The Circumpolar Landcover unit database provides landcover information in high detail, spatially (10m) and thematically (23 units). Such detail is needed for a wide range of applications targeting climate change impacts and ecological research questions. The landcover unit retrieval scheme used provides unprecedented detail. The landcover units have been derived by fusion of satellite data using Sentinel-1 (synthetic aperture radar) and Sentinel-2 (multispectral). The units reflect gradients of moisture as well as vegetation physiognomy. The original database covered the Arctic north of the tree line. It has been extended towards south, providing additional detail within the tundra-taiga transition zone in permafrost regions. The available spatial detail provides the means to assess the complexity of this zone in addition to information on recent disturbance related to for example wildfire and thermokarst lake change. Bartsch, A., Efimova, A., Widhalm, B., Muri, X., von Baeckmann, C., Bergstedt, H., Ermokhina, K., Hugelius, G., Heim, B., & Leibmann, M. (2023). Circumpolar Landcover Units (1.0) [Data set]. Zenodo. https://doi.org/10.5281/zenodo.8399018

The identification of spatial soil moisture patterns is of high importance for various applications in high-latitude permafrost regions but challenging with common remote sensing approaches due to high landscape heterogeneity. Seasonal thawing and freezing of near-surface soil lead to subsidence–heave cycles in the presence of ground ice, which exhibit magnitudes of typically less than 10 cm. Our investigations document higher Sentinel-1 InSAR (interferometric synthetic aperture radar) seasonal subsidence rates (calculated per thawing degree days – a measure of seasonal heating) for locations with higher near-surface soil moisture compared to drier ones. Based on this, we demonstrate that the relationship of thawing degree days and subsidence signals can be interpreted to assess spatial variations in soil moisture. A range of challenges, however, need to be addressed. We discuss the implications of using different sources of temperature data for deriving thawing degree days on the results. Atmospheric effects must be considered, as simple spatial filtering can suppress large-scale permafrost-related subsidence signals and lead to the underestimation of displacement values, making Generic Atmospheric Correction Online Service for InSAR (GACOS)-corrected results preferable for the tested sites. Seasonal subsidence rate retrieval which considers these aspects provides a valuable tool for distinguishing between wet and dry landscape features, which is relevant for permafrost degradation monitoring in Arctic lowland permafrost regions. Spatial resolution constraints, however, remain for smaller typical permafrost features which drive wet versus dry conditions such as high- and low-centred polygons.

The paper presents research findings of the climatic factors responsible for the activation of thermal denudation processes leading to the formation of thermocirques in the central part of the Yamal Peninsula in the north of West Siberia. Based on a comparison of multi-temporal remote sensing (2010, 2013 and 2018) coupled with climate data, an analysis of the thermocirques activity in 2010–2018 was carried out. Thermocirques are specific topographic forms that arise because of the activation of cryogenic earth flows, the formation of which is caused by an increased seasonal thawing of the upper part of the ground ice on the slopes as compared to the previous years. Analysis of the monitoring data showed that in 2012 and 2013 all the types of surfaces are characterized by a significant increase in seasonal thawing compared to the previous period 1993–2011 (12 % increase on slopes), due to the summer air temperature, the amount of summer precipitation and the increased duration of the warm period. The results of the thermocirques activity analysis are shown on a map. The results of this local study were compared with those of a regional (Yamal and Gydan Peninsulas) remote sensing study of thermocirques. This showed a higher accuracy of the local study based on field monitoring and very-high-resolution satellite imagery. The analysis of the thermocirques activity showed that 1) over the period from 2010 to 2018 thermal denudation activity in the study area increased due to the anomalous climatic conditions in the spring-summer season of 2012, and then gradually decreased; 2) in addition to “classical” thermocirques, which were at different stages of activity in the time periods analyzed (2010, 2013 and 2018), a significant number of embryonic thermocirques were identified. Such thermocirques, just as the majority of small “classical” thermocirques, can only be identified on very-high-resolution satellite imagery.

The results of the application of geo-radar profiling for the study of soils and underlying rocks of polygonal bogs of the Pur-Taz interfluve (North of Western Siberia), functioning in natural and anthropogenic disturbed conditions, are presented. The research area belongs to the southern tundra with a predominantly continuous distribution of permafrost rocks. The construction of highways in the North of Russia is one of the main factors of anthropogenic impact on the tundra geosystems of the cryolithozone, affecting the temperature regimes of soils and the depth of permafrost. The features of spatial differentiation of the depth of occurrence of permafrost rocks on the site of polygonal swamps intersected by a federal highway were determined by the methods of geo-radar profiling. Georadiolactic profiling made it possible to determine the configuration of the depth of the permafrost roof both in natural and anthropogenic disturbed areas of polygonal swamps. The maximum lowering of the permafrost roof is determined at the base of the road embankment and does not exceed a depth of three meters. Despite the deep occurrence of the MMP roof under the road embankment, the thickness of the thawed buried peat horizons here is similar to that of the seasonally shallow layer of undisturbed peat polygons. The features of spatial differentiation of the depth of the permafrost roof in the polygonal swamps intersected by the bulk highway in the North of Western Siberia are similar to those characteristic of regions with a continuous low-temperature cryolithozone. The method of manual probing of the permafrost roof was used to verify the results of geo-radar profiling within undisturbed areas.

Summary Climate changes occurring in the Arctic regions cause the transformation of permafrost conditions, including thawing of permafrost. In the last decade, cryogenic processes have been intensifying in the Arctic, including the southern tundra of Western Siberia. In the peat bogs of the khasyreys of the Pur-Taz interfluve, thermokarst processes along polygonal-wedge ice and thermal erosion are especially widespread. However, there is a significant lack of research related to the impact of transport infrastructure on polygonal peatlands. The Ground Penetrating Radar (GPR) method has shown itself to be effective in solving geocryological problems associated with areas of development of peatlands. This work is devoted to the use of GPR for assessing the warming effect of a road in a complex of geocryological works. All profiles crossed the road, the main emphasis was on the warming effect of the road and roadside depressions on the permafrost roof. The anthropogenic impact on the permafrost roof is clearly reflected in its position on the ground penetrating radar data.

В 2021 г. продолжен мониторинг глубины сезонного протаивания, температуры многолетнемерзлых пород, активности криогенных процессов, связанных с вытаиванием подземных льдов, и изменений, происходящих с полигональными торфяниками на полуострове Ямал, севере Пур-Тазовского междуречья и Гыданского полуострова. Представлены основные результаты исследований.

Построена теоретическая модель влияния климатических изменений и техногенного воздействия на прибрежную полосу озер и рельефа полигональных торфяников на севере Пур-Тазовского междуречья. Выделены 3 участка, на которых наблюдаются максимальные изменения полигональных торфяников. Выявлены статистические данные по степени трансформации торфяников и проводится мониторинг на этих участках.

Remote sensing methods make it possible to evaluate the reaction of the cryolithozone and tundra landscapes in hard-to-reach Arctic areas based on the indicators of modern climate changes. In 2016–2019, numerous organic frost boils were discovered on the peatland surfaces of drained lakes in the southern tundra of the Pur-Taz interfluve in the northern part of West Siberia and studied. It is established that the formation of frost boils caused by organic mass injections occurs in the summertime and that they indicate local deepening of seasonal thawing. Frost boils emerging at peatlands in summertime was identified after analysis of UAV survey in 2019. Local deepening of seasonal thaw layer on polygonal peatlands is evidence of permafrost reaction to global warming.

Various climatic parameters (average annual, winter, and summer air temperature, winter and summer total precipitation) and their temporal variability are analyzed to explain the activation of cryogenic processes in Central Yamal. The effect of fluctuations of these parameters on the thaw depth and ground temperature is analyzed. The regression analysis is carried out to reconstruct ground temperature during earlier periods of time in the years preceding the activation of thermal denudation and the formation of gas emission craters.

В 2018 году продолжены комплексные исследования криолитозоны, начатые в 2016 г. в северо- восточной части Пур-Тазовского междуречья. Проводится мониторинг глубины сезонного протаивания в различных ландшафтных условиях от дренированных водоразделов до полигональных торфяников. На одном из торфяников отслеживаются изменения рельефа за счет вытаивания полигонально-жильного льда, изучается морфология льда и криолитологическогостроениявмещающихотложений. Вовремяполевойкампании 2018 г. заложеныдополнительные площадки мониторинга глубины протаивания. Для изучения детальной пространственной дифференциации глубины протаиванияиопределениятехногенногоиестественноговоздействиянаучасткахсполигонально-жильнымильдами выполнены георадиолокационные исследования. Продолжено сопоставление ботанического состава современной растительности и многолетнемерзлого торфа, изучение почв пятен-медальонов в контуре торфяника. Начаты работы по оценке дефляционного влияния на осадконакопление минеральных пород в пределах торфяника. Started in 2016 complex studies of the cryolithozone in northeastern part of the Pur-Taz interfluve continue in 2018. Seasonal thaw depth in different landscapes from drained watersheds to polygonal peatlands is monitored. On one of the peatlands, the relief changes due to the melting of polygonal-wedge ice are observed, the morphology of ice and the cryolithological structure of the enclosing sediments are studied. During the field campaign of 2018 additional sites for thaw depth monitoring were established. To study the detailed spatial differentiation of thaw depth and to determine technogenic and natural impacts in the areas with polygonal-wedge ice georadar survey was performed. We continued the comparison of modern vegetation botanical composition with a permafrost peat and the study of spot-medallions soil in the peatland was carried on. We carried out the first stage assessment of the deflation impact on the mineral sedimentation within the peatland.

Formation of gas emission craters (GEC) is a new process in the permafrost zone, leading to considerable terrain changes. Yet their role in changing the relief is local, incomparable in the volume of the removed deposits to other destructive cryogenic processes. However, the relief-forming role of GECs is not limited to the appearance of the crater itself, but also results in positive and negative microforms as well. Negative microforms are rounded hollows, surrounded by piles of ejected or extruded deposits. Hypotheses related to the origin of these forms are put forward and supported by an analysis of multi-temporal satellite images, field observations and photographs of GECs. Remote sensing data specifically was used for interpretation of landform origin, measuring distances and density of material scattering, identifying scattered material through analysis of repeated imagery. Remote-sensing and field data reliably substantiate an impact nature of the hollows around GECs. It is found that scattering of frozen blocks at a distance of up to 293 m from a GEC is capable of creating an impact hollow. These data indicate the influence of GEC on the relief through the formation of a microrelief within a radius of 15–20 times the radius of the crater itself. Our study aims at the prediction of risk zones.

Study area in continuous permafrost zone, characterized by tabular ground ice distribution, is known for active slope processes. In 90-s main attention was paid to translational landslides (active layer detachments). Due to climate trends summer temperature became warmer, active layer depth increased. As a result, active-layer base ice thawed and stopped development of translational landslides. At the same time, tabular ground ice table got involved into seasonal thaw and triggered earth flows at the lake shores, the second known type of cryogenic landslides found previously mainly at the sea coasts. Earth flows are the main process in thermal denudation: a complex of processes responsible for formation of thermocirques. Thermocirques are semi-circle shaped depressions resulting from massive ground ice thaw and removal of detached material downslope. Monitoring of thermocirque activation and development allows analyzing climatic controls of thermal denudation, and rates of thermocirque enlargement. At present in the Yamal Peninsula tundra predominance of processes associated with tabular ground ice thaw (cryogenic earth flows) over the processes associated with the ice formation at the bottom of the active layer (cryogenic translational landslides) is observed. This is caused by deepening of the active layer and exposure of the massive ground ice (tabular ground ice or ice-wedges) within permafrost to first seasonal and then perennial thaw. Activation of thermal denudation which started on Yamal Peninsula in summer 2012, is associated with extremely warm spring and summer of this year, and the warmest July of 2013. By the end of the warm season thawing of the top of icy permafrost and tabular ground ice on some slopes resulted in cryogenic landsliding in the form of earth flows and further thermocirque development. Thermocirques may form on slopes of various aspects but develop faster on south-facing slopes.

We have carried out paleomagnetic studies of the Upper Vendian sedimentary rocks from the Bashkirian Meganticlinorium (Southern Ural). The rocks were sampled at three localities spread over more than 100 km. Totally, more than 300 samples were collected from about 40 sampling sites. Stepwise thermal demagnetization up to 700°C revealed a stable component of magnetization of either polarity in 25 sites. The fold test and the reversal test for this component are positive, which is usually regarded as a sound argument in favor of the primary origin of magnetization. However, the Basu paleomagnetic pole (longitude 187.3°E, latitude 1.1°N) is located near the Late Ordovician-Early Silurian segment of the apparent polar wander path for Baltica, which might indicate a Paleozoic remagnetization of Vendian rocks. In this work we analyze different interpretations of the obtained results and evaluate the reliability of the Late Riphean and Vendian paleomagnetic data for Baltica.