Thermohaline Structure of Waters and Oxygen Content in the Cold Intermediate Layer in the Coastal Water Areas of Crimea (Black Sea)

E. E. Sovga✉, T. V. Khmara, S. K. Konovalov

Marine Hydrophysical Institute of RAS, Sevastopol, Russian Federation

✉ e-mail: esovga@mhi-ras.ru

Abstract

Purpose. The purpose of the study is to assess changes in the thermohaline structure and oxygen content in the cold intermediate layer (CIL) of the coastal shelf waters along the Southern Coast of Crimea in 1986–2000 and 2007–2023.

Methods and Results. A dataset comprising 13,286 measurements of temperature, electrical conductivity and hydrostatic pressure was analyzed. The measurements were conducted at two polygons (Goluboy Bay, including the Katsiveli oceanographic platform, and Yalta Bay) using the Sea-Bird 911plus CTD probe (Sea Bird Electronics, USA) in 1986–2000 and 2007–2023, and the IDRONAUT OCEAN SEVEN 320Plus M hydro-chemical sounding CTD complex in 2022–2023. For the first time in the Crimean shelf waters, an increase in dissolved oxygen content within the CIL has been identified, despite rising water temperature and density over the past 15 years, based on the data averaged across two periods (spanning ~ 40 years). In 1986–2000, the average temperature in the CIL core did not exceed 8 °C, whereas in 2022–2023, values ranged from 8.1 to 8.9 °C. The average density at 100 m depth increased from 14.57 to 15.25 kg/m3.

Conclusions. For the first time, the long-term dynamics of dissolved oxygen content in the CIL have been characterized for the Crimea shelf water areas. The results indicate that the response of the shelf ecosystem of the Southern Coast of Crimea to external impacts (climatic changes) is more pronounced than in the deep sea. Even a minor absolute increase in water temperature and density has been accompanied by substantial restructuring of the hydrological structure and anomalies in CIL formation. The reasons for the anomalies in the Southern Coast of Crimea require further study.

Keywords

cold intermediate layer, long-term dynamics, thermohaline structure, conditional density, dissolved oxygen, shelf area of the Southern Coast of Crimea

Acknowledgements

The study was conducted as part of the state assignment of FSBSI FRC MHI under themes FNNN-2024-0001 “Oceanological Processes” and FNNN-2024-0016 “Coastal Research”.

Original russian text

Original Russian Text © E. E. Sovga, T. V. Khmara, S. K. Konovalov, 2025, published in MORSKOY GIDROFIZICHESKIY ZHURNAL, Vol. 41, Iss. 6, pp. 719–731 (2025)

For citation

Sovga, E.E., Khmara, T.V. and Konovalov, S.K., 2025. Thermohaline Structure of Waters and Oxygen Content in the Cold Intermediate Layer in the Coastal Water Areas of Crimea (Black Sea). Physical Oceanography, 32(6), pp. 743-754.

References

  1. Ivanov, V.A. and Belokopytov, V.N., 2013. Oceanography of the Black Sea. NASU of Ukraine, MHI, 210 p.
  2. Belokopytov, V.N., 2010. Interannual Variations of the Renewal of Waters of the Cold Intermediate Layer in the Black Sea for the Last Decades. Physical Oceanography, 20(5), pp. 347-355. https://doi.org/10.1007/s11110-011-9090-x
  3. Ovchinnikov, I.M. and Popov, Yu.I., 1987. Evolution of the Cold Intermediate Layer in the Black Sea. Oceanology, 27(3), pp. 555-560.
  4. Stanev, E.V., Peneva, E. and Chtirkova, B., 2019. Climate Change and Regional Ocean Water Mass Disappearance: Case of the Black Sea. Journal of Geophysical Research: Oceans, 124(7), pp. 4803-4819. https://doi.org/10.1029/2019JC015076
  5. Masevich, A.V. and Konovalov, S.K., 2022. Oxygen Dynamics during the Period of Dystrophic Processes in the Black Sea. Physical Oceanography, 29(1), pp. 83-97. https://doi.org/10.22449/1573-160X-2022-1-83-97
  6. Ivanov, L.I., Beşiktepe Ş. and Özsoy E., 1997. The Black Sea Cold Intermediate Layer. In: E. Özsoy, and A. Mikaelyan, eds., 1997. Sensivity to Change: Black Sea, Baltic Sea and North Sea. NATO ASI Series; vol. 27. Dordrecht: Kluwer Academic Publishers, pp. 253-264. https://doi.org/10.1007/978-94-011-5758-2_20
  7. Oguz, T., Besiktepe, S., Ivanov, L.I. and Diacanu, V., 1997. On the ADCP-Derived Rim Current Structure, CIW Formation and the Role of Mesoscale Eddies on the CIW Transport in the Black Sea: Results from April 1993 Observations. In: L. I. Ivanov and T. Oguz, eds., 1997. NATO TU-Black Sea Project: Ecosystem Modeling as a Management Tool for the Black Sea. Environmental Security. NATO ASI Series; vol. 47. Dordrecht: Kluwer Academic Publishers, pp. 93-118.
  8. Oguz, T. and Beşiktepe, Ş., 1999. Observations on the RIM Current Structure, CIW Formation and Transport in the Western Black Sea. Deep-Sea Research Part I: Oceanographic Research Papers, 46(10), pp. 1733-1753. https://doi.org/10.1016/S0967-0637(99)00028-X
  9. Stanev, E.V., Bowman, M.J., Peneva, E.L. and Staneva, J.V., 2003. Control of Black Sea Intermediate Water Mass Formation by Dynamics and Topography: Comparison of Numerical Simulations, Surveys and Satellite Data. Journal of Marine Research, 61(1), pp. 59-99. https://doi.org/10.1357/002224003321586417
  10. Polonsky, A.B. and Popov, Yu.I., 2011. [Conditions for the Formation of Cold Intermediate Layer Waters in the Black Sea]. Sevastopol: NASU, 54 p. (in Russian).
  11. Kuklev, S.B., Zatsepin, A.G. and Podymov, O.I., 2019. Formation of the Cold Intermediate Layer in the Shelf-Slope Northeastern Part Zone of the Black Sea. Journal of Oceanological Research, 47(3), pp. 58-71. https://doi.org/10.29006/1564-2291.JOR-2019.47(3).5 (in Russian).
  12. Podymov, O.I., Zatsepin, A.G. and Ocherednik, V.V., 2021. Increase of Temperature and Salinity in the Active Layer of the North-Eastern Black Sea from 2010 to 2020. Physical Oceanography, 28(3), pp. 257-265. https://doi.org/10.22449/1573-160X-2021-3-257-265
  13. Kuklev, S.B. and Kukleva, O.N., 2023. Formation Features of the Cold Intermediate Layer in the Shelf Slope Zone of the Northeastern Part of the Black Sea during the Period 2019-2022. Hydrosphere Ecology, 1(9), pp. 26-33. https://doi.org/10.33624/2587-9367-2023-1(9)-26-33 (in Russian).
  14. Morozov, A.N. and Mankovskaya, E.V., 2021. Spatial Characteristics of the Black Sea Cold Intermediate Layer in Summer, 2017. Physical Oceanography, 28(4), pp. 404-413. https://doi.org/10.22449/1573-160X-2021-4-404-413
  15. Morozov, A.N. and Mankovskaya, E.V., 2020. Cold Intermediate Layer of the Black Sea According to the Data of Field Research in 2016-2019. Ecological Safety of Coastal and Shelf Zones of Sea, (2), pp. 5-16. https://doi.org/10.22449/2413-5577-2020-2-5-16 (in Russian).
  16. Morozov, A.N. and Mankovskaya, E.V., 2023. Spatial and Temporal Variability of Hydrophysical Parameters of the Northern Black Sea Waters from 2021 Measurements. Ecological Safety of Coastal and Shelf Zones of Sea, (4), pp. 6-18.
  17. Kuznetsov, A.S. and Ivashchenko, I.K., 2023. Features of Forming the Alongcoastal Circulation of the Coastal Ecotone Waters nearby the Southern Coast of Crimea. Physical Oceanography, 30(2), pp. 171-185. https://doi.org/10.29039/1573-160X-2023-2-171-185
  18. Ivanov, V.A. and Mikhailova, E.N., 2008. [Upwelling in the Black Sea]. Sevastopol: ECOSI-Gidrofizika, 91 p. (in Russian).
  19. Khaliulin, A.Kh., Godin, E.A., Ingerov, A.V., Zhuk, E.V., Galkovskaya, L.K. and Isaeva, E.A., 2016. Ocean Data Bank of the Marine Hydrophysical Institute: Information Resources to Support Research in the Black Sea Coastal Zone. Ecological Safety of Coastal and Shelf Zones of Sea, (1), pp. 82-89 (in Russian).
  20. Myslivets, V.I., Rimskiy-Korsakov, N.A., Korotaev, V.N., Pronin, A.A. and Porotov, A.V., 2021. Geophysical and Geomorphological Studies of the Crimean Shelf. In: ROSGEO, 2021. Proceedings of the IV International Geological and Geophysical Conference and Exhibition “GeoEurasia-2021. Geological Exploration in Modern Realities”. Vol. 2. Tver: PolyPRESS LLC, pp. 244-247 (in Russian).
  21. Carpenter, J.H., 1965. The Accuracy of the Winkler Method for Dissolved Oxygen Analysis. Limnology and Oceanography, 10(1), pp. 135-140. https://doi.org/10.4319/lo.1965.10.1.0135
  22. Ivanov, L.I., Konovalov, S., Belokopytov, V. and Ozsoy, E., 1998. Regional Peculiarities of Physical and Chemical Responses to Changes in External Conditions within the Black Sea Pycnocline: Cooling Phase. In: L. I. Ivanov and T. Oguz, eds., 1998. NATO TU-Black Sea Project: Ecosystem Modeling as a Management Tool for the Black Sea. NATO ASI Series; vol. 2. Dordrecht: Kluwer Academic Publishers, pp. 53-68.
  23. Sovga, E.E., Khmara, T.V. and Mezentseva, I.V., 2025. Intensity of Coastal Upwellings of the Southern Coast of Crimea and Their Impact on the Oxygen Regime of the Water Area. Ecological Safety of Coastal and Shelf Zones of Sea, (1), pp. 96-111.

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