Specific Effects of the 1988 Earthquake on Topography and Glaciation of the Tsambagarav Ridge (Mongolian Altai) Based on Remote Sensing and Field Data

Strong earthquakes could serve as a trigger for glacier detachment and associated ice–rock avalanches. The 1988 Tsambagarav earthquake (M = 6.4) initiated collapse of part of the glacier tongue and a further ice–rock avalanche with an abnormal 5 km long path in Zuslan valley, Tsambagarav ridge (Mongolian Altai). Early documentation of surface effects in 1988, remote sensing and field data gathered 16 and 30 years after this event allowed for the assessment of the seismic impact on a reduction of “damaged” glacier under conditions of global warming as well as estimating topography changes in this arid and seismically active area. Because of the earthquake, the glacier immediately lost 10.4 % of its area (0.1 km2 of tongue surface). Additionally, 56% of its area was lost during 1988–2015, shrinking much faster than neighboring glaciers of similar size and exposition. Collapse of snow–ice cornice in the accumulation zone could play a key role in rapid acceleration of the detached ice block and abnormally long path of the ice–rock avalanche. A large amount of debris material provided more than 16 years of ice melting. Downstream, the valley avalanche debris cover repeats the topography of underlying Pleistocene moraines, which should be considered in regional paleogeographical reconstructions. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Funding: The study was supported by State Assignment of IGM SB RAS and partly funded by Russian Science Foundation (grant 22-27-00447)

Современное состояние и динамика нивально-гляциальных систем массивов Монгун-Тайга и Таван-Богдо-Ола

Climate-induced variations of glacio-nival systems (snow patches, glaciers, stone-ice formations) of the high-mountain massifs Mongun-Taiga and Tavan-Bogdo-Ola (north slope) were investigated for 1966-2013 period using results of field observations and analysis of aerial photos. Regional 25-year climatic cycles of the variations have been determined. Characteristics of response of glacio-nival objects to the climate changes were obtained. Results of preliminary mass balance calculations made for the 2012/13 glaciological year and values of the mass balance index calculated for the period 1966-2013 for the Seliverstov Glacier together with recorded climate cooling, increase of snow accumulation, and slowing down of glacier snout retreats give evidence to beginning of new 25-year cycle that is expected to be more favorable phase for existence of the above glacio-nival systems. Five-phase scheme of retreats of the valley glaciers happened after the LIA maximum was constructed on the basis of results of field observations performed for many years. Each phase is characterized by different retreat mechanisms as well as by different response to the same climate change that can be used as a basis for forecasting of future glacial dynamics. Rates of the thermokarst processes determined from observations and general mechanisms of dynamics of stone-ice formations are also discussed in the paper.Исследуются современная динамика параметров климата юго-восточного Алтая и реакция на них элементов нивально-гляциальных систем: снежников, ледников и каменно-ледовых образований. Установлено замедление отступания концов ледников в 1967–1981 и 2008–2013 гг., согласующееся с периодами относительного похолодания и увеличения осадков. Выполнены предварительные балансовые расчёты для 2012/13 гляциологического года и вычислены значения индекса баланса массы для периода 1966–2013 гг. для ледника Селиверстова. Приведены результаты измерений скоростей термокарстовых процессов на моренах малой ледниковой эпохи, ядро которых сложено погребённым ледниковым льдом

Изотопно-геохимические исследования нивально-гляциальных систем горного массива Табын-Богдо-Ола (Западная Монголия)

Results of investigation of glacio-nival systems made in the Tabyn-Bogdo-Ola mountains (Western Mongolia) are presented in the paper. Average content of δ18О in the Tsagan-Us river water amounts to 17.44‰ that is almost equal to the isotope content in the clear glacier runoff near the edge of the Kozlov Glacier (−17.43‰). It means that the isotope content in water doesn’t significantly change over a distance of 30 km along the Tsagan-Us river. Hence, it appears that for this distance the river has no additional non-glacial feed. The magnitude 17.4±0.1‰ can be considered as the average content of isotopes in the glacio-nival system in the Tabyn-Bogdo-Ola mountain massif. This value can also be the precipitation-weighted average isotope content in the solid precipitations which are accumulated in glaciers of this massif. Seasonal isotope fluctuations are partly preserved in the snow-firn mass in the accumulation area of the Kozlov Glacier. A rate of annual accumulation was estimated by multiplying the apparent thickness (160 cm) of an annual layer into the snow density. According to our observations, it is equal to 800 mm w.e./year during 2013–2014. Accumulation is increased due to the wind and avalanche transportation of snow. During the ablation season, summer and spring snowfalls over the Kozlov Glacier area melt. Thus, it is possible to suppose that the autumn snowfalls play the important role in the accumulation. We may also suppose that the main source of the moisture for the Tabyn-Bogdo-Ola massif is located somewhere in the Inner Asia.По результатам полевых работ 2013 и 2014 г. выполнен анализ изотопных характеристик образцов речной воды, снега и осадков. Оценена степень сохранности сезонного изотопного сигнала в снежно-фирновой толще, а также показана возможность использования изотопно-геохимического метода в гидрологических исследованиях. В области питания ледника Козлова получены оценки годовой аккумуляции в 800 мм. в.э. Показано, что основной источник осадков, питающих массив, – Внутренняя Азия

Особенности уровенного режима приледниковых моренно-подпрудных озёр в стадии роста (на примере озёр горного массива Таван-Богдо-Ола, Юго-Восточный Алтай)

Assessment of the dynamics of high-altitude glacial lakes is becoming increasingly important in the context of modern climate instability. The formation of new periglacial lakes and the growth of existing lakes as a result of the reduction of glaciers are recorded almost all over the world, including Russia. A rapid increase of a periglacial lake size may lead to the formation of an outburst flood. In this context, in order to prevent outburst floods, it is necessary to investigate outburst hazard lakes at all stages of their development. The periglacial lakes of the Altai mountains have been little-studied in comparison with other mountainous areas. At the same time, they are also characterized by the formation of new lakes during the period of climate nonstationarity. It was confirmed by the identified statistically significant trends in average monthly air temperatures during the ablation period. Based on the analysis of multi-temporal satellite images, it was found that the number of new periglacial lakes in the high-altitude territories of the Altai Republic (Katunsky ridge, North-Chuya ridge, South-Chuya ridge and the Tavan-Bogdo-Ola mountain massif) is increasing exponentially. For a more detailed survey and field hydrological studies, the authors chose the recently formed periglacial Lake Barsovo and periglacial Lake Gachi-Kol. Both lakes located within the northen slope of the Tavan-Bogdo-Ola mountain massif. Field observations, which were carried out in July-August 2021, have shown that both lakes are currently at the transgressive stage of development (growth stage). The transgressive phase of the lakes development is characterized by a rapid increase in size by the end of the warm period and a complex level regime on both diurnal and annual scales, due to the fact that both lakes are adjacent to the glacier.На основе анализа изменчивости гидролого-морфометрических характеристик озёр с применением спутниковых изображений и данных полевых гидрологических наблюдений, выполненных авторами в июле – августе 2021 г., описаны особенности гидрологического режима двух приледниковых озёр с трансгрессивной фазой развития, расположенных на территории горного массива Таван-Богдо-Ола (Республика Алтай)

Современное оледенение хребта Цамбагарав (северо‑западная Монголия) и его изменение с максимума малого ледникового периода

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.На основе полевых наблюдений и дешифрирования космических снимков составлены каталоги и карты современных ледников горного хребта Цамбагарав, существующих в условиях аридного климата северо‑западной Монголии. Реконструированы положение, размеры и характеристики ледников хребта в малый ледниковый период и проанализированы особенности их последующего сокращения

Современное оледенение хребта Чихачева (Юго-Восточный Алтай) и его динамика после максимума малого ледникового периода

Glaciation of the Chikhachev ridge (South-Eastern Altai) remains poorly known: field observations were not performed since the mid-twentieth century, available schemes and estimates of the glaciation and its scale made on the basis of remote sensing cover only a part of the glaciers, reconstructions of the Little Ice Age (LIA) glaciations are absent. This research was based on interpretation of the satellite images: Landsat-4 (1989), Landsat-7 (2001), and Spot-5 (2011), as well as with the use of data of the field season of 2015. Characteristics of glaciations of the Chikhachev ridge as the whole and of its individual centers (Talduair massif, Mongun-Taiga-Minor massif, and southern part of the Chikhachev ridge) were determined for the first time. Recent glaciation is represented by 7 glaciers with their total area of 1.12 km2 in the Talduair massif, by 5 glaciers with total area of 0.75 km2 in the Mongun-Taiga-Minor massif, and by 85 glaciers with total area of 29 km2 in the southern part of the Chikhachev ridge. Since the LIA maximum, areas of glaciers decreased by 61% in the Talduair massif, by 74% in the Mongun-Taiga-Minor massif, by 56% in the southern part of the Chikhachev ridge with simultaneous lifting of the firn line by 50 m, 65 m, and 70 m, respectively.The largest rates of the glacier contractions were determined for the period 1989–2011. Different mechanisms of the glacier retreats were shown by the example of the glacier complexes Burgastyn-Gol (one-sided retreat and disintegration) and the Grigorjev glacier (gradual retreat of the tongue). Retreat of the Grigorjev glacier has been reconstructed for the period from the LIA maximum until 2015. Average rate of the retreat increased from 1,6 m/year in 1957–1989 up to 11,3 m/year in 2011–2015. The present-day scales of the glaciers and rates of their retreating do not significantly differ from estimations made by other researchers for the nearest centers of glaciation of the Altai arid part. Stabilization of the temperature against the background of increasing precipitation suggests that in future retreating of small glaciers will slow down.На основе дешифрирования космических снимков и полевых исследований составлены каталоги и карты современных ледников малоисследованных центров оледенения Юго-Восточного Алтая: массивов Талдуайр, Монгун-Тайга-малая и южной части хребта Чихачева. Реконструировано оледенение хребта в малую ледниковую эпоху по снимкам 1989, 2001, 2011 гг. и результатам полевых исследований 2015 г.; выявлена динамика оледенения в целом и конкретных ледниковых комплексов

Влияние землетрясения 1988 г. на оледенение и рельеф массива Цамбагарав (Западная Монголия)

Early documentation of the consequences of the Tsambagarav earthquake happened on July 23, 1988 (M = 6.4) compiled by Soviet and Mongolian specialists allowed the authors, using the example of Tsambagarav (Mongolian Altai), to assess the impact of the seismic process on the reduction of mountain glaciation and topography of the trough valleys in the arid region of Central Asia. In 1988, in upper part of the Zuslan river valley, 13 days after the earthquake, the release of a fragment of one of the glaciers gave rise to an ice-rock avalanche «on an air cushion». Its deposits with a thickness of up to 30 m blocked the valley over a distance of 5 km. Analysis of space images taken in different time together with field researches revealed that as a result of the earthquake the glacier № 15 simultaneously lost 0.1 km2 of its tongue (10.4% of total area), as the whole in 1988–2015 it lost 56% of its area, whereas neighboring glaciers № 16 and 17, similar in size and the same exposure, lost significantly less – 35 and 15% of the area, respectively. Rapid shrinking of not only the glacier tongue, but also of its accumulation zone; the established deficit of ice volume in the broken off ice fragment (in comparison with initial assessment), and the abnormally long path of the avalanche made it possible to clarify the factors and mechanism of its initiation: the fall of the ice-snow ledge from the accumulation zone could lead to the rapid release of the broken ice fragment in the tongue part of the glacier. In 2004, 16 years after the avalanche, the buried ice in its deposits was still partially preserved, having completely degraded by 2019. The long time of the ice degradation process was caused by the high content (about half of the volume) of debris that armored the surface of avalanche sediments. The debris material of the avalanche repeats the relief of the underlying Pleistocene moraines, which may complicate the reconstruction of the number, scale and age of glacial events in avalanchehazardous areas. The relatively high rate of leveling of the avalanche traces and, as a consequence, the difficulties of their subsequent identification in the relief allow us to assume a greater number of avalanche releases, including seismic ones, in the recent geological past than it can be established at present in the Altai ridges.Ледник № 15 (по [3]), потерявший в результате Цамбагаравского землетрясения 1988 г. магнитудой М = 6,4 фрагмент языка (10,4% всей площади) и часть объёма в области аккумуляции, в период 1988–2015 гг. сократился на 56%, что больше сокращения соседних ледников (15–35%). Погребённый лёд в отложениях ледово-каменной лавины, заполнивших долину р. Зуслан на протяжении 5 км, частично сохранялся и в 2004 г.; полностью он растаял к 2019 г. Обломочный материал лавины повторяет рельеф подстилающих плейстоценовых морен, что может осложнить реконструкцию ледниковых событий в регионе. Уточнены факторы, определившие возникновение лавины на «воздушной подушке»

Особенности формирования ледникового стока на северном макросклоне массива Табын-Богдо-Ола по изотопным данным

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.Определены различия изотопного состава основных стокоформирующих компонентов на северном макросклоне массива Табын-Богдо-Ола. По изотопному разделению дана оценка доли ледникового стока в середине сезона абляции для крупнейших ледников массива. Выявлены отличия в изотопном составе талых ледниковых вод российской и монгольской частей массива, отмечена возможная связь между морфологическим типом ледников и долей талых снежных вод в стоке

On the interplay between Babai and Černý’s conjectures

Motivated by the Babai conjecture and the Černý conjecture, we study the reset thresholds of automata with the transition monoid equal to the full monoid of transformations of the state set. For automata with n states in this class, we prove that the reset thresholds are upperbounded by 2n2 -6n + 5 and can attain the value (Formula presented). In addition, we study diameters of the pair digraphs of permutation automata and construct n-state permutation automata with diameter (formula presented). © Springer International Publishing AG 2017