Dynamics and energetics of surface and internal semidiurnal tides in the White Sea

Surface and internal tides are calculated using the three-dimensional nonlinear finite-element thermohydrodynamic model QUODDY-4, which can reproduce all known features of the spatial structure of the surface wave M, in the White Sea. It is also found that, in the White Sea, there are two sources of internal tidal waves (ITWs): the first is located north of the inlet to Onega Bay, where the bottom slopes are critical or supercritical, and the second is located at the outlet from the White Sea Throat, where the bottom slopes are subcritical, but the barotropic velocities are much higher than at the gate to Onega Bay. The ITWs have amplitudes of up to similar to 8 m and dissipate locally, having no time to propagate far beyond their sources. This is explained by the closeness to the critical latitude and, consequently, by a marked decrease in the velocity of ITW energy transfer. There are two more characteristic features of ITWs in the White Sea. The first is that the peak baroclinic velocities are located roughly along the characteristics, which serves as an indicator of a coherent ray pattern. The second feature is a single-mode (corresponding to the first baroclinic mode) vertical structure of the baroclinic velocity and components of the local budget of baroclinic tidal energy. Variations in the integral (over area) components of the baroclinic and barotropic tidal-energy budget during a tidal cycle are presented. It was shown that, the cycle-mean integral rate of barotropic-to-baroclinic energy conversion is 2.54 x 10(7) W and the density of the total baroclinic tidal energy is 98 J m(-2). These values are significantly lower than similar estimates attributed to areas of continental slopes, seamounts, ridges, and islands of the open ocean.