Water exchange between the Sea of Azov and the Black Sea through the Kerch Strait

Abstract

The Sea of Azov is a small, shallow, and freshened sea that receives a large freshwater discharge. Under certain external forcing conditions low-salinity waters from the Sea of Azov flow into the north-eastern part of the Black Sea through the narrow Kerch Strait and form a surface-advected buoyant plume. Water flow in the Kerch Strait also regularly occurs in the opposite direction, which results in the spreading of a bottom-advected plume of saline and dense waters from the Black Sea into the Sea of Azov. In this study we focus on the physical mechanisms that govern water exchange through the Kerch Strait and analyse the dependence of its direction and intensity on external forcing conditions. Analysis of satellite imagery, wind data, and numerical modelling shows that water exchange in the Kerch Strait is governed by a wind-induced barotropic pressure gradient. Water flow through the shallow and narrow Kerch Strait is a one-way process for the majority of the time. Outflow from the Sea of Azov to the Black Sea is induced by moderate and strong north-easterly winds, while flow into the Sea of Azov from the Black Sea occurs during wind relaxation periods. The direction and intensity of water exchange have wind-governed synoptic and seasonal variability, and they do not depend on the rate of river discharge to the Sea of Azov on an intraannual timescale. The analysed data reveal dependencies between wind forcing conditions and spatial characteristics of the buoyant plume formed by the outflow from the Sea of Azov.Published by Copernicus Publications on behalf of the European Geosciences Union.

Water Exchange Between the Gulf of Ob and the Kara Sea During Ice-Free Seasons: The Roles of River Discharge and Wind Forcing

“…The observed variability of salinity is 30-33, which corresponds to variability of density 1,024-1,027 kg/m 3 , i.e., ∼0.3% of relative variation. The role of the barotropic pressure gradient typically dominates the role of the baroclinic pressure gradient in water exchange processes in large estuaries (Osadchiev, 2017;Zavialov et al, 2020).…”

Influence of estuarine tidal mixing on structure and spatial scales of large river plumes

“…As a result, dynamics and variability of river plumes are key factors for understanding mechanisms of spreading, transformation, and redistribution of continental discharge and river-borne constituents in coastal seas and their influence on adjacent continental shelves (Geyer et al, 2004;Hickey et al, 2010;Hetland and Hsu, 2013). World river plumes are characterized by wide variety of structure, morphology, and dynamical characteristics caused by large differences in regional features (Chant, 2011;Horner-Devine et al, 2015;Osadchiev and Korshenko, 2017;Osadchiev and Sedakov, 2019;Zavialov et al, 2020), in particular, estuarine conditions (Guo and Valle-Levison, 2007;Nash et al, 2009;Lai et al, 2016;Osadchiev, 2017).…”

Dissolved Methane in Coastal Waters of the Northeastern Black Sea

“…The wind-dependent character of the water exchange between the Sea of Azov and the Black Sea [15] may be the reason that in May 2016 we did not record a peak of methane concentrations near the southeastern coast of the Crimean Peninsula (Figure 9). This distribution graph illustrates the general trend of an increase of methane content when approaching the coast, which was also noted in measurements on sections of previous years.…”

“…Moreover, this runoff can significantly increase during and shortly after intense precipitation events, which can occur in the considered area in all months of the year with maximal amounts in June, thereby strongly influencing water quality and causing active sediment load at large segments of the shelf [13]. On the other hand, the inflow of the Azov Sea water through the Kerch Strait to the Anapa shelf and southeastern shelf of the Crimean Peninsula [14,15] contributes to sediment, nutrient, and pollutant loading [16]. Recent studies [17,18] showed the spatiotemporal distribution of methane content in the northeastern Black Sea from the Kerch Strait to Sochi and from the coast to the border of the Russian economic zone, revealing the seasonal dependence of the intermediate aerobic maximum of methane content.…”