Water exchange of the Azov Sea according to the data of measurements in 2021

The paper presents the results of marine expeditionary research aboard the R/V Deneb of the Southern Scientific Centre of the Russian Academy of Sciences in the Sea of Azov in November and December 2021. Investigations covered the areas of inflow of river (Taganrog, Temryuk bays), as well as the Black Sea (Kerch Strait) waters. Measurements of the currents and parameters of the thermohaline structure were carried out onboard the vessel using an Aanderaa RCM 9 LW current recorder, additionally equipped with pressure, temperature, and conductivity sensors. The considered data expand the understanding of the nature of the sea water circulation. Measurements of the currents of the Kerch Strait were carried out with an east-north-east wind at a speed of 8 m/s. Despite of the intense northern current (up to 28 cm/s), the salinity turned out to be lower than the values typical for the Sea of Azov. In the Temryuk Bay, cyclonic circulation cells 10-15 km in diameter were found. Measurements carried out in December 2021 twice recorded different phases of seiche fluctuations in the eastern part of the Taganrog Bay of the Sea of Azov. Velocity maxima near the bottom were recorded in both cases. In the period from December 1 to December 4, the wind of the southern component was observed, on December 5 there was a change to the north-north-east wind, and the currents acquired a pronounced compensatory character. It has been established that the Black Sea current of the Kerch Strait most often develops with the winds of the eastern component. The Ekman purely drift current from the southern and northern sides of the Kerch Strait is complicated by a number of factors, among which seiches can play a very important role. The closed shape of the basin limits the development of wind currents, compensatory countercurrents are formed. The nodal lines, under the influence of the Coriolis force, acquire a rotating character, masses of water, dissolved salts and suspensions are transferred. Seiches, depending on the phase, can both strengthen and weaken the currents of the Kerch Strait, blocking water exchange. This function of the natural oscillations of the Sea of Azov significantly distinguishes the Sea of Azov from water bodies - analogs, where either density currents are formed or tides prevail.