Parameterization of Solar Radiation Absorption by Snow–ice Cover in the Thermodynamic Sea Ice Model of the Sea of Azov

Purpose. The work is aimed at assessing the influence of choice of the parameterization scheme of the snow and ice radiation features upon reproduction of seasonal evolution of the snow–ice cover thickness and temperature distribution in it in the Taganrog Bay top part. Methods and Results. Thermal seasonal dynamics of the snow–ice cover thickness in the northeastern part of the Taganrog Bay was studied using a non-stationary thermodynamic model of sea ice. The model reproduces formation of ice and accumulation of snow on its surface, spatial-temporal change in their thermophysical characteristics, melting of the snow–ice cover, vertical distribution of temperature, and solar radiation absorbed in its thickness at a preset timed data on the meteorological parameters. In the numerical solution of the heat conductivity equation for snow and ice including a radiation source, a computational grid permitting to maintain spatial resolution of the temperature profiles in the snow–ice cover during its melting and growth was applied. Two variants of parameterization of solar radiation transfer in the sea ice were considered. The first version assumed exponential decay of radiation with the constant transmittance and extinction coefficients. In the second one, a two-layer scheme of the solar radiation penetration into ice was used; it simulated the near-surface transition layer. Attenuation of intensity of solar radiation in the snow thickness was described by the Bouguer–Lambert law with the extinction coefficient both as independent of the snow thermophysical characteristics and as represented by the function of its density. The numerical experiments with the purpose to reproduce seasonal evolution of the snow–ice cover thickness and its vertical temperature profile in the Taganrog Bay top part were performed for the winter season, 2016/17. Comparative analysis of the simulation results and the sea ice thickness values taken from the ESIMO ice maps made it possible to choose a combination of the model parameters that provides the best correspondence between the calculated and actual values. Conclusions. It is shown that in reproducing the seasonal changes in the ice cover thickness in the Taganrog Bay top part in winter, 2016/17, the choice of the transmittance and extinction coefficients for white ice represented by the cloudiness functions, on the one hand, and the thickness of the layer with the most intense absorption of short-wave radiation ~ 4 cm, on the other, turned out to be the most justified.

Numerical Study of the Process of Salt Water Inflow to the Don Mouth from the Taganrog Bay

Purpose. Numerical study based on the model example is aimed at examining the process of the salt water inflow to the Stary Don sleeve from the Taganrog Bay due to the wind water surge. Methods and Results. Complex mathematical model of the flow and salt distribution in the open riverbed is described. The section of the River Don, consisting of the Stary Don sleeve and a part of the main channel was considered. Salt is delivered through the host reservoir – the Taganrog Bay. The model is described by the system of Saint-Venant equations and the convection-diffusion equation. The problem is solved by the finite-difference methods. The results of the numerically studied influence of the sea surface level in the Taganrog Bay both on the flow nature in the Don Delta area and the degree of salt penetration upstream of the river are obtained. It was numerically established that the flow rate did not significantly affect salt concentration in the Don main channel. Conclusions. The computational experiments showed that the decisive factor in the process of the salt water inflow to the Don Delta from the Taganrog Bay consisted in the sea level significant increase resulting from extreme wind surges; and the preceding runoffs enhanced this effect even greater. The represented model gives an idea of the general trend in the process of the Don Delta possible salinization as a result of the surge phenomena.

Numerical Study of the Process of Salt Water Inflow to the Don Mouth from the Taganrog Bay

Purpose. Numerical study based on the model example is aimed at examining the process of the salt water inflow to the Stary Don sleeve from the Taganrog Bay due to the wind water surge. Methods and Results. Complex mathematical model of the flow and salt distribution in the open riverbed is described. The section of the River Don, consisting of the Stary Don sleeve and a part of the main channel was considered. Salt is delivered through the host reservoir – the Taganrog Bay. The model is described by the system of Saint-Venant equations and the convection-diffusion equation. The problem is solved by the finite-difference methods. The results of the numerically studied influence of the sea surface level in the Taganrog Bay both on the flow nature in the Don Delta area and the degree of salt penetration upstream of the river are obtained. It was numerically established that the flow rate did not significantly affect salt concentration in the Don main channel. Conclusions. The computational experiments showed that the decisive factor in the process of the salt water inflow to the Don Delta from the Taganrog Bay consisted in the sea level significant increase resulting from extreme wind surges; and the preceding runoffs enhanced this effect even greater. The represented model gives an idea of the general trend in the process of the Don Delta possible salinization as a result of the surge phenomena

Potentially toxic elements in floodplain soils the Don River basin of Southern Russia

<p>Large rivers and their deltaic parts and adjacent coastal zones are subjected to strong anthropogenic influence and are often considered as hotspots of environmental pollution. The Don River basin is a highly urbanized area with developed agriculture and industry which negatively affect water quality, aquatic ecosystems and soils. The main objectives of the proposed research were to determine the levels of potentially toxic elements (PHEs) in soils of various aquatic landscapes of the study area, as well as to reveal the relationships between the content of exchangeable PTEs and the physical-chemical properties of floodplain soils.</p><p>Depending on the soil-landscape and hydrological conditions and taking into account the intensity of anthropogenic influence, the following zones were identified: the lower Don floodplain from the Tsimlyansk Reservoir to the source of the Mertvy Donets River, Don Delta, the coastal zone of the Taganrog Bay, the mouths of small rivers flowing into the bay, and Taganrog city, an industrial port center on the northern coast of the bay.</p><p>The floodplain and coastal landscapes of the study area are dominated by Fluvisols. Solonchaks, Arenosols and Haplic Chernozems which are background soils of the region are less common. Soil samples were collected in summer 2020 from the surface soil horizon (0–20 cm deep). The particle size analysis was conducted using the pipette method; the total organic carbon content in the soils was determined using the dichromate oxidation; the pH was measured by potentiometry in the supernatant suspension of soil and water in a ratio of 1:2.5. The total concentrations of Cr, Mn, Ni, Cu, Zn, Cd, and Pb were determined by X-ray fluorescence analysis using a Spectroscan MAX-GV spectrometer (Spectron, Russia), and the content of exchangeable forms extracted from the soil by NH4Ac buffer solution with pH 4.8 and soil/solution ratio of 1:10 for 18 h was determined by atomic absorption spectrophotometry.</p><p>The obtained results showed that soils of the Lower Don and Taganrog Bay coastal zone are rather contrasted in terms of properties and metal contents, which indicates the variability of landscapes, natural and anthropogenic processes in the studied systems. High CV values for Pb, Zn, Cd and Cr indirectly indicate strong anthropogenic influence on these environments. The results of PCA analysis showed that there are two association of metals in terms of geochemical behaviour and sources. The first one included Cr-Zn-Pb-Cd, the elements of anthropogenic origin, the second Mn, Ni, and Cu, which are probably of mixed origin. The obtained results showed that the coastal zone is a diverse and complex system subjected to anthropogenic activities, which is pronounced in the enrichment of aquatic soils with a number of metals and higher proportions of exchangeable forms from different types of sources.</p><p>This work was funded by the Russian Science Foundation, grant no. 20-14-00317.</p>

ASSESSMENT OF THE DEVELOPMENT OF MODERN GEOECOLOGICAL PROCESSES ON THE COAST OF THE TAGANROG BAY OF THE AZOV SEA (WITHIN THE BOUNDARIES OF THE CITY OF TAGANROG, ROSTOV REGION)

The study of the geoecological problems of the coastal zone of the Taganrog Bay is still not given due attention by the administrative authorities. Although it is the deterioration of the geoecological situation that deserves special attention. In this regard, the assessment of the development of modern ecological and geological processes is an urgent task. The coast of the Taganrog Bay has an exceptionally advantageous geographical position, and has a significant natural resource potential, which contributes to the development of various types of economic activities and causes a deep transformation of the natural complex of the coastal zone

ON TWO MODELS RELATED TO THE FLOODING AND DEPOSITION OF THE DON DELTA

The results of modeling changes in the water surface level in the eastern part of the Taganrog Bay and the main Don branches in its delta area are presented. A numerical study of the process of saltwater inflow from the Taganrog Bay to the Don delta has been carried out. The hydrodynamics in the Taganrog Bay, as well as the saltwater transport process, are specified using the corresponding two-layer models. A system of Don arms is presented in the form of a graph, the edges of which correspond to open channels, and the vertices correspond to branching points and end nodes. The flow in the main Don branches is described by the Saint-Venant equation. It is assumed that there is no distributed lateral inflow, and the channel cross-section has a parabolic profile. Saltwater inflow into the arms is described by a one-dimensional transport equation. Boundary conditions are specified for each sleeve. At the branching nodes, conditions are set for the equality of the water levels, as well as the equality of the inflowing and outflowing discharges. The description of the algorithm of the process of flooding/drainage of the Don delta area is given. Considering the values of the depths at the nodes of the flat grid, the cells located in water or on land are determined. A logical array characterizing the type of cells (“water”, “land”) sets the configuration of the entire computational domain. Comparison of the calculation results with the observed values of salinity and water level is carried out.

Fast ice dynamics of the sea of Azov in the XXI centure

The article is dedicated to the investigation of the fast ice dynamics for the period 2000–2020 according to satellite data and field observations using GIS technologies. We used data from International Data Center – Sea Ice and coastal observation points to analyze long-term changes. Data processing and analysis was carried out using the ArcGIS 10.4 software package. As a result, data were obtained on the spatial and temporal variability of fast ice in the Sea of Azov for the 2000–2020. The area and width of fast ice, the periods of formation, destruction and duration were analyzed. The maps of the fast ice formation frequency were constructed for each month of the winter period: December–March. It is shown that the duration of fast ice on all coastal observation points decreased: for points on the northern coast Taganrog and Mariupol—by 3–5 days, for points on the southern coast of Taganrog Bay—Yeisk and Dolzhanskaya—by 10–12 days, for point Genichesk—7 days. Average long-term fast ice area for 2000–2020 is 1800 km2. But against the background of an increase in winter air temperatures, the fast ice area is decreasing, and in the last winter periods it is not observed. The width of the fast ice at the northern coast of the Sea of Azov and the Taganrog Bay is 5–10 km. In the western and southeastern parts of the sea (sections Temryuk, Arabatskaya and Obitochny), the fast ice width is 2–5 km on average over the winter and was observed in 25 % of cases.