Ground Temperature Of Permafrost Research Articles

Analysis on the synergistic variation of soil freezing and pile foundation bearing capacity in permafrost regions

The construction of bored piles in permafrost regions disturbs the thermal stability of frozen soil, leading to decreased early bearing capacity of the pile foundation. As the permafrost ground temperature influences the area, the pile-soil gradually undergoes refreezing, resulting in a continuous enhancement of the pile foundation's bearing capacity. To study the synergistic variation law of soil refreezing and bearing capacity of bridge pile foundation in permafrost regions, two test piles with a length of 15 m and a diameter of 1.2 m were poured based on the actual bridge engineering construction project in the permafrost region of Daxing’an mountains, China. The intelligent temperature monitoring system was set up inside and in the area where the test pile was located. Combined with the collected temperature data, the refreezing state of pile-soil was comprehensively judged. The self-balancing method was employed to assess the bearing capacity of pile foundation before and after refreezing, unveiling the variation patterns in friction resistance at different soil layers and pile-end resistance. On this basis, a finite element model was established to analyze the interaction between pile side friction and pile tip resistance at varying depths of frozen soil. The test and analysis results revealed that the permafrost temperature in the pile foundation area was −1.9℃.Following pile-soil refreezing, the ultimate bearing capacity of the pile foundation increased by 2232 kN, and the growth rate was 42.9%. The friction resistance of each soil (rock) layer on the pile side increased, with the growth rate ranging from 15% −75%.

Multisite evaluation of physics-informed deep learning for permafrost prediction in the Qinghai-Tibet Plateau

Prediction of the permafrost ground temperature is challenging due to its complex nonlinear process. Coupling physical models and machine learning has shown great potential in big data analysis, but its performance in permafrost prediction is still unclear. In this study, we proposed a physics-informed deep learning framework (i.e., PI-LSTM) to predict permafrost ground temperature profiles. The framework combines physical information with a long short-term memory (LSTM) network by two-stage training (pretraining and fine-tuning). The output of a Geophysical Institute Permafrost Laboratory 2 (GIPL2) model was used to pretrain the LSTM model. Borehole ground temperature measurements were used to fine-tune the pretrained LSTM model. Validation at multiple sites in various situations in the Qinghai-Tibet Plateau (QTP) shows that the accuracy and efficiency of the PI-LSTM model are dramatically higher than those of the original LSTM or GIPL2 model. Depending on the fine-tuning data sampling frequencies, the performance of the PI-LSTM model improved by an average of 27% (6–56%) and 69% (64–71%) compared to the LSTM and GIPL2 models, respectively. Even when only one year of observations was used to fine-tune the model, the RMSE of the simulated near-surface ground temperature profiles in the next decade did not substantially decline. The incorporation of physical information also contributes to the simulation efficiency. The PI-LSTM model converges faster than the LSTM model, and the training epochs are reduced by 70% (67–73%) during the fine-tuning step. This study demonstrates that integrating physical information into deep learning is promising for improving permafrost predictions.

Elevation dependency of future degradation of permafrost over the Qinghai-Tibet Plateau

Global warming has caused widespread permafrost degradation, but the geographic regularity of permafrost degradation is unknown. Here, we investigated the three-dimensional features of future permafrost degradation on the Qinghai-Tibetan Plateau. Our findings show that permafrost degradation under shared socioeconomic pathways (SSPs) has obvious three-dimensional characteristics. In comparison to latitude and aridity, permafrost degradation is closely related to elevation, i.e. it slows with elevation, a phenomenon known as elevation-dependent degradation. The pattern of elevation-dependent degradation is consistent across four subzones and is strongly linked to thermal conditions that vary with elevation. Under SSP2-4.5, SSP3-7.0, and SSP5-8.5 scenarios, remarkable elevation-dependent warming (EDW) is observed at 3600–4900 m, but changes in mean annual ground temperature of permafrost and EDW as altitude rises are anti-phase. Under any SSP, the magnitude of mean annual air temperature along altitude belts determines the degree of permafrost degradation (R 2 > 0.90). This research provides new insight on the evolution of permafrost.

Spatial Distribution and Variation Characteristics of Permafrost Temperature in Northeast China

Frozen soil is an important environmental factor in cold regions. Warming climate will increase the risk of permafrost thawing, i.e., accelerated carbon release, reduced super-frozen soil water, intensified desertification and destruction of infrastructure. Based on MOD11A2 and MYD11A2 products of MODIS Terra/Aqua, the distribution and change of surface frost number under the influence of normalized difference vegetation index and forest canopy closure in Northeast China from 2003 to 2019 were produced. From 2012 to 2015, the area of the regions where the surface frost number was higher than 0.5 continued to decrease in Northeast China. Taking 2013 as the time turning point, two periods of changes in the distribution of surface frost number in Northeast China were divided, namely, into 2003–2013 and 2014–2014. The spatial distribution of permafrost temperature is simulated by establishing the numerical relationship between the surface frost number and the annual average ground temperature of permafrost. From 2003 to 2019, the area of permafrost changed from 32.77 × 104 to 27.10 × 104 km2. The distribution characteristics show that the area with permafrost temperature below −4 °C accounts for 0.1%, and below −3.0 °C accounts for 3.45%. The permafrost with lower temperature is mainly distributed in the Greater Khingan Mountains, from the northernmost Mohe to the Aershan in the middle of the ridge. The area where the permafrost temperature ranges from −2 to 0 °C is the largest, accounting for 73.81% of the total area. The distribution of permafrost temperatures in the Greater Khingan Mountains is mainly between −1.5 and −3 °C, while that in the Lesser Khingan Mountains is mainly between −2.0 and 0 °C. The altitude is the main factor controlling the permafrost temperature distributed at high latitudes in Northeast China. This work will provide more detailed basic data for regional research on frozen soil and the environment in Northeast China.

Thermal effect of thermokarst lake on the permafrost under embankment

In permafrost regions of the Qinghai-Tibet Plateau, road disaster caused by permafrost degradation cannot be ignored. As a common thermal disaster in permafrost regions, thermokarst lake has serious thermal erosion on permafrost and results in permafrost degradation aggravating. This study focused on two subgrade cross-sections of Gonghe-Yushu Highway in the Qinghai-Tibet Plateau to analyze thermal effect of thermokarst lake on the permafrost under embankment. The analysis infers that thermokarst lake can transfer heat to permafrost under the embankment, as a heat resource, and the heat flux decreases with the distance away from thermokarst lake in horizontal and vertical direction. Thermokarst lake can cause average ground temperature of permafrost under the embankment increasing, and with less distance from the thermokarst lake the temperature increases more severely. Thermokarst lake results in 14 m thickness melting interlayer in soil under lake and change shape of melting area.

Estimation of ground temperatures in permafrost regions of the Qinghai-Tibetan Plateau from climatic variables

Ground temperature is an important factor influencing ground source heat pumps, ground energy storage systems, land-atmosphere processes, and ecosystem dynamics. This paper presents an accurate development model (DM) based on a segment function: it can derive ground temperatures in permafrost regions of the Qinghai-Tibetan Plateau (QTP) from air temperature in case of shallow soil depths and without using air temperature data in case of deep soil depths. Here, we applied this model to simulate the active layer and permafrost ground temperature at the Tanggula observation station. The DM results were compared with those from the artificial neural network (ANN), support vector machine (SVM), and multiple linear regressions (MLR) models, which were based on climatic variables from prior models and on ground temperatures derived from observations at different depths. The results revealed that the effect of air temperature on simulated ground temperatures decreased with increasing depth; moreover, ground temperatures fluctuated greatly within the shallow layers but remained rather stable with deeper layers. The results also indicated that the DM has the best performance for the estimation of soil temperature compared to the MLR, SVM, and ANN models. Finally, we obtained the three average statistics indexes, i.e., mean absolute error (MAE), root mean square error (RMSE), and the normalized standard error (NSEE) at TGL site: they were equal to 0.51 °C, 0.63 °C, and 0.15 °C for the ground temperature of active layer and to 0.08 °C, 0.09 °C, and 0.07 °C for the permafrost temperature.

The Role of Winter Warming in Permafrost Change Over the Qinghai‐Tibet Plateau

AbstractWinter warming is fast than summer warming on the Qinghai‐Tibet Plateau (QTP). However, no assessment of winter warming effects on permafrost has been attempted. Here we conducted hypothetical control experiments and used the Noah land surface model to evaluate the impacts of winter warming on the QTP permafrost. The results show that air temperature in winter (November–April) was increasing at a rate of 0.66 °C/decade during 1980s−2000s, over double that in summer (May–October). The mean annual ground temperature of permafrost increased by 0.13 °C/decade. The summer warming dominated the variations in thermal regime of permafrost before 2000. After that, the influence of winter warming on permafrost thermal regime has gradually grown and exceeded that of summer warming. Winter warming has amplified the thermal degradation of permafrost. Our findings reveal that alpine continuous permafrost on the northern QTP has experienced a prominent regional warming due to rapid winter warming since 2000.

Computing a ground appropriateness index for route selection in permafrost regions

Abstract The reasonable calculation of ground appropriateness index in permafrost region is the precondition of highway route design in permafrost region. The theory of knowledge base and fuzzy mathematics are applied, and the damage effect of permafrost is considered in the paper. Based on the idea of protecting permafrost the calculation method of ground appropriateness index is put forward. Firstly, based on the actual environment conditions, the paper determines the factors affecting the road layout in permafrost areas by qualitative and quantitative analysis, including the annual slope, the average annual ground temperature of permafrost, the amount of ice in frozen soil, and the interference engineering. Secondly, based on the knowledge base theory and the use of Delphi method, the paper establishes the knowledge base, the rule base of the permafrost region and inference mechanism. The method of selecting the road in permafrost region is completed and realized by using the software platform. Thirdly, taking the Tuotuo River to Kaixin Mountain section of permafrost region as an example, the application of the method is studied by using an ArcGIS platform. Results show that the route plan determined by the method of selecting the road in permafrost region can avoid the high temperature and high ice content area, conform the terrain changes and evade the heat disturbance among the existing projects. A reasonable route plan can be achieved, and it can provide the basis for the next engineering construction.

Numerical study of the thermal characteristics of a shallow tunnel section with a two-phase closed thermosyphon group in a permafrost region under climate warming

Permafrost is very sensitive to temperature changes. Climate warming would cause the increase of ground temperature and accelerate the degradation of permafrost. One of the important future issues is how to control ground temperature to meet the demand of the engineering stability in permafrost regions under climate warming. In this study, a two-phase closed thermosyphon (TPCT) group is applied to adjust and control the ground temperature for a shallow tunnel section in a permafrost region. A composite heat transfer model, including the air turbulent heat transfer inside the tunnel, the air-TPCT-soil coupled heat transfer for the TPCT group, and the heat conduction with phase change in the soil layers and the tunnel structure layers, is developed for the tunnel with a TPCT group. The numerical results indicate that under the climate warming, the TPCT group can cool down the soil layers in the shallow tunnel section and ensure the thermal stability of the tunnel. Therefore, we conclude that it is an effective method to adjust the ground temperature of permafrost, without active control instrumentation or aid of other external energy. The research results could also provide help for applications of TPCTs in other cold regions engineering.

Variations in the ground temperatures of permafrost in the two watersheds of the interior and eastern Qilian Mountains

The Qilian Mountains, which are composed of a series of approximately northwest–southeast-oriented mountains, are one of main alpine permafrost areas in the Qinghai–Tibet Plateau in northwestern China. From east to west, variations in permafrost environments are remarkable. The source areas of the Shule River (SASR) and the Datong River (SADR) are located in the interior and eastern part of the Qilian Mountains. In this study, variations in the ground temperatures of permafrost in the two watersheds represented the characteristics of interior and eastern permafrost environments in the Qilian Mountains. A total of 20 and 30 boreholes, along with ground temperatures measured at 10–15 m depths, were collected in the two areas. The maximum ground temperature in the SASR was 0.7 °C, and the minimum was −3.4 °C. The variations in the ground temperatures can be explained by elevation and local slope facing. The lapse rates of the ground temperatures with elevation were 5.9 °C/km for the south-facing slope, 8.0 °C/km for the gentle flat terrain and approximately 5.7 °C/km for the north-facing slope. It was estimated that the 0 °C ground temperature was located at approximately 3800 m in the flat terrains, at approximately 3880 m on the south-facing slope terrains, and at approximately 3710 m on the north-facing slope terrains. In the SADR, the maximum and minimum ground temperatures were 2.54 and −2.78 °C, respectively. The elevation, vegetation types and soil moisture content can explain most of the variations in the ground temperatures. The lower limits of the permafrost were 3620 m for the wet meadow and 3710 m for the moist meadow. The lapse rates of the ground temperatures with elevation were 3.4 °C/km for wet meadow and 3.0 °C/km for moist meadow. The differences in the ground temperatures of the two areas were primarily caused by regional climatic differences, particularly the varying precipitation and evaporation. However, more areas must be studied to elucidate the regional differentiation of permafrost distribution and the underlying reasons for this differentiation.

Spatiotemporal characteristics of freezing and thawing of the active layer in the source areas of the Yellow River (SAYR)

Based on the analysis of data on temperatures and moisture of soils in the active layer at four different permafrost sites in the source areas of the Yellow River (SAYR) in 2010–2012, the freeze–thaw processes of soils in the active layer were compared and contrasted for understanding the spatiotemporal variations. At the four studied sites, the thickness and mean annual temperature of permafrost are different. The temperatures at the top of permafrost (TTOP), i.e., the maximum depth(s) of seasonal frost and/or thaw penetration, are −1.9 °C at the Chalaping site (CLP), −0.9 °C at the site on the southern bank of the Zhaling Lake (ZLH), −0.4 °C at the Maduo Town site (MDX), and 1.1 °C at the site on the northern bank of the Eling Lake (ELH). Differences in the mean annual ground temperature of permafrost and TTOPs may be responsible for the differentiations in the freeze–thaw processes of soils in the active layer. With rising TTOPs, the ground thawing started earlier: CLP in early June, ZLH in late May, MDX in early May, and ELH in mid-April, while the freezing began later: CLP in early October, ZLH in early to mid-October, MDX in mid-October, and ELH in the mid- to late October. With increasing TTOPs, the freeze-up periods for permafrost sites were shortened: 202 days at CLP, 130 days at ZLH, 100 days at MDX, and the period of complete thaw was 89 days at ELH. At the CLP and ZLH sites, the two-directional ground freezing (downwards from ground surfaces and upwards from the permafrost table) and thawing finished in the same year, but the ground freezing at the MDX continued to the end of the next January, with very slow freezing rates in the end. At the ELH site, ground freezing kept on until early May when thawing began on the surface, and upward and downward thawing became increasingly stable in late June to early July. At each site, with rising TTOPs, the downward freezing accelerated in comparison with the upward freezing, and with an increasing proportion of downward frozen depth, and with the larger ratios of freezing to thawing duration. In summary, the patterns of thawing and freezing processes in the active layer in the SAYR differ from those in other parts of the Qinghai–Tibet Plateau to a noticeable extent.

Numerical simulation of gas production potential from permafrost hydrate deposits by huff and puff method in a single horizontal well in Qilian Mountain, Qinghai province

Based on the geological data of the Qinghai-Tibet plateau permafrost, such as the permafrost ground temperature, the thermal gradient within and below the frozen layer, we numerically investigate the gas production potential from hydrates at the DK-3 drilling site of the Qilian Mountain permafrost, which is located in the north of the Qinghai-Tibet plateau. We employ the huff and puff method using a single horizontal well in the middle of the Hydrate-Bearing Layer (HBL). The simulation results indicate that desirable gas-to-water ratio and energy efficiency can be obtained under suitable injection and production conditions in the huff and puff process. However, the absolute gas production rate remains low during the whole production process. The sensitivity analysis indicates that the gas production performance is strongly dependent on the intrinsic permeability of the hydrate deposits, the sediment porosity, the injection and production rates, the temperature of the injected water, the irreducible water saturation and P01. The relative permeability exponents appear to have limited effect on the gas production behavior using the huff and puff method. The sensitivity analysis also indicates that the production potential of the natural gas hydrate deposit will be better than that of pure methane hydrate in this simulation.

New discoveries on the effects of desertification on the ground temperature of permafrost and its significance to the Qinghai-Tibet Plateau

The desert and permafrost conditions of the Qinghai-Tibet Plateau are unique. However, the effects of desertification on the ground temperature of permafrost are currently unclear. Recently, understanding this problem has become more urgent because of increasing desertification on the plateau. For this reason, an observational field experiment was undertaken by the authors at Honglianghe on the Qinghai-Tibet Plateau. Thermistor ground temperature probes were used, and synchronized contrasting observations were made in an open area. Observations of the ground temperature of permafrost below sand layers with a range of thicknesses were made from May 2010 to April 2011. The sand layers were found to play a key role in the protection of the underlying permafrost. The ground temperature below a permafrost table overlain by a thick sand layer was lower than that of the average annual temperature for the natural ground surface, and the temperature drop was roughly constant at 0.2°C. During the warmer part of the year (May to September), the maximum temperature drops over the five months were 3.40, 3.72, 4.85, 3.16, and 1.88°C, respectively. The ground temperature near a permafrost table overlain by a thin sand layer was also lower than that of the average annual temperature for the natural ground surface. However, in this case the average of the annual maximum temperature drop was significantly less, 0.71°C. The scientific significance of our preliminary conclusions is not only to present an exploration of the interaction between desertification and permafrost, but also to provide new engineering ideas for protecting the permafrost in regions where construction is required on the Qinghai-Tibet Plateau.

EFFECT OF SANDY SEDIMENTS PRODUCED BY THE MECHANICAL CONTROL OF SAND DEPOSITION ON THE THERMAL REGIME OF UNDERLYING PERMAFROST ALONG THE QINGHAI‐TIBET RAILWAY

ABSTRACTTo date, the mechanical control of drifting sand is the main method used for the protection of the Qinghai‐Tibet Railway from damage. The thermal effect of sandy sediments which are held in place on the underlying permafrost is a key area of interest and the focus of this paper. A ground temperature investigation of the permafrost along the railway route was undertaken and results were related to the different mechanical control measures used to control moving sand which had resulted in varying sandy sediment thicknesses. The studies were conducted in the Hongliang River area of the Qinghai‐Tibet Plateau from June 2010 to September 2010 using thermistor sensors. The results showed that the permafrost ground temperature and its daily variation, as well as the thawing depth of the active layer, decreased after the setting‐up of sand movement controls which had resulted in the accumulation of thick sandy sediments within the outside fringe of sand‐control engineering, or a covering of thin sandy sediments within the inside trackside (fringe) of sand‐control engineering. Below the thick sandy sediment cover accumulated by sand‐blocking fences, the average maximum temperature decreased. Average temperature decreased and the average depth of seasonal thawing (average thinning) were 3·38°C, 0·54°C and 0·48 m, respectively. Below the thin sand sediment cover accumulated by the checkerboard sand barriers, the values for the same parameters were 1·02°C, 0·21°C and 0·5 m, respectively. This study found that the mechanical control of sand does not only protect the railway from obstruction, but also facilitates permafrost stability, which in turn can help promote safety in railway operations. Copyright © 2011 John Wiley & Sons, Ltd.

Assessing the permafrost temperature and thickness conditions favorable for the occurrence of gas hydrate in the Qinghai–Tibet Plateau

Permafrost accounts for about 52% of the total area of the Qinghai–Tibet Plateau, and the permafrost area is about 140 × 10 4 km 2. The mean annual ground temperature of permafrost ranges from −0.1 to −5 °C, and lower than −5 °C at extreme high-mountains. Permafrost thickness ranges from 10 to 139.4 m by borehole data, and more than 200 m by geothermal gradients. The permafrost geothermal gradient ranges from 1.1 °C/100 m to 8.0 °C/100 m with an average of 2.9 °C/100 m, and the geothermal gradient of the soil beneath permafrost is about 2.8–8.5 °C/100 m with an average of 6.0 °C/100 m in the Qinghai–Tibet Plateau. For a minimum of permafrost geothermal gradients of 1.1 °C/100 m, the areas of the potential occurrence of methane hydrate (sI) is approximately estimated to be about 27.5% of the total area of permafrost regions in the Qinghai–Tibet Plateau. For an average of permafrost geothermal gradients of 2.9 °C/100 m, the areas of the potential occurrence of methane hydrate (sI) is approximately estimated about 14% of the total area of permafrost regions in the Qinghai–Tibet Plateau. For the sII hydrate, the areas of the potential occurrence of sII hydrate are more than that of sI methane hydrate.

Modeling on Gas Hydrate Formation Conditions in the Qinghai‐Tibet Plateau Permafrost

AbstractBased on the field‐investigated gas geochemistry, the modeling of gas hydrate formation conditions is conducted in the Qinghai‐Tibet plateau permafrost (QTPP) in combination with predecessors' data such as the permafrost ground temperature (T0), the thermal gradient within the frozen layer (G1) and the thermal gradient below the frozen layer (G2). The modeled results show that the permafrost characteristics generally meet the requirements for gas hydrate formation conditions in the study area. Gas composition, temperaturerelated permafrost parameters (e.g. T0,G1,G2) are the most important factors affecting gas hydrate formation conditions in the study area, whose spatial variations may cause the heterogeneity of gas hydrate occurrences. The most probable gas composition to form gas hydrate is the hybrid of methane and weight hydrocarbon gases (ethane and propane). In the predicted gas hydrate locations, the minimal upper depth of gas hydrate occurrence is less than one hundred meters and the maximum lower depth can reach one thousand meters with the thickness up to several hundred meters. Compared with Canadian Mallik gas hydrate field, the QTPP is favorable for gas hydrate formation in aspects of G1, G2 and gas composition, except for relatively thin permafrost, still suggesting great gas hydrate potentials.

Effect of Climatic Warming on Pile Creep in Permafrost

Climatic warming trends may induce long-term warming trends in permafrost ground temperatures at depth. In warmer discontinuous permafrost, the effects of such warming trends on the integrity of foundations on permafrost may be more pronounced. Structures placed on pile foundations in the Arctic have not addressed the potential effects of climatic warming in the part. This paper carries out some one-dimensional geothermal analyses to determine the effects of climatic warming on the ground temperature profile around a pile foundation, and examines the effects on the long-term creep response of a loaded pile. An existing geothermal simulator was modified to incorporate the creep calculation at each time step, and predictions for the creep settlement of a pile in a set of typical permafrost conditions have been made. The analysis indicates that permafrost at depth along the pile shaft has considerable thermal inertia, and does not warm significantly for the first 10–15 years of the simulation. Pile creep, after this time, is accelerated to some extent, induced by the effects of pile warming, averaged over the full length of pile.