Underwater Ridge Impact on the Motion of Anticyclonic Eddies over a Sloping Bottom as a Result of the Topographic Beta-Effect: Laboratory Experiment

A. G. Zatsepin1, 2, D. N. Elkin1, 2, ✉

1 Shirshov Institute of Oceanology of RAS, Moscow, Russian Federation

2 Marine Hydrophysical Institute of RAS, Sevastopol, Russian Federation

✉ e-mail: dmelkin@mail.ru

Abstract

Purpose. The work is purposed at investigating the underwater ridge impact on the motion of anticyclonic eddies over a sloping bottom as result of the topographic beta-effect in the laboratory conditions..

Methods and Results. The experiments are carried out in a cylindrical tank located on a rotating platform. A cone is placed into the tank so that its base coincides with the cylinder lower base. The cone height is less than the base radius. Before the start of each experiment, the tank is filled with fresh or salt water of certain salinity. The fluid layer height exceeds that of the cone in the tank. The anticyclonic eddies are generated using a local constant source of a blue-colored fresh water flow. The source is located directly below the water layer surface at a distance equal to a half of the tank’s radius from its center. Having achieved the critical diameter, the generated eddies drift along the isobaths in the “western” direction (“north” is at the cone top in the tank center) due to the topographic beta-effect. The experiments were carried out over the cone with a smooth surface, and over the cone with a ridge on its side whose height was significantly smaller than that of the cone located on the path of the eddy drift. In the experimental runs with the ridge, the drift both of barotropic (fresh water in the tank) and baroclinic (salt water in the tank) eddies slowed down as compared to the eddy drift velocities in the absence of the ridge. After crossing the ridge, the orbital velocity of the eddies also decreased significantly.

Conclusions. Field observations and numerical modeling of the Sevastopol anticyclonic eddy in the Black Sea moving over the continental slope along the isobaths in the southwestern direction showed that the eddy motion slowed down in the area of the underwater ridge formed by a local rise in the bottom relief between two canyons – the Danube and the Western Dnieper paleochannels. The results of the laboratory experiment have confirmed the data of field observations and numerical modeling on a slowdown of the Sevastopol eddy motion and a decrease in its orbital velocity while crossing the underwater ridge due to the topographic beta-effect.

Keywords

rotating fluid, sloping bottom, numerical modeling, fluid motion, eddy motion, bathymetry

Acknowledgements

The work was carried out with financial support of the RSF grant No. 21-77-10052 and within the framework of the theme of state assignment FMWE-2021-0002 (IO RAS). The authors are grateful to Arseniy Aleksandrovich Kubryakov for his proposal to perform the laboratory experiment on studying the impact of an underwater ridge on the motion of mesoscale eddies over a sloping bottom in a rotating fluid.

Original russian text

Original Russian Text © A. G. Zatsepin, D. N. Elkin, 2024, published in MORSKOY GIDROFIZICHESKIY ZHURNAL, Vol. 40, Iss. 2, pp. 298–311 (2024)

For citation

Zatsepin, A.G. and Elkin, D.N., 2024. Underwater Ridge Impact on the Motion of Anticyclonic Eddies over a Sloping Bottom as a Result of the Topographic Beta-Effect: Laboratory Experiment. Physical Oceanography, 31(2), pp. 271-283.

References

  1. 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. 80-91. https://doi.org/10.1016/j.dsr.2014.12.002
  2. Zatsepin, A.G., Emel'yanov, S.V., Denisov E.S., Kremenetskiy, V.V., Poyarkov, S.G., Stroganov, O.Yu., Denisov, E.S., Stanichnaya, R.R. and Stanichny, S.V., 2005. Effect of Bottom Slope and Wind on the Near-Shore Current in a Rotating Stratified Fluid: Laboratory Modeling for the Black Sea. Oceanology, 45(Suppl. 1), pp. S13-S26.
  3. Ivanov, V.A. and Belokopytov, V.N., 2013. Oceanography of Black Sea. Sevastopol: ECOSI-Gidrofizika, 210 p.
  4. Kubryakov, A.A. and Stanichny, S.V., 2015. Mesoscale Eddies in the Black Sea from Satellite Altimetry Data. Oceanology, 55(1), pp. 56-67. https://doi.org/10.1134/S0001437015010105
  5. Ginzburg, A.I., Kostyanoy, A.G., Nezlin, N.P., Solov'yev, D.M., Stanichnaya, R.R. and Stanichnyy, S.V., 2001. Anticyclonic Eddies over the Northwestern Continental Slope in the Black Sea and Transport of Chlorophyll-Rich Waters into Its Abyssal Basin. Mapping Sciences and Remote Sensing, 38(2), pp. 130-143. https://doi.org/10.1080/07493878.2001.10642171
  6. Ginzburg, A.I., Kostianoy, A.G., Soloviev, D.M. and Stanichny, S.V., 2000. Remotely Sensed Coastal/Deep-Basin Water Exchange Processes in the Black Sea Surface Layer. In: D. Halpern, ed., 2000. Satellites, Oceanography and Society. Elsevier Oceanography Series, vol. 63. Chapter 15. New York: Elsevier Science, pp. 273-287. https://doi.org/10.1016/S0422-9894(00)80016-1
  7. Oguz, T., 2002. Role of Physical Processes Controlling Oxycline and Suboxic Layer Structures in the Black Sea. Global Biogeochemical Cycles, 16(2), 1019. https://doi.org/10.1029/2001GB001465
  8. Shapiro, G.I., Stanichny, S.V. and Stanychna, R.R., 2010. Anatomy of Shelf–Deep Sea Exchanges by a Mesoscale Eddy in the North West Black Sea as Derived from Remotely Sensed Data. Remote Sensing of Environment, 114(4), pp. 867-875. https://doi.org/10.1016/j.rse.2009.11.020
  9. Kubryakov, A.A., Stanichny, S.V., Zatsepin, A.G. and Kremenetskiy, V.V., 2016. Long-Term Variations of the Black Sea Dynamics and Their Impact on the Marine Ecosystem. Journal of Marine Systems, 163, pp. 80-94. https://doi.org/10.1016/j.jmarsys.2016.06.006
  10. Ginzburg, A.I., Kostianoy, A.G., Nezlin N.P., Soloviev, D.M. and Stanichny, S.V., 2002. Anticyclonic Eddies in the Northwestern Black Sea. Journal of Marine Systems, 32(1-3), pp. 91-106. https://doi.org/10.1016/S0924-7963(02)00035-0
  11. Staneva, J.V., Dietrich, D.E., Stanev, E.V. and Bowman, M.J., 2001. Rim Current and Coastal Eddy Mechanisms in an Eddy-Resolving Black Sea General Circulation Model. Journal of Marine Systems, 31(1-3), pp. 137-157. https://doi.org/10.1016/S0924-7963(01)00050-1
  12. Kostianoy, A.G. and Zatsepin, A.G., 1989. Laboratory Experiments with Baroclinic Vortices in a Rotating Fluid. Elsevier Oceanography Series, 50(C), pp. 691-700. https://doi.org/10.1016/S0422-9894(08)70215-0
  13. Zatsepin, A.G. and Didkovskii, V.L. On one Mechanism for the Formation of Mesoscale Eddy Structures in the Ocean Slope Zone. Doklady Akademii Nauk, 347(1), pp. 109-112 (in Russian).
  14. Zatsepin, A.G., Didkovski, V.L. and Semenov, A.V., 1998. Self-Oscillatory Mechanism of Inducing a Vortex Structure by a Stationary Local Source over a Sloping Bottom in a Rotating Fluid. Oceanology, 38(1), pp. 43-50.
  15. Kamenkovich, V.M., Koshlyakov, M.N. and Monin, A.S., eds., 1986. Synoptic Eddies in the Ocean. Environmental Fluid Mechanics, vol. 5. Dordrecht: Springer, 444 p. https://doi.org/10.1007/978-94-009-4502-9
  16. Shapiro, G.I., 1984. Structure of the Mesoscale Vortex Lens in the Ocean Thermocline. Doklady Akademii Nauk SSSR, 276(6), pp. 1477-1479 (in Russian).
  17. Zatsepin, A.G., Elkin, D.N. and Shvartsman, D.R., 2023. Preliminary Results of Laboratory Investigations of the Evolution of Non-Frontal Eddies in a Two-Layered Rotating Fluid. Journal of Oceanological Research, 51(1), pp. 5-35. https://doi.org/10.29006/1564-2291.JOR-2023.51(1).1 (in Russian).
  18. Kubryakov, A.A., Mizyuk, A.I. and Stanichny, S.V., 2024. Stationarity and Separation of the Sevastopol Eddies in the Black Sea: The Role of Eddy-Topographic Interaction and Submesoscale Dynamics. Journal of Marine Systems, 241, 103911. https://doi.org/10.1016/j.jmarsys.2023.103911

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