Seiche Oscillations in the Sea of Azov Based on Tide Gauge Observations

The Sea of Azov is one of the most isolated and shallowest seas in the World Ocean. It can be considered as a closed basin for mesoscale processes. Due to the absence of strongly pronounced induced oscillations, the main mesoscale process is seiches. The present study is based on long-term hourly data from 14 coastal tide gauges of the Sea of Azov. A high quality of the data allows performing spectral analysis and studying the features of the natural oscillations of the basin. The following seiche periods were detected at almost all the coastal stations: 14.1, 6.7, and 3.2 hours. For some stations, periods of 22.5, 11.6, 5.8, 4.9, and 4.2 hours were revealed. Their spatial structure was estimated by the cross-spectral analysis: an assumption was made about the presence of a nodal line at the entrance to the Taganrog Bay and antiphase oscillations in the southwestern and northeastern parts of the sea. The absence of some periods of natural oscillations, which were discovered by numerical modelling, in the spectra indicates a poor manifestation of the corresponding modes in real natural conditions.