Mixing and Deep Water Renewal in a Numerical Model of the Strait of Georgia

The Strait of Georgia is a large (several baroclinic Rossby radii wide), semi-enclosed basin between Vancouver Island and the mainland of British Columbia and Washington. Many rivers release fresh water into the system, the most dominate source being the Fraser River, which sets an estuarine-like exchange with the Pacific Ocean. Deep, salty water enters the system through Juan de Fuca Strait and then passes over steep topography where it endures intense tidal mixing through the complicated passages of Haro Strait. Periodically, pulses of salty water descend from the sills of Haro Strait into the Strait of Georgia basin. These pulses are modulated by tidal mixing and are strongly linked to the spring/neap tidal cycle. We discuss how well this process is represented in a numerical model of this system. Initially, too much mixing over the sills resulted in renewal pulses and intermediate layers that were too fresh. We will discuss modifications to the model's lateral and vertical mixing parametrizations, vertical resolution and open boundary conditions and their effect on the deep water renewal process