Purpose. The purpose of the study is to analyse the spectral structure of fluctuations in current velocities and sea level elevations in the Sea of Azov over a climatic period, to reveal the spatial and seasonal features of these fluctuations in the mesoscale and synoptic ranges (from hours to dozens of days), as well as to assess the intra-annual variability of current velocities in the central part of the sea.

Methods and Results. The primary research method consisted of numerical modeling which involved a unified hydrodynamic model taking into account the interrelationships between wind waves, currents, and sea level under shallow water conditions. The model was previously verified using the experimentally obtained sea state parameters. The required hydrodynamic parameters were calculated for a 46-year climatic period (1979–2024). The output data consisted of three-dimensional spatial fields of current velocity components and sea level in the Sea of Azov at a 1 h resolution. The main periods of hydrodynamic parameter oscillations – 0.5, 1, 3.6–4.2, 5.6–7.1, and 13.6–14.8 days – were identified based on spectral analysis. The energy of fluctuations increased with the period; two-week fluctuations were the most intense. The power of current velocity fluctuations in the surface layer was 2–3 times higher than that in the bottom layer. At periods exceeding one day, the velocity fluctuations of surface and bottom currents slightly dominated in spring, whereas sea level fluctuations at periods of 5.6–7.1 and 13.6–14.8 days were maximal in autumn, and those at periods of 3.6–4.2 days were maximal in spring. For all the parameters, diurnal fluctuations were maximal in summer, and semidiurnal ones in autumn. The spatial distribution of sea level fluctuations exhibited clear zonality: the highest amplitudes at periods exceeding 3 days were observed in the northeastern and southwestern parts of the sea, at diurnal periods in the eastern and western parts, and at semidiurnal periods in the southeastern and northwestern parts. In the central part of the sea, two peaks were well pronounced in the spectrum of the meridional velocity component: the annual (dominant) and semi-annual ones; in the zonal component, a 0.7-year period (∼ 260 days) was added to them. In the frequency spectra, the low-frequency fluctuations (∼ 2 and 4 years) were weakly pronounced.

Conclusions. The obtained spectral characteristics demonstrate the response of the shallow Sea of Azov to atmospheric forcing. The spatial and seasonal variability of fluctuations can be used both for verifying the hydrodynamic models and for assessing the climatic variability of currents in the region.