Monitoring the Change in the Caspian Sea Level Affected by Atmospheric Parameters Using Remote Sensing Data

The Caspian Sea level (CSL) fluctuations are driven by reciprocal hydro-meteorological processes which extend not only over the entire catchment area but also far beyond. According to the research literature, CSL has dropped approximately 3 m in the short-term period of 1929-1977. The origin of CSL changes and the future of these changes are still being debated. In this study, changes in precipitation, runoff, and evaporation in the catchment area, river discharge, sea surface temperature (SST), and also CSL change were investigated over 40-year. Study results revealed two major changes in the increasing trend of SST anomalies. With an increasing trend in the CS level with 0.03 slope, the results indicated an increase in SST by more than 1.5°C during the study period, which can be a response to the increase in air and land surface temperature on a regional and global scale. The decline in river discharge levels has also been significant in recent decades. These changes were more obvious in the volga river, which provides more than 80% of the CS balance. Reconstruction of long-term CSL change with daily water level data between 1981 and 2020 through fluxes also showed that the average sea level rise was about 20 cm/yr in the 1981-1995 period while a decrease of 6 cm/yr during the 1996-2020 period was clearly visible in the results of the water balance equation. Moreover, according to the observed peak values of the four parameters of precipitation, evaporation, runoff, and SST, the trend of increasing sea surface temperature and decreasing precipitation (with a slope of -1.8 mm/40yr) is more consistent with CSL change.