Features of River Plume Formation in a Shallow Lagoon (the Case of the Sivash Bay, the Sea of Azov)

V. V. Fomin, A. A. Polozok*

Marine Hydrophysical Institute of RAS, Sevastopol, Russia

* e-mail: polozok.umi@gmail.com

Abstract

Features of the thermohaline structure of the waters of lagoons and bays have a significant impact on the biological diversity, productivity and quality of the waters of these areas. In this paper, the characteristics of a freshwater plume in the area of the Salgir River outlet into the Sivash Bay are studied. The study was performed on the basis of a three-dimensional hydrodynamic model POM with 10 m horizontal resolution and 0.1 m vertical one. Data from field observations of river runoff, temperature and salinity of river and sea water, which were carried out in the area of the mouth of the Salgir River in June 2021, were used as input parameters of the model. Based on a series of numerical experiments, the influence of various types of currents on the position, shape and size of the plume was studied. It is shown that under the influence of river runoff a plume several hundred meters in size is formed at the debouchment from the river mouth. Due to the rotation of the Earth, the shape of the plume is asymmetric. This asymmetry appears regardless of the presence of any currents in the basin. Alongshore currents cause a decrease in the transverse size of the plume by a factor of two. When the wind is directed towards the shore, the plume is blocked, and fresh water spreads in a narrow strip on both sides of the river mouth. The plume is concentrated in the upper layer 20–40 cm thick. The thickness of the plume shows the smallest value in the immediate vicinity of the river mouth due to the rise of fresh water coming from the bottom layers of the river to the surface of the basin.

Keywords

Sea of Azov, Crimea, Salgir, Sivash, fresh runoff, river plume, mathematical modeling

Acknowledgments

The study was carried out within the theme of the Marine Hydrophysical Institute of RAS no. 0555-2021-0005 “Coastal studies”. Model calculations were carried out on the MHI computing cluster.

For citation

Fomin, V.V. and Polozok, A.A., 2022. Features of River Plume Formation in a Shallow Lagoon (the Case of the Sivash Bay, the Sea of Azov). Ecological Safety of the Coastal and Shelf Zones of the Sea, (3), pp. 28–42. doi:10.22449/2413-5577-2022-3-28-42

DOI

10.22449/2413-5577-2022-3-28-42

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