Numerical model of the hydrodynamics of the Black Sea and the Sea of Azov with variational initialization of temperature and salinity

A numerical primitive-equation model of the hydrodynamics of the Black Sea and the Sea of Azov in σ-coordinates is proposed. The model has a resolution of ～4 × 4 km in horizontal coordinates with 40-σ levels in the vertical and includes the four-dimensional variational initialization of temperature and salinity fields. A numerical initialization algorithm combines splitting methods and adjoint equations. Flow, temperature, sea level, and salinity fields driven by atmospheric forcing are calculated for the year 2008. The calculations are made in a variational initialization — prediction regime. Temperature and salinity fields are initialized at the end of each month. The optimality system includes forward and adjoint transport-diffusion equations for heat and salt that are linearized on the assimilation interval. Results of three numerical experiments with different sets of assimilated data in comparison with the prediction obtained from the forward model are discussed.     

Modelling of the Sea of Azov ecosystem

The method of mathematical model self-organization is applied to handle observations of the hydrological, chemical and biological parameters of the Sea of Azov, conducted from 1926 through to 1985, in order to identify model equations of the latter's ecosystem. A set of 43 evolutionary equations have been employed to generate a picture of the ecosystem parameters' continuous variability and to identify relationships between them. Model calculations of the total catch of freshwater fishes, primary productivity, zoobenthos, phytoplankton, and other characteristics have demonstrated their being in good agreement with the observations conducted from 1950 to 1985. A prediction of the ecosystem parameters' evolution for the period from 1985 to 1995 has been made. Translated by Vladimir A. Puchkin.     

Experimental studies of the deep turbid layer in the Black Sea

Data compiled in the course of hydro-optical studies are reported. The main interest is focused on the problem of the existence of a deep turbid layer (DTL) over the continental slope, where it is better pronounced than in the central Black Sea. Analysis of the collected data allows a supposition as to the relationship between the DTL structure and the peculiarities of water dynamics.Translated by Vladimir A. Puchkin.     

Mathematical modeling of the terrigenous sedimentation in the Sea of Azov

Based on balance calculations with the use of a spatially detailed mathematical model for transport and sedimentation of the particulate matter adjusted to the conditions of the Sea of Azov, particular spatiotemporal features of the terrigenous sedimentation in the second half of the 20th century are recognized. The general tendency for the deceleration of the accumulation of terrigenous sediments and for the decrease in the areas with a negative balance of the terrigenous matter is related to the 2.5-fold fall in the volumes of the matter supplied from land. During the period considered, the intensity of the sedimentation decreased from 1000 to 400 g/m²/year. The accumulation of terrigenous sediments proceeds in the regions where the sources of the matter supply are concentrated and where features of the bottom morphology and hydrodynamical activity are favorable for the sedimentation: in Taganrog and Temryuk bays. In the central part of the sea, the intensity of the sedimentation comprises a value of about 300 g/m²/year. In Taganrog Bay and in the sea proper, areas with a negative balance of terrigenous sedimentary matter increased up to 30%.     

Numerical study of the Azov Sea level seiche oscillations

Seiche oscillations of the Azov Sea level are studied on the basis of the developed two-dimensional numerical hydrodynamic model grounded on the shallow water theory and recent data on the morphometric characteristics of the Sea of Azov. Frequency and spatial characteristics of the first five modes corresponding to seiche oscillations of the Azov Sea level are computed. It is shown that the frequency and spatial characteristics of the first five modes obtained for the Sea of Azov level changes correspond to seiche oscillations. The calculated parameters are compared with the field observations, which show their realistic character.     

Petroleum hydrocarbons and particulate organic matter in the Sea of Azov waters

The paper discusses the results of investigations on contamination of the Sea of Azov by petroleum hydrocarbons and particulate organic matter. After cessation of open sea observations in 1992, the contamination of the sea by petroleum hydrocarbons is predicted for the period from 1993 to 1997. Translated by Vladimir A. Puchkin.     

Changes in Salinity and Species Composition of Ichthyofauna in the Sea of Azov

Oceanology - Impact of salinity changes on the composition of the Sea of Azov ichthyofauna is considered. To date, not only the quantitative, but also the qualitative composition of ichthyofauna...     

Temporary ice microalgae community in Taganrog Bay of the Azov Sea

The temporary ice algae community in the mixing zone of brackish and fresh waters of the Taganrog Bay of the Azov Sea is described. A high abundance and biomass of planktonic algae and a high chlorophyll a concentration have been registered in samples of under-ice water taken on February 2013. The mass development of the diatom Stephanodiscus hantzschii Grunow blooming on the ice in the eastern part of Taganrog Bay is described for the first time. The quantitative data on the under-ice microalgae community and the related hydrochemistry are published. The obtained results could be used in total productivity estimates in the Azov Sea.     

Investigation of the characteristics of surge phenomena in the Sea of Azov

We present the results of numerical simulation of currents and sea level for the Sea of Azov. In calculations, we use a three-dimensional nonlinear mathematical model taking into account the tangential wind stresses. We present the results of numerical analysis of the fields of currents and the amplitudes of oscillations of the sea level at the coastal stations as functions of the maximum velocity and the period of constant action of the west wind. __________ Translated from Morskoi Gidrofizicheskii Zhurnal, No. 1, pp. 12–25, January–February, 2008.     

Currents of the Azov Sea during the Don River Low-Water Period

Oceanology - The water exchange between the Black Sea and the Azov Sea is investigated on the base of the marine observations aboard the R/V Deneb in 2018 and 2019. The surveys were conducted under...     

A model of the dynamics of the ecosystem of the Sea of Azov

We use many-year archival observations of hydrologic and hydrobiologic state of the Sea of Azov for the identification of the structure of a model of its ecosystem. The ecosystem model, supplemented with expert estimates of bioresource consumption (fish reserve), contamination level, and possible ecologic fines for violation of the sea natural state, is formalized by the method of system dynamics. Hereat, the major part of influence functions is found in terms of observational data with application of self-organization algorithms. We also present the results of simulated experiments with the model of the ecosystem, which enable us to analyse scenarios of its behaviour under the influence of various external factors (wind, river discharge, water exchange with the Black Sea, etc.). Translated by Peter V. Malyshev and Dmitry V. Malyshev     

Specific features of temporal and spatial distributions of light hydrocarbons in the Sea of Azov

New data from recent surveys investigating the geochemistry of light hydrocarbons over a 4-year period in the Chernomorneftegaz petroleum license area in the central Sea of Azov are presented in this paper. The distributions of light hydrocarbons in both marine sediments and seawater were studied, and stable anomalies of hydrocarbons detected. Based on complex interpretations of geochemical and geophysical data, it has been shown that migration from the deep part of the sediment cover to the surface (seabed) is the main factor which determines the spatial distribution of hydrocarbons in the modern seabed sediments and seawater. The contribution of microbial and anthropogenic processes is insignificant.     

刻赤海峡和亚速海的生成年代

为了普查和勘探陆架上的新油田和固体矿产,研究俄罗斯南部海洋具有非常现实的意义。正是在这里,解决着亚速海一黑海盆地的地层和古地理,以及与同时代形成的地中海和里海沉积层对比的主要问题。     

Simulation of seiche oscillations in the Sea of Azov,using the finite element technique

A mathematical model based on the finite element technique is applied to study seiche oscillations in the Sea of Azov in an approximation of the linear theory for long waves. The model has been used to compute periods of the initial ten seiche modes.Translated by Vladimir A. Puchkin.     

Vertical transport in the Black Sea

Investigations of the vertical exchange coefficientK _z , considering turbulent and advective transport, are summarized. The values ofK _z are determined from the climaticT, S characteristics, heat and salinity fluxes, and the rate of the low-Bosporus water transformation over the entire Black Sea water column; namely, in the upper mixed layer, the active layer, the cold intermediate layer, the halocline, and in the deep and near-bottom waters. A characteristic for annual fluctuations ofK _z in the active layer is given; it is noted that the coefficient tends to grow in transit from the centre of the cyclonic gyre toward its periphery.Translated by V. Puchkin.     

Distribution of macroalgae and seaweed in the Azov Sea,Kerch Strait,and Taman Bay

The analysis of the macroalgae distribution along the salinity gradient in the Azov Sea, the Kerch strait, and Taman Bay during the summer allowed finding two macroalgae complexes. The first complex (brackish) is formed by algae belonging to the Enteromorpha, Cladophora, Rhizoclonium, and Chaetomorpha genera in the Taganrog Gulf. The second complex (marine) with dominating algae belonging to the Enteromorpha, Chaetomorpha, Ceramium, and Polysiphonia inhabits the littoral part of the Azov Sea itself, the Kerch Strait, and Taman Bay. The saprobe analysis of the flora showed that the majority of macroalgae species inhabiting the Azov Sea are represented by meso- and polysaprobes and a small number of oligosaprobe species inhabit the Kerch Strait. The biggest species diversity of macroalgae was noted in the southwestern part of the sea; the value of Shannon’s index was 0.65 in the Taganrog Gulf, 1.04 in the Azov Sea, 1.38 in Taman Bay. The leading role in the littoral communities of Taganrog Gulf belongs to aquatic flowering plants with Potamogeton perfoliatus being dominant; as the salinity increases, the share of such species as P. pectinatus, Zostera marina, Z. noltii, Ruppia maritime, and Zannichellia major starts to increase.     

Long-term variability of the water transparency (Secchi Depth) in the Sea of Azov

The spatial, seasonal, and interannual variability of the water’s transparency (Secchi depth) in the Sea of Azov is studied using the database of long term transparency measurements for the 1922–2009 period and relevant materials on the meteorological, hydrological, and hydrobiological parameters of the environment. We identified four main types of seasonal variability of the water’s transparency depending on the local conditions. The mean values of the Secchi depth are calculated for the different periods, which are distinguished by the differences in the relative role of the water transparency factors associated both with the climatic variations and the human activities.