Permafrost Regions Research Articles

Rill erosion and controlling factors on highway side-slopes in the permafrost region

Rill erosion and controlling factors on highway side-slopes in the permafrost region

Research on the Geosynthetic-Encased Gravel Pile Composite Highway Foundation in Low-Temperature Stable Permafrost Regions

In low-temperature stable permafrost regions, both active and passive cooling measures are commonly employed to ensure the long-term stability of highway structures. However, despite adopting these measures, various types of structural issues caused by permafrost degradation remain prevalent in high-grade highways. This indicates that in addition to preventing permafrost melting, structural reinforcement of the foundation is still necessary. Based on the analysis of the long-term foundation temperature field and settlement using the finite element method, which was validated through an indoor top-down freeze–thaw cycle test, this paper explores, for the first time, the feasibility of applying geosynthetic-encased gravel pile composite highway foundations—previously commonly used for permafrost destruction—in low-temperature stable permafrost areas where permafrost protection is the primary principle. By analyzing the long-term temperature field, settlement behavior, and pile–soil stress ratios of permafrost foundations influenced by both the highway structure and composite foundation, it was found that when the pile diameter is 0.5 m, pile spacing is 2 m, and pile length is 11 m, the mean monthly ground temperature of the permafrost foundation will not be significantly affected. Therefore, the properly designed geosynthetic-encased gravel pile composite highway foundation can be adopted in low-temperature stable permafrost regions where permafrost protection, rather than destruction, is required.

Sensibility in the impact of aeolian sand cover on permafrost degradation in Qinghai-Xizang Plateau

Abstract Environmental transformations and intensifying desertification across the Qinghai-Xizang Plateau significantly influence permafrost degradation, heightening risks associated with carbon emissions, thermal hazards, and infrastructural damage. However, the specific response of permafrost to desertification remains insufficiently understood. Here, we employed numerical modelling to examine the sensitivity of the impact of aeolian sand cover (ASC) on permafrost degradation. Our findings reveal that the thickness and moisture content of ASC profoundly affects permafrost degradation. Moreover, permafrost thermal stability and the rate of climatic warming modulate this degradation process. The simulation results identify two critical thickness thresholds for ASC: 20 cm and 80-120 cm. Specifically, dry ASC thinner than 20 cm accelerates permafrost degradation driven by desertification, whereas ASC thicker than 20 cm mitigates this effect. Furthermore, increased moisture in ASC extends the thickness thresholds to 80-120 cm. These results suggest that climatic variations in the Qinghai-Xizang Plateau, particularly transitions towards either warming-drying or warming-wetting, will markedly influence the response of permafrost to desertification. Notably, a warming-drying climate may reduce the potential degradation of permafrost caused by desertification. This study provides a critical reference for understanding the impact of aeolian desertification on permafrost in regions beyond the Qinghai-Xizang Plateau. It holds significant policy implications for environmental conservation and infrastructure development within the plateau.

A quasi‐continuous long‐term (5 Ma) Mid‐European mountain permafrost record based on fluvial magnetic susceptibility and its contribution to the explanation of Plio–Pleistocene glaciations

The low field magnetic susceptibility (χLF) measured in the 1116‐m‐long Dévaványa core (Pannonian Basin) is a quasi‐continuous record of the Plio–Pleistocene Mid‐European mountain permafrost development. The continuity of fluvial conditions is confirmed by seismic data, and the detrital origin of magnetite is indicated by frequency‐dependent susceptibility measurements, scanning electron microscope, and hysteresis investigations. The χLF record is correlated to the δ18O curve (LR04) supported by palaeomagnetic data. The colour of samples documents precession and obliquity cycles in local facies variations, but the χLF indicates the dominance of 100‐ka eccentricity cycles in the linked mountainous permafrost events. Comparison with orbital solutions revealed that the long‐term development of permafrost occurs as a result of amplitude modulation of the 100‐ka eccentricity cycles. Increases in amplitude of the 100‐ka cycles inhibits permafrost development due to shortened winters. Thus, if extremes are present, the permafrost regions are limited or disappear, but if the 100‐ka eccentricity cycles are attenuated, permanent frost can extend into the temperate zone. This amplitude modulation may also be responsible for the early glaciations during the Pliocene, for the intensification of Northern Hemisphere glaciation, foreshadows cooling in the forthcoming 405‐ka term, and allows the change from 41‐ka cycles to 100‐ka ones in the Mid‐Pleistocene Transition to be explained. The 41‐ka cycles are the result of obliquity‐controlled changes close to the polar cycles, while 100‐ka cycles occur when the amplitude attenuation of the 100‐ka eccentricity cycles enables extended glaciations that suppress the regular 41‐ka cycles. Higher mountains in the catchments enable higher resolution of permafrost records documenting even smaller glaciations. However, the similarities in the overall trends in χLF records of catchment areas with 1500‐m difference in their altitude is a potential counter‐argument when considering the role of tectonic elevations in the expansions of mountainous permafrost.

Soil Texture Mapping in the Permafrost Region: A Case Study on the Eastern Qinghai–Tibet Plateau

Soil Texture Mapping in the Permafrost Region: A Case Study on the Eastern Qinghai–Tibet Plateau

An Analysis of Vertical Infiltration Responses in Unsaturated Soil Columns from Permafrost Regions

Rainfall infiltration affects permafrost-related slope stability by changing the pore water pressure in soil. In this study, the infiltration responses under rainfall conditions were elucidated. The instantaneous profile method and filter paper method were used to obtain the soil–water characteristic curve (SWCC) and hydraulic conductivity function (HCF). During the rainfall infiltration test, the vertical patters of volumetric moisture contents, total hydraulic head or suction and wetting front were recorded. Advancing displacement and rate of the wetting front, the cumulative infiltration, the instantaneous infiltration rate, and the average infiltration rate were determined to comprehensively assess the rainfall infiltration process, along with SWCC and HCF. Additionally, the effects of dry density and runoff on the one-dimensional vertical infiltration process of soil columns were evaluated. The results showed that the variation curve of wetting front displacement versus time obeys a power function relationship. In addition, the infiltration rate–time relationship curve and the unsaturated permeability curve could be roughly divided into three stages, and the SWCC and HCF calculated by volumetric moisture content are more sensitive to changes in dry density than to changes in runoff or hydraulic head height.

Hydro-thermal processes and deformation of highway embankment in the active layer in a high-latitude permafrost region of Inner Mongolia in Northeast China

Construction of embankments in the permafrost region significantly changes the heat exchange conditions and hydrothermal transport processes between permafrost and the external environment, causing changes in the state of permafrost under the embankment, which in turn affects the long-term stability of embankment impacts. Considering more complex forest environment and higher technical standard for expressway than ordinary highway, the hydrothermal and deformation characteristics of the embankment are investigated through a full-scale field experimental embankment of the Genhe-Labdalin highway. Further, the study delves into the influence of changes in the active layer thickness, hydrothermal processes, and water above the frozen layer on embankment stability. The main conclusions are as follows: 1) The permafrost table, temperature, moisture and deformation of the embankment showed lateral heterogeneity, with the three-former showing a “concave shape” and the left side (sunny slope) being lower than the right side (shady slope). 2) The permafrost table appears to be unconnected (thawing interlayer), creating preferential flow, thaw zones and even through-thaw zones. 3) Accompanied by the freezing and thawing process of the embankment, the deformation of the pavement is less delayed. These findings will be helpful for better understanding the hydrothermal characteristics of embankments in different frozen ground regions, and for providing important technical guidance to ensure the safe operation of engineering projects.

GPR-based depth estimation of ground interfaces in permafrost region: Electromagnetic method and cone penetration assessment

GPR-based depth estimation of ground interfaces in permafrost region: Electromagnetic method and cone penetration assessment

Water and carbon fluxes from a supra-permafrost aquifer to a stream across hydrologic states

Supra-permafrost aquifers within the active layer are present in the Arctic during summer. Permafrost thawing due to Arctic warming can liberate previously frozen particulate organic matter (POM) in soils to leach into groundwater as dissolved organic carbon (DOC). DOC transport from groundwater to surface water is poorly understood because of the unquantified variability in subsurface properties and hydrological environments. These dynamics must be better characterized because DOC transport to surface waters is critical to predict the long-term fate of recently thawed carbon in permafrost environments. Here, we used distributed Darcy’s Law calculations to quantify groundwater and DOC fluxes into Imnavait Creek, Alaska, a representative headwater stream in a continuous permafrost watershed. We developed a statistical ensemble approach to model the parameter variability and range of potential contributions of steady-state groundwater flow to the creek. We quantified the model prediction uncertainty using statistical sampling of in-situ, active-layer soil hydro-stratigraphy (water table, ice table, and soil stratigraphy), high-resolution topography data, and DOC data. Moreover, the predicted groundwater discharge values representing all possible hydrologic conditions towards the end of the thawing season were also considered given the potential variability in saturation. The model predictions were similar to and span most of the observed range of Imnavait Creek streamflow, especially during recession periods, and also during saturation excess overland flow. As the Arctic warms and supra-permafrost aquifers deepen, groundwater flow is expected to increase. This increase is expected to impact stream, river, and lake biogeochemical processes by dissolving and mobilizing more soil constituents in continuous permafrost regions. This study highlights how quantifying the uncertainty of hydro-stratigraphical input parameters helps understand and predict supra-permafrost aquifer dynamics and connectivity to aquatic systems using a simple, but scalable, modeling approach.

The Fate of Deep Permafrost Carbon in Northern High Latitudes in the 21st Century: A Process‐Based Modeling Analysis

AbstractWarming in permafrost regions stimulates carbon (C) release through decomposition, but increasing atmospheric CO2 and available soil nitrogen enhance plant productivity at the same time. To date, a large uncertainty in the regional C dynamics still remains. Here we use a process‐based biogeochemical model by considering C exposure from thawed permafrost and observational data to quantify permafrost C emissions and ecosystem C budget in northern high latitudes in the 21st century. Permafrost degradation will make 119.3 Pg and 251.6 Pg C available for decomposition by 2100 under the Shared Socioeconomic Pathway (SSP)126 and SSP585, respectively. However, only 4–8% of the newly thawed permafrost C is expected to be released into the atmosphere by 2100. Cumulatively, permafrost degradation will reduce ecosystem C stocks by 3.37 Pg and 15.37 Pg under the SSP126 and SSP585, respectively. Additionally, CO2 fertilization effects would stimulate plant productivity and increase ecosystem C stocks substantially. The combined effects of climate change, CO2 fertilization, and permafrost degradation on C fluxes are typically more profound than any single factor, emphasizing the intricate interplay between these elements in shaping permafrost C‐climate feedbacks. Our study suggests that the majority of the thawed C will remain sequestered in previously frozen layers in this century, posing a significant challenge to climate change mitigation efforts once any process accelerates the decomposition of this huge amount of thawed C.

Thawing Permafrost Is Affecting Climate, but It’s Unclear by How Much

Models produce widely varying estimates of how ecosystems in the northern permafrost region are currently affecting the global greenhouse gas budget.

Anomalous wet summers and rising atmospheric CO2 concentrations increase the CO2 sink in a poorly drained forest on permafrost

At the northern high latitudes, rapid warming, associated changes in the hydrological cycle, and rising atmospheric CO2 concentrations, [CO2], are observed at present. Under rapid environmental changes, it is important to understand the current and future trajectories of the CO2 budget in high-latitude ecosystems. In this study, we present the importance of anomalous wet conditions and rising [CO2] on the long-term CO2 budget based on two decades (2003-2022) of quasicontinuous measurements of CO2 flux at a poorly drained black spruce forest on permafrost peat in interior Alaska. The long-term CO2 budget for the black spruce forest was a small sink of -53 ± 63 g C m-2 y-1. The CO2 sink increased from 49 g C m-2 y-1 for the first decade to 58 g C m-2 y-1 for the second decade. The increased CO2 sink was attributed to an 11.3% increase in gross primary productivity (GPP) among which 9% increase in GPP was explained by a recent increase in precipitation. Furthermore, a 3% increase in GPP in response to a 37-ppm increase in [CO2] was estimated from the data-model fusion. Our study shows that understanding the coupling between hydrological and carbon cycles and the CO2 fertilization effect is important for understanding the current and future carbon budgets of high-latitude ecosystems in permafrost regions.

Review article: Retrogressive thaw slump characteristics and terminology

Abstract. Retrogressive thaw slumps (RTSs) are spectacular landforms that occur due to the thawing of ice-rich permafrost or melting of massive ground ice, often in hillslope terrain. RTSs occur in the Arctic, the subarctic, and high mountain (Qinghai–Tibet Plateau) permafrost regions and are observed to expand in size and number due to climate warming. As the observation of RTSs is receiving more and more attention due to their important role in permafrost thaw; impacts on topography; mobilization of sediment, carbon, nutrients, and contaminants; and their effects on downstream hydrology and water quality, the thematic breadth of studies increases and scientists from different scientific backgrounds and perspectives contribute to new RTS research. At this point, a wide range of terminologies originating from different scientific schools is used, and we identified the need to provide an overview of variable characteristics of RTSs to clarify terminologies and ease the understanding of the literature related to RTS processes, dynamics, and feedbacks. We review the theoretical geomorphological background of RTS formation and landform characteristics to provide an up-to-date understanding of the current views on terminology and underlying processes. The presented overview can be used not only by the international permafrost community but also by scientists working on ecological, hydrological, and biogeochemical consequences of RTS occurrence and by remote-sensing specialists developing automated methods for mapping RTS dynamics. The review will foster a better understanding of the nature and diversity of RTS phenomena and provide a useful base for experts in the field but also ease the introduction to the topic of RTSs for scientists who are new to it.

Characteristics, impacts and future research directions of Mongolian peatlands

Mongolia is an important peatland distribution area in the world. Over the past few decades, Mongolian peatlands have undergone significant degradation due to climate change and human activities, yet there remains substantial uncertainty about the impacts of Mongolian peatland changes on regional environment and human society. Here, compiling the data of peatland distribution, climate, human activity, as well as the permafrost, we systematically review the distribution, changes, and the ecosystem service values of the Mongolian peatlands in the face of climate warming and intensifying human activities. The current data show that the total area of peatland in the Mongolian is 15500~27000 km2, and most of the peatlands are distributed in permafrost regions, while the accuracies of these maps were not assessed. In addition to climate warming, overgrazing, mining activities, and transportation, we suggest permafrost degradation also poses significant threatens on the peatlands. Although the importance of Mongolian peatlands has been recognized, the ecosystem service values, including water provision, habitat quality, carbon fixation, soil conservation, and wind erosion prevention largely remain unknown. Currently, efforts have been made to protect the Mongolian grassland, but there are no specific measures to combat peatland degradation. To better understand the changes and roles of peatland ecosystems in regulating regional development, we propose three research directions for future studies: 1) produce a detailed map of peatland distribution based on field survey data, new remote sensing data, and new algorithms; 2) Unveil the mechanisms underlying the interaction of peat, vegetation, and permafrost; 3) Evaluate the ecosystem services of Mongolian peatlands. These knowledges are the scientific foundation to propose and implement measures to protect, maintain, and sustainably utilize peatlands in Mongolia.

Risk assessment of transmission towers based on variable weight theory and matter-element extension model

Abstract The risk assessment of transmission towers is a critical approach to ensuring the safe and stable operation of power grids. In response to the increasingly frequent and severe impacts of seasonal permafrost on transmission towers in permafrost regions, this paper proposes a novel risk assessment method based on Variable Weight Theory and the Matter-Element Extension Model. By incorporating key influencing factors—such as the number of freeze-thaw cycles, soil moisture content, temperature fluctuations, soil dry density, melting settlement coefficient, and porosity ratio—an indicator system tailored to risk assessment in seasonal permafrost regions is established. Utilizing the Matter-Element Extension Model, this approach applies Variable Weight Theory to integrate both the best-worst method and the entropy weight method for calculating subjective and objective indicator weights. The risk level of the towers is then determined by their proximity to risk thresholds. Finally, a case study involving transmission towers in a specific region of a province in China is presented, where the assessment results are compared with the actual conditions to validate the rationality and effectiveness of the proposed method.

Pot‐Cover Effect in Permafrost Embankment: In Situ Experiment Evidence and Mechanism Simulation

ABSTRACTUnder the influence of large temperature differences in an impermeable pavement layer of wide embankment in permafrost regions, liquid water accumulates at the bottom of the impermeable cover. The phenomenon is known as the pot‐cover effect and leads to an increase in soil water content and a reduction in bearing capacity of wide embankments. At present, water vapor and liquid water migrations and their effect on embankment thermal‐moisture stability have not been fully confirmed. To better understand the moisture transport and accumulation process within embankments, hydrothermal field monitoring was conducted from 2009 to 2011 on an asphalt concrete layer highway in Beiluhe, central Tibet Plateau. The field monitoring results show that soil moisture content between 50 and 250 cm below the pavement continuously increases with the number of freeze‐thaw cycles, with the largest increase during the 2 years being 6.4%. Then, a coupled hydro‐vapor‐thermal transport model was established and verified. Furthermore, the model was used to analyze the numerical recurrence of the pot‐cover effect. The simulation indicates that the upward migration of liquid water during the freezing period is less than the downward migration during the thawing period, while vapor migrates downward during the thawing period but upward during the freezing period. The migration of water vapor within the embankment during the freezing period is the main cause of the pot‐cover effect in permafrost regions. In addition, the research results can provide new ideas for understanding the internal mechanism of thermal‐moisture dynamics of the embankment and the stability prediction of permafrost engineering.

Enhancing artificial permafrost table predictions using integrated climate and ground temperature data: A case study from the Qinghai-Xizang highway

The complexities of permafrost changes, driven by climate warming and engineering activities, coupled with challenges in data acquisition, make it crucial and challenging to accurately predict the artificial permafrost table, particularly for subgrades in high-temperature unstable permafrost regions. To address this, this study developed a hybrid machine learning model (RF-LSTM-XGBoost) for permafrost table prediction. By analyzing climate change and ground temperature data from various positions and depths along the subgrade in the Tuotuo River section of the Qinghai-Xizang Highway, the Spearman correlation coefficient method was initially used to determine the important influencing factors. Random Forest (RF), Long Short-Term Memory Neural Network (LSTM), and Extreme Gradient Boosting (XGBoost) models were used to predict the artificial permafrost table, and grid search and cross-validation methods were employed to optimize the hyperparameters of each model. A linear weighted combination method based on the minimum cumulative absolute error was utilized to merge the models, and its performance was compared with the individual RF, LSTM, and XGBoost models. Subsequently, the feature importance of the variables in the machine learning model was analyzed. The results indicated a strong correlation between artificial permafrost table changes and factors such as daily average atmospheric temperature, subgrade surface ground temperature, and subgrade surface ground heat flux during the freezing-thawing cycle. The combined model highlighted daily atmospheric temperature as the most influential predictor, followed by ground heat flux, with the surface ground temperature being less impactful. The combined model demonstrated improved predictive accuracy, with MSE, MAPE, RMSE, MAE, and R2 values of 0.003, 0.052, 0.0085, 0.029, and 0.989, respectively, surpassing those of individual models. This model offers a rapid, accurate, and reliable approach for permafrost table prediction, advancing subgrade stability research in challenging permafrost environments.

Vegetation Changes from 2014 to 2023 in the Mongolian Plateau Permafrost Region Under Climate Change

Vegetation Changes from 2014 to 2023 in the Mongolian Plateau Permafrost Region Under Climate Change

Higher Stability of Soil Organic Matter near the Permafrost Table in a Peatland of Northeast China

Understanding the stability of soil organic matter (SOM) is essential for making accurate predictions regarding carbon release rates. However, there is limited information on the role of chemical composition of dissolved organic matter (DOM) in SOM stability. To address this gap, the peatland soil profile in the discontinuous frozen soil region of Northeast China was selected as the focus of this research, and a comprehensive analysis was conducted on the differences between the molecular composition of DOM and the stability of SOM. The results indicate a significant carbon accumulation phenomenon near the permafrost table. Through analyses using TG-50, δ13C, and δ15N, it was determined that SOM near the permafrost table exhibits high stability, whereas SOM within the permafrost layer demonstrates poor stability. Investigations utilizing UV-vis, 3D-EEM, FT-IR, and 1H-NMR technologies revealed that DOM near the permafrost table is of high quality and highly aromatic. Furthermore, compared to near the permafrost table, humic acid materials in the permafrost layer decreased by 17%, while protein materials increased by 17%. These findings offer a novel perspective on the understanding of SOM stability in peatland soil profiles within discontinuous permafrost regions.

Numerical evaluation of ground source heat pumps in a thawing permafrost region

Permafrost degradation poses significant environmental and geological challenges in Arctic and subarctic regions, particularly in areas like Umiujaq, Canada. The warming climate leads to thawing permafrost, causing ground instability, disrupting hydrology, and impacting local built environment. This study evaluates the use of Ground Source Heat Pump (GSHP) operation for mitigating ground subsidence in a permafrost region using a two-dimensional Thermo-Hydro-Mechanical (THM) coupled finite element analysis considering the ground poro-elastic and poro-plastic responses. The research uses a single-well scenario to demonstrate the interactions among thermal, hydraulic, and mechanical processes. The impact of GSHP operation under different temperature management strategies, including a scenario with a constant GSHP temperature of −5 °C throughout the year is numerically investigated. Results indicate that GSHP operation exacerbates ground deformation near the borehole, particularly during winter months. However, maintaining GSHP operation throughout the entire year can mitigate extreme subsidence fluctuations, leading to a more stable subsurface environment. While GSHP systems provide effective thermal regulation, their operation can introduce mechanical stresses that potentially disturb the ground close to the borehole. Therefore, careful design, operation, and further research are essential to balance thermal benefits with ground stability in permafrost regions.