Thermocline Dynamics in the Zone of the Rim Current Action in Winter Period (Based on to the Drifter Experiment Data)

А. A. Sizov✉, T. M. Bayankina, N. E. Lebedev

Marine Hydrophysical Institute of RAS, Sevastopol, Russian Federation

✉ e-mail: sizov_anatoliy@mail.ru

Abstract

Purpose. The paper is aimed at studying the thermocline response to slow (during a few days) and fast (up to two days) change of the current velocity, and also the process of changing in depth of the upper mixed layer lower boundary depending on the current velocity (at that the process is accompanied by the thickness and temperature gradient alteration in the thermocline).

Methods and Results. The thermocline responses were analyzed using the data on the upper layer temperature derived from the drifter experiment in 2012‒2014. The drifters equipped with the thermal chains made it possible to measure temperature in the upper layer up to 80 m. The data covering the cold period (December – March) and obtained in five sub-regions in the Rim Current zone in the western and eastern parts of the sea were analyzed. The sub-regions were chosen proceeding from absence of the synoptic and mesoscale eddies in them. In each sub-region, the drifter position was estimated relative to the core of the Rim Current. Based on the mean daily sea temperature, the thermocline profiles were constructed, the thermocline boundaries, depth of the upper mixed layer lower boundary, the thermocline thickness and the temperature gradient in it were determined. The analysis showed that in case of a slow increase (decrease) in the current velocity, in all the sub-regions, there were a deepening (rise) of the upper mixed layer lower boundary, a decrease (increase) in the thermocline thickness and an increase (decrease) of the temperature gradient in it. This process is explained by possible propagation of the internal waves induced by the Rim Current velocity varying in the thermocline.

Conclusions. The results obtained showed that the fluctuation of the Rim Current velocity increased (decreased) the depth of the upper mixed layer lower boundary, the change of which was associated with an increase (decrease) in the thermocline thickness and in the temperature gradient in it. The drifters' data are significantly "noisy" due to the spatial inhomogeneities of the temperature field in the sea upper layer. Therefore, to obtain more accurate estimates of the processes, a study at the anchored measuring platforms installed in the zone of the Rim Current action is required.

Keywords

upper mixed layer, thermocline, geostrophic velocity, surface velocity, Rim Current, drifter

Acknowledgements

The investigation was carried out within the framework of the state task on theme No. 0555-2021-0002 “Fundamental studies of interaction processes in the ocean-atmosphere system conditioning regional spatial-temporal variability of natural environment and climate”.

Original russian text

Original Russian Text © А. A. Sizov, T. M. Bayankina, N. E. Lebedev, 2022, published in MORSKOY GIDROFIZICHESKIY ZHURNAL, Vol. 38, Iss. 1, pp. 73-88 (2022)

For citation

Sizov, A.A., Bayankina, T.M. and Lebedev, N.E., 2022. Thermocline Dynamics in the Zone of the Rim Current Action in Winter Period (Based on to the Drifter Experiment Data). Physical Oceanography, 29(1), pp. 67-82. doi:10.22449/1573-160X-2022-1-67-82

DOI

10.22449/1573-160X-2022-1-67-82

References

  1. Bulgakov, N.P., 1975. Convection in the Ocean. Moscow: Nauka, 272 p. (in Russian).
  2. Dobrovolsky, A.D., Ed., 1977. Convective Mixing in the Sea. Moscow: University Press, 239 p. (in Russian).
  3. Samodurov, A.S. and Chukharev, A.M., 2006. Estimation to Intensity of Vertical Turbulent Exchange in Upper Layer of the Black Sea according to In Situ Measurements. In: MHI, 2006. Ekologicheskaya Bezopasnost' Pribrezhnykh i Shel'fovykh Zon i Kompleksnoe Ispol'zovanie Resursov Shel'fa [Ecological Safety of Coastal and Shelf Zones and Comprehensive Use of Shelf Resources]. Sevastopol: ECOSI-Gidrofizika. Iss. 14, pp. 524-529 (in Russian).
  4. 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), 492-504. https://doi.org/10.1134/S0001437017040142
  5. 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).
  6. Tolstosheev, A.P., Lunev, E.G. and Motyzhev, S.V., 2014. Analysis of In-Situ Experiments with Temperature-Profiling Drifters in the Black Sea and Other Areas of the World Ocean. Morskoy Gidrofizicheskiy Zhurnal, (5), pp. 9-32 (in Russian).
  7. Kubryakov, A.A. and Stanichny, S.V., 2012. Reconstruction of Mean Dynamic Topography of the Black Sea for Altimetry Measurements. Izvestiya, Atmospheric and Oceanic Physics, 48(9), pp. 973-979. https://doi.org/10.1134/S0001433812090095
  8. Kubryakov, A.A. and Stanichny, S.V., 2012. Reconstruction of Mean Dynamic Topography of the Black Sea for Altimetry Measurements. Izvestiya, Atmospheric and Oceanic Physics, 48(9), pp. 973-979. https://doi.org/10.1134/S0001433812090095
  9. Sizov, A.A., Bayankina, T.M. and Yurovsky, A.V., 2019. Study of the Process of the Black Sea Upper Layer Mixing in the Zone of the Rim Current Activity in Winter Based on the Drifters Data. Physical Oceanography, 26(3), pp. 260-270. doi:10.22449/1573-160X-2019-3-260-270
  10. Ivanov, V.A. and Belokopytov, V.N., 2013. Oceanography of the Black Sea. Sevastopol, 210 p.
  11. Kubryakov, A.A., Belokopytov, V.N., Zatsepin, A.G., Stanichny, S.V. and Piotukh, V.B., 2019. The Black Sea Mixed Layer Depth Variability and Its Relation to the Basin Dynamics and Atmospheric Forcing. Physical Oceanography, 26(5), pp. 397-413. doi:10.22449/1573-160X-2019-5-397-413
  12. Ginzburg, A.I., Zatsepin, A.G., Kostianoy, A.G. and Sheremet, N.A., 2008. Mesoscale Water Dynamics. In: A. G. Kostianoy and A. N. Kosarev, eds., 2008. The Black Sea Environment. Handbook of Environmental Chemistry, vol. 5. Berlin; Heidelberg: Springer, pp. 195-215. doi:10.1007/698_5_062
  13. Kubryakov, A.A. and Stanichny, S.V., 2015. Seasonal and Interannual Variability of the Black Sea Eddies and Its Dependence on Characteristics of the Large-Scale Circulation. Deep Sea Research Part I: Oceanographic Research Papers, 97, pp. 80-97. doi:10.1016/j.dsr.2014.12.002
  14. Maxworthy, T., Leilich, J., Simpson, J.E. and Meiburg, E.H., 2002. The Propagation of a Gravity Current into a Linearly Stratified Fluid. Journal of Fluid Mechanics, 453, pp. 371-394. doi:10.1017/S0022112001007054
  15. Gritsenko, V.A. and Chubarenko, I.P., 2010. On Features of Structure of Bottom Gravity Current Frontal Zone. Oceanology, 50(1), pp. 28-35. https://doi.org/10.1134/S0001437010010030
  16. Oguz, T. and Besiktepe, S., 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

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