Nº 3 (2024)

Invasions of cold air masses into the atmosphere over the Black Sea in winter cause the intensive cooling of the surface water layer and contribute to the formation and development of a cold intermediate layer. Although such invasions are relatively rare, they regularly recur in winter. The article studies characteristics of the probability of cold invasions into the atmosphere of the Black Sea region. The article studies series of daily wind data, as well as data on sensible and latent heat fluxes and sea temperature in winter at various points in the west and east of the northern and central parts of the Black Sea. The cases of cold air masses invasion characterized by strong northerly winds were highlighted. The article considered statistical parameters of the winds in points characteristic of the north-westerly, northerly and north-easterly winds in the open central part of the sea and points in the coastal north-western and north-eastern regions. Wind roses and graphs of cumulative distributions were constructed for the offshore points which allowed determining the periods of recurrence of strong northerly winds in winter. A direct dependence of the magnitude of heat fluxes from the sea surface on the north wind speed in winter was revealed. It is shown that cold invasion led to seawater cooling as illustrated by the decrease in seawater temperature at the surface and at 50 m depth in 2012.

Based on numerical simulation, the paper studies the spatiotemporal distribution of CO₂ fluxes through the free surface of the Black Sea. The basic equation for solving this problem is the three-dimensional evolutionary transport–diffusion equation for the concentration of dissolved inorganic carbon. The simulation uses hydrodynamic fields resulting from a previous physical reanalysis as input parameters. A model of the lower level of the Black-Sea ecosystem food chain is used to describe the influence of biological factors on the dissolved carbon dioxide distribution. The concentration and equilibrium partial pressure of dissolved carbon dioxide in the sur-face layer of the Black Sea were calculated from the numerical simulation results. It is shown that the time dependence of these quantities is highly seasonal. The seawater temperature significantly affects the solubility of carbon dioxide and therefore its fluxes. The equilibrium partial pressure of carbon dioxide averaged over the area of the Black Sea is minimal in January–February and maximal in June–July. Accordingly, in the warm season, the flux of carbon dioxide is directed mainly from the sea to the atmosphere; in the cold season, the sea mainly absorbs carbon dioxide. Biological factors also influence the CO₂ content in the sea. Thus, at the beginning of the year, a high concentration of phytoplankton is observed almost throughout the entire Black Sea water area, which is why the absorption of carbon dioxide predominates during photosynthesis. In summer, the release of carbon dioxide predominates due to plankton respiration and oxidation of organic matter. The simulation results are in fairly good agreement with in situ measurements of the partial pressure of dissolved carbon dioxide obtained during scientific cruises.

Accumulative marine coastal forms of the Azov-Black Sea basin are a key element of coastal abrasion-accumulative geosystems and a valuable commercial resource. Monitoring of the accumulative forms dynamics in the region is a necessary component for successful management of the coastal zone and timely adoption of measures for coastal protection. The purpose of the work is to determine the qualitative and quantitative characteristics of the transformation of the Lake Bogaily Barrier Beach influenced by storms, in particular the extreme storm of November 26–27, 2023. The work uses materials from long-term monitoring observations, satellite images, simulation results of hydrological and lithodynamic processes, literary and archival sources. It was established that in the last 60 years the configuration and topography of the studied accumulative form have changed significantly. Periods were noted when the morphological and dynamic features of the accumulative form did not undergo fundamental changes as well as periods of their significant transformation. In particular, during the storm on November 26–27, 2023, the configuration and topography of the Lake Bogaily Barrier Beach was completely redesigned. The paper reveals characteristic features of the accumulative form dynamics during the storm. The accumulative body was displaced into the water area of the lake. The magnitude of this displacement significantly exceeded that of the retreat of the adjacent bedrock shores. The longitudinal and transverse structure within the barrier beach that existed for several decades has been completely transformed. It is concluded that any extreme storms play a decisive role in the variability of coastal accumulative forms in the region.

Artificial beaches are one of the most effective methods of protecting shores and hydraulic structures under shortage of natural beach-forming material. This work investigates the influence of extreme storms on the erosion zone width of an artificial pebble beach located in front of a vertical concrete seawall in the village of Koktebel (Feodosia, Crimea). The storm power index in the central part of Koktebel Bay was calculated on the basis of wind wave reanalysis data for 1979–2020 obtained using the SWAN spectral model and ERA-Interim and ERA5 surface wind fields. We identified 146 storm situations with duration of at least 12 hours. Three most extreme storms were analyzed: in terms of power index (660 m²×h), the storm of 26–29 January 1988; in terms of mean significant wave height (3.6 m), the storm of 10–11 November 2007; and in terms of duration (95 h), the storm of 25–29 September 2017. The profile deformations of the artificial pebble beach attached to a vertical concrete seawall were calculated for the first and second storms using a one-dimensional version of the XBeach (eXtreme Beach behavior) numerical model. It was shown, that under the impact of storm waves, the coast steepness near the coastline changes gradually and material from the beach nearshore part slid down the underwater slope leading to a local depth decrease near the shore. It was found, that the underwater erosion zone width of the beach was three times greater than the surface one. The most significant deformations of the beach profile occurred during the first 6 hours of storm action, and then the rate of beach deformation decreased. It was obtained that the coastline in the area of interest could retreat up to 10 m under the impact of an extreme storm. The study revealed that ≥ 20 m wide pebble beaches (a mean particle size of 30 mm) would fully absorb the wave energy of extreme storms and provide adequate protection for the coastal zone of Koktebel Bay.

For 2022–2023, the concentrations of trace elements (Be, V, Fe, Co, Ni, Cu, Zn, As, Se, Mo, Cd, Sb, Tl, Pb, Ag) were determined in the aquatic ecosystem of the North Crimean Canal, adjacent irrigated soils and cultivated irrigated agricultural crops. The content of all studied elements was determined in their acidic concentrates and mineralizates in accordance with State Standard of Russia 56219-2014 by mass spectrometry with inductively coupled plasma on a PlasmaQuant MS Elite mass spectrometer (AnalytikJena, Germany) on the basis of the collective use center “Spectrometry and Chromatography” A.O. Kovalevsky Institute of Biology of the Southern Seas of RAS. The concentrations of heavy metals and trace elements in the aquatic ecosystem of the North Crimean Canal allowed safe use of the Dnieper water both for drinking and for other economic needs of Crimea. The maximum relative increase in the heavy metals pool due to irrigation of fields with the Dnieper water was for Mo (up to 0.1 %), Zn, Sb and Pb (no more than 0.04 %), which cannot affect the ecological state of the irrigated lands. In soils, a systematic excess of the maximum permissible concentrations was observed for Cd (up to 230 %) both in rice and wheat fields as well as in virgin lands. In rice and wheat crops, the maximum permissible levels for grain and grain fodder for Fe, Ni, Cd, As were exceeded. In the wheat ear, maximum permissible levels were exceeded for Fe (by 24 %), Ni (by 110 %) and As (by 70 %). Maximum permissible concentrations in rice grain were exceeded for Cu (by 29 %), Cd (by 150 %) and Pb (by 438 %), and in wheat grain – for Cd (by 360 %) and Pb (by 300 %). It was revealed that insignificant amounts of trace elements brought with the Dnieper water through the North Crimean Canal cannot have a noticeable effect on the irrigated farmland of Crimea. The detected excesses of maximum permissible concentrations and maximum permissible levels of trace elements in soils and agricultural crops are probably due to the activities of industrial enterprises in the north of the peninsula.