Estuarine Circulation of the Salish Sea

The tidally averaged circulation of estuaries typically consists of a two-layer exchange flow, with ocean water pulled in as the deeper layer due to mixing with buoyant river water. The exchange flow is often much larger than the river flow and so controls residence time and biogeochemical fluxes.

A realistic numerical simulation of the large, complex, estuary-fjord system of the Salish Sea is analyzed for the exchange flow. It is found that time-dependence is of leading importance in the salt budget. In addition the strength of the exchange flow varies little over a year, despite the large annual variation of river flow. Instead, during times of low river flow the system grows progressively saltier and less stratified.

Vertical fluxes are analyzed using the "Efflux-Reflux" framework of Cokelet and Stewart (1985). Results highlight the large amount of water recycled in the system. Implications for passive tracers, water age, and active tracers are discussed.