Numerical modelling of the tides in the Caspian Sea

Abstract. The Caspian Sea is the largest enclosed basin on the Earth and a unique object for analysis of tidal dynamics. The Caspian Sea has independent tides only, which are generated directly by tide-forming forces. Based on the Princeton Ocean Model (POM) the spatial and temporal features of tidal dynamics in the Caspian Sea were described in detail. Detailed tidal charts for amplitudes and phase lags of the major tidal harmonics, form factor, tidal range and velocity of tidal currents were plotted. Semidiurnal tides in the Caspian Sea are determined by a Taylor amphidromic system with counterclockwise rotation. The largest M2 amplitude is 6 cm and is located in the Turkmen Bay. The Absheron Peninsula splits this system into two separate amphidromies with counterclockwise rotation to the north and to the south of it. The maximum K1 amplitudes (up to 0.7–0.8 cm) are located in: (1) the southeastern part of the Caspian Sea, (2) the Turkmenbasy Gulf, (3) the Mangyshlak Bay, and (4) the Kizlyar Bay. The semidiurnal tides prevail over diurnal tides in the Caspian Sea. The maximum tidal range has been observed in the Turkmen Bay, up to 21 cm. The highest velocity of the total tidal currents is observed in the straits to the north and south of Ogurja Ada, up to 22 cm/s and 19 cm/s, respectively. Were made numerical experiments with tidal simulation using different mean sea level MSL of the Caspian Sea (from −25 m to −30 m). Numerical experiments indicate that the spatial features of tides are strongly sensitive to the MSL changes.