Multiyear variability of aufies area in the Selenga River basin and its determining hydrometeorological factors

Aufeis are widespread in the permafrost zone, including the Selenga River basin. They are considered as indicators of dynamic groundwater reserves and often cause damage to settlements and infrastructure. In this study, a representative set of aufeis in the Selenga River basin was compiled based on a previously developed GIS dataset. Landsat and Sentinel-2 satellite images for 1990–2024, acquired immediately after snowmelt, were used to estimate the aufeis area and its multi-year changes. Changes in aufeis area were compared with meteorological parameters derived from the weather station data and ERA5 reanalysis. We found that the average aufeis area decreases by 3.5% per 10 years. At the same time, interannual variations of the area of individual aufeis are generally poorly correlated. The aufeis area has a negative correlation with air temperature in December, March and April, as cold weather in these months favours increase of ice-covered area. A significant increase in air temperature in April in recent decades may be one of the reasons for the overall decrease in the aufeis area. A correlation has also been found with the amount of precipitation in the previous year and particularly in the period from June to September. The largest aufeis area has been observed in 1995–1996, after 1993–1994 which was the wettest year of the period. The lowest aufeis area corresponds to the driest years 2014–2016. On average, the meteorological variables explain 52% of the interannual variability of the aufeis area, but for individual aufeis this value ranges from 7 to 63%. Such differences are due to the different origin of the considered aufeis and possible changes in the hydrogeological conditions, the identification of which requires field studies.