Sea-level rise impacts on longitudinal salinity for a low-gradient estuarine system
Salinity response to sea-level rise is evaluated for a low-gradient, tidally active estuary, the lower St. Johns River, Florida. A high-resolution numerical model is forced by continuous data of water levels and freshwater inflows for the offshore and upstream boundaries, respectively. The modeling approach is configured for salinity simulation over a 10-year record, 1997–2007, and validated at four salinity-gauging stations inside the river. The initial condition of salinity field was found to be a critical factor in the numerical simulation. Adjustments in the initial salinity condition of ± 10% required 6–9 months for the model salinity solution to dynamically equilibrate with the applied boundary conditions. Model predictions of salinity response to sea-level rise of 0.05, 0.15, and 0.30 m were diagnosed in terms of salinity change. Salinity was found to increase over the entire river, regardless of the magnitude of sea-level rise. Linear rates of salinity increase were predicted as high as 6 ppt m−1 inside the river. The change in salinity was nonuniform throughout the system and exhibited a moderate-to-strong nonlinear component. The results uncover a hotspot in the river where salinity was predicted to increase as much as ~ 2.3 ppt due to the nonlinear system response to sea-level rise.
Computational support was provided by the University of North Florida. The authors thank the two anonymous reviewers and editorial team for providing insightful comments that served to improve the manuscript.
This research was funded in part by the St. Johns River Report Team and the Taylor Engineering Research Institute.
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