Numeric hydrodynamic model of tidal phenomena in the Keret Bay (Kandalaksha Bay, White Sea)
In the current paper the model of Keret Bay is described based on algorithms of famous numerical hydrodynamic model POM (Princeton Ocean Model). Numerical experiments with various types of the open boundary conditions show that the model skill score of small tidal basins is fully determined by open boundary conditions. The use of the tidal sea level oscillation at open boundary condition gives insufficient results. The best skill score is achieved by setting the radiation open boundary condition while using current and sea level data. In this case, a comparison of the model-based results and sea level and current measurements shows the best agreements: the correlation coefficient between the modeled sea level and the measurements is up to 1, and the correlation coefficient between the simulated and observed currents equals to 0.9. The root-mean-square error (RMSE) is 2 times smaller than permissible error, both for sea level and currents. The analysis of the model results shows that sea level changing occurs at all area synchronically, but there is a several minutes time-lag between high water at Podpakhta Strait and Lebyazhya Bay and high water at Keret Bay. The parameters of the tidal ellipses of 16 constituents were calculated using the harmonic analysis. It was found that for a period of one month the maximal velocities of tidal currents (up to 80 cm/s) are noted in narrow and shallow parts of Podpakhta Strait. In the Keret Bay the maximal velocities of tidal currents exceed 30 cm/s at narrow places of Srednyaya Salma and Uzkaya Salma straits. Tidal currents have basically reverse character. The residual tidal phenomena were estimated by averaging the model results of sea level and currents. The residual tidal level almost completely coincides with the mean sea level. The field of residual tidal circulation contains cyclonic vortices in the Lebyazhya Bay, Podpakhta Strait and in central part of Keret Bay. Residual vortices in the Lebyazhya Bay and Podpakhta Strait have significant velocities and can form common circulation in those basins. For Keret Bay, the inter-tidal zones areas and their temporal variabilities are calculated by numerical model. In the future, the described model can be used to discover distribution of river water, formation of thermohaline structures, to calculate pollution and plankton transits.