High-resolution modelling of a large-scale river plume
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Evolution of a large-scale river plume is studied numerically using the Massachusetts Institute of Technology general circulation model. The model parameters were set close to those observed in the area of the Columbia River mouth. The fine-resolution grid along with the non-hydrostatic dispersion included in the model allowed for the reproduction of detailed inner plume structure, as well as a system of internal waves radiated from the plume’s boundary. It was found that not only first-mode but also second- and third-mode internal waves are radiated from the plume at the latest stages of its relaxation when the velocity of the front propagation drops below an appropriate wave phase speed of internal baroclinic mode. The model output shows that the amplitude of these high-mode waves is of the same order as the leading first-mode waves, which in combination with the specific vertical structure (location of the maximum structure function beyond the pycnocline layer) creates favourable conditions for the generation of shear instabilities. High-resolution model output also reveals evidence of a fine internal structure of the plume characterized by the presence of secondary fronts inside the plume and secondary internal wave systems propagated radially from the lift-off area to the outer boundary. These structures intensify the mixing processes within the propagating plume with predominance of the entrainment mechanism developing on the lower boundary between the plume’s body and underlying waters. The scheme of horizontal circulation in the plume was reproduced by the methodology of Lagrange drifters released near the mouth at different depths.
KeywordsRiver plume Numerical model Internal waves
Thanks to Plymouth University’s Marine Institute which supported this work.
- Chant RJ, Wilkin J, Zhang W, Choi B-J, Hunter E, Castelao R, Glenn S, Jurisa J, Schoflield O, Houghton R, Kohunt J, Frazer TK, Moline MA (2008) Dispersal of the Hudson Rive plume in the New York Bight: synthesis of observational and numerical studies during LaTTE. Oceanography 21:148–161CrossRefGoogle Scholar
- Hickey BM, Kudela RM, Nash JD, Bruland KW, Peterson WT, McCready P, Lessard EJ, Jay DA, Banas NS, Dever EP, Kosro PM, Kilcher LK, Horner-Devine AR, Zaron ED, McCabe RM, Peterson JO, Orton PM, Pan J, Lohan MC (2010) River influence on shelf ecosystem: introduction and synthesis. J Geophys Res 115:C00B17. doi: 10.1029/2009JC005452 CrossRefGoogle Scholar