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In Northeast China, permafrost is controlled by a combination of biotic, climatic, physiographic, and anthropogenic factors. Due to the complexity of these governing or influencing factors, it is challenging to exactly describe the features of the Xing’an permafrost in Northeast China. By integrating remote sensing (RS) and geographic information system (GIS) technologies, we have quantified these influencing factors of permafrost changes as an important approach to understanding the nature of latitudinal and mountain permafrost in Northeast China at the mid-latitudes in the Northern Hemisphere. In this study, we combine Geographical Detector (Geodetector) model, trend analysis, and multi-source RS data to quantify the controlling or influencing factors of permafrost thermal state and of permafrost changes, and explain the interactions among permafrost, environment, and climate. The results indicate that, at the regional scale, changes in the thermal state of permafrost are primarily governed or influenced by mean annual land surface temperature (MALST), precipitation, and snow cover duration (SCD). Topographic factors also affect the spatial patterns of permafrost development. Additionally, in the context of climate warming, the insulation effect of snow cover on the permafrost is weakened, or has been weakening. Moreover, the interactive effects among various factors significantly enhance their explanatory power for changes in the thermal state of permafrost. The study emphasizes the complexity of the interactions among permafrost, climate, and the environment, and highlights the significance of understanding these interactions for regional socio-economic development, ecological management, carbon pool stabilization, and research on future climate change in Northeast China.

The degradation of Xing’an permafrost affects the stability of carbon pool and carbon emissions of the hemiboreal ecosystem in Northeast China. Due to the lack of long-term monitoring and detailed research, changes in carbon stock in terrestrial ecosystems in the Xing’an permafrost regions in Northeast China remain little known. In this study, we conducted more accurate simulations for the aboveground biomass (AGB), belowground biomass (BGB), dead organic carbon (DOC), and soil organic carbon (SOC) in the top 0–30 cm in permafrost regions in Northeast China using the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model. The model was applied using multi-period land use/land cover (LULC) and carbon density data from the late 1980s, 2000, 2010, and 2020. In Northeast China, the permafrost extent shrank rapidly by 108,600 km2 from 365,300 km2 in the 1980s to 256,700 km2 in the 2010s. The total carbon stock in permafrost regions in Northeast China was estimated at 4293.04 Tg C in the 1980s and at 4049.56 Tg C in the 2010s. Based on the permafrost extent of the 1980s, it was estimated that from the late 1980s to 2020, the LULC transformation resulted in the reduction of carbon stock by 33.53 Tg C, while the carbon fixation of vegetation growth increased by 1205.18 Tg C, i.e. a net carbon accumulation of 1149.15 Tg C. However, this estimate of the increasing carbon pool still awaits more systematic studies on the carbon budgets at larger soil depths of the top 2–3 m soils. This estimate can provide a timely preliminary estimate of the carbon pool as the baseline in the permafrost region of Northeast China for national and regional initiatives of carbon neutralization.

Abstract Rivers originating from the Tibetan Plateau (TP) provide water to more than 1 billion people living downstream. Almost 40% of the TP is currently underlain by permafrost, which serves as both an ice reserve and a flow barrier and is expected to degrade drastically in a warming climate. The hydrological impacts of permafrost thaw across the TP, however, remain poorly understood. Here, we quantify the permafrost change on the TP over 1980–2100 and evaluate its hydrological impacts using a physically‐based cryospheric‐hydrological model at a high spatial resolution. Using the ensemble mean of 38 models from the Coupled Model Intercomparison Project Phase 6 (CMIP6), the near‐surface permafrost area and the total ground ice storage are projected to decrease by 86.4% and 61.6% during 2020–2100 under a high‐emission scenario, respectively. The lowering of the permafrost table and removal of permafrost as a flow barrier would enhance infiltration and raise subsurface storage capacity. The diminished water supply from ground ice melt and enhanced subsurface storage capacity could jointly reduce annual runoff and lead to exacerbated regional water shortage when facing future droughts. If the most severe 10‐year drought in the historical period occurs again in the future, the annual river runoff will further decrease by 9.7% and 11.3% compared with the historical dry period due to vanishing cryosphere in the source area of Yellow and Yangtze River. Our findings highlight the importance to get prepared for the additional water shortage risks caused by pervasive permafrost thaw in future water resources management across the TP.

Permafrost in Northeastern China is not only controlled by latitude and elevation, but also locally environmental factors, such as vegetation cover and human activities. During 2009–2022, thinning active layer, increasing annual maximum frost depth in talik zones and lowering ground temperature above the depth of dividing point (DDP) between permafrost cooling and warming have been observed in many places, possibly due to the global warming hiatus (GWH). However, the responses of permafrost below DDP did not show a clear trend to the GWH, despite an evident ground warming. The warming and degradation of permafrost below DDP in the Da Xing’anling Mountains are more strongly influenced by the overall climate warming than by regional GWH. This study improves our understanding of changing permafrost temperature and its drivers. It also helps to provide data support and references for the management of the ecological and hydrological environment of the northern Da Xing’anling Mountains and the Heilongjiang-Amur River Basin.

Background: Increased leisure-time physical activity (LTPA) is linked with decreased mortality risk, while also with increased left ventricular mass, which may induce left ventricular hypertrophy (LVH). We investigated whether LVH modifies the association between higher LTPA and lower mortality risk in population at high cardiovascular risk. Methods: In a prospective national cohort, we used the left ventricular mass/body surface area (LVM/BSA) method to define LVH. Baseline LTPA was self-reported and divided into: low (

In order to improve the utilization rate of coal gangue and expand the application range of coal gangue concrete (CGC), a certain proportion of steel fiber was added to the concrete, and the freeze–thaw cycles (FTCs) and flexural tests were used to explore the effects of different mass replacement rates of coal gangue (0%, 25%, 50%, 75%, and 100%) and different proportions of the volumetric blending of the steel fiber (0%, 0.8%, 1.0%, and 1.2%) on the frost resistance of steel fiber-reinforced CGC (SCGC). The governing laws of mass loss rate, relative dynamic elastic modulus and load–midspan deflection curve were obtained on the base of the analysis of testing results. The damage mechanisms of the SCGC under the FTCs were analyzed using the results of scanning electron microscopy (SEM). Based on the Lemaitre’s strain equivalence principle and Krajcinovic’s vector damage theory, a damage evolution model of the SCGC under the FTCs was established by introducing the damage variable of the SCGC satisfying Weibull distribution. The results show an increasing mass loss rate of the SCGC and a decreasing relative dynamic elastic modulus with an increasing mass replacement rate of coal gangue. The proper content of the steel fiber can reduce the mass loss rate of concrete by 10~40% and the relative loss rate of dynamic elastic modulus of concrete by 2~8%, thus significantly improving the ductility and toughness of the concrete. The established damage evolution model is well validated by the experimental results, which further help to improve the modelling accuracy. This study provides key experimental data and a theoretical basis for a wider range of proper utilization of coal gangue in cold regions.

Anticipated permafrost thaw in upcoming decades may exert significant impacts on forest soil nitrogen (N) dynamics. The rate of soil N mineralization (Nmin) plays a crucial role in determining soil N availability. Nevertheless, our understanding remains limited regarding how biotic and abiotic factors influence the Nmin of forest soil in response to permafrost thaw. In this study, we investigated the implications of permafrost thaw on Nmin within a hemiboreal forest based on a field investigation along the degree of permafrost thaw, having monitored permafrost conditions for eight years. The results indicate that permafrost thaw markedly decreased Nmin values. Furthermore, Nmin demonstrated positive associations with soil substrates (namely, soil organic carbon and soil total nitrogen), microbial biomass carbon and nitrogen, and soil moisture content. The decline in Nmin due to permafrost thaw was primarily attributed to the diminished quality and quantity of soil substrates rather than alterations in plant community composition. Collectively, our results underscore the pivotal role of soil substrate and microbial biomass in guiding forest soil N transformations in the face of climate-induced permafrost thaw.

Using high-precision CT scanning equipment, two series of tests on frost and salt weathering were conducted to investigate the characteristics of pore change in tuff. Experiments on frost and salt aging were performed with pieces of tuff from the same area of southeast China. One set of tuff samples was soaked in saturated sodium sulfate or magnesium sulfate solutions for 60 days. Another set of tuff samples were subjected to 60 freeze–thaw cycles after being submerged in saturated sodium sulfate or magnesium sulfate solutions for 48 h. Our study demonstrates that processes such as salt erosion and freeze–thaw affect the pore evolution of tuffs significantly. Tuff lost 1.56% of its mass after being submerged in magnesium sulfate solutions for 60 days, while tuff submerged in sodium sulfate solutions gained a negative 0.33% of its mass. After 60 freeze–thaw cycles, the mass loss of tuff samples immersed in sodium sulfate, magnesium sulfate, and distilled water solutions was 3.52%, 3.58%, and 3.82%, respectively. The average porosity of the magnesium sulfate and sodium sulfate test groups increased by 6.59% and 4.14%, respectively, when the number of days of salt erosion was extended from 10 to 60 days. The average porosity of tuff samples immersed in magnesium persulfate and sodium sulfate solutions increased by 2.25% and 2.18%, respectively, as the number of freeze–thaw cycles went from 10 to 60.

Study region: The source region of the Yellow River, China (SAYR) Study focus: This study focuses on demonstrating the impact of seasonal freeze-thaw process on the seasonally arsenic (As) and lead (Pb) concentration in the water bodies, such as river, lake, and spring. 113 surface water samples in April (freeze permafrost), 164 in July (active layer in permafrost thawed), and 86 soil samples at various depths in July were collected. Statistical correlation and principle analysis were applied to find the connection between tracer metals in water bodies and the various environmental factors. The percentage of soil particle size (5–50 µm), which can reflect the intensity of the freeze-thaw process in the permafrost soil, influenced the soil and water As and Pb trace metal concentrations differently in the permafrost area. New hydrological insights for the region: In April, the average As concentrations were 23.4 ± 16.7, 39.4 ± 32.6, 26.5 ± 24.4 μg/L, respectively in river, lake and spring water samples, and Pb concentrations were 34.9 ± 27.1, 47.4 ± 38 and 48.9 ± 33.4 μg/L. While the As concentrations in waters in July all decreased by 2 or 3 times compared with those in April, Pb concentrations slightly increased. Permafrost thawing enhanced the weathering of As and Pb, but the high As adsorption on fine soil particles, resulting from the seasonal freeze-thaw cycles, leaded to the significant decrease in the water As concentration in July, in addition to the rainfall dilution. The slight increase in Pb water concentration in July suggesting the effects of enhanced weathering and dilution were equally important. The higher As and Pb concentrations around the large Gyaring and Ngoring lakes than other SAYR area, shaping the spatial distribution of As and Pb, might be due to evaporative enrichment and the high phosphate content in the lakes. Results are helpful in assessing the ecological impact of trace metals in the permafrost area with climate change.

Dissolved organic carbon (DOC) is the main participant in carbon cycles through water pathways. Recent studies have highlighted the roles of aquatic systems in landscape and watershed carbon budgets. This study is based on 261 samples collected between 2016 and 2017, from individual water types (e.g., river/stream, lake/pond, icing/spring, snow/rain, groundwater/ice, and others) in the source area of the Yellow River (SAYR). These samples were analyzed for examining the distributive features of DOC in aquatic systems, especially in relation to environmental factors. It shows that: 1) DOC concentrations in permafrost-related waters (7.2–234.4 mg C·L−1) were often the highest among all aquatic DOC sources (lakes/ponds: 21.3 ± 34.1 mg C·L−1, rivers/streams: 4.3 ± 3.7 mg C·L−1, and groundwater: 1.8 ± 1.4 mg C·L−1); 2) the seasonality of riverine DOC showed declining features in 2016 and high in summer/autumn, followed by a spring freshet in 2017, and a close association with intra-annual precipitation modes; 3) the main controls of aquatic DOC are permafrost presence, precipitation, and NDVI, and they contribute to 38% of variances of environmental variables in affecting variations in aquatic DOC in the SAYR; and 4) a literature review on biodegradable DOC (BDOC) of varied aquatic DOC pools indicates the highest DOC concentrations (48–1,548 mg C·L−1) and BDOC (23–71%) of ground-ice meltwater. Thus, we suggest that in the SAYR, permafrost dynamics dominate aquatic DOC distribution, and permafrost thaw may alter aquatic DOC budgets, eventually becoming an additional source for atmospheric carbon emissions.

Engineering corridors on the Qinghai–Tibet Plateau have substantially modified the regional ecosystem functions and environment, resulting in changes in the alpine ecosystem. In addition, the building and operation of these engineering corridors have led to rapid permafrost degradation, which in turn has impacted local vegetation along these corridors. This study investigated vegetation changes and their driving factors by the methods of coefficient of variation, correlation analysis, and GeoDetector in a 30 km wide buffer zone at each side along the National Highway G214 (G214) at the northern and southern flanks of the Bayan Har Mountains in part of the source area of the Yellow and Yangtze rivers on the southern Qinghai Plateau, West China. The following results were obtained: (1) The Normalized Difference Vegetation Index in Growing Season (NDVIgs) rose slightly in 2010–2019, with an average annual change rate of 0.006/a. Patterns of NDVIgs along the G214 exhibited “low at the northern flank and high at the southern flank of the Bayan Har Mountains”. (2) Spatially, average NDVIgs increased from the first buffer zone at the distance of 0–10 km from the highway centerline to the second buffer zone at 20–30 km perpendicularly away from the G214. Furthermore, the first buffer zone had the lowest coefficient of variation, possibly due to a low vegetation recovery as a result of the greatest influence of the G214 on NDVIgs at 0–10 km. (3) Furthermore, annual precipitation (AP) was the dominant factor for significantly (p < 0.01) and positively influencing the variations in NDVIgs (R = 0.75, p < 0.01). Additionally, NDVIgs was more strongly influenced by the two combined factors than any single one, with the highest q-value (0.74) for the interactive influences of AP and annual average air temperature (AAAT) and followed by that of the AP and mean annual ground temperature (MAGT) at the depth of zero annual amplitude (15 m). Evidently, the construction and operation of the G214 have directly and indirectly affected vegetation through changing environmental variables, with significant impacts on NDVIgs extended at least 20 km outwards from the highway. This study helps better understand the environmental impacts along the engineering corridors in elevational permafrost regions at mid and low latitudes and their management.

As one of the best indicators of the periglacial environment, ice-wedge polygons (IWPs) are important for arctic landscapes, hydrology, engineering, and ecosystems. Thus, a better understanding of the spatiotemporal dynamics and evolution of IWPs is key to evaluating the hydrothermal state and carbon budgets of the arctic permafrost environment. In this paper, the dynamics of ground surface deformation (GSD) in IWP zones (2018–2019) and their influencing factors over the last 20 years in Saskylakh, northwestern Yakutia, Russia were investigated using the Interferometric Synthetic Aperture Radar (InSAR) and Google Earth Engine (GEE). The results show an annual ground surface deformation rate (AGSDR) in Saskylakh at −49.73 to 45.97 mm/a during the period from 1 June 2018 to 3 May 2019. All the selected GSD regions indicate that the relationship between GSD and land surface temperature (LST) is positive (upheaving) for regions with larger AGSDR, and negative (subsidence) for regions with lower AGSDR. The most drastic deformation was observed at the Aeroport regions with GSDs rates of −37.06 mm/a at tower and 35.45 mm/a at runway. The GSDs are negatively correlated with the LST of most low-centered polygons (LCPs) and high-centered polygons (HCPs). Specifically, the higher the vegetation cover, the higher the LST and the thicker the active layer. An evident permafrost degradation has been observed in Saskylakh as reflected in higher ground temperatures, lusher vegetation, greater active layer thickness, and fluctuant numbers and areal extents of thermokarst lakes and ponds.

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.

Ground ice in permafrost stores substantial amounts of dissolved organic carbon (DOC) upon thaw, which may perpetuate a carbon feedback in permafrost regions, yet little is known to date about the dynamics of DOC and source variability of ground ice on the Tibetan Plateau. Here, the high-resolution data of DOC in ground ice (4.8 m in depth) from two permafrost profiles on the Northeastern Tibetan Plateau (NETP) were firstly presented. We quantified the DOC concentrations (mean: 9.7–21.5 mg/L) of ground ice and revealed sizeable—by a factor of 7.0–36.0—enrichment of the ground ice relative to the other water elements on the TP. Results indicated remarkable depth differences in the DOC of ground ice, suggestive of diverse sources of DOC and different sequestration processes of DOC into ice during permafrost evolution. Combined with DOC and carbon isotopes (δ13CDOC), we clarified that decomposition of soil organic matter and leaching of DOC from organic layers and surrounding permafrost sediments are the important carbon sources of ground ice. The DOC sequestration of ground ice in the upper layers was related to the active layer hydrology and freeze–thaw cycle. However, the permafrost evolution controlled the decomposition of organic carbon and sequestration of DOC in the deep layers. A conceptual model clearly illustrated the dynamics of DOC in ground ice and suggested a significant impact on the carbon cycle on the NETP. The first attempt to explore the DOC in ground ice on the NETP is important and effective for further understanding of carbon cycle under permafrost degradation on the Tibetan Plateau.

Carbon storage is an important component of ecosystem services. Under climate warming and human activities, land use/land cover (LULC) have been undergoing tremendous change, leading to spatio-temporal variations in carbon storage. Based on seven series of LULC data and combined with carbon module of Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) model, spatial-temporal changes in LULC types and carbon storage were analyzed and estimated for Heilongjiang Province, Northeast China. Results show varied carbon storage among different types of LULC. Forest and cropland are the dominant LULC types in Heilongjiang Province, Northeast China, accounting for 46–49% (20.90 × 104–22.12 × 104 km2) and 30–37% (13.56 × 104–16.70 × 104 km2) of the total area. Areal extents of forest, grassland, and unused land declined from 1980 to 2015, by 1.22, 0.84, and 1.11 × 104 km2, respectively; while those of cropland and construction land expanded, by 3.14 and 0.08 × 104 km2, respectively. From 1980 to 2015, carbon storage displayed consistent change trends with those of LULC types: carbon storage of forest, grassland, and unused land decreased by 236.22, 116.61 and 21.82 × 106 Mg C, respectively; and those of cropland and construction land increased by 414.65 and 0.99 × 106 Mg C, respectively. The total carbon storage in the study region was 6,863.06 × 106–6,907.64 × 106 Mg C, for which the forest, cropland, and grassland were the major contributor (6,778.75 × 106–6,840.57 × 106 Mg C). Due to the conversion of large extents of forest, grassland, and unused land to cropland, which facilitated the formation of carbon sinks and thus enlarged the carbon storage by 45.36 × 106 Mg C from 1980 to 2015. Frequent forest fires, urban expansion, farmland reclamation, and engineering construction were the important factors of changes in the LULC, accelerating permafrost degradation and leading to obvious changes in the total carbon storage in the Heilongjiang Province, Northeast China. Therefore, the estimation of carbon storage in different LULC types can provide important data support and have important implications for evaluation of ecosystem services and carbon cycle.

Response of pore-water pressure has crucial effect on the engineering geological performance of permafrost ground. However, there is a dearth of literature on the measurement of pore-water pressure in frozen soils due to challenges with regard to technical and operational method. To validate the generation of pore-water pressure and to reveal its variation property in frozen soils at subfreezing temperatures close to 0°C, a miniature pressure transducer was utilized to conduct a number of confined compression tests. Double-wall structure avoided damage to the transducer during frozen soil sampling. The transducer at sample bottom perceived a pressure fluctuation as varying air pressure imposed on sample surface, proving the connectivity among the pores in frozen soils with a hysteretic effect on pressure transmission. Pore-water pressure experienced a progressive increase followed by a slow dissipation under invariable load and temperature conditions when water drainage was permitted, while a monotonic increase in pressure was observed for an undrained sample. With decreasing temperature, a smaller peak and a more dilatory dissipation were displayed. When the sample was exposed to a stepwise warming process, a similar performance for the pressure was obtained with abrupt rise at the turning point of temperature.

In the northern Da Xing’anling Mountains in Northeast China on the southern margin of the Eastern Asia permafrost body, the ground thermal state and boreal ecological environment are sensitive to climate change and human activities. Since the 1980s, the Hola Basin here has been continuously and extensively developed. In particular, open pits and later backfilling in strip coal mining alters land–atmospheric hydrothermal exchanges in permafrost regions, leading to serious damages to the permafrost environment and boreal forest. After mining, pits need to be backfilled timely and properly for hydrothermal recovery of Xing’an permafrost and the boreal ecological environment. In this study, based on the comparative analysis of monitored ground temperatures in backfilled and undisturbed areas, influencing factors of thermal recovery after backfilling were analyzed through numerical simulations. Results show that the thermal recovery of permafrost in the backfilled area is closely related to temperature, depth, material, and soil moisture content of backfill. The warmer, finer, and thicker the backfill soils, the longer the permafrost recovery. Thermal recovery of permafrost also depends on the moisture content of backfill; the shortest recovery occurs at 15–25% in the backfilled soil moisture content. Based on numerical simulations and combined with enlightenments from features of the ecosystem-protected Xing’an permafrost in Northeast China, a composite configuration of organic soil, crush-rock layer, and proper re-vegetation measures is advised. Based on prudent regulation of heat transfer modes, this composite backfilling method can effectively cool the backfilled ground and can even possibly offset the climate warming.

Long-distance pipelines are threatened by a variety of natural geological hazards. A stress monitoring system driven by the strain-stress solution algorithm was proposed; it can achieve real-time maximum axial stress measurement by installing vibrating wire gauges (VWGs) on the surface of the pipe. To verify the effectiveness of the algorithm, a large-scale pipe mechanical loading experiment combined with a finite element model (FEM) was conducted. The results show that VWGs were reliable with a relative error of 1.19%∼7.98% compared with resistance strain gauges (SGs). The FEM was also reliable with a maximum relative error of 4.04% compared with theoretical analysis. When the reasonable combination modes of VWGs were chosen utilizing the least square method, the error of the pipe stress detection algorithm could be controlled within the range of −13.33∼16.66%. This pipeline stress monitoring technology can meet the requirement of 24-hour dynamic monitoring of the underground pipeline’s mechanical state, realizing the early warning of geohazards.

With increasing gas resource development in the Arctic region, gas pipeline installations in permafrost regions are becoming important. Frost heave of pipeline foundation soils may occur when a chilled gas pipeline passes through unfrozen areas with frost-susceptible soils. The stress and strain behaviors caused by the differential frost heave will directly affect the safety of the pipeline. A nonlinear finite element model (FEM) computing the mechanical responses of the buried gas pipeline subjected to frost heave load was established and successfully validated with the results of a large-scale indoor pipe-soil interaction experiment carried out in Caen in France. Utilizing C# language and object-oriented visual programming techniques, a new customized parametric strain calculation software was developed. The effects of pipe diameter, pipe wall thickness, pipe internal pressure, and peak soil resistance on the longitudinal strain of X60, X70, and X80 steel pipes have been investigated quantitatively. For the first time, a fitting semiempirical equation and trained backpropagation neural network (BPNN) for predicting pipeline strain demand subjected to frost heave load were proposed based on 2688 groups of FEM results. The comparison results have proved their high accuracy and lower running time cost. The proposed new methods can be applied in the strain-based pipeline design and safety evaluation of pipelines in service. It is in the hope of supplementing existing theory and identifying new approaches for arctic gas pipeline installations.

Permafrost impacts the subsurface hydrology and determines the transport of buried biochemical substances. Current evaluations of permafrost mostly focus on the overlying active layer. However, the basic but missing information of permafrost thickness constrains the quantification of trends and effects of permafrost degradation on subsurface hydrological processes. Our study quantified the long-term variations in permafrost thickness on the Tibetan Plateau (TP) between 1851 and 2100 based on layered soil temperatures calculated from eight earth system models (ESMs) of Coupled Model Intercomparison Project (the sixth phase) and validated by field observations and previous permafrost pattern from remote sensing. The calculated permafrost distribution based on ESMs was validated by the pattern derived from the MODIS datasets and field survey. Our results show that permafrost thicker than 10 m covers approximately 0.97 million km2 of the total area of the TP, which represents an areal extent of over 36.49% of the whole TP. The mean permafrost thickness of the TP was 43.20 m between 1851 and 2014, and it would decrease at an average rate of 9.42, 14.99, 18.78, and 20.75 cm per year under scenarios SSP126, SSP245, SSP370, and SSP585 from 2015 to 2100, respectively. The permafrost thickness will decrease by over 50 cm per year in Qiangtang Basin under SSP585. Our study provides new insights for spatiotemporal changes in permafrost thickness and a basic dataset combined results of remote sensing, field measurements for further exploring relevant hydrological, geomorphic processes and biogeochemical cycles in the plateau cryospheric environment.

Pipeline corridors have been rapidly increasing in length and density because of the ever growing demand for crude oil and natural gas resources in hydrocarbon-rich permafrost regions. Pipeline engineering activities have significant implications for the permafrost environment in cold regions. Along these pipeline corridors, the shrubification in the right-of-way (ROW) has been extensively observed during vegetation recovery. However, the hydrothermal mechanisms of this ROW shrubification have seldom been studied and thus remain poorly understood. This paper reviews more than 112 articles mainly published from 2000 to 2022 and focuses on the hydrothermal mechanisms of shrubification associated with environmental changes induced by the rapidly degrading permafrost from pipeline construction and around the operating pipelines under a warming climate. First, the shrubification from pipeline construction and operation and the ensuing vegetation clearance are featured. Then, key permafrost-related ROW shrubification mechanisms (e.g., from the perspectives of warmer soil, soil moisture, soil type, soil nutrients, topography and landscapes, and snow cover) are discussed. Other key influencing factors on these hydrothermal and other mechanisms are hierarchically documented as well. In the end, future research priorities are identified and proposed. We call for prioritizing more systematic and in-depth investigations and surveys, laboratory testing, long-term field monitoring, and numerical modeling studies of the ROW shrubification along oil and gas pipelines in permafrost regions, such as in boreal and arctic zones, as well as in alpine and high-plateau regions. This review can improve our understanding of shrubification mechanisms under pipeline disturbances and climate changes and help to better manage the ecological environment along pipeline corridors in permafrost regions.

With the climate warming leading to thawing permafrost, the trace metal releasing from the permafrost is of increasing importance. The source area of the Yellow river (SAYR) in Tibet Plateau, underlain by permafrost which provides important source water, was investigated. One hundred and eleven water samples across SAYR were collected in April 2014, when permafrost thawing began and the precipitation season had not arrived yet. It was found that the arsenic concentration level was relatively higher than other pristine surface water in the world, but similar to other source regions on the Tibetan Plateau, showing SAYR is pristine and can serve as a reference region for determining the human influence on permafrost-affected landscapes. The positive correlation of arsenic with sulfate suggested that the arsenic was predominantly derived from the weathering process of arsenic-rich sulfides. Climate warming enhanced thawing depth of permafrost may accelerate the release and mobilization of arsenic to the surface water.

During operation, a buried pipeline is threatened by a variety of geological hazards, particularly in permafrost regions, where freezing-thawing disasters have a significant influence on the integrity and safety of the buried pipelines. The topographical environmental conditions along the pipeline, as well as the influence of frost heave and thaw settlement on the pipeline’s foundation soil, must be considered in the design and construction stage. Theoretical analysis, numerical modeling, field testing, and mitigation measures on vital energy pipelines in permafrost have been widely documented, but no attempt has been made to review the freezing-thawing disasters, current research methodologies, and mitigation strategies. This article reviews the formation mechanisms and mitigation measures for frost hazards (e.g., differential frost heave, thaw settlement, slope instability, frost mounds, icing, river ice scouring, and pipeline floating) along buried pipelines in permafrost regions and summarizes and prospects the major progress in the research on mechanisms, analysis methods, model test, and field monitoring based on publications of studies of key energy pipelines in permafrost regions. This review will provide scholars with a basic understanding of the challenging freezing-thawing hazards encountered by energy pipelines in permafrost regions, as well as research on the stability and mitigation of pipeline foundation soils plagued by freezing-thawing hazards in permafrost regions under a warming climate and degrading permafrost environment.

Thermal properties are important for featuring the water-heat transfer capacity of soil. They are also key to many processes in earth sciences, such as the land surface processes and ecological and geoenvironmental dynamics and their changes in permafrost regions. With loose and porous structures, the organic matter layer in soil strata substantially influences soil thermal conductivity. So far, thermal conductivity of mineral soils has been explored extensively and in depth, but there are only limited studies on that of organic soils. In this study, influences of soil temperature, soil moisture saturation (SMS), and soil organic matter (SOM) content on soil thermal conductivity were analyzed on the basis of laboratory experiments on the silt-organic soil mixtures of varied mixing ratios. Results show that soil thermal conductivity declines slowly with the lowering temperatures from 10 to 0°C; however, it increases and finally stabilizes when temperature further lowers from 0 to -10°C. It is important to note that thermal conductivity peaks in the temperature range of -2~0°C (silty and organic-poor soil) and -5~0°C (organic-rich soil), possibly due to phase changes of ice/water in warm permafrost. Under both thawed and frozen states, soil thermal conductivity is positively related with SMS. However, with rising SOM content, the growth rate of soil thermal conductivity with SMS slows gradually. Given the same SMS, soil thermal conductivity declines exponentially with increasing SOM content. Based on the experimental and theoretical analyses, a new empirical computational formula of soil thermal conductivity is established by taking into account of the SOM content, SMS, and soil temperature. The results may help better parameterize in simulating and predicting land surface processes and for optimizing frozen soil engineering designs and provide theoretical bases for exploring the dynamic mechanisms of environmental changes in cold regions under a changing climate.

Under a warming climate, permafrost degradation has resulted in profound hydrogeological consequences. Here, we mainly review 240 recent relevant papers. Permafrost degradation has boosted groundwater storage and discharge to surface runoffs through improving hydraulic connectivity and reactivation of groundwater flow systems, resulting in reduced summer peaks, delayed autumn flow peaks, flattened annual hydrographs, and deepening and elongating flow paths. As a result of permafrost degradation, lowlands underlain by more continuous, colder, and thicker permafrost are getting wetter and uplands and mountain slopes, drier. However, additional contribution of melting ground ice to groundwater and stream-flows seems limited in most permafrost basins. As a result of permafrost degradation, the permafrost table and supra-permafrost water table are lowering; subaerial supra-permafrost taliks are forming; taliks are connecting and expanding; thermokarst activities are intensifying. These processes may profoundly impact on ecosystem structures and functions, terrestrial processes, surface and subsurface coupled flow systems, engineered infrastructures, and socioeconomic development. During the last 20 years, substantial and rapid progress has been made in many aspects in cryo-hydrogeology. However, these studies are still inadequate in desired spatiotemporal resolutions, multi-source data assimilation and integration, as well as cryo-hydrogeological modeling, particularly over rugged terrains in ice-rich, warm (>−1 °C) permafrost zones. Future research should be prioritized to the following aspects. First, we should better understand the concordant changes in processes, mechanisms, and trends for terrestrial processes, hydrometeorology, geocryology, hydrogeology, and ecohydrology in warm and thin permafrost regions. Second, we should aim towards revealing the physical and chemical mechanisms for the coupled processes of heat transfer and moisture migration in the vadose zone and expanding supra-permafrost taliks, towards the coupling of the hydrothermal dynamics of supra-, intra- and sub-permafrost waters, as well as that of water-resource changes and of hydrochemical and biogeochemical mechanisms for the coupled movements of solutes and pollutants in surface and subsurface waters as induced by warming and thawing permafrost. Third, we urgently need to establish and improve coupled predictive distributed cryo-hydrogeology models with optimized parameterization. In addition, we should also emphasize automatically, intelligently, and systematically monitoring, predicting, evaluating, and adapting to hydrogeological impacts from degrading permafrost at desired spatiotemporal scales. Systematic, in-depth, and predictive studies on and abilities for the hydrogeological impacts from degrading permafrost can greatly advance geocryology, cryo-hydrogeology, and cryo-ecohydrology and help better manage water, ecosystems, and land resources in permafrost regions in an adaptive and sustainable manner.

A huge amount of carbon (C) is stored in permafrost regions. Climate warming and permafrost degradation induce gradual and abrupt carbon emissions into both the atmosphere and hydrosphere. In this paper, we review and synthesize recent advances in studies on carbon stocks in permafrost regions, biodegradability of permafrost organic carbon (POC), carbon emissions, and modeling/projecting permafrost carbon feedback to climate warming. The results showed that: (1) A large amount of organic carbon (1460–1600 PgC) is stored in permafrost regions, while there are large uncertainties in the estimation of carbon pools in subsea permafrost and in clathrates in terrestrial permafrost regions and offshore clathrate reservoirs; (2) many studies indicate that carbon pools in Circum-Arctic regions are on the rise despite the increasing release of POC under a warming climate, because of enhancing carbon uptake of boreal and arctic ecosystems; however, some ecosystem model studies indicate otherwise, that the permafrost carbon pool tends to decline as a result of conversion of permafrost regions from atmospheric sink to source under a warming climate; (3) multiple environmental factors affect the decomposability of POC, including ground hydrothermal regimes, carbon/nitrogen (C/N) ratio, organic carbon contents, and microbial communities, among others; and (4) however, results from modeling and projecting studies on the feedbacks of POC to climate warming indicate no conclusive or substantial acceleration of climate warming from POC emission and permafrost degradation over the 21st century. These projections may potentially underestimate the POC feedbacks to climate warming if abrupt POC emissions are not taken into account. We advise that studies on permafrost carbon feedbacks to climate warming should also focus more on the carbon feedbacks from the rapid permafrost degradation, such as thermokarst processes, gas hydrate destabilization, and wildfire-induced permafrost degradation. More attention should be paid to carbon emissions from aquatic systems because of their roles in channeling POC release and their significant methane release potentials.

Human activities have substantially altered present-day flow regimes. The Headwater Area of the Yellow River (HAYR, above Huanghe’yan Hydrological Station, with a catchment area of 21,000 km2 and an areal extent of alpine permafrost at ~86%) on the northeastern Qinghai-Tibet Plateau, Southwest China has been undergoing extensive changes in streamflow regimes and groundwater dynamics, permafrost degradation, and ecological deterioration under a warming climate. In general, hydrological gauges provide reliable flow records over many decades and these data are extremely valuable for assessment of changing rates and trends of streamflow. In 1998–2003, the damming of the Yellow River by the First Hydropower Station of the HAYR complicated the examination of the relations between hydroclimatic variables and streamflow dynamics. In this study, the monthly streamflow rate of the Yellow River at Huanghe’yan is reconstructed for the period of 1955–2019 using the double mass curve method, and then the streamflow at Huagnhe’yan is forecasted for the next 20 years (2020–2040) using the Elman neural network time-series method. The dam construction (1998–2000) has caused a reduction of annual streamflow by 53.5–68.4%, and a more substantial reduction of 71.8–94.4% in the drier years (2003–2005), in the HAYR. The recent removal of the First Hydropower Station of the HAYR dam (September 2018) has boosted annual streamflow by 123–210% (2018–2019). Post-correction trends of annual maximum (QMax) and minimum (QMin) streamflow rates and the ratio of the QMax/QMin of the Yellow River in the HAYR (0.18 and 0.03 m3·s−1·yr−1 and −0.04 yr−1, respectively), in comparison with those of precorrection values (−0.11 and −0.004 m3·s−1·yr−1 and 0.001 yr−1, respectively), have more truthfully revealed a relatively large hydrological impact of degrading permafrost. Based on the Elman neural network model predictions, over the next 20 years, the increasing trend of flow in the HAYR would generally accelerate at a rate of 0.42 m3·s−1·yr−1. Rising rates of spring (0.57 m3·s−1·yr−1) and autumn (0.18 m3·s−1·yr−1) discharge would see the benefits from an earlier snow-melt season and delayed arrival of winter conditions. This suggests a longer growing season, which indicates ameliorating phonology, soil nutrient availability, and hydrothermal environments for vegetation in the HAYR. These trends for hydrological and ecological changes in the HAYR may potentially improve ecological safety and water supplies security in the HAYR and downstream Yellow River basins.

Land use and cover changes (LUCC) in permafrost regions have significant consequences on ecology, engineered systems, and the environment. Obtaining more details about LUCC is crucial for sustainable development, land conservation, and environment management. The Hola Basin (957 km2) in the northernmost part of Northeast China, a boreal forest landscape underlain by discontinuous, sporadic, and isolated permafrost, was selected for the case study. The LUCC was analyzed using the Landsat archive of satellite images from 1973 to 2019. A thematic change detection analysis was performed by combining the object-based image analysis (OBIA) and the Support Vector Machine (SVM) algorithm. Four types of LUCC (forest, grass, water, and anthropic) were extracted with an overall accuracy of 80% for 1973 and >90% for 1986, 2000, and 2019. Forest, the dominant class (750 km2 in 1973), declined by 88 km2 (11.8%) from 1973 to 1986 but had a recovery of 78 km2 (12.5%) from 2000 to 2019. Grass, the second-largest class (187 km2 in 1973), increased by 86 km2 (46.5%) between 1973 and 1986 and decreased by 90 km2 (40%) between 2000 and 2019. The anthropic class continuously increased from 10 km2 (1973) to 37 km2 (2019). Major features in LUCC are attributed to rapid population growth, resource exploitation, agriculture intensification, economic development, and frequent forest fires. Under a pronounced climate warming, these drivers have been accelerating the degradation of permafrost, subsequently triggering natural hazards and deteriorating the ecological environment. This study represents a benchmark for sustainable LUCC management in the Hola Basin, Northeast China.

Abstract Desertification of tundra regions may form an escalating cycle with permafrost degradation where more permafrost thaw leads to continued desertification. This traditional viewpoint has been challenged in recent reports that state desertification protects the underlying permafrost. However, our measurements of soil temperature from nine sites in the Honglianghe River Basin, interior Qinghai-Tibet Plateau, show that desertification can degrade permafrost. If one compares the permafrost temperatures at sites with thin sand covers (e.g. site Yu-7, permafrost temperature of −0.64 °C; site Yu-6, permafrost temperature of −1.15 °C) with that of site Xie-1 (−0.65 °C, with a 120-cm-thick sand cover), the permafrost temperature is not significantly different. It is clear that a thick sand cover does not influence the underlying permafrost temperature. Our observations support traditional geocryological knowledge which states that, under most circumstances, desertification does not protect, but rather degrades, permafrost.

The stability of permafrost is of fundamental importance to socio-economic well-being and ecological services, involving broad impacts to hydrological cycling, global budgets of greenhouse gases and infrastructure safety. This study presents a biophysical permafrost zonation map that uses a rule-based geographic information system (GIS) model integrating global climate and ecological datasets to classify and map permafrost regions (totaling 19.76 × 10 ^6 km ^2 , excluding glaciers and lakes) in the Northern Hemisphere into five types: climate-driven (CD) (19% of area), CD/ecosystem-modified (41%), CD/ecosystem protected (3%), ecosystem-driven (29%), and ecosystem-protected (8%). Overall, 81% of the permafrost regions in the Northern Hemisphere are modified, driven, or protected by ecosystems, indicating the dominant role of ecosystems in permafrost stability in the Northern Hemisphere. Permafrost driven solely by climate occupies 19% of permafrost regions, mainly in High Arctic and high mountains areas, such as the Qinghai–Tibet Plateau. This highlights the importance of reducing ecosystem disturbances (natural and human activity) to help slow permafrost degradation and lower the related risks from a warming climate.

The framework of Quaternary permafrost in China was reconstructed for the first time on the basis of available periglacial, glacial, and other proxies. During the Early Pleistocene (2.68–0.80 Ma BP), permafrost advanced southwards to 47–50° N in northern China and possibly occurred in alpine regions in western China. During the Middle Pleistocene (800–130 ka BP), permafrost occurred extensively on the Qinghai-Tibet Plateau (QTP) and in alpine or mountainous regions of northern, western, central, and northeastern China. The Great Interglacial occurred afterward and before the Last Glaciation, but the evidence of permafrost for this period has been seldom found. Permafrost evolution of the Last Glaciation (72–19 ka BP) in China is divided into: Expansion (72~50 ka BP), degradation (50–26 ka BP), and intensive expansion during the Last Permafrost Maximum (LPMax, 26–19 ka BP) with a permafrost extent of 5.3 × 106~5.4 × 106 km2, and when major features of present permafrost took shape. Permafrost fluctuated during the Younger Dryas (12.9–11.7 ka BP). Since the Holocene, permafrost in China expanded and retreated to lesser extents, forming the current permafrost environment. The Holocene evolution of permafrost was divided into: Unstable climate but stable permafrost during the early Holocene (11.7~8.5–7.0 ka BP); permafrost degradation during the Last Permafrost Minimum (LPMin, or the Holocene Megathermal; 8.5–7.0~4.0–3.0 ka BP) and the Medieval Warm Period (MWP; 1.0~0.5 ka BP); permafrost expansion during the Neoglaciation (4.0–3.0~1.0 ka BP) and the Little Ice Age (LIA; 0.5~0.1 ka BP); and recent permafrost degradation (20th century to the present). However, this review paper only provides the framework of Quaternary permafrost in China and some preliminary discussions. Many key questions await further investigations.

Degradation of permafrost with a thin overlying active layer can greatly affect vegetation via changes in the soil water and nutrient regimes within the active layer, while little is known about the presence or absence of such effects in areas with a deep active layer. Here, we selected the northeastern Qinghai-Tibet Plateau as the study area. We examined the vegetation communities and biomass along an active layer thickness (ALT) gradient from 0.6 to 3.5 m. Our results showed that plant cover, below-ground biomass, species richness, and relative sedge cover declined with the deepening active layer, while the evenness, and relative forb cover showed a contrary trend. The vegetation indices and the dissimilarity of vegetation composition exhibited significant changes when the ALT was greater than 2.0 m. The vegetation indices (plant cover, below-ground biomass, evenness index, relative forb cover and relative sedge cover) were closely associated with soil water content, soil pH, texture and nutrient content. Soil water content played a key role in the ALT–vegetation relationship, especially at depths of 30–40 cm. Our results suggest that when the ALT is greater than 2.0 m, the presence of underlying permafrost still benefits vegetation growth via maintaining adequate soil water contents at 30–40 cm depth. Furthermore, the degradation of permafrost may lead to declines of vegetation cover and below-ground biomass with a shift in vegetation species.

Groundwater icings, typical features of permafrost hydrology, are indicative of hydrothermal interactions between surface and ground waters, and permafrost. Their main morphological parameters, i.e., icing area and volume, are generally estimated with low accuracy. Only scarce field observational data on icing volume and seasonal development exist to date. Our study evaluates and compares performance of several widely used techniques of icing morphometric estimation, based on field data, collected on a giant Icing #2 in the Samokit River basin, southern Yakutia. Groundwater icing area was estimated by: (a) staking, (b) unmanned aerial vehicle (UAV) surveys, and (c) satellite imagery analysis. Icing #2 area in late February was between 1.38·106 m2 and 1.68·106 m2, icing volume, between 1.73·106 m3 and 4.20·106 m3, depending on the technique used. Staking is the least accurate, but also the only direct technique, which is hence used as a baseline tool in our study. Staking-based assessment of icing morphometry is the most conservative, while UAV-based estimates of icing area are higher by 14% to 17%, and of icing volume, by 74% to 142%, compared to staking. The latter appears, in our case, to be the least accurate method, although a direct one. It requires a sufficient number of staking points and transects, which should be set up to represent all icing zones, i.e., channel branches and alluvial islands. Photogrammetry based on UAV surveys has numerous advantages, i.e., higher precision of a per pixel icing volume calculation, based on an ice-free valley bottom digital surface model (DSM), and potential reusability of a resulting DSM. However, positioning precision suffers from the overlay of multiple flyovers required because of battery replacements, and, in our case, an insufficient number of ground control points. Satellite imagery along with B.L. Sokolov’s empirical approach were used to estimate the annual maximum icing area and volume, and the empirical estimates tend to converge to satellite-based values. Finally, all thing being equal, UAV-based photogrammetry shows higher precision in estimating the icing morphometrical parameters.

The buried China-Russia Crude Oil Pipeline (CRCOP) across the permafrost-associated cold ecosystem in northeastern China carries a risk of contamination to the deep active layers and upper permafrost in case of accidental rupture of the embedded pipeline or migration of oil spills. As many soil microbes are capable of degrading petroleum, knowledge about the intrinsic degraders and the microbial dynamics in the deep subsurface could extend our understanding of the application of in-situ bioremediation. In this study, an experiment was conducted to investigate the bacterial communities in response to simulated contamination to deep soil samples by using 454 pyrosequencing amplicons. The result showed that bacterial diversity was reduced after 8-weeks contamination. A shift in bacterial community composition was apparent in crude oil-amended soils with Proteobacteria (esp. α-subdivision) being the dominant phylum, together with Actinobacteria and Firmicutes. The contamination led to enrichment of indigenous bacterial taxa like Novosphingobium, Sphingobium, Caulobacter, Phenylobacterium, Alicylobacillus and Arthrobacter, which are generally capable of degrading polycyclic aromatic hydrocarbons (PAHs). The community shift highlighted the resilience of PAH degraders and their potential for in-situ degradation of crude oil under favorable conditions in the deep soils.

The China-Russia Crude Oil Pipeline (CRCOP) goes through 441 km permafrost soils in northeastern China. The bioremediation in case of oil spills is a major concern. So far, little is known about the indigenous bacteria inhabiting in the permafrost soils along the pipeline. A pilot 454 pyrosequencing analysis on the communities from four selected sites which possess high environment risk along the CRCOP is herein presented. The results reveal an immense bacterial diversity than previously anticipated. A total of 14448 OTUs with 84834 reads are identified, which could be assigned into 39 different phyla, and 223 families or 386 genera. Only five phyla sustain a mean OTU abundance more than 5% in all the samples, but they altogether account for 85.08% of total reads. Proteobacteria accounts for 41.65% of the total OTUs or 45% of the reads across all samples, and its proportion generally increases with soil depth, but OTUs numerically decline. Among Proteobacteria, the abundance of Beta-, Alpha-, Delta- and Gamma- subdivisions average to 38.7% (2331 OTUs), 37.5% (2257 OTUs), 10.35% (616 OTUs), and 6.21% (374 OTUs), respectively. Acidobacteria (esp. Acidobacteriaceae), Actinobacteria (esp. Intrasporangiaceae), Bacteroidetes (esp. Sphingobacteria and Flavobacteria) and Chloroflexi (esp. Anaerolineaceae) are also very common, accounting for 8.56% (1237 OTUs), 7.86% (1136 OTUs); 7.35% (1063 OTUs) and 8.27% (1195 OTUs) of total libraries, respectively. The ordination analysis indicates that bacteria communities in the upper active layer cluster together (similar), while bacterial consortia from the lower active layer and permafrost table scatter (less similar). The abundance of Rhodococcus (12 OTUs), Pseudomonas (71 OTUs) and Sphingomonas (87 OTUs) is even less (