from Discovery Passage to Baynes Sound in a monthly climatology based on simulations from fall 2014 to present. We will analyze the relative contributions of southward advection of nitrate supplied through tidally-enhanced mixing in Discovery Passage and of local upwelling. This assessment will be based on analysis of SalishSeaCast simulations as well as additional numerical tracer experiments. We will discuss the importance of the phenomenon as a source of nutrients to the euphotic zone, fueling primary production in the northern Strait of Georgia.