On the Dynamics of Waters in Kara-Bogaz-Gol (Satellite Information)

Kara-Bogaz-Gol (KBG) is a hypersaline reservoir (with water salinity varying from 40 to 270‰), which is an effective evaporator of water from the Caspian Sea entering in the bay through the strait of the same name. At the end of 2020, the water level in the bay, according to the HydroWEB LEGOS (France) system, dropped to –29.25 m BS, which is 0.75 m below the Caspian level. The area and volume of the bay at the same time amounted to approximately 17 300 km 2 and 60 km 3 . The depth of the bay did not exceed 5–7 m. Sentinel‑2 optical satellite images with spatial resolution of 10 m (four images from July 16 to July 31, 2021, and image from October 9, 2021), OLI Landsat-8 IR image (July 20, 2021, 100-m resolution), all MODIS_ Terra_Corrected Reflectance_True Color optical images available for 2021 (250-m resolution), IR images of the NOAA‑15 , -16 , and -18 satellites in 2001–2005 (1-km resolution) and MODIS-Aqua image (a combination of RGB channels 1, 4, and 3) from October 2, 2005, were used to reveal the structure of the transformed Caspian waters at the exit from the strait, their manifestation in the temperature field, the routes of further propagation of the flow from the mixing zone, and the possibility of vortex formation in the waters of the bay. It is shown that water flows into the bay through numerous branches of the strait delta in jets, the boundaries of which are identified even at a distance of several kilometers from the channel. The temperature contrast between the water in the jets at the exit from the strait and in the bay in the summer season, when the water in the bay is warmer than the water in the Middle Caspian (especially during the period of intense upwelling near the eastern coast of the sea), can reach 10–11°C. The direction of flow propagation with sharp frontal boundaries from the area of mixing of sea and bay waters is diverse: it can be directed (presumably depending on the wind direction) along the coast to the north or southeast, to have the shape of an elliptical lens with clear frontal boundaries against the background of the flow propagating along the coast or a mushroom shape oriented perpendicular to the coast. In KBG, eddy structures of different scales (from about 7 to 50 km) are observed in different parts of the water area both in the visible range of the spectrum and in IR images (the tracers are the difference in the color of the waters of the bay and the Caspian waters, turbidity, and temperature contrasts). The manifestation of the Langmuir circulation on the surface of the bay on October 9, 2021, with a distance between convergence lines of 50–100 m at a northeast wind of 3.3 m/s and an air temperature of 14.5°C is considered.