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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.

Aufeis formation in the winter season in settlements located in continuous, discontinuous, and isolated permafrost regions of Mongolia has become one of the urgent problems that must be solved in the settlement areas. In this study, the reasons for the formation of Aufeis in the settlement area of Erdenebulgan Soum, Khuvsgul Province, located in the Eg River valley, were clarified. In addition to the analysis of geomorphology and permafrost survey materials, the research was based on satellite image data and calculated using the methods of normalized snow index (NDSI) and snow water index (SWI). In the Eg River valley, the normative depth of seasonal freezing and thawing of subsoil ranges from 2.2-3.7 meters. Depending on the freezing of the winter season, there were long, short, and straight rows of cracks and fractures in the vicinity of river diversions, floodplains, terraces, or along the settlement zone. Over the past 10 years, the average size of the Aufeis area was 5555.8 m², and the average Aufeis volume was 5000.2 m³. In 2022, the Aufeis area increased sharply to 6,381.3 m², which can be related to that year's precipitation and soil temperature fluctuations. According to the area and volume classification of Aufeis in Mongolia, the research area belongs to the III class of medium-sized category, but it is exposed to the space of Aufeis distribution due to the improper expansion of the settlement area and wrong planning. According to the changes in the satellite map over the last 30 years, the diversion of the Eg River has caused the spatial distribution of the Aufeis to move towards the settlement area. This study is important for the planning of the spatial location of towns to determine the methods of pre-research and prevention of permafrost-related phenomena and engineering geomorphological problems.

Knowledge of the duration and distribution of seasonal snow cover is important for understanding the hydrologic regime in mountainous regions within semi-arid climates. In the headwater of the semi-arid Sugnugur catchment (in the Khentii Mountains, northern Mongolia), a spatial analysis of seasonal snow cover duration (SCD) was performed on a 30 m spatial resolution by integrating the spatial resolution of Landsat-7, Landsat-8, and Sentinel-2A images with the daily temporal resolution of Moderate Resolution Imaging Spectroradiometer (MODIS) snow products (2000&ndash, 2017). Validation was achieved using in situ time series measurements from winter field campaigns and distributed surface temperature loggers. We found a mean increase of SCD with altitude at approximately +6 days/100 m. However, we found no altitude-dependent changes in snow depth during field campaigns. The southern exposed valley slopes are either snow free or covered by intermittent snow throughout the winter months due to high sublimation rates and prevailing wind. The estimated mean SCD ranges from 124 days in the lower parts of the catchment to 226 days on the mountain peaks, with a mean underestimation of 12&ndash, 13 days. Snow onset and melt dates exhibited large inter-annual variability, but no significant trend in the seasonal SCD was evident. This method can be applied to high-resolution snow mapping in similar mountainous regions.

Understanding paleo—and recent environmental changes and the dynamics of individual drivers of water availability is essential for water resources management in the Mongolian Altai. Here, we follow a holistic approach to uncover changes in glaciers, permafrost, lake levels and climate at the Tsengel Khairkhan massif. Our general approach to describe glacier and lake level changes is to combine traditional geomorphological field mapping with bathymetric measurements, satellite imagery interpretation, and GIS analyses. We also analysed climate data from two nearby stations, and measured permafrost temperature conditions at five boreholes located at different elevations. We identified four glacial moraine systems (M4-M1) and attribute them to the period from the penultimate glaciation (MIS 4/5) until the Little Ice Age (MIS 1). During the Local Last Glacial Maximum (LLGM; MIS 2), a glacier reached down into the western Kharganat Valley and blocked it, resulting in the formation of the endorheic Khar Lake basin. Subsequently, the lake was fed mainly by precipitation and permafrost meltwater. In recent years, glaciers have been in strong recession, yet Khar Lake levels have remained relatively stable, which is in contrast to mainly decreasing lake levels in other regions throughout Mongolia. While temperatures in the Altai are increasing (leading to increasing evaporation), precipitation in higher elevations has increased, which—in addition to increased glacier and permafrost melting—would counteract the increasing aridity effects. A systematic and holistic monitoring of glaciers, permafrost, lake levels and climate in the Mongolian Altai is necessary, and results from (sub-)disciplines need to be correlated.