Received November 14, 2022; revised May 24, 2023; accepted June 27, 2023The characteristic feature of the Putorana Plateau is that the glaciological objects here are mostly represented by small glaciers and perennial snow patches. Their regime and morphology have so much common features that separation of these two categories of nival glacial formations from one another is extremely difficult problem. The distinctions between results of earlier studies carried out in the 1970s (the USSR Glacier Inventory estimated local resources at 22 glaciers with a total area of 2.5 km2) and at the beginning of the current century (in 2005, V.A. Sarana identified 61 glaciers with a total area of 7 km2) are too large to make any reliable conclusions about the current trends of the Putoran glaciation. In such conditions, the materials of rare field monitoring work performed on individual nival-glacial bodies become very valuable. Three expedition seasons of 2002–2004 included thorough geodetic and mass-balance measurements on 3 reference objects on the northern ledge of Lama Mts. – Prives (No. 30) Glacier, Marlborough (No. 31) Glacier and Strudoms snow patch. Similar field monitoring was repeated in summer’2019. The change in their configuration according to digital photography data, including the results of the analysis of satellite images, make possible to reveal that interannual fluctuations in the area of each glacier occur due to different vector displacements of its different sections along their entire perimeters. In 2019, the somewhat unexpected good budget state of all 3 monitored objects was detected. It manifested itself in growth of their areas and increased fraction of firn basin as well as in larger water equivalent of the firn residue as this followed from results of snow surveys. This fact contradicts the previous conclusion about the steady trend of deglaciation on the Putorana Plateau. The favourable condition for small glaciers occurred here in 2019 was mainly caused by reduced ablation owing to the weakened insolation that resulted from tremendous forest fires in Siberia, remarkable by their abnormal intensity in this year.

This study fills a gap in the long-term prediction of changes in parameters of the Elbrus glaciers, using the GloGEMflow-debris model to simulate the glacier evolution. The part 1 provides a detailed description of the model architecture. The model consists of three blocks in which the calculation of the surface mass balance, glacier flow and moraine transformation is carried out. The area and thickness of the moraine cover increase as glaciers degrade. This is important to consider, as a thicker layer of moraine reduces the ice melting. For predictive calculations, the data on temperature and precipitation for five SSP climate scenarios are taken from the CMIP6 project. A temperature index method is used to calculate the surface mass balance, taking into account the influence of the moraine cover: the ablation of pure ice is adjusted in accordance with the area and thickness of the moraine cover. The ice flow block is used to update the geometry of glaciers and moraine cover. The adaptation of the model to the glaciers of Elbrus includes the adjustment of the block of the moraine cover evolution, which corresponds to the geological features of the region. Thus, the accumulation of moraine on the glaciers of the volcanic peak through erosion of slopes and landslides can be neglected, it is considered to be the bottom moraine, thrown up along the shear planes, the main source of surface moraine on the glaciers of Elbrus. Hence, the debris-cover source in the model is specified to be the result of bedrock erosion rather than slope erosion. The paper discusses calibration processes that allow using simple modeling methods, such as the temperature index method for calculating the surface mass balance, and to simulate the real behavior of glaciers. Despite the fact that the validation of the model revealed a slight underestimation of mass loss at the beginning of the XXI century, the general patterns of mass loss are reproduced correctly, although the energy balance has not been explicitly described. Thus, the adjustment of the model ensures its adaptation to the glaciation conditions on Elbrus.

Probable scenarios of future changes in the Elbrus glaciers and associated with them phenomena such as formation of glacial lakes and remaining ice masses buried under the debris cover are considered. The SSP scenarios (SSP1-1.9, SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP5-8.5) were used for of future climate forcing. Glacier dynamics was simulated using the GloGEMflow model, which was improved by including a module of evolving debris cover. According to the prognostic calculations of the surface mass balance of the glaciers, the loss of ice mass on the Elbrus will accelerate until the end of the 2030s, reaching approximately -1.1 +/- 0.3 m w. e. yr.-1. The volume of the glacier ice is expected to be reducing almost linearly until about 2040, after which the mass loss rate will slow down. Under the warmest climate change scenarios (SSP5-8.5, SSP3-7.0), almost all of the remaining ice masses in the North Caucasus will be concentrated on Elbrus by the end of the century. At the same time, by 2100 the glaciers of Elbrus themselves will retreat up to 4000 m above sea level and higher. In case of moderate warming (SSP1-1.9, SSP1-2.6) the position of glacier fronts may be stabilized at an altitude of 3600-3700 m. The study concerns also the dynamics of the debris cover, predicting its doubling in area and average thickness of 0.22 m by 2040. Although the effect of the debris cover on the total volume of ice on Elbrus is estimated to be minimal, it can temporarily slow down melting of the frontal parts and areas of dead (remaining) ice. According to our estimates, the retreat of the Elbrus glaciers may result in formation of up to 17 new lakes, of which six may potentially be temporarily dammed by dead (remaining) ice zones (up to 60 m thick for Djikaugenkioz). It is expected that the largest lake may be formed on the Djikaugenkioz plateau, it will be dammed by moraine with ice buried under it in the period from 2035 to 2045 if no sufficiently efficient runoff channels will appear. The approximate time and place of formation of such ice masses near the sites of lake formation, depending on the climatic scenario, are shown in the paper, since it is important from the point of view of the risk of outburst floods in the 21st century. Under moderate warming (scenario SSP1-2.6), up to 8 lakes are likely to be formed at the site of retreating glaciers Ulluchiran, Djikaugenkioz, and Bolshoy Azau. All of them may appear in the first half of the century, regardless of the climatic scenario.

Downward long-wave radiation plays a significant role in the formation of the net radiation regime on the surface of a mountain glacier. For this reason, it should be taken into account in glaciological calculations, especially in the warm period of the year, during the melting season. Glaciological models often ignore particular components of the long-wave radiation flux, for example, radiation reflected from the mountain slopes surrounding the glacier. The choice of the algorithm for parameterization of downward radiation and cloudiness affects the accuracy of model calculations. In the article, we analyze the well-known parameterization algorithms for atmospheric downward radiation from the point of view of their applicability in glaciological modeling in a specific geographical region, in the Inner Tien Shan. The results of calculation are compared with the measurements on the Karabatkak glacier (the northern slope of the Terskey Ala-Too ridge). We substantiate the choice of algorithms simple cloud parameterization scheme and consider the influence of the surrounding relief.

Mass balance bn is the most important indicator of a glacier evolution. However, after the decay of the USSR direct measurements of bn performed in 1985–1989 in the Inner Tien Shan, including the Sary-Tor Glacier in Ak-Shiyrak Massif, had been desisted. As a result the available series of the data were limited 1989. Measurements in this area were renewed only in 2015. This paper is devoted to restoring the continuity of the mass-balance series over the period of the gap in measurements and extending this series down to 1929, i.e. to the beginning of regular meteorological observations on the reference HMS Tien Shan (3660 m a.m.s.l.). Accumulation was reconstructed using a linear relationship of bn with the air temperature and precipitation sum. Reconstruction of ablation was based on its cubic relationship with the temperature (modified Krenke– Khodakov formula) or on two-parameter linear approximation using the air temperature and wind velocity. Thereby, the decade of direct instrumental measurements (1984/85–1988/89 and 2014/15–2018/19) resulted in deriving and analyzing continuous 90-year-long series of annual values of bn and its constituents, analytical type of referent glacio-meteorological equations being assumed unchanged in time. Reconstruction for the Sary-Tor Glacier reveals a dominant trend towards the mass loss with rare and short-time episodes of retarding the negative tendencies. The comparison made with the long series of mass balance of other glaciers in Asia indicates a certain degree of synchronicity, which is slightly disturbed in recent years: the degradation of Sary Tor Glacier tends to progress more intensively. Conclusions about its evolution are particularly relevant in connection with the assumption about the impact of the Kyrgyz-Canadian gold mining company «Kumtor Gold Company» on local ecosystems against the background of its interest in expanding the mining zone to the bowels of the Earth under the tongue of this glaciological object.

Mass balance bn is the most important indicator of a glacier evolution. However, after the decay of the USSR direct measurements of bn performed in 1985-1989 in the Inner Tien Shan, including the Sary-Tor Glacier in Ak-Shiyrak Massif, had been desisted. As a result the available series of the data were limited 1989. Measurements in this area were renewed only in 2015. This paper is devoted to restoring the continuity of the mass-balance series over the period of the gap in measurements and extending this series down to 1929, i.e. to the beginning of regular meteorological observations on the reference HMS Tien Shan (3660 m a.m.s.l.). Accumulation was reconstructed using a linear relationship of bn with the air temperature and precipitation sum. Reconstruction of ablation was based on its cubic relationship with the temperature (modified Krenke-Khodakov formula) or on two-parameter linear approximation using the air temperature and wind velocity. Thereby, the decade of direct instrumental measurements (1984/85-1988/89 and 2014/15-2018/19) resulted in deriving and analyzing continuous 90-year-long series of annual values of bn and its constituents, analytical type of referent glacio-meteorological equations being assumed unchanged in time. Reconstruction for the Sary-Tor Glacier reveals a dominant trend towards the mass loss with rare and short-time episodes of retarding the negative tendencies. The comparison made with the long series of mass balance of other glaciers in Asia indicates a certain degree of synchronicity, which is slightly disturbed in recent years: the degradation of Sary Tor Glacier tends to progress more intensively. Conclusions about its evolution are particularly relevant in connection with the assumption about the impact of the Kyrgyz-Canadian gold mining company "Kumtor Gold Company" on local ecosystems against the background of its interest in expanding the mining zone to the bowels of the Earth under the tongue of this glaciological object.

Solar irradiance is the most important factor which determines the thermal conditions of mountain glaciers. We use trigonometric formulae to calculate direct solar radiation incoming on any arbitrary oriented surface under the condition of absence of the atmosphere. Shading effect from the surrounding relief can also be evaluated rather precisely. Nevertheless, in order to obtain correct results, it is necessary to take into account atmospheric transmissivity, diffuse radiation, and influence of cloudiness. The paper presents a model for calculation of shortwave radiation, utilizing up-to-date data on the atmospheric composition and schemes for parameterization of the atmospheric transmissivity, which have never been implemented in glaciological applications before. Validation of the model was carried out using observational data on the global radiation on two weather stations established on Karabatkak glacier (Inner Tien Shan).

Solar irradiance is the most important factor which determines the thermal conditions of mountain glaciers. We use trigonometric formulae to calculate direct solar radiation incoming on any arbitrary oriented surface under the condition of absence of the atmosphere. Shading effect from the surrounding relief can also be evaluated rather precisely. Nevertheless, in order to obtain correct results, it is necessary to take into account atmospheric transmissivity, diffuse radiation, and influence of cloudiness. The paper presents a model for calculation of shortwave radiation, utilizing up-to-date data on the atmospheric composition and schemes for parameterization of the atmospheric transmissivity, which have never been implemented in glaciological applications before. Validation of the model was carried out using observational data on the global radiation on two weather stations established on Karabatkak glacier (Inner Tien Shan).