Volume 65, Nº 1 (2025)

Total air content (TAC) is a multi-proxy property of polar ice, which is thought to contain evidence of past changes in local insolation, summer temperature, meteorological conditions, and the elevation of glaciers at the site of ice formation. By revisiting two equally accurate TAC records obtained at the Vostok and EPICA DC drilling sites, we attempt a careful assessment of the contributions of different natural components (orbital and non-orbital, global and local), and of experimental uncertainties to the total variance of the TAC data. We show that a major contribution (~74 % of the total variance) is made by the non-thermal variations of the close-off porosity, which includes the local insolation signal (~44 %) and the non-orbital variations of the firn properties related to changes in weather conditions (~30 %). The insolation signal has been used to produce TAC-based timescales for the EPICA DC and Vostok ice cores (Raynaud et al., 2007; Lipenkov et al., 2011). In this paper, in order to better estimate the uncertainties of this dating technique, we compare the individual TAC timescales obtained for the two ice cores in their overlap age interval (150–390 ka) assuming that the insolation-related variations should be the same and synchronous at the two sites, which sit at similar latitudes. We prove that CWT analysis is the most reliable technique for tuning the experimental TAC records to their local summer insolation targets (ISI). It provides excellent reproducibility of the deduced TAC timescales (0.3±0.2 ka) and good synchronization of the records obtained from the different ice cores even though the scattering of the TAC data is large. Finally, using the same CWT technique we come to the construction of the coherent TAC-based orbital timescales for Vostok and EDC ice cores. Comparison of the TAC timescales with the optimized chronologies AICC2012 and AICC2023 for the Vostok and EDC cores showed that their discrepancy, as a rule, does not exceed 2 ka, which is consistent with both the standard error of the TAC-based dating method (±2.1 ka) and the standard errors of the AICC2012 (±1.9…4.8 ka) and AICC2023 (±0.8…2.6 ka) reference chronologies themselves. We show that the increase in the uncertainty of orbital dating can be related to the natural weakening of variations of local insolation in some periods of time. The decrease in amplitude of the ISI variations implies reduction of the insolation signal and increase of the noise/signal ratio in the air content record. We did not find high-amplitude short-term (millennial scale) non-orbital TAC variations that were synchronous in both the ice cores that were studied. On the other hand, some of these variations are well reproduced by measurements in the replicate ice cores drilled several tens of metres apart, which confirms their significance and link with changes in the local conditions of ice formation. Based on our study, we argue that applying a multi-core and dual-proxy (TAC and O₂/N₂) approach would be advantageous for comprehensive investigation of the uncertainties associated with the combined use of TAC and O₂/N₂ records for orbital dating of existing (Vostok, EDC, Dome Fuji) and future ice cores, including those which will be drilled in central Antarctica as part of the Oldest Ice projects.

The aim of this work is to investigate dynamics of lakes on Fedchenko glacier on Pamir mountains, as the area growth of lakes causes faster filtration, lower surface albedo and as consequence raises speed of the glacier and intensity of melting. Lowest part of this glacier has continuous debris cover, low velocities and nearly horizontal surface, which increases the likelihood of lakes in each season. This paper provides insight into the dynamics of the total area of lakes on the last 11.5 km of Fedchenko during 2016–2021, and provides a comparison of the area within and between each season at three altitudinal levels. Lake outlines are identified by combining two indexes – Normalised Difference Water Index and Modified Soil-Adjusted Vegetation Index – which were range-cut in range to separate water from other surfaces on the glacier. The changes in the patterns of seasonal lakes dynamics can be due to various reasons, so temperature and precipitation data are used to analyze the changes in supraglacial lake regime. Result shows that lakes occupy a small percentage of the total area – about 2% for the whole period, with a minimum of 0.7% in 2016 and a maximum of 2.2% in 2020. However, there are significant changes in the dynamics of the lakes, with the amplitude of area doubling from 0.15 km² to 0.3 km² over the period 2016–2021, with an increase in the absolute seasonal maximum value by 0.2 km². The regime also changes rapidly over the six years, from normal with an area peak only in late May in 2016–2018 to more chaotic regime with several peaks, usually two, in May and July, in 2019–2021. An important role in the analysis is played by two largest lakes on Fedchenko Glacier – moraine–dammed lake at the highest altitude range (3300–3600 m a.s.l.) and proglacial lake at the lowest altitude range (2900–3100 m a.s.l.) – which mainly have opposite dynamics comparing to small supraglacial lakes. They are continuously filling up until the end of ablation season, but the result shows that their relative area growth is less than growth of new smaller lakes over a period of six years. The rapid area growth and more chaotic dynamics of supraglacial lakes can indicate specific influence of climate changes on glaciers.

In this study, we compared ERA5-Land reanalysis data on snow water equivalent (SWE) with values of SWE obtained from snow-measuring surveys on 18 field (non-forest) and 17 forest routes in the Perm Territory for 1967–2023 and analyzed the long-term trends of SWE. In general, the ERA5-Land reanalysis reproduces SWE in the Perm region satisfactorily. Mean relative error for SWE in March does not exceed 15%. The average correlation coefficient between the reanalysis data and the same from the observations is 0.72 for non-forest locations and 0.83 for locations in forest. In the southern part of the region, the reanalysis does mainly overestimate SWE by 10–40 mm, while in the north and east of the territory, there is an underestimation of the same order. The greatest divergence between snow surveys and reanalysis are found during snowmelt season, especially for non-forest snow-measuring routes. As it follows the ERA5-Land data, average date of formation of the SWE maximum in the southern part of the region is close to March 25, and in the eastern mountainous part it falls on the second decade of April, which is 4–7 days later than according to snow surveys in the forest. According to the ERA5-Land data and observations, a statistically significant negative trend of SWE was revealed all over the territory in the first half of the cold season, especially pronounced in November. It is related to the autumn warming and a shift of snow cover onset to later dates. In March, the negative trend according to the ERA5 data is statistically significant only in the southern part of the region, where it reaches –12 mm/10 years, but no statistically significant decrease in SWE is found according to the snow survey data. In May, a significant reduction of SWE in the northeast of the region (up to 15 mm/10 years) is found, which is due to the warming in April and May, and an earlier start of snowmelt. A comparison with the snow survey data shows that the reanalysis reproduces well the inter-annual variability of SWE accumulated by March, especially in forest locations. A statistically significant increase in SWE was revealed on five snow measuring routes in field, while a statistically significant decrease – on two forest routes, which is not confirmed by the reanalysis data. These discrepancies may be related to changes in local snow accumulation conditions on snow-measuring routes.

Visual slope observations are still the main method of avalanche detection. As a result, avalanche statistics, especially in remote mountain areas, remain incomplete. Like earthquake forecasting, the avalanche prognosis is a complex task that requires a complete set of data on avalanche activity in the region and meteorological observations. To begin this process, it is necessary to create a remote all-weather automated avalanche monitoring system. The Kola Branch of the Geophysical Service of the Russian Academy of Sciences initiated developing a hardware and software package for the avalanche monitoring. The main function of this complex is the registration of seismic and infrasound signals. Over the last five years, a series of experiments have been conducted in the Khibiny Mountains aimed at registration of forced avalanche releases carried out by the avalanche safety service. During the experiments, signals produced by avalanches were recorded using a broadband seismometer and an array of three low-frequency microphones installed at varying distances from an avalanche source. The results obtained demonstrated the high recording capability of the infrasound method, but also revealed problems associated with the use of the seismic method. Technical solutions have been found and prototypes of software for automated detection of target signals have been created. Thus, the experimental complex to monitor avalanche activity in the Khibiny Mountains has been established. The operation of the complex has shown that infrasound signals generated by the movement of snow mass on the mountain slope allow detecting avalanches with a volume of about 5 thousand m³ at a distance of 7 km. The smallest recorded avalanche had a volume of 0.5 thousand m³ and was located in 2.5 km away from the station.

The paper considers a forecast of avalanche danger in the Caucasus at the end of the 21^st century based on the climatic avalanche indicator criterion developed at Moscow State University, using the results of the CMIP6 Earth System Models (ESM). The quality of models’ estimates of modern winter climate in the Caucasus has been evaluated. The best models were selected, for which the average temperature error is –0.6 °C, precipitation error is 10%. According to these models’ data, by the end of the XXI century the average winter air temperature in the Caucasus will be 4–6 °C higher than the present one, and the precipitation sum will exceed the modern value by 25%. The frequency of seasons with extreme moisture will increase 2–3 times (monthly precipitation more than 100 mm). The seasonal maximum precipitation at the end of the 21^st century will shift to March, while extremely dangerous avalanche winters are usually accompanied by a January maximum precipitation with a significant negative temperature anomaly. Experiments were also conducted with the numerical model SNOWPACK, which showed that despite the positive precipitation anomaly and the possible occurrence of cold winters, the most typical situation by the end of the 21^st century will be the formation of a homogeneous snow column with low density, or heavily watered snow cover. Both situations are not avalanche-prone. Therefore, the background forecast of avalanche danger for the years 2071–2100 can be formulated as follows: a significant decrease in the frequency of the most destructive large avalanches from dry snow in high-mountain areas and their disappearance in mid-mountain areas, and a tendency to an increase in the number of less dangerous avalanches from loose and wet snow.

The study examines the seasonal and interannual variability of the location and area of flaw polynyas in the Laptev Sea. It utilizes AARI regional charts of ice conditions in SIGRID-3 format covering the years 1997 to 2023 as initial data. The analysis is based on an algorithm developed previously for calculating the frequency of occurrence of multiple vector polygon intersections. As a result, monthly charts (from December to May) were created to show the spatial distribution of zones with a 50% occurrence frequency. The time series of the annual average of this indicator demonstrates a positive trend. The seasonal variations of the polynyas show a distinct pattern: in the first half of the season, the polynyas in the western part of the sea are typically open and wide. However, during spring, the extent of polynyas in the eastern part increases, while those in the western part decrease. This positive trend is observed in both parts of the sea throughout the season, with significant values noted during the spring months (April and May) in the western area. This is particularly important, as the polynya during this period marks the beginning of summer melting, which can have significant implications. By analyzing all polynas polygons from the study period (1997–2023), we identified polygons of recurring polynyas (with a 75% occurrence frequency) and stable polynyas (with a 50% occurrence frequency). It was discovered that the criterion for recurring polynyas corresponds only to a small section along the fast ice of Teresa Klavens and Thaddeus Bays. Notably, the Western New Siberian polynya has a 50% occurrence frequency and is located in a narrow strip northwest of Kotelny Island. Previous studies indicate that this section is part of the Great Siberian Polynya; however, it is evident that its development has been limited in recent decades. In contrast, the sections of the Northern-Eastern Taimyr and Anabro-Lena polynyas are significantly larger and exhibit high occurrence frequencies. This scenario may be linked to changes in large-scale atmospheric circulation and the dominance of western circulation patterns.

Aufeis is a surface accumulation of ice which is formed as layer-by-layer freezing of underground or river water periodically pouring onto the surface in winter. In July 2022, a geophysical survey was carried out in the valley of the Kyubyume River. The study was performed for the purpose to check a possibility to use GPR (150 and 250 MHz) for investigating internal structure of ice bodies, locations of underchannel taliks, and inferred zones of groundwater discharges, as well as revealing ice bodies in the gravel-pebble alluvium of the aufeis glade. The thickness of the aufeis amounted to 2.2 m, the geological cross-section was sounded down to depths of 4.5–8 m. Profiles were studied at right angles to the main channel of the river, including with access to the shoal of the glade. The measurement results did show that the layered ice of the aufeis is not a homogeneous medium for the GPR method, so this method may be used to study structure of the ice, and to investigate the processes of the aufeis formation. Two layers with a thickness of 1.1 m and 0.9 m were isolated in the aufeis ice, with ε = 4.1 and ε = 3.4, respectively. In the underlying alluvium, a cross bedding of the channel deposits was found that was the result of the river watercourse migration. In the sand and pebble deposits underlying the aufeis, a sub-horizontal layer was identified at depths of 2.5–3 m, which is presumably a lens of high-icy sedimentary rocks or underground ice.

The article presents the investigation of mineral particles from an ice core obtained from Ushkovsky volcano (Kamchatka) in the fall of 2022. The 14-meter-long ice core was studied to identify the causes of mineral dust concentration variability and to determine its sources. Insoluble solid particles, including volcanic ash and mineral dust, were analyzed using stereomicroscopy and X-ray diffraction. Minimum and maximum dust concentration values were 356.4 ppb and 45 969 ppb, respectively, with an average dust mass concentration across all data at 5 099 ppb and a median of 2 784 ppb. The results show a cyclic particle distribution linked to seasonality, with notable concentration peaks likely associated with volcanic activity and the transport of mineral dust from arid regions. It was found that surface melting leads to the leaching of calcium and magnesium ions from layers containing insoluble particles. The displacement of cation peaks relative to dust concentration peaks is variable and likely depends on the meteorological characteristics of individual summer seasons. Mineralogical analysis of the samples shows the presence of plagioclase, as well as clay and ferro-magnesial silicates and amorphous silica. Plagioclase dominates at all depths, indicating a predominance of volcanic ashes in the composition of insoluble impurities. The ratio of non-clay minerals (pyroxenes, amphiboles, and amorphous silica) can be used as markers of local transport, while the presence of clay minerals (smectite, kaolinite, chlorite) is suggested as an indicator of long-range transport. Thus, Kamchatka ice cores can be used to study the processes of mineral particle transport in the atmosphere, provided a comprehensive approach is applied, including mineral composition and chemical composition analyses as well as isotopic methods to determine material origin.

The study of the geological structure, dynamics of the ice sheet and the interaction of the subglacial systems of East Antarctica provides a unique opportunity to analyze the fundamental processes shaping the climate and geological evolution of our planet (Litvinenko, 2020). Conducting these studies is inextricably linked to the process of improving methods, technologies and techniques of geological, geophysical and drilling operations (Gorelik, 2024; Talalay, 2016). During the season of the 70^th Russian Antarctic Expedition (2024–2025), the staff of the Empress Catherine II Saint Petersburg Mining University will carry out comprehensive research at the Vostok and Progress stations, including; the development of new and improvement of existing technologies for drilling glaciers, the study of the physical-mechanical properties of firn, atmospheric and lake ice; the study of structural geological features and reconstruction of the tectonic evolution of the coastal regions of East Antarctica.