Coupling of Estuarine Circulations in a Network of Fjords

Abstract

The Kitimat Fjord System in the northern British Columbia coast features a network of deep channels, islands, and shallow sills. In particular, the fresh water leaving Gardner Canal bifurcates at a triple junction: (1) north through a shallow sill (100‐m deep) to Devastation Channel and then out through Douglas Channel and (2) west along Verney Passage then passing over a shallow sill (35 m) to Wright Sound. The partitioning of the fresh water leaving Gardner Canal has substantial implications for interpreting estuarine circulation and water exchange of the system. In this study, the partitioning of the fresh water at the triple junction is quantified by using observations and a circulation model. The model is based on FVCOM with ~200‐m horizontal resolution in the narrow channels and forced by tides, winds, and river discharges. The remotely sensed freshwater plume, surface drifter trajectories, and temperature profiles suggest that the fresh water from Gardner Canal contributes to the estuarine circulation in the Douglas Channel. A passive tracer evolving with the advection and diffusion processes in the circulation model is used as a proxy to quantify the freshwater transport. The results show that the majority of low salinity water leaving Gardner Canal at the triple junction flows northward into the Douglas Channel through the Devastation Channel and the synoptic variability of the freshwater partition is modulated by strong wind events. A synthesis of various circulations in the abovementioned connecting channels around the Hawkesbury Island indicates a net anticyclonic circulation.

Effect of Freshwater Discharge From Estuary Dam on Residual Circulation in Bifurcated Channel

“…Unlike Shan et al. (2019), this study cannot reflect the cross‐sectional area, so the unit of freshwater transport is m 2 s −1 . The salinity and velocity data at A8 used the data obtained during the neap tide of this study, and the methods and results are described in Sections 3.1 and 4.2, respectively.…”

“…To examine the influence of the Earth rotation on the freshwater plume in the Yeongsan River estuary, the Rossby internal radius of deformation ( R 0 = $$\sqrt{{g}^{\prime }H}/f$$) is estimated by the equation presented in Shan et al. (2019), where H is the upper layer depth of the stratification, f is the Coriolis parameter, and the g ′ = g ( ρ 2 − ρ 1 )/ ρ 1 is the reduced gravity. ρ 1 and ρ 2 are the average densities of the upper and lower layers of the stratification, respectively.…”

Oxygen dynamics in a deep‐silled fjord: Tight coupling to the open shelf

“…1; Shaw and Lintern 2016; Shaw et al 2017), which are considerably deeper (690, 400, and 425 m) than the shelf outside the fjord system (~ 150 m). The fjord system extends more than 300 km from its entrance to the hydraulic head at the head of Gardner Canal (Shan et al 2019). Further background is provided in Supporting Information for Introduction.…”

Surface Drift and Dispersion in a Multiply Connected Fjord System

“…A more detailed description of the ADCP and CTD data collected in the Kitimat fjord system between 2013 and 2016 is given in the supporting information and in Wright et al ( , 2017 and Wan et al (2017). Further descriptions of the Kitimat fjord system are given by Webster (1980), Macdonald et al (1983), andShan et al (2019).…”