5.1. Nutrient Enrichment of the Northern CCS

[44] The Juan de Fuca Eddy has been described as an “upwelling center”, allowing water to be raised from deeper depths than in classical wind‐driven upwelling [Freeland and Denman, 1982]. Upwelling in the eddy enriches the deep waters that flow into Juan de Fuca Strait as part of the estuarine circulation return flow. The penetration into the strait of this nutrient‐rich water mass is evident in a vertical section of ambient nitrate concentration measured in September 2003 (Figure 13). At the mouth of the strait, nitrate concentrations below 100 m (the approximate depth of the division between inflow and outflow) are >34 μM. Similar concentrations are present in bottom water along the strait axis, reaching ∼150 km east of the Strait entrance where strong mixing in shallow regions of high tidal currents mixes them upwards.