Journal of Climate Research

Journal of Climate Research

Investigation of Atmospheric Factors Affecting Fluctuations in the Water Level of the Caspian Sea from 1992 to 2022

Document Type : Original Article

Authors
mehriar alimohammadi 1
Arsalan Gholinejad 2
Hadi Najari kahnooj 3
Ali Mohammadi 4
Ahmad Zadeghabadi 5
1 Department of Special Operations and Coast reconnaissance, Imam Khomeini University of Marine Sciences, Nowshahr
2 Senior expert in non-active defense, Imam Khomeini University of Marine Sciences Nowshahr
3 Senior expert in Navigation and Marine Science Management, Imam Khomeini University of Marine Sciences, Nowshahr
4 Assistant Professor, Department of Meteorology and Oceanography, Imam Khomeini University of Marine Sciences, Nowshahr
5 PhD in Meteorology, Hormozgan University, Bandar Abbas
10.22034/jcr.2024.198107
Abstract
Rapid fluctuations in the Caspian Sea's water level play an important role in determining the extent of erosion hazards, adverse environmental consequences, degradation and drying of coastal areas, wetlands and coastal bays, and the loss of economic resources and the destruction of maritime industries.

The effects of climate change on the Caspian Sea have led many scientists to pursue research and scientific topics related to climate change in order to achieve their goals. These studies are performed to determine temperature, evaporation, salinity, pressure, density, wind direction, wind speed and other related phenomena. In this study, we intend to investigate the climatic factors affecting the water level of the Caspian Sea using ECMWF data.

The data were received by the ECMWF and the Ports Authority. In this study, using ECMWF data from 1992 to 2022, which includes the amount of precipitation on the Caspian Sea, the rate of evaporation from it and the average temperature of the Caspian Sea, the factors affecting water level fluctuations in the Caspian Sea were investigated. Reliable library sources were used to determine the inflow of rivers into the Caspian Sea. Using ProUCL software, the data trends of precipitation, evaporation, temperature, and river water flow from 1992 to 2022 were drawn. Using the same software, the Mann-Kendall trend test was used to determine the trend of the data. Caspian Sea fluctuation data was received from Ports Organization.

The graph of the precipitation trend in the whole area of the Caspian Sea showed that in the period from 1992 to 2022, the precipitation decreased by 90 cubic kilometers. According to the Mann-Kendall test and considering that the p-value of 0.0009 was obtained, it can be said that this decreasing trend is significant with a confidence level of 99%.

The diagram of the evaporation trend in the entire area of the Caspian Sea showed that in the period from 1992 to 2022, evaporation increased by 103 cubic kilometers. According to the Mann-Kendall test and considering that the p-value of 0.0001 was obtained, it can be said that this decreasing trend is significant with a confidence level of 99%.

As a general result, evaporation has an increasing trend while precipitation has a decreasing trend. In the next section, in order to investigate the main cause of the increase in evaporation, the sea level temperature trend chart is analyzed.

Sea surface temperature as one of the main criteria in heat exchange and an indicator in assessing the potential for evaporation from the water surface, which is one of the main components of output in the Caspian water balance, in studying the trend of water level changes and assessing the causes of fluctuations in the Caspian Placed. The rising temperature of the Caspian Sea, especially in recent years, has been a factor in reducing the water level. The graph of sea surface temperature changes in the whole area of the Caspian Sea showed that the average temperature has increased by 1.1 degrees Celsius in the period from 1992 to 2022. According to the Mann-Kendall test and considering that the p-value of 0.0000 was obtained, it can be said that this increasing trend is significant with a confidence level of 99%.

The average annual inflow of Volga water into the Caspian Sea is about 240 billion cubic meters, and the annual estimate of the total inflow of the rivers leading to the Caspian is 300 billion cubic meters. From other important rivers such as Kura, Ural, Etrak, Sefidroud, Haraz, a total of 34 billion cubic meters of water enters the Caspian Sea. The recent decrease in water level is while the amount of water entering the Volga River, as the supplier of most of the river water to this sea, has decreased by about 22% in 2019, which can be considered as one of the effective reasons for the decrease in the recent water level.

The main reason for the increase in sea level temperature is the increase in greenhouse gases, which prevents the release of ground radiation. Therefore, the trend of increasing temperature, which is directly related to increasing water evaporation, in Nowshahr station and the entire Caspian Sea area is one of the effective factors in increasing the water level fluctuations of the Caspian Sea, which has reduced the water level of this sea.

The water flow of the Volga River shows a decreasing trend due to the decreasing trend of precipitation. As a general result, climate change is reducing precipitation, increasing temperature and increasing evaporation, and ultimately lowering the surface of the Caspian Sea, a trend that will continue for years to come.
Keywords
Caspian Sea
level
precipitation
evaporation
sea surface temperature
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Journal of Climate Research
Volume 1403, Issue 58 - Serial Number 58
Vol. 15, No. 58, ُSummer 2024
Autumn 2024
Pages 141-157