Vertical Mixing in the Main Pycnocline of the Black Sea in Summer

A. N. Morozov

Marine Hydrophysical Institute of RAS, Sevastopol, Russian Federation

e-mail: anmorozov@mhi-ras.ru

Abstract

Purpose. The study is aimed at assessing the parameters of vertical turbulent mixing in the main pycnocline of the Black Sea based on the data on current velocity and density measured by standard hydrological instruments.

Methods and Results. The data collected during six summer cruises of R/V Professor Vodyanitsky in the central sector of the northern sea area in 2016–2021 were used in the research. Temperature, salinity and current velocity profiles were measured by the CTD/LADCP probes. The vertical turbulent diffusion coefficient was calculated with the G03 parameterization. The applied relations are given. The values of the required parameters on the isopycnal surface with the conditional density value 15 kg/m3 are used as the initial data. Their filtered dependencies on its depth are substituted into the calculated relations. It is found that a well-pronounced maximum of specific kinetic energy is observed on average when the isopycnal depth is 77 m. The values of the shear/strain ratio and the canonical internal wave spectrum are close. The average value of the measured shear constitutes about one third of the value of the canonical internal wave spectrum. The average value of the vertical turbulent diffusion coefficient is 10−6 m2/s. Its value in the central sea area is comparable to the heat molecular diffusion coefficient. At the isopycnal depth 90 m the maximum value reaching 1.6·10−6 m2/s, is shifted to the right relatively the Rim Current at a horizontal distance of about 26 km. The average value of the turbulent kinetic energy dissipation rate is 2·10−9 W/kg.

Conclusions. The value of the vertical turbulent diffusion coefficient calculated based on the data collected with a depth resolution of about 10 m agrees well with the estimates obtained from the data of microstructure probes. However, the results of the study should be considered preliminary; in order to obtain a more convincing confirmation of their correctness, it is advisable to conduct synchronous measurements using the microstructure probes and standard hydrological instruments.

Keywords

Black Sea, main pycnocline, vertical turbulent mixing, Rim Current, current velocity shear, strain

Acknowledgements

The study was carried out as part of the state assignment theme FSBSI FRC MHI FNNN-2024-0012, titled “Operational Oceanology”.

Original russian text

Original Russian Text © A. N. Morozov, 2025, published in MORSKOY GIDROFIZICHESKIY ZHURNAL, Vol. 41, Iss. 3, pp. 251–263 (2025)

For citation

Morozov, A.N., 2025. Vertical Mixing in the Main Pycnocline of the Black Sea in Summer. Physical Oceanography, 32(3), pp. 271-282.

References

  1. Zatsepin, A.G., Golenko, N.N., Korzh, A.O., Kremenetskii, V.V., Paka, V.T., Poyarkov, S.G. and Stunzhas, P.A., 2007. Influence of the Dynamics of Currents on the Hydrophysical Structure of the Waters and the Vertical Exchange in the Active Layer of the Black Sea. Oceanology, 47(3), pp. 301–312. https://doi.org/10.1134/S0001437007030022
  2. Munk, W.H., 1966. Abyssal Recipes. Deep Sea Research and Oceanographic Abstracts, 13(4), pp. 707-730. https://doi.org/10.1016/0011-7471(66)90602-4
  3. Nan, F., Xue, H., Yu, F., Ren, Q. and Wang, J., 2022. Diapycnal Mixing Variations Induced by Subthermocline Eddies Observed in the North Pacific Western Boundary Region. Frontiers in Marine Science, 9, 997599. https://doi.org/10.3389/fmars.2022.997599
  4. Takahashi, A. and Hibiya, T., 2019. Assessment of Finescale Parametrizations of Deep Ocean Mixing in the Presence of Geostrophic Current Shear: Results of Microstructure Measurements in the Antarctic Circumpolar Current Region. Journal of Geophysical Research: Oceans, 124(1), pp. 135-153. https://doi.org/10.1029/2018JC014030
  5. Gregg, M.C. and Yakushev, E., 2005. Surface Ventilation of the Black Sea’s Cold Intermediate Layer in the Middle of the Western Gyre. Geophysical Research Letters, 32(3), L021580. https://doi.org/10.1029/2004GL021580
  6. Samodurov, A.S., Chukharev, A.M., Kazakov, D.A., Pavlov, M.I. and Korzhuev, V.A., 2023. Vertical Turbulent Exchange in the Black Sea: Experimental Studies and Modeling. Physical Oceanography, 30(6), pp. 689-713.
  7. Zatsepin, A.G., Ostrovskii, A.G., Kremenetskiy, V.V., Nizov, S.S., Piotukh, V.B., Soloviev, V.A., Shvoev, D.A., Tsibul’sky, A.L., Kuklev, S.B. [et al.], 2014. Subsatellite Polygon for Studying Hydrophysical Processes in the Black Sea Shelf-Slope Zone. Izvestiya, Atmospheric and Oceanic Physics, 50(1), pp. 13-25. https://doi.org/10.1134/S0001433813060157
  8. Podymov, O.I., Zatsepin, A.G. and Ostrovsky, A.G., 2017. Vertical Turbulent Exchange in the Black Sea Pycnocline and Its Relation to Water Dynamics. Oceanology, 57(4), pp. 492-504. https://doi.org/10.1134/S0001437017040142
  9. Podymov, O.I., Zatsepin, A.G. and Ostrovskii, A.G., 2023. Fine Structure of Vertical Density Distribution in the Black Sea and Its Relationship with Vertical Turbulent Exchange. Journal of Marine Science and Engineering, 11(1), 170. https://doi.org/10.3390/jmse11010170
  10. Morozov, A.N. and Lemeshko, E.M., 2014. Estimation of Vertical Turbulent Diffusion Coefficient by CTD/LADCP-measurements in the Northwestern Part of the Black Sea in May, 2004. Morskoy Gidrofizicheskiy Zhurnal, (1), pp. 58-67 (in Russian).
  11. Ivanov, V.A. and Morozov, A.N., 2018. Vertical Mixing in the Active Layer of the Black Sea. Doklady Earth Sciences, 482(2), pp. 1328-1330. https://doi.org/10.1134/S1028334X18100069
  12. 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).
  13. Gregg, M.C., Sanford, T.B. and Winkel, D.P., 2003. Reduced Mixing from the Breaking of Internal Waves in Equatorial Waters. Nature, 422(6931), pp. 513-515. https://doi.org/10.1038/nature01507
  14. Henyey, F.S., Wright, J. and Flatté, S.M., 1986. Energy and Action Flow through the Internal Wave Field: An Eikonal Approach. Journal of Geophysical Research: Oceans, 91(C7), pp. 8487-8495. https://doi.org/10.1029/JC091iC07p08487
  15. Gregg, M.C., 1989. Scaling Turbulent Dissipation in the Thermocline. Journal of Geophysical Research: Oceans, 94(C7), pp. 9686-9698. https://doi.org/10.1029/JC094iC07p09686
  16. Wijesekera, H., Padman, L., Dillon, T., Levine, M., Paulson, C. and Pinkel, R., 1993. The Application of Internal-Wave Dissipation Models to a Region of Strong Mixing. Journal of Physical Oceanography, 23(2), pp. 269-286. https://doi.org/10.1175/1520-0485(1993)023%3C0269:TAOIWD%3E2.0.CO;2
  17. Polzin, K.L., Toole, J.M. and Schmitt, R.W., 1995. Finescale Parameterizations of Turbulent Dissipation. Journal of Physical Oceanography, 25(3), pp. 306-328. https://doi.org/10.1175/1520-0485(1995)025%3C0306:FPOTD%3E2.0.CO;2
  18. Kunze, E., Firing, E., Hummon, J.M., Chereskin, T.K. and Thurnherr, A.M., 2006. Global Abyssal Mixing Inferred from Lowered ADCP Shear and CTD Strain Profiles. Journal of Physical Oceanography, 36(8), pp. 1553-1576. https://doi.org/10.1175/JPO2926.1
  19. Ferron, B., Kokoszka, F., Mercier, H. and Lherminier, P., 2014. Dissipation Rate Estimates from Microstructure and Finescale Internal Wave Observations along the A25 Greenland–Portugal OVIDE Line. Journal of Atmospheric and Oceanic Technology, 31(11), pp. 2530-2543. https://doi.org/10.1175/JTECH-D-14-00036.1
  20. Fine, E.C., Alford, M.H., MacKinnon, J.A. and Mickett, J.B., 2021. Microstructure Mixing Observations and Finescale Parameterizations in the Beaufort Sea. Journal of Physical Oceanography, 51(1), pp. 19-35. https://doi.org/10.1175/JPO-D-19-0233.1
  21. Baumann, T.M., Fer, I., Schulz, K. and Mohrholz, V., 2023. Validating Finescale Parameterizations for the Eastern Arctic Ocean Internal Wave Field. Journal of Geophysical Research: Oceans, 128(11), e2022JC018668. https://doi.org/10.1029/2022JC018668
  22. Sasaki, Y., Yasuda, I., Katsumata, K., Kouketsu, S. and Uchida, H., 2024. Turbulence across the Antarctic Circumpolar Current in the Indian Southern Ocean: Micro-Temperature Measurements and Finescale Parameterizations. Journal of Geophysical Research: Oceans, 129(2), e2023JC019847. https://doi.org/10.1029/2023JC019847
  23. 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
  24. Morozov, A.N. and Mankovskaya, E.V., 2022. Vertical Mixing in the Black Sea Active Layer from Small-Scale Measurement Data. Ecological Safety of Coastal and Shelf Zones of Sea, (4), pp. 25-38. https://doi.org/10.22449/2413-5577-2022-4-25-38

Download the article (PDF)

We use Yandex Metrics. Read more.

Мы используем Яндекс Метрику. Подробнее.