Changes in the area of lakes in different natural regions of Mongolia and climate effect

Монгол орны байгалийн янз бүрийн бүсүүд дэх нууруудын талбайн өөрчлөлт ба уур амьсгалын нөлөө

Abstract

There has not been much study done to explain how recent climate change affects the water surface area changes in lakes in different natural areas of Mongolia. Four lakes between 48° - 50° in Mongolia were chosen for this investigation because they have the same climatic and solar radiation patterns. The case studies of the Khoton Lake in the high mountain region, Terkhin Tsagaan in the forest-steppe region, Khukh Lake in the steppe region, and Namir (Khar Us) in the Govi region emphasized the relationship between lakes surface area and climate variables, which are temperature and precipitation. In the study, statistical analysis methods, the Mann-Kendall test (MK), the innovative trend analysis method (ITAM), the Sen's Slope Estimator Test (SET), and the normalized difference water index (NDWI) method were used. During the past 30 years, calculations based on satellite imagery of the lake area in different natural zones have shown a decreasing trend for the lake area. After 2000, all-natural regions saw a sharp rise in the long-term average air temperature. High mountain regions have seen an increase in precipitation since 2000, Forest-steppe regions have increased since 2010, and steppe and gobi regions have declined since 2000. Lake areas in the high mountain and forest-steppe regions showed a steady decreasing trend starting in 2000, while lakes in the steppe and Gobi regions showed a gradually creasing trend starting in 2010. The increase in the average annual air temperature (Z=1.17) in the high mountain region was more closely related to the changes in the lake region. On the other hand, the area in the forest-steppe zone was better correlated with the quantity of precipitation (Z=1.93). The effect of air temperature (Z=1.21) on the area of lakes in the steppe zone was more relevant, while the amount of precipitation was slightly related. Rainfall (Z=-1.80) was more related to the area of lakes in the Gobi region, while the air temperature was less related. The novelty of the research is that it has been clarified that the lake changes in the area in different natural regions are influenced differently by the climate.