Analysis of Hydrological Changes in Mineral Lakes in Northern Eurasia Based on SMOS Satellite Data

Abstract

The climatic changes taking place in Northern Eurasia, which have become especially aggravated in the past few decades, in combination with the anthropogenic impact on ecosystems, are causing noticeable changes in the hydrological characteristics of mineral lakes. Based on the results of daily measurements of brightness temperature T_b from the SMOS (Soil Moisture and Ocean Solution) satellite, the long-term seasonal dynamics of hydrological changes in some large mineral lakes of Northern Eurasia (Caspian Sea, Kara-Bogaz-Gol Bay, Aral Sea, lakes Sarykamyshskoe, Kulunda, Ubsu-Nur) from 2012 to 2022 was studied. The analysis of the seasonal and interannual dynamics of T_b and thermodynamic temperature of the underlying surface was performed on the basis of the SMOS L1C and MODIS MOD11A1 (Moderate Resolution Imaging Spectroradiometer) products, respectively. Four periods were identified with different behavior of the radiative characteristics of mineral lakes, associated with a decrease in temperature below the freezing point of salt water, the formation and melting of ice cover on the water surface, changes in the area of the water table, and salinity of water. In the northern Caspian Sea, the influence of the phenological phases of ice cover on the change in the microwave radiation of the underlying surface was noted. The features of microwave radiation of the western (deep water) and northern parts of the Aral Sea are studied. The seasonal dynamics of T_b is associated with the processes of formation of ice cover on the water surface. Judging by the changed seasonal dynamics of the T_b, the Sarykamysh Lake was transformed into a year-round ice-free lake. Peculiarities of the seasonal dynamics of T_b for Lake Ubsu-Nur are revealed that may be associated with rainfall in the winter–spring season, as well as with the early opening of rivers and flooding of the ice cover of the lake with river water.