Satellite monitoring of changes in the state and boundaries of the Bolshoy Azau glacier and transformation of periglacial landscapes in Рrielbrusye over 2015–2025

Abstract

The study presents satellite monitoring of changes in the state and boundaries of the Bolshoy Azau Glacier and the transformation of periglacial landscapes over the period 2015-2025. Based on Sentinel-2 (Level-2A) multispectral data, using the Normalized Difference Snow Index (NDSI), visual interpretation, and the NDVI vegetation index, the assessment of glacier area dynamics, the ratio of clean and debriscovered ice, and the features of primary succession on deposited moraines was made. It was established that over the ten-year period the total glacier area decreased by 4.53 km² (24.1%). The proportion of debriscovered ice increased from 2.9% to 50.4%, accompanied by the active transformation of debris-covered ice into deglaciated moraine deposits, the area of which reached 4.45 km². Analysis of NDVI values on these moraines revealed extremely low values (mean 0.0018), indicating the initial stage of primary succession or its near absence. The obtained results indicate the persistence of high geomorphological instability within the periglacial zone and an increased risk of glacial debris flows in the upper reaches of the Baksan River basin. It is shown that even a temporary slowdown in deglaciation rates does not guarantee landscape stabilization. The use of geoinformation analysis and remote sensing technologies ensured high accuracy of calculations and broad temporal coverage for monitoring and studying the dynamics of glacier surface changes, and also allowed identification of the spatiotemporal patterns of glaciation degradation and analysis of the transformation of adjacent geosystems under contemporary climate change conditions.