Coastal ocean modelling with SLIM: Application to the Columbia River ROFI

Vallaeys, Valentin;Kärnä, Tuomas;Baptista, Antoniò M.;Deleersnijder, Eric;Hanert, Emmanuel
(2015) 14th International workshop on Multiscale (Un-)structured mesh numerical Modeling for coastal, shelf and global ocean dynamics (IMUM 2015) — Location: Portland, Oregon (USA) (28.September.2015)

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Unstructured grid models allow highly flexible spatial discretization and therefore accurate representation of complex phenomena, such as the hydrodynamics in Regions Of Freshwater Influence (ROFI) of large rivers, characterized by large density variations, rapid flow dynamics and complex topography. The whole river- sea continuum can therefore be simulated seamlessly. The complex interactions between tides, river inflow and ocean dense waters in shallow areas lead to strong density gradients and rapid currents, often difficult to handle in a numerical model. Many models tend to stabilize the computations by adding diffusion, leading to overly-smoothed fronts. The aim of this study is to analyze the baroclinicity of the SLIM model. SLIM 3D is a baroclinic discontinuous Galerkin finite element model. It has so far only been used to model very shallow areas, such as an idealised Rhine ROFI or subregions of the Great Barrier Reef. The ability of stabilizing the density field by adding as less diffusion as possible is assessed through two different test cases. We first analyze the performance of the SLIM model on the lock-exchange test case. As coastal waters feature strong density gradients, the baroclinicity needs stabilization. Therefore, we study the use of different limiters. We then analyze the plume of the Columbia River as simulated with SLIM in two different regimes of the Columbia River ROFI. The horizontal structure is discussed and compared to another model of the region based on SELFE. The key features of the simulated plume in different regimes are also discussed.
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Vallaeys, V., Kärnä, T., Baptista, A. M., Deleersnijder, E., & Hanert, E. (2015). Coastal ocean modelling with SLIM: Application to the Columbia River ROFI. 14th International workshop on Multiscale (Un-)structured mesh numerical Modeling for coastal, shelf and global ocean dynamics (IMUM 2015), Portland, Oregon (USA). https://hdl.handle.net/2078.5/184756