Characteristics of glacierization of the Tsambagarav mountain ridge were determined on the basis of images obtained from satellites Corona, Landsat‑5, Spot‑4, Landsat‑8 together with results of field investigations. Inventories of glaciers located on the ridge had been prepared for three time periods: 1968, 2006, and 2015. Glacierization of the ridge during the Little Ice Age (LIA) maximum was then reconstructed. In 2015, 67 glaciers formed the ridge glacierization with their total area 68.41 km2. Mean weighed altitude of the firn line averaged 3748 m. The flat‑top glaciers accounted for almost 40% of the glacierization area, and the glaciers composed 6 complexes. For the period of the LIA maximum, 73 glaciers had been reconstructed, their total area was 128.4 km2, and the calculated firn line altitude – 3583 м; these glaciers were combined into two complexes where the flat‑top glaciers predominated as well. By 1968, the area of the glacierization decreased by 36%, and the firn line altitude increased by 89 m. By 2006, area of glaciers decreased down to 71.32 km2, and the firn line altitude increased more by 60 m. Finally, in 2006–2015, area of the glacierization contracted additionally by 2.91 km2, and the firn line altitude still more increased by 16 m. Over the whole period from the LIA maximum, the flat‑top glaciers reduced the most. The general rate of contraction of glaciers tends to increase. Reconstructed rates of retreating of the valley glaciers of the Tsambagarav ridge are similar to estimates of other researchers made for the nearest centers of glacierization. Continuation of the current trend to a rise of summer temperature and a growth of precipitation should result in primary fast degradation of the flat‑top glaciers and reorganization of morphological structure of the glacierization.
SummaryAs of 2015, 16 glaciers, their total area 23.46 km 2 and the weighted-mean altitude of the firn line 3335 m, were isolated on the Northern slope of the of the Tavan-Bogdo-Ola massif (Altai) on the basis of field studies and analysis of satellite images (Landsat-7, SPOT-5, Geoeye-1, CARTOSAT-1). The differences in elevation of the firn lines on the West and East of the investigated area reach 460 m, while the intensity of glaciation differs in 2 times due to changes of annual precipitation from 360 mm in the East to 880 mm in the West. Data on the glaciation had been improved and complemented for three time sections
This investigation is based on measurements of stable isotopes concentrations (δD and δ18О) in water, snow and ice samples. Glaciers are composed of ice, snow, and fi n of atmospheric origin. The isotopic composition of these components is different, so when melting they form the melted glacial water with different isotope characteristics. Summer precipitation contains the heaviest isotopes, but only a small part of them remains on the glacier. The average isotopic composition of glacier ice represents the average composition of precipitation that accumulates on it. However, snow and fi n of different seasons can occur on the glacier surface, the isotopic composition of which differs from the isotopic composition of glacier ice. At different times of the ablation season different parts of the glacier melt, therefore the isotopic composition of melt waters will be different. Differences in the isotopic composition of the major runoff-forming components on the Northern slopes of the massif Tabyn-Bogdo-Ola had been identified. A part of melting ice in the formation of the runoff on this massif is determined by estimation of the isotopic composition of snow, ice, and fi n on different glaciers of this region. The average δ18О of snow on the glacier surface is −11.9‰, and this snow can be attributed to the precipitation fallen in late spring or early summer. Measured average isotopic composition of precipitation (δ18О = −11.9‰) was compared with the online calculator of the isotope content in precipitation (OIPC). The isotopic composition of glacial melt waters on the Northern macro-slope in the middle of July 2015 (δ18О = −15.3‰) differs from the isotopic composition of the territory of the Mongolian part of the massif (δ18О = −17.4‰) obtained from results of the analysis of eight samples taken at different edges of the glaciers at the beginning of August 2013. Isotopic separation shows important role of summer snow in feeding the glacial rivers of the massif even in the middle of the ablation season, especially for glaciers in the central part of the massif. The role of seasonal snow in feeding the glacier streams depends on the morphological type of glacier. It is maximum for corrie glaciers and minimum for the valley ones.
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