Hydrophysical Structure and Current Dynamics of the Kodor River Plume

This work is focused on the river plume generated by the Kodor River which is the largest river of Abkhazia and the northeastern coast of the Black Sea. Based on in situ hydrological data, quadcopter aerial images and satellite observations, hydrophysical structure and circulation in the Kodor plume was studied at different river discharge conditions. Discharge of the Kodor River, which inflows to sea from several deltaic branches forms a relatively shallow plume with large area, as compared to the Mzymta River, the largest estuarine river of the study region, at similar hydrological, meteorological, and oceanographic conditions. Due to its small vertical size and large salinity gradient at the border with the subjacent saline sea, the Kodor plume is characterized by quick response on wind forcing variability. The Kodor plume also has large spatial inhomogeneity, caused by its formation conditions (several closely located freshwater sources prone to abrupt discharge variability), as well as regional bathymetry (interaction between the plume and shoals). During low discharge period, the inflowing Kodor River has relatively low kinetic energy, which causes abrupt deceleration of the jet in the sea area adjacent to the river mouth. As a result, the inertia of the inflowing jet abruptly decreases and large velocity and salinity gradients are formed in vicinity of river estuary, which hinder formation of anticyclonic circulation at the near-field part of the plume. This feature induces transport of freshwater discharge off the river mouth and its accumulation in the far-field part of the small plume under moderate wind forcing conditions that is not typical for large river plumes. The obtained results are important for understanding general aspects of dynamics of buoyant plumes formed by rivers with small discharge rates.