ИЗМЕНЕНИЯ ЛЕДНИКА ЧАЛААТИ (ГРУЗИНСКИЙ КАВКАЗ) С МАЛОГО ЛЕДНИКОВОГО ПЕРИОДА ПО ДАННЫМ КОСМОГЕННЫХ ИЗОТОПОВ (10BE) И ДЕНДРОХРОНОЛОГИИ

International audienceGlacier variations over the past centuries are still poorly documented on the southern slope of the Greater Caucasus. In this paper, the change of Chalaati Glacier in the Georgian Caucasus from its maximum extent during the Little Ice Age has been studied. For the first time in the history of glaciological studies of the Georgian Caucasus, 10Be in situ Cosmic Ray Exposure (CRE) dating was applied. The age of moraines was determined by tree-ring analysis. Lichenometry was also used as a supplementary tool to determine the relative ages of glacial landforms. In addition, the large-scale topographical maps (1887, 1960) were used along with the satellite imagery - Corona, Landsat 5 TM, and Sentinel 2B. Repeated photographs were used to identify the glacier extent in the late XIX and early XX centuries. 10Be CRE ages from the oldest lateral moraine of the Chalaati Glacier suggest that the onset of the Little Ice Age occurred ~0.73±0.04 kyr ago (CE ~1250-1330), while the dendrochronology and lichenometry measurements show that the Chalaati Glacier reached its secondary maximum extent again about CE ~1810. From that time through 2018 the glacier area decreased from 14.9±1.5 km2 to 9.9±0.5 km2 (33.8±7.4% or ~0.16% yr-1), while its length retreated by ~2280 m. The retreat rate was uneven: it peaked between 1940 and 1971 (~22.9 m yr-1), while the rate was slowest in 1910-1930 (~4.0 m yr-1). The terminus elevation rose from ~1620 m to ~1980 m above sea level in ~1810-2018.Для реконструкции колебаний ледника Чалаати в Грузии использовались космические снимки, старые карты, повторные фотографии, дендрохронология, лихенометрия и анализ космогенных изотопов. Максимальное наступание ледника в начале малого ледникового периода произошло в ~1250-1330 гг., второй максимум, когда ледник достиг почти такой же длины, датируется примерно 1810 г. С этого времени до 2018 г. площадь ледника уменьшилась с 14,9±1,5 до 9,9±0,5 км2 (33,8±7,4%, или ~0,16% год-1), а его длина сократилась на ~2280 м