Permafrost Distribution Research Articles

Spectral induced polarization imaging to investigate an ice-rich mountain permafrost site in Switzerland

Abstract. Spectral induced polarization (SIP) measurements were collected at the Lapires talus slope, a long-term permafrost monitoring site located in the western Swiss Alps, to assess the potential of the frequency dependence (within the frequency range of 0.1–225 Hz) of the electrical polarization response of frozen rocks for an improved permafrost characterization. The aim of our investigation was to (a) find a field protocol that provides SIP imaging data sets less affected by electromagnetic coupling and easy to deploy in rough terrains, (b) cover the spatial extent of the local permafrost distribution, and (c) evaluate the potential of the spectral data to discriminate between different substrates and spatial variations in the volumetric ice content within the talus slope. To qualitatively assess data uncertainty, we analyse the misfit between normal and reciprocal (N&R) measurements collected for all profiles and frequencies. A comparison between different cable setups reveals the lowest N&R misfits for coaxial cables and the possibility of collecting high-quality SIP data in the range between 0.1–75 Hz. We observe an overall smaller spatial extent of the ice-rich permafrost body compared to its assumed distribution from previous studies. Our results further suggest that SIP data help to improve the discrimination between ice-rich permafrost and unfrozen bedrock in ambiguous cases based on their characteristic spectral behaviour, with ice-rich areas showing a stronger polarization towards higher frequencies in agreement with the well-known spectral response of ice.

Variation characteristics and quantitative study of permafrost degradation in the upper reaches of Heihe River, China

To quantitatively investigate the permafrost degradation and its effects on hydrological processes in the upper reaches of Heihe River, a surface frost number model was firstly constructed to simulate the permafrost distribution and degradation from 1980 to 2015. The variation characteristics of the DDF, permafrost area, low limit of permafrost, and active layer thickness were then determined in the study area. Furthermore, the Budyko framework was applied to quantify the contribution of permafrost degradation to runoff. The results indicated that the permafrost degradation was significant in the past 36 years, with an average decreasing rate of 80.4 km2/a in the permafrost area, an average increasing rate of 13 m/a and 0.61 cm/a in the low limit elevation and in the active layer thickness, respectively. It is also found that basin characteristic parameter in the Budyko framework is closely related to permafrost degradation in cold regions, 40% of whose change is contributed by permafrost degradation. In addition, it is revealed that permafrost degradation contributed more than 20% to runoff change in study area. This investigation also indicated that the runoff response to permafrost degradation has a 3 months delayed effect. This study deepens the understanding of the impact of permafrost degradation on hydrological processes.

Influence of permafrost and hydrogeology on seasonal and spatial variations in water chemistry of an alpine river in the northeastern Qinghai-Tibet Plateau, China

Known as the third pole of the world, the Qinghai-Tibet Plateau has been experiencing rapid permafrost warming and thawing over the last few decades. However, the impact of permafrost distribution and hydrogeology on river hydrochemistry in alpine areas remains unclear. This study conducted four sampling campaigns to reveal the temporal and spatial variations in and factors driving river hydrochemistry in the upper reaches of the Heihe River, the northeastern Qinghai-Tibet Plateau. We found that the concentrations of major ions and total dissolved solids (TDS) in river water showed substantial seasonal variations; the concentrations were generally lower during the initial thawing and thawed periods than during the initial freezing period. However, solute fluxes during the thawed period were much higher than those during the frozen period. The concentrations of major ions and TDS gradually decreased to a minimum from the permafrost meander (PM) section to the seasonal frost meander (SFM) section and then increased the seasonal frost canyon section. Using the revised forward model, we found that river solutes were contributed by carbonate weathering (mean 38.9%) > sulfide oxidation (22.9%) > evaporite dissolution (20.2%) > atmospheric precipitation (8.7%) > silicate weathering (5.0%) > glacial meltwater (4.3%). The higher TDS, Na+, Cl−, Ca2+, Mg2+, and SO42− concentrations in the PM section reflected the influence of freeze-out fractionation. The concentrations of major ions and TDS were lowest in the SFM section, indicating that the riparian porous aquifer was essential in regulating river hydrochemistry, thus reducing its spatiotemporal variations in the alpine area. In the mountain glacier–hillslope–riparian porous aquifer–river system, the river was mainly recharged by groundwater with insufficient water–rock interactions due to the rapid flow owing to the high elevation difference and high permeability of the riparian quaternary porous aquifers. Our findings provide insights into the construction of hydrogeochemical models in alpine areas and are practically important for the scientific management of water resources in the Qinghai-Tibet Plateau.

Temperature Change in the Chambers of Underground Structures when operating Diesel Units

The thermal regime of underground cryolithozone structures for various purposes, both related and not related to mining production, is an important factor determining their reliable and safe operation. In this regard, the forecast of the thermal regime in mine workings is a mandatory and important element in the justification of design solutions for the construction and reconstruction of underground structures in the areas of distribution of continuous and island permafrost. One of the main sources of heat generation in the workings is the work of diesel equipment, which is widely used, both in the development of mineral deposits by the underground method, and to ensure technological processes in underground structures of non-mining profile. The purpose of the research was to quantitatively assess the effect of diesel installations on the thermal regime in the underground structures of the cryolithozone. The results of numerical calculations are presented in the form of 2D and 3D graphs, which allow you to visually assess the effect of diesel equipment on the increment of air temperature in the underground structure, depending on the time of year and the efficiency of the diesel installation. It is shown, in particular, that in the most probable range of changes in the efficiency of a diesel installation, the air temperature can vary from 3.2 to 6.3 °C, depending on the standard values of the ventilation air flow. It is established that the temperature increment does not depend on the number of simultaneously operating diesel units and is determined only by the specific standard air flow (m3 / s per 1 kW of installation power).

Spatial and Temporal Variability of Permafrost in the Western Part of the Russian Arctic

Climate warming in the Russian Arctic over the past 40 years shows a variety of patterns at different locations and time periods. In the second half of the 20th century, the maximum rates of warming were characteristic of the subarctic permafrost regions of Russia. But in the 21st century, the locations of the greatest rates of climate warming moved to the Arctic zone of Russia. It was one of the reasons for a sharp increase in permafrost temperatures, an increase in the depth of seasonal thaw, and the formation of closed taliks. It was found that as a result of climate change, the differences in permafrost temperatures between different cryogenic landscapes in the area of continuous and discontinuous permafrost distribution have decreased, and in the area of sporadic permafrost distribution are now practically absent. The thermal regime of the ground shows dramatic changes everywhere with a pronounced reduction in the depth of zero annual amplitude.

Impacts of Permafrost Degradation on Hydrology and Vegetation in the Source Area of the Yellow River on Northeastern Qinghai-Tibet Plateau, Southwest China

Under a persistent warming climate and increasing human activities, permafrost in the Source Area of the Yellow River (SAYR) has been degrading regionally, resulting in many eco-environmental problems. This paper reviews the changes in air temperature and precipitation over the past 60 years and presents the distribution and degradation of alpine permafrost in the SAYR. The review is focused on the permafrost degradation–induced changes in hydrology, wetlands, thermokarst lakes, ponds, and vegetation. Mean annual air temperatures have been rising at an average rate of 0.4°C/10a over the past 60 years, while precipitation has increased only slightly (16 mm/10a). Borehole temperature monitoring at the depth of 15 m shows the permafrost warming rates of 0.01–0.21°C/10a in the Headwater Aera of the Yellow River. As a result of permafrost thaw, the amount of surface waters has declined while groundwater storage has increased. Due to permafrost degradation, the supra-permafrost water table lowers gradually, resulting in a reduction in areal extents of wetlands and lakes in the SAYR. We further renamed the concept of the burial depth of the ecologically-safe supra-permafrost water table, the minimum depth of the groundwater table for sustaining the normal growth of alpine grassland vegetation, for the SAYR to describe the relationship between the lowering permafrost table and succeeding alpine vegetation. Furthermore, we recommended more studies focusing on snow cover and carbon stock and emissions related to permafrost degradation under a warming climate. We also advised to timely establish the long-term monitoring networks for the rapidly changing mountain cryosphere, alpine ecology, alpine hydrology, eco-hydrology, cryo-hydrogeology, and carbon fluxes. Moreover, process-based models should be developed and improved to better simulate and predict the responses of alpine ecosystem changes to the interacting cryospheric and other environmental variables and their ecological and ecohydrological impacts in the SAYR and downstream Yellow River basins. This study can help better manage the ecological and hydrological environments in the Upper Yellow River that are sensitive to changes in the alpine climate and cryosphere.

Alpine permafrost could account for a quarter of thawed carbon based on Plio-Pleistocene paleoclimate analogue

Estimates of the permafrost-climate feedback vary in magnitude and sign, partly because permafrost carbon stability in warmer-than-present conditions is not well constrained. Here we use a Plio-Pleistocene lacustrine reconstruction of mean annual air temperature (MAAT) from the Tibetan Plateau, the largest alpine permafrost region on the Earth, to constrain past and future changes in permafrost carbon storage. Clumped isotope-temperatures (Δ47-T) indicate warmer MAAT (~1.2 °C) prior to 2.7 Ma, and support a permafrost-free environment on the northern Tibetan Plateau in a warmer-than-present climate. Δ47-T indicate ~8.1 °C cooling from 2.7 Ma, coincident with Northern Hemisphere glacial intensification. Combined with climate models and global permafrost distribution, these results indicate, under conditions similar to mid-Pliocene Warm period (3.3–3.0 Ma), ~60% of alpine permafrost containing ~85 petagrams of carbon may be vulnerable to thawing compared to ~20% of circumarctic permafrost. This estimate highlights ~25% of permafrost carbon and the permafrost-climate feedback could originate in alpine areas.

Multi-Parameter Protocol for Geocryological Test Site: A Case Study Applied for the European North of Russia

An increase in air temperature leads to a significant transformation of the relief and landscapes of the Arctic. The rate of permafrost degradation, posing a profound change in the Arctic landscape, depends on air temperature, vegetation cover, type of soils, surface and ground waters. The existing international circumpolar programs dedicated to monitoring the temperature state of permafrost TSP (Thermal State Permafrost) and active layer thickness CALM (Circumpolar Active Layer Monitoring) are not sufficient for a comprehensive characterization of geocryological conditions. Yet, no standardized protocol exists for permafrost monitoring and related processes. Here, we propose a novel multi-parameter monitoring protocol and implement it for two sites in the European part of the Russian Arctic: the Yary site along the coast of the Baydaratskaya Bay in the Kara Sea (68.9° N) within the continuous permafrost area and the Hanovey site in the Komi Republic (67.3° N) within the discontinuous permafrost area. The protocol includes drilling boreholes, determining the composition and properties (vegetation cover and soils), snow cover measurement, geophysical imaging, active layer estimation and continuous ground temperature measurements. Ground temperature measured in 2014–2020 revealed that amplitudes of surface temperature fluctuations had no significant differences between the Yary and Hanovey sites, while that the mean annual temperatures between the areas had a considerable difference of greater than 3.0 °C. The period of the presence of the active layer changed with the year (e.g., ranging between 135 and 174 days in the Yary site), showing longer when the air temperatures in summer and the preceding winter were higher. Electrical resistivity tomography (ERT) allowed determining the permafrost distribution and active layer thicknesses. Thermometry results were consistent with our geophysical data. Analyzing the composition and properties of frozen soils helped better interpret the data of geophysical and temperature measurements. By integrating the study of the soil properties, ground temperatures, and ERT, our work allowed us to fully characterize these sites, suggesting that it helps better understand the thermal state at any other research sites in the European north of Russia. Our suggested monitoring protocol enables calibrating and verifying the numerical and analytical models of the heat transfer through the earth’s surface.

Permafrost in monitored unstable rock slopes in Norway – new insights from temperature and surface velocity measurements, geophysical surveying, and ground temperature modelling

Abstract. The warming and subsequent degradation of mountain permafrost within alpine areas represent an important process influencing the stability of steep slopes and rock faces. The unstable and monitored slopes of Mannen (Møre and Romsdal county, southern Norway) and Gámanjunni-3 (Troms and Finnmark county, northern Norway) were classified as high-risk sites by the Norwegian Geological Survey (NGU). Failure initiation has been suggested to be linked to permafrost degradation, but the detailed permafrost distribution at the sites is unknown. Rock wall (RW) temperature loggers at both sites have measured the thermal regime since 2015, showing mean rock surface temperatures between 2.5 and −1.6 ∘C depending on site and topographic aspect. Between 2016 and 2019 we conducted 2D and 3D electrical resistivity tomography (ERT) surveys on the plateau and directly within the rock wall back scarp of the unstable slopes at both sites. In combination with geophysical laboratory analysis of rock wall samples from both sites, the ERT soundings indicate widespread permafrost areas, especially at Gámanjunni-3. Finally, we conducted 2D thermal modelling to evaluate the potential thermal regime, along with an analysis of available displacement rate measurements based on Global Navigation Satellite System (GNSS) and ground- and satellite-based interferometric synthetic aperture radar (InSAR) methods. Surface air and ground temperatures have increased significantly since ca. 1900 by 1 and 1.5 ∘C, and the highest temperatures have been measured and modelled since 2000 at both study sites. We observed a seasonality of displacement, with increasing velocities during late winter and early spring and the highest velocities in June, probably related to water pressure variations during snowmelt. The displacement rates of Gámanjunni-3 rockslide co-vary with subsurface resistivity and modelled ground temperature. Increased displacement rates seem to be associated with sub-zero ground temperatures and higher ground resistivity. This might be related to the presence of ground ice in fractures and pores close to the melting point, facilitating increased deformation. The study demonstrates and discusses the possible influence of permafrost, at least locally, on the dynamics of large rock slope instabilities.

In-situ temperatures and thermal properties of the East Siberian Arctic shelf sediments: Key input for understanding the dynamics of subsea permafrost

Significant reserves of methane (CH4) are held in the Arctic shelf, but the release of CH4 to the overlying ocean and, subsequently, to the atmosphere has been believed to be restricted by impermeable subsea permafrost, which has sealed the upper sediment layers for thousands of years. Our studies demonstrate progressive degradation of subsea permafrost which controls the scales of CH4 release from the sediment into the water-atmospheric system. Thus, new knowledge about the thermal state of subsea permafrost is crucial for better understanding of the permafrost -hydrate system and associated CH4 release from the East Siberian Arctic Shelf (ESAS) – the broadest and shallowest shelf in the World Ocean, which contains about 80% of subsea permafrost and giant pools of hydrates. Meanwhile, the ESAS, still presents large knowledge gaps in many aspects, especially with respect to subsea permafrost distribution and physical properties of bottom sediments. New field data show that the ESAS has an unfrozen (ice-free) upper sediment layer, which in-situ temperature is −1.0 to −1.8 °C and 0.6оС above the freezing point. On one hand, these cold temperature patterns may be related to the presence of subsea permafrost, which currently primarily occurs in the part of the ESAS that is shallower than 100 m, while ice-bearing sediments may also exist locally under deeper water in the Laptev Sea. On the other hand, the negative bottom sediment temperatures of −1.8 °C measured on the Laptev Sea continental slope sediments underlying water columns as deep as down to 330 m may result from dissociation of gas hydrates or possibly from dense water cascading down from the shelf. In contrast, data collected on recent expeditions in the northern Laptev shelf, zones of warmer bottom temperatures are coinciding with methane seeps, likely induced by seismic and tectonic activity in the area. These warm temperatures are not seen in the East Siberian Sea area, not even in areas of methane seeps, yet with little seismic activity.The thermal conductivity and heat capacity of bottom sediments recorded in the database of thermal parameters for the ESAS areas mainly depend on their lithification degree (density or porosity), moisture content, and particle size distribution. The thermal conductivity and heat capacity average about 1.0 W/(m·K) and 2900 kJ/(m3·K), with ±20% and ±10% variance, respectively, in all sampled Arctic sediments to a sub-bottom interval of 0–0.5 m.

Kinematics of an Alpine rock glacier from multi-temporal UAV surveys and GNSS data

The quantification of rock glacier dynamics has gained increasing importance in recent years. In this study, the spatial and temporal flow patterns of perennially frozen debris in the active Gran Sometta rock glacier (Western Italian Alps) were investigated with repeated Unmanned Aerial Vehicle (UAV) surveys (2016–2019), Global Navigation Satellite System (GNSS) campaigns (2012−2020), geophysical prospections (2015) and ground surface temperature data (2014–2020).UAV data were used to generate maps of changes and elevation differences of the rock glacier surface by 3D point cloud comparison to evaluate surface lowering and accumulation processes. Horizontal velocities were quantified by an automatic image correlation technique and the results were then compared with horizontal surface velocities from GNSS measurements on selected points. The horizontal velocities estimated with the automatic method agree well with the GNSS velocities with an R2 = 0.99 and a RMSE lower than 0.07 m/y.Point cloud comparisons show surface lowering in the orographic left-hand side of the terminal part and in the central body of the rock glacier. The upper part exhibits almost absence of subsidence and any movement. This is explained by the lack of permafrost in this sector due to its overriding by the development of a small glacier during the Little Ice Age. As a result of the downslope movement, zones of surface rising occurred at the advancing front and at the moving ridge and furrow complexes. Surface velocity decreases from the orographic left to the right-hand side of the rock glacier tongue, where a thaw subsidence of up to 0.05 m/y was also observed. According to the GNSS measurements, the range of flow velocity of the rock glacier increased from 0.17–1.1 m/y in 2013 to 0.21–1.45 m/y in 2015 and then decreased until 2018 when the smallest surface velocity is detected. Since 2018, the creep velocities gradually started to increase again reaching values of 0.23 m/y up to a maximum of 1.9 m/y in the orographic left-hand side of the rock glacier tongue. This agrees with observations from other rock glaciers in the European Alps in recent decades.The complex Gran Sometta rock glacier dynamics can be explained by the heterogeneous distribution of permafrost and related subsurface perennially frozen ground which is thick enough (about 20–30 m) for permafrost creep to occur. Creep rates of the rock glacier permafrost depend also on the ground thermal regime: annual warmer surface conditions promote an acceleration of the creep rates within the rock glacier permafrost, whereas ground surface cooling causes a slight deceleration.

Global permafrost simulation and prediction from 2010 to 2100 under different climate scenarios

This paper aims to simulate and predict global permafrost distribution, and analyse its change from 2010 to 2100 under different climate scenarios. Based on different factors (topography, land cover, climate and location) and global permafrost distribution status, logistic regression model (LRM) is chosen and constructed to simulate and predict the global permafrost distributions. Thus, the global permafrost distributions at T1 (2010–2040), T2 (2040–2070) and T3 (2070–2100) are predicted under different climate scenarios (RCP26, RCP45 and RCP85). From T1 to T3, the area of global permafrost has the largest degradation under RCP85 scenarios. From RCP26 to RCP85 at T3, the area of the degraded permafrost reached 0.671 × 108 km2. The degraded permafrost mainly distributes in east Asia, west Asia, north Europe and north America. The west Asia has the highest degrading distance, about 600 km under the situations of both RCP85 from T1 to T3 and from RCP26 to RCP85 at T3.

Distribution of permafrost and gas hydrates in relation to intensive gas emission in the central part of the Laptev Sea (Russian Arctic)

This article describes the results of a comprehensive analysis of the causes of intensive gas emission over a large zone (ca. 80 × 220 km) of the Central Laptev shelf area. The upper parts of 28 sections of common depth point (CDP) seismic lines acquired by the JSC MAGE, covering a total length of 5930 km over an area of 55,000 km2, were interpreted and 519 anomalous objects potentially connected with gas saturation were revealed. For the first time, the boundary between frozen and thawed sediments was defined in the Laptev Sea. The absence of subsea permafrost and gas hydrates in the intensive gas seepage zone was determined. The connection between gas seeps and deep-seated faults identified in seismic sections was substantiated. This study demonstrated that seismotectonic factors caused a large spatial window of long-term Earth degassing with direct intensive migration of deep thermogenic gas to the hydrosphere through a system of faults. A zone of potential gas hydrate distribution was observed on the continental slope.

Formation and distribution of permafrost and taliks under channels of the Lena River Delta

Formation and distribution of permafrost and taliks under channels of the Lena River Delta

Impact of Glacier Changes and Permafrost Distribution on Debris Flows in Badswat and Shishkat Catchments, Northern Pakistan

Impact of Glacier Changes and Permafrost Distribution on Debris Flows in Badswat and Shishkat Catchments, Northern Pakistan

Analysis of the operation of the railway track in conditions of low-draining mares and high-temperature permafrost (on the example of the area of the Bureysky reservoir bypass).

The subject of research is the earthwork of the railway track and artificial structures on hazy weak-draining areas in the areas of permafrost distribution on the bypass of the Bureyskaya HPP reservoir within the Verkhnebureinskaya depression. The purpose is to identify the conditions and causes of adverse processes and phenomena that have arisen during operation. The objectives of the research are to identify the main causes and conditions for the manifestation of unfavorable geocryological processes and phenomena – waterlogging, flooding, stagnation of water, degradation of permafrost, sediment of the roadbed. Design errors are analyzed and recommendations are given for the application of design solutions in accordance with the state and dynamics of geocryological conditions and the requirements of the current regulatory documents for the areas of distribution of low-level marys and high-temperature permafrost. For the first time, a comprehensive analysis of the conditions and causes causing adverse processes and phenomena was carried out for the described territory. Inefficient constructions and design solutions have been identified. Optimal design solutions and measures are recommended to ensure the stable and safe operation of transport facilities in the region in conditions of low-drainpipe and high-temperature permafrost. For the studied area, the characteristic features are the significant swampiness of the territory, and the wide distribution of low– and high-temperature permafrost soils of the merging type. There are cases of irrational and inefficient design. It is not uncommon to use unsuitable soils for filling the roadbed and its elements. Also, the excess of the volume of earthworks during construction. Under these conditions, it is recommended: When designing a railway track plan, trace the line through local elevated terrain areas, in order to ensure the necessary slope of the design profile of drainage ditches of at least 4 ppm. Drainage ditches along the path should be located at a distance that excludes the inflow of water into the base of the roadbed.

Сезонная динамика содержания липидов и жирных кислот в тканях злаков Avena sativa и Bromopsis inermis

Yakutia is a zone of continuous permafrost distribution, and its uniqueness lies in the fact that it has a kind of hidden biological resource that allows herbivores to survive even in conditions of limited floristic diversity. The current paper focuses on the disclosure of this resource, which we believe is in the nutritional value of permafrost plants. We have studied the content of total lipids and their essential polyunsaturated fatty acids in summer and autumn vegetative plants. According to the goal stated, we have pioneered the use of thin-layer and gas-liquid chromatography and mass spectrometry to show seasonal changes in the content of total lipids and their essential polyunsaturated fatty acids in the following plants: annual Avena sativa L. of standard and late sowing dates, and perennial Bromopsis inermis Leys before and after summer mowing in the conditions of Central Yakutia. Artificial shortening of the vegetation period of grasses has led to their preservation by natural cold (green cryo-feed). We have found that an increase in the amount of lipids in cereal plants occurs with the onset of low hardening air temperatures in the autumn period, in particular, a significant increase in linoleic С18:2(ω-6) and α-linolenic С18:3(ω-3) acids compared with indicators of summer vegetative plants. The detected process may indicate an increase in the energy intensity of frozen feed, thereby determining the important role of cryo-feed for pre-winter fat accumulation in herbivores in the cryolithozone. In the body of animals, soluble sugars of autumn vegetative or winter-green plants growing or frozen by natural cold and used as autumn and winter feed are converted into medium- and long-chain essential polyunsaturated fatty acids of the omega-6 and omega-3 families (arachidonic, and eicosapentaenoic and docosahexaenoic acids, respectively) and to a large extent help to winter. The use of grown green cryo-feed as a vitamin supplement for farm animals during a long stall period will open up new opportunities in increasing the productivity of livestock breeding in Yakutia in the future and help optimize the flow of substances and energy along the trophic cryo-feed – animal – human chain. Essential PUFAs, namely linoleic and α-linolenic acids, play an essential role in health and prolonging human life.

21st century permafrost distribution under the scenario of RCP2.6 and RCP8.5 in Mongolia

Permafrost in Mongolia is at the southern edge of the Siberian permafrost, which is most vulnerable to climate change. In this study, we used ERA5-Land data to determine the distribution of permafrost in Mongolia, and used MIROC5 data for future projection of the soil temperature. The future change of soil temperature obtained during 2020–2100 under Representative Concentration Pathways (RCP) scenarios was RCP 2.6 and RCP 8.5 respectively. This is a first attempt to identify the distribution of permafrost using ERA5-Land data in Mongolia. We examined the projection of permafrost distribution using RCP 2.6 and RCP 8.5 scenarios in Mongolia. The rapid increase of near-surface temperature was obtained in RCP8.5 scenario during 2020-2100. Soil temperature also has a high increasing trend similar to the near-surface temperature in the RCP 8.5 scenario. Future projection suggests that permafrost will completely thaw in Mongolia when area-averaged soil temperature in Mongolia exceeds 1.8°C in comparison with the current climate.

A Comparative Study of Active Rock Glaciers Mapped from Geomorphic- and Kinematic-Based Approaches in Daxue Shan, Southeast Tibetan Plateau

Active rock glaciers (ARGs) are important permafrost landforms in alpine regions. Identifying ARGs has mainly relied on visual interpretation of their geomorphic characteristics with optical remote sensing images, while mapping ARGs from their kinematic features has also become popular in recent years. However, a thorough comparison of geomorphic- and kinematic-based inventories of ARGs has not been carried out. In this study, we employed a multi-temporal interferometric synthetic aperture radar (InSAR) technique to derive the mean annual surface displacement velocity over the Daxue Shan, Southeast Tibet Plateau. We then compiled a rock glacier inventory by synergistically interpreting the InSAR-derived surface displacements and geomorphic features based on Google Earth images. Our InSAR-assist kinematic-based inventory (KBI) was further compared with a pre-existing geomorphic-based inventory (GBI) of rock glaciers in Daxue Shan. The results show that our InSAR-assist inventory consists of 344 ARGs, 36% (i.e., 125) more than that derived from the geomorphic-based method (i.e., 251). Only 32 ARGs in the GBI are not included in the KBI. Among the 219 ARGs detected by both approaches, the ones with area differences of more than 20% account for about 32% (i.e., 70 ARGs). The mean downslope velocities of ARGs calculated from InSAR are between 2.8 and 107.4 mm∙a−1. Our comparative analyses show that ARGs mapping from the InSAR-based kinematic approach is more efficient and accurate than the geomorphic-based approach. Nonetheless, the completeness of the InSAR-assist KBI is affected by the SAR data acquisition time, signal decorrelation, geometric distortion of SAR images, and the sensitivity of the InSAR measurement to ground deformation. We suggest that the kinematic-based approach should be utilized in future ARGs-based studies such as regional permafrost distribution assessment and water storage estimates.

Freeze-Thaw Deformation Cycles and Temporal-Spatial Distribution of Permafrost along the Qinghai-Tibet Railway Using Multitrack InSAR Processing

The Qinghai-Tibet Railway (QTR) is the railway with the highest elevation and longest distance in the world, spanning more than 1142 km from Golmud to Lhasa across the continuous permafrost region. Due to climate change and anthropogenic activities, geological disasters such as subsidence and thermal melt collapse have occurred in the QTR embankment. To conduct the large-scale permafrost monitoring and geohazard investigation along the QTR, we collected 585 Sentinel-1A images based on the composite index model using the multitrack time-series interferometry synthetic aperture radar (MTS-InSAR) method to retrieve the surface deformation over a 3.15 × 105 km2 area along the QTR. Meanwhile, a new method for permafrost distribution mapping based on InSAR time series deformation was proposed. Finally, the seasonal deformation map and a new map of permafrost distribution along the QTR from Golmud to Lhasa were obtained. The results showed that the estimated seasonal deformation range of the 10 km buffer zone along the QTR was −50–10 mm, and the LOS deformation rate ranged from −30 to 15 mm/yr. In addition, the deformation results were validated by leveling measurements, and the range of absolute error was between 0.1 and 4.62 mm. Most of the QTR was relatively stable. Some geohazard-prone sections were detected and analyzed along the QTR. The permafrost distribution results were mostly consistent with the simulated results of Zou’s method, based on the temperature at the top of permafrost (TTOP) model. This study reveals recent deformation characteristics of the QTR, and has significant scientific implications and applicational value for ensuring the safe operation of the QTR. Moreover, our method, based on InSAR results, provides new insights for permafrost classification on the Qinghai-Tibet Plateau (QTP).