ИСТИНА

Mountain glaciers contain valuable high-resolution paleoclimatic information on a regional scale. As paleoclimatic archives the Caucasus glaciers remain under investigated. Only a few glaciers in Caucasus minimally affected by seasonal melting and thus preserve an undisturbed climatic record of the chemical composition of atmospheric aerosols in Eastern and Western Europe. These glaciers are located on Elbrus Mnt., the Bezengi Wall, Kazbek Mnt., and the Karaugom Plateau. Previous studies provided a detailed reconstruction of ammonia pollution in the atmosphere of southeastern Europe based on the analysis of an ice core drilled in 2009 on the western plateau of Elbrus Mnt. Here, we present the results of ammonium concentration measurements in 20.55 m and 23.7 m ice cores from the western plateau of Elbrus, drilled in 2013 and 2017, respectively, which extend the data previously published from the 2009 study. We compare these results with data obtained from a 12.3 m Kazbek ice core in 2014 and the firn section of a 92.36 m Bezengi ice core drilled in 2021. The data resolution of different ice cores varies from 4 to 20 cm with a distinct seasonal signal identified in all cases, allowing for the precise dating of the glacier ice layers. Additionally, we compare the new ammonium data from the ice cores of the Caucasus with ammonium records from ice cores drilled in other mountain regions. Based on this comparison, we examine the applications of ammonium in paleoclimatic reconstructions, discuss the specifics of its measurements and interpretation. We are grateful to Michel Legrand and Sussanne Preunkert for their help with ice core analysis and in interpreting the data. The study was supported by grant of the Ministry of Science and Higher Education of Russian Federation (agreement № 075-15-2024-554 of 24.04.2024).