Glacier change on the Qinghai-Tibet Plateau is an important part of the study of regional water cycle and climate response， and has important significance for the stability of Asian Water Tower. Glacier mass balance is one of the important indicators of glacier response to climate change. Xiao Dongkemadi Glacier is the first glacier in the hinterland of the Qinghai-Tibet Plateau to carry out glacier mass balance observation， and understanding its mass balance change mechanism is of great significance to study the interaction between glaciers and climate in the Qinghai-Tibet Plateau. Using the stakes， snow pits1 and meteorological data of Xiao Dongkemadi Glacier from 2005 to 2023， based on the data quality control program of time series inspection， statistical method detection and outlier correction， this paper eliminated significant outliers from the original data and improved the data reliability， and calculated and analyzed the mass balance characteristics of Xiao Dongkmadi Glacier. By analyzing the mass balance and meteorological factors on the 100-meter scale， the characteristics of the temporal and spatial evolution of the glacier mass balance and its driving mechanism are systematically revealed. The results show that in the past 20 years， the glacier presents a receding pattern of “accelerated melting at low altitude and weak compensation at high altitude”， with a cumulative mass balance of （-6 286±154） mm w.e. and a cumulative thickness thinning of （6.98±0.17） m. Although the mass balance of Xiao Dongkemadi Glacier fluctuates over the years， the continuously enhanced negative balance trend proves that the glacier is still in a serious mass deficit state for a long time， and the overall melting trend has not changed. During 2005 to 2023， the mass balance of the observation points was positively correlated with the elevation， and the mass balance gradient showed a slight increase in the annual fluctuation. The mass balance of glaciers showed significant altitude differentiation， with the mean mass balance gradient of （0.64±0.11） m w.e.·（100m）-1， and the ablation range expanded to the higher altitude， and the ablation boundary increased by about 60 m， reflecting the vertical effect of climate warming. Differences in topographic radiation led to differences in ablation within the same altitude zone， and the lateral drift shielding effect reduced local ablation. From 2005 to 2023， the Equilibrium Line Altitude （ELA） of Xiao Dongkemadi Glacier changed greatly and showed a slight upward trend in general. The annual average ELA was （5 740±20） m， and the ELA reached 5 660 m in 2023. Accumulation Area Ration （AAR） showed a significant downward trend （51.64%→50.70%）， and the actual AAR values were lower than the AAR0 equilibrium value （52%） of Xiao Dongkemadi Glacier in theoretical stable state， which also confirmed the continuous shrinking of the glacier. The analysis shows that temperature rise is the core driving force， and every 1 ℃ increase in summer mean temperature and average annual temperature can lead to a decrease in annual mass balance （0.18~0.21）±0.11 m w.e. The slight increase in precipitation ［16.5 mm·（10a）-1］ is not enough to compensate for the melting and area reduction caused by temperature rise. In this paper， we systematically analyze the driving mechanism of the mass balance change of Xiao Dongkemadi Glacier， focusing on the modulation of the spatial gradient characteristics of temperature， precipitation and albedo with the terrain， and the response of the glacier mass balance to the key factors. The study shows that the response of glacier mass balance to climate change is nonlinear due to the influence of topographic conditions on the spatial gradient of climate factors. Multivariate correlation analysis reveals the negative feedback effects of temperature， net radiation and positive feedback effects of precipitation， and the regulation mechanism of energy-mass balance of glaciers in the hinterland of the Qinghai-Tibet Plateau is dominated by albedo factors.
The changes in Qilian Mountain glaciers are not only a direct reflection of climate change， but also has an important impact on fresh water resources. In recent years， the glaciers in Qilian Mountain have been in a state of retreat and instability， to deeply understand the response of the glaciers in the Qilian Mountain to climate change in the 21st century and the magnitude of the change， clarify the characteristics of the Qilian Mountain glaciers change， the process and the reasons， and further predict the trend and magnitude of glacier change， and analyze the Qilian Mountain glaciers destabilization and imbalance in the climate warming background of the mechanism， we selected the Qiyi Glacier， which is strongly influenced by the westerllies， and the Lenglongling No.2 Glacier， which is strongly influenced by the monsoon as examples by analyzing remote sensing images and numerical simulation， it is found that the two glaciers show obvious retreat at the end of the glacier in 1990 to 2022， with the area reduced by 10.28% and 19.04% respectively， and the retreat rate of Lenglongling No.2 Glacier is obviously larger than that of Qiyi Glacier， which is attributed to the fact that the eastern part of the Qilian Mountain is warmer than the western part， and the eastern part of the glacier has decreased in precipitation. To explore the future changes of the two glaciers， the OGGM model considering glacier flow was driven by CMIP6 model data.The relative errors were within 2.5% by comparing the glacier area of the two glaciers simulated by the model and the visually interpreted area from 2008 to 2022. The simulated values of the mass balance of the Qiyi Glacier were more in line with the observed values， with an average difference of 88 mm w.e. Between the two mass balances， the difference between the two is 88 mm w.e.， which indicates that the OGGM model can simulate the glacier changes better.The simulation results show that under the high-emission scenario （SSP5-8.5）， the area and volume of the Qiyi Glacier will decrease by 77% and 94%， and the area and volume of the Lenglongling No.2 Glacier will decrease by 93% and 99% by 2060， and by the 21st century 80s， the air temperature in the area of the Qiyi Glacier will increase by 4.1 ℃ compared with that of the period of 1990 to 2015， while the increase in precipitation will not be obvious， and the glacier will be completely extinguished by that time. In contrast， temperatures in the eastern section of the Qilian Mountain will rise even faster， and it is predicted that the Lenglongling No.2 Glacier will be completely extinct around 2075. Even under the most optimal carbon emission scenario （SSP1-2.6）， a temperature increase of 1.0 ℃ in the Qilian Mountain by 2050 compared with the 1990 to 2015 prognosis will lead to the retreat of both glaciers into ice buckets by 2080 when the area and volume of Qiyi Glacier will be only 22% and 8% of that of 2020， and the Lenglongling No.2 Glacier will be only 17% and 6%. The rapid ablation of glaciers will cause changes in glacier runoff， and the runoff of the Qiyi Glacier and the Lenglongling No.2 Glacier will peak in 2035 and 2024， respectively， and the runoff of the two glaciers will be reduced by 28.98% and 41.82% by the end of the century under the SSP5-8.5 scenario， respectively. Therefore， regardless of climate scenarios， Qilian Mountain glaciers will retreat significantly in the 21st century， or even disappear， due the temperature， precipitation atmospheric circulation， and other influences， which will also make the eastern Qilian Mountain glaciers than the western glaciers retreat faster. Clarifying the trend and magnitude of glacier changes， and understanding the process mechanism of Qilian Mountain glaciers imbalance and destabilization in the context of climate change will deepen our understanding of the current and future glacier changes in the Qilian Mountain region， so as to cope with the environmental and water resource problems caused by the glacier changes， which require us to plan in advance.
The chain reaction of glacial lake outburst floods in the alpine and high altitude mountains area poses a significant threat due to its extensive impact range， large flood scale， and high flow velocity. Traditional prevention and control measures downstream of the disaster chain are often difficult to implement and economically unfeasible. Moreover， the primary triggering factors， such as ice collapses， are usually located at altitudes above 5，000 m， making access and engineering interventions extremely challenging. To address these issues， this study proposes a novel prevention and control approach focusing on the overflow outlet of the moraine dam， based on field investigations and statistical analysis. A new integrated protective system， combining rigid and flexible reinforcement layers， is developed to enhance the stability of the moraine dam’s armor layer at the overflow section. The system consists of scaffold steel pipes， high-strength metal flexible nets， and anchor rods， forming a “rigid-flexible integrated plate-like” protective structure. Laboratory physical model experiments were conducted to verify its effectiveness under simulated flood conditions. The results indicate that as protection measures are strengthened， the initiation flow velocity of the armor layer increases significantly. Compared to the unprotected state， a single-row rigid connection provides a minimal increase in stability， whereas a double-row rigid connection increases the initiation flow velocity by approximately 2%， a triple-row rigid connection by about 5%， and the combined rigid-flexible system by approximately 8%. The effectiveness of the protection system improves with an increase in the protected area， demonstrating its potential for mitigating moraine dam breaches. This research provides a feasible and technically viable solution for preventing moraine dam failures in high-altitude， cold environments. The proposed system offers advantages in terms of adaptability， cost-effectiveness， and ease of implementation in remote mountainous regions. It has the potential to serve as an effective first line of defense against glacial lake outburst floods and contribute to disaster risk reduction in alpine and high-altitude areas.
As a representative permafrost region in Northeast China， the Da Xing’anling Mountains have undergone extensive and rapid degradation of permafrost under the joint influences of climate change and human activities. Permafrost degradation has led to more frequent frost and thaw hazards. In order to systematically feature the distributive patterns， mechanisms， processes and trends of frost hazards and permafrost degradation in the northern Da Xing’anling Mountains， the Northeast Forestry University and Heilongjiang Provincial Institute of Natural Resources Survey， and others， jointly formed a survey and research team for frost and thaw hazards in the Da Xing’anling Mountains. The team conducted two surveys of frost and thaw hazards in permafrost regions in the northern Da Xing’anling Mountains from August to September 2023 along key infrastructures lines in the Da Xing’anling Mountains in the northern part of Northeast China （mainly including national highways G301， G10 and G111， G331， G332 and border patrol roads， forest railways （Yalin and Nenlin）， and CRCOPs and their access roads. They employed various technologies such as unmanned aerial vehicles （UAVs） for capturing basic location， vegetation， and terrain data； electrical resistivity tomography （ERT） to measure soil resistivity up to 20 m deep for assessing permafrost and talik， and； ground temperature measurements with the LCD-105 digital thermometer （range： -50 to 200 ℃） down to 2 m depth. High-precision terrain scanning was also performed using the Beidou Haida TS5 RTK receiver. Results show that asphalt pavement has the largest thaw settlement lengths and depths， and asphalt pavement is mainly characterized by subgrade thaw settlement （including subgrade tilt and rolling pavement surfaces）， while concrete pavement is mainly characterized by long-distance longitudinal cracks， and railways and China-Russia Crude oil pipelines （CRCOPs） are mainly characterized by subgrade thaw settlement. The average damage range of different pavements is ranked as follows： experimental section （length： 159 m， settlement： 71 cm）， asphalt + cement pavement （length： 129 m， settlement： 59 cm） > asphalt pavement （length： 78 m， settlement： 59 cm） > cement pavement （length： 37 m， settlement： 48 cm）. In terms of longitude， permafrost on the west slope of Da Xing’anling is well developed， and the thawing and settlement hazard range on the east slope is much larger than that on the west slope. In terms of latitude， permafrost development in high-latitude areas is better than that in low-latitude areas. The permafrost in low-latitude areas is severely degraded， and the thawing and settlement hazard range is large and concentrated. The geographical differentiation characteristics of thaw settlement and subsidence hazards are obvious： thaw hazards are distributed in locations with high annual average ground temperature， high soil moisture， flat terrain， better permafrost conservation conditions and shallow burial depth of the permafrost table. Thaw hazards pose a threat to the safe operation of the foundations of transportation infrastructures： the horizontal impact range of the two crude oil pipelines （CRCOPs I and II （Mohe-Daqing section）） on permafrost is greater than that of highways， and the vertical （depth） impact range of the two is similar. The local terrain formed by transportation infrastructure （sunny-shadowy slopes and water accumulation at the feet of the slopes） is an important factor causing thaw hazards. The probe digital thermometer is a fast， convenient and economical way to measure shallow ground temperature. This study provides some baseline data for the monitoring and management of frost hazards in Northeast China， as well as multi-element data for engineering construction and later maintenance in permafrost regions of Northeast China. At the same time， this study has some limitations in research scopes， insufficient coverage of frost hazards types， and inadequacies in comprehensive monitoring of frost hazards， which await further clarification， elaboration and improvement in the followed stages of field surveys and monitoring work.
This study focuses on the macroscopic and microscopic mechanical properties of frozen clay in the subgrade along the G0613 Xining-Lijiang Expressway， from Gonghe to Yushu. Different temperature and confining pressure conditions were applied in indoor triaxial tests to obtain stress-strain curves under various experimental conditions， revealing the shear strength parameters and their variations for different working conditions. Additionally， a discrete element model of frozen clay was established based on the discrete element method. After parameter calibration， it was compared with the indoor test results to provide supplementary analysis of the micro-mechanisms of frozen clay specimen changes during loading. The research findings indicate that the specimen exhibits strain hardening at high confining pressures and strain softening at low confining pressures， with evident bulging phenomenon. As the freezing temperature decreases， the shear strength and cohesion of the frozen clay significantly increase， with minimal change in the internal friction angle. The numerical simulation process， including contact force chains， particle velocities， and displacements， closely matches the indoor test results， and it provides an explanatory analysis of the bulging phenomenon at the microscale. After loading， significant damage occurs in the inter-particle bonding， and the damage mechanism is further analyzed.
Frost heave in cold regions demands measures to enhance the mechanical properties of soils. Modified geopolymer solidified soil was selected by using metakaolin and alkaline activator solidified silty clay as raw materials， sisal fiber and nano-silica as improved materials， respectively. The mechanical properties of modified geopolymer-solidified soils （GSS） under the freeze-thaw cycles were investigated via unconfined compressive strength （UCS） test， freeze-thaw cycle test， scanning electron microscope test and X-ray diffraction test. The number of freeze-thaw cycles， sisal fiber and nano-SiO2 content on the solidification effect and mechanical properties of silty clay were analyzed， and the curing mechanism and sustainability of the selected materials were explored. The results showed that the mechanical properties of the modified GSS were significantly affected by the first freeze-thaw cycle. The UCS of the samples decreased as the number of freeze-thaw cycles increased， and the GSS was damaged after nine freeze-thaw cycles. Besides， sisal fiber inhibited the hydration reaction， with dense gel products forming on the fiber surface during the curing process. Conversely， nano-silica filled partial pores within the samples and promoted hydration reactions， thereby enhancing the strength of the samples. The addition of sisal fiber reduced the carbon emission of the GSS， and the nano-SiO2 effectively reduced the
In recent years， most of the tunnels built in the cold area are frequently damaged by freezing， and the lining of the tunnels is seriously cracked due to freezing and expansion. A large number of studies have shown that the water storage space between the lining and the surrounding rock produces freezing and expansion forces due to the water-ice phase change， and the freezing and expansion forces act directly on the lining， which is the direct cause of various types of tunnel freezing phenomena. Therefore， the calculation of tunnel freezing and expansion force is one of the problems that need to be solved in the anti-freezing design of tunnels in cold areas. At present， the overall freezing and thawing circle freezing and expansion model is the most widely used and widely recognized freezing and expansion force calculation model， which is crucial for the design of tunnels in cold areas. This paper firstly analyses the strength theory of the mechanical state of frozen surrounding rock， and discusses in detail the various types of strength theories and their characteristics adopted in the overall freezing and thawing circle freezing and expansion model. Subsequently， the overall freezing and thawing circle freezing and expansion physical model is discussed from the elastic and elastic-plastic perspectives， and the freezing and expansion force elastic and elastic-plastic calculation models are summarized from the two perspectives of uniform freezing and non-uniform freezing and expansion assumptions； regarding the freezing and expansion force elasticity calculation model， three types of freezing and expansion deformation models， which include isotropic uniform freezing and expansion， assumption of the constant inner diameter and the increase of the outer diameter， and assumption of the inner diameter and the increase of the outer diameter， are explained in this paper. Increase， three types of freezing deformation under the assumption of freezing deformation elasticity calculation model of freezing expansion force calculation ideas and solution methods， summarized at this stage of the inhomogeneous freezing expansion representation and inhomogeneous freezing expansion under the assumption of the expression of the freezing expansion factors. Regarding the elastic-plastic calculation model of freezing expansion force， the connection between the elastic and elastic-plastic freezing expansion force calculation models is firstly analyzed， and the plastic zone calculation method of the elastic-plastic calculation model of freezing expansion force under the assumption of uniform freezing expansion， and the expression method of the freezing expansion influencing factors of the elastic-plastic calculation model of freezing expansion force under the assumption of inhomogeneous freezing expansion， are systematically sorted out. On the basis of summarising the existing research on the freezing expansion force in cold tunnels， it is known that the displacement release of frozen surrounding rock and lining， freeze-thaw cycle， transverse isotropy， stress damage and yield state are the key factors affecting the freezing expansion force. On this basis， the further research direction of freezing expansion force calculation mode of cold tunnel is discussed in terms of the representation method of inhomogeneous freezing expansion， the development direction of the freezing expansion factors and freezing expansion force， and the application situation， in order to provide a reference for the design of the cold tunnel engineering construction.
With the rapid advancement of China’s economy and accelerating urbanization， the proportion of subways in urban transportation networks is steadily increasing. The artificial ground freezing method is an essential construction technique for tunneling through soft， water-saturated soil layers. The frost heave-induced deformation of the ground surface resulting from this method may adversely affect adjacent existing engineering structures. In extreme scenarios， it could lead to significant economic losses and pose a threat to human safety. Therefore， considering the crucial factor of ground surface deformation caused by soil frost heave becomes imperative during the horizontal freezing construction of shallow buried tunnels. The investigation into the redistribution of the soil layer displacement field induced by artificial ground freezing and its resulting ground surface uplift deformation has garnered significant attention among scholars； however， certain limitations are present. To overcome the limitation of previous studies that overlook the spatial variability in frost heave ratio resulting from a non-uniform temperature field， the article proposes an innovative methodology for quantifying ground surface deformation induced by frost heave during underground tunnel construction. The proposed method integrates the principles of superposition and the theory of random media within the framework of thermo-elasticity mechanics， utilizing the concept of an equivalent thermal expansion coefficient. The presented approach was employed to calculate ground surface deformation induced by soil frost heave due to single-loop distribution freezing pipes， based on an engineering case study. The rationality and applicability of the presented method were demonstrated through a comparison with observed values. The calculation results obtained from this method demonstrate a markedly higher degree of agreement with the observed values compared to those achieved by conventional approaches and finite element method （FEM）. Conventional approaches typically assume a constant frost heave ratio and estimate stress and deformations using the principles of thick-walled cylinders. The FEM is based on the principles of “cold expansion and hot contraction” and employs thermal-mechanical coupling to simulate frost heave phenomena induced by artificial ground freezing. In contrast to the presented approach， the conventional model fails to consider the reduction in soil frost heave ratio near the outer side of a frozen soil wall due to higher temperatures， leading to an overestimation of computational results. Compared to FEM， the approach proposed in this study is more straightforward and practical， while also providing deeper insights into underlying mechanical principles. In addition， the investigation focused on the distribution of ground surface frost heave deformation induced by the artificial ground freezing， taking into account the influences of refrigerant medium temperature， burial depth of the tunnel center， and freezing front extension coefficient ε. The results indicate that as the refrigerant medium temperature decreases， there is a notable overall increase in ground surface deformation， with particularly pronounced effects observed above the center of the tunnel. The appropriate selection of coolant medium temperature is crucial for ensuring the safety and stability of adjacent existing structures. The central buried depth of the tunnel， to some extent， reflects the average embedment depth of freezing pipes and serves as a critical factor influencing ground surface frost heave deformation. With an increase in the burial depth of the tunnel， both the maximum deformation caused by ground frost heave and its influence range gradually diminish. The distribution of ground surface frost heave deformation is closely correlated with the depth of the tunnel center， which in turn governs the magnitude and extent of ground surface deformation. The maximum ground surface frost heave deformation and the affected area exhibit a slight increase as ε increases， although this increment is not significant. This study can provide reference for the application of artificial ground freezing technology in high-risk underground engineering projects.
Slope instability and collapse due to freeze-thaw cycles are significant challenges in infrastructure development in permafrost regions. To explore and analyze the causes and stability variation patterns of slope instability in seasonally frozen soil areas in Southwest China， this study focuses on the slopes of the Batang region. A research approach combining theoretical analysis， numerical simulation， and laboratory experiments is employed. A permeability coefficient model for the negative temperature zone， considering the unfrozen water and pore ice states， is applied within a soil hydrothermal coupling model. Through direct shear tests， the variation patterns of shear strength parameters for remolded slope soils were further obtained. Using the COMSOL finite element software， a customized slope stability model was developed. The slope height was set to 10 m with a gradient of 1∶1.5， and both the slope top and bottom extended 50 m and 60 m， respectively， with the slope base extending 10 m downward. This model was used to analyze the changes in temperature and seepage fields， as well as the slope instability mechanisms induced by freeze-thaw cycles affecting the soil’s shear strength parameters. Results show that the modified hydrothermal model， which incorporates the adjusted permeability coefficient， has higher accuracy， as verified by comparing the calculated values with those from one-dimensional soil column experiments. Temperature fluctuations within 1 m of the slope surface are significant. From January to March， air temperatures remain low， with deeper soil temperatures being relatively high， and soil temperature increases monotonically with depth. Between April and September， surface soil temperatures rise faster than the deeper layers， which maintain relatively high temperatures. From October to December， surface temperatures decrease more rapidly than in deeper layers， where temperatures remain relatively stable. The seepage field shows minimal variation beyond 2.5 m depth. From November to March， the slope surface freezes first， leading to a decrease in water content， although internal moisture migration is limited. Water content initially decreases with depth， then increases. Between April and June， during the thawing period， shallow soil melts， with water content decreasing with depth. From July to October， the water content initially increases with depth before decreasing again. In March， water content variation with depth is most pronounced， and due to the surface thawing while the subsurface remains frozen， excess water above the frozen layer cannot drain effectively， resulting in the lowest slope stability with a safety factor of only 1.59. The mechanism of slope failure in seasonally frozen regions is attributed to saturation above the thaw-freeze interface during the thawing period， where water cannot drain， reducing soil friction and leading to slope collapse. By dynamically adjusting the soil strength parameters to calculate slope stability， it is determined that the most significant strength degradation occurs at the thaw-freeze interface， primarily resulting in shallow slides within 1.2 m of the surface. The sliding surface is relatively flat and arc-shaped， with the primary failure mode being slumping collapse. This study provides valuable insights for slope design and disaster prevention in Southwest China， particularly for engineering projects in seasonally frozen regions， offering significant practical implications.
At 23：59 on December 18， 2023， a magnitude MS 6.2 earthquake struck Jishishan County， Gansu Province. Simultaneously， a mudflow geological disaster occurred in Qijiagou， Zhongchuan Township， Minhe County， Qinghai Province， resulting in severe casualties and property damage. Through field investigations， high-precision remote sensing image interpretation， and laboratory experiments， the causes， dynamic mechanisms， and kinematic characteristics of the mudflow disaster chain in the Zhongchuan Township area were analyzed and numerically simulated. Using parameters determined from field surveys and laboratory experiments， the FLO-2D model was employed to simulate the initiation， movement， and deposition processes of the mudflow in Qijiagou. The study revealed that the maximum velocity of the mudflow near the confluence of Zhangjiagou and Qijiagou， where the terrain is highly undulating， reached nearly 10 m·s-1， with a maximum mud depth of approximately 16 m. The simulation results were consistent with the measured data. The numerical simulation method adopted in this study can effectively describe the characteristics of the mudflow during its movement and deposition stages， providing valuable insights for the prediction and prevention of similar mudflow disasters.
The impact of geological hazards on tunnel structural stability in cold regions， such as freeze-thaw cycles in surrounding rock， cannot be ignored. Thus， unsteady temperature field of the shallow buried tunnel surrounding rock in cold regions is studied analytically. After the conversion of the shallow buried circular tunnel surrounding rock region into an annular region by conformal transformation， the equation is decomposed into a steady heat transfer equation and an unsteady heat transfer equation linearly based on superposition principle combined with temperature boundary conditions. Finally， the explicit analytical solution for the unsteady temperature field of the tunnel envelope is derived by variable separation method and variable substitution. Comparisons among results of this analytical solution， finite element data and existing article data show a reasonable similarity， which verifies the correctness of this analytical solution， demonstrating a higher operational efficiency compared to numerical methods. Parametric analysis of the analytical solution shows both the increase in thermal diffusivity rate of the surrounding rock and tunnel radius will accelerate the unsteady heat conduction process of the surrounding rock， while the increase in tunnel depth will slow down the heat conduction process above the vault； The unsteady temperature fields of the normal lines at different angles from the tunnel lining are compared and analyzed， which shows that as the normal line becomes more horizontal， the temperature of the points with the same distance from the tunnel lining varies more in steady state， and the more distant those points from the tunnel lining is， the more the temperature varies at steady state， and the angular distribution of the tunnel surrounding rock temperature field shows weak symmetry； The analysis of unsteady component of temperature field above the tunnel vault shows that the shorter the distance to the tunnel vault and the time elapsed for heat conduction are， the larger the proportion of the unsteady component in the analytic solution is. This study is informative for the prediction of temperature response of tunnel structure in cold regions.
Thermal conductivity is an important parameter to measure the heat transfer ability of materials. In order to improve the prediction accuracy of thermal conductivity of unsaturated frozen soil， a thermal conductivity prediction model for unsaturated frozen soil is proposed based on the principle of minimum thermal resistance and the homogenization method， and the accuracy of the model is tested by using diverse data sets. On this basis， the factors affecting the thermal conductivity of unsaturated frozen soil were analyzed by using the Sobol index sensitivity analysis method. The following conclusions can be drawn from the above study： （1） The prediction model of thermal conductivity coefficient of unsaturated frozen soil constructed based on the principle of minimum thermal resistance and the homogenization method has high reliability and generalization， and the deviation of the predicted value of thermal conductivity coefficient from the experimental value is only 2% by taking the arithmetic average of the prediction results of the transverse thermal resistance infinity model and the transverse thermal resistance infinitesimal model as the equivalent thermal resistance of the unit body. （2） The thermal conductivity of unsaturated frozen soil decreases with the increase of porosity， and when the porosity increases from 0.2 to 0.8， the thermal conductivity decreases by about 50%； the increase of
The cold region of northwest China is covered with a large area of loess layer. The structure of loess is loose and the porosity is large. Moreover， due to the influence of periodic freeze-thaw cycles， the loess subgrade is prone to frost heave and thaw settlement damage， which seriously affects the serviceability of road engineering in similar areas. In order to reduce the freeze-thaw disease of loess， the commonly used prevention and control method is to use cement and lime modified loess as roadbed filler. However， this improvement is not only costly but also not conducive to the sustainable development of the environment. The current green and economical and effective improvement methods are still insufficient， and related research is urgently needed. In recent years， the use of biopolymers to improve soil has become a research hotspot in the field of rock and soil improvement because of its natural， environmentally friendly， easy to obtain and cheap. Biopolymers are environmentally friendly materials with high yield， so they have broad application prospects in soil improvement. Among them， xanthan gum and guar gum are the most widely used in engineering， so we try to use biopolymer to improve the loess in the northwest cold region. In order to explore the freeze-thaw characteristics of biopolymer modified loess， the most representative xanthan gum and guar gum in biopolymer were selected to improve loess respectively， and the indoor freeze-thaw cycle test combined with electron microscope scanning test was carried out to study and analyze the loess improved by xanthan gum and guar gum. The results show that： （1） Both xanthan gum and guar gum modified loess can reduce the temperature fluctuation and temperature difference during the freeze-thaw cycle， and slow down the rate of temperature change. The test results show that the temperature control effect of modified loess is the best when 1.5% xanthan gum and 2.0% guar gum are added alone， and the temperature control effect of xanthan gum modified loess is better than that of guar gum modified loess. （2） After adding xanthan gum and guar gum， it can effectively reduce the water supplement and water migration of the improved loess， and alleviate the water redistribution caused by the freeze-thaw cycle. Among them， single-doped 1.5% xanthan gum and single-doped 0.5% guar gum have the best control effect on soil moisture. The water migration of the modified loess decreased by 91% and 75%， respectively， indicating that guar gum can achieve the best improvement effect at a smaller dosage. （3） Both xanthan gum and guar gum can inhibit the frost heave and thaw settlement deformation of loess， thereby reducing the frost heaving ratio and thaw settlement coefficient during the freeze-thaw cycle. Among them， 0.5% xanthan gum and 0.5% guar gum alone have the best effect， reducing the average frost heaving ratio and the average thaw settlement coefficient by 21.4%， 14.3% and 40%， 60%， respectively. （4） Biopolymer not only improves the microscopic pore structure of loess， but also enhances the anti-deformation ability of loess by means of cementation and encapsulation. Both xanthan gum and guar gum can improve the water and heat transfer and pore structure of loess， thereby reducing the frost heave and thaw settlement deformation of the improved loess. Combined with the improvement effect of two biopolymers on soil temperature， moisture and deformation， the results show that the improvement effect of xanthan gum is better than that of guar gum. The above research results can provide reference for the prevention and control of loess freeze-thaw diseases and loess improvement research in the cold region of Northwest China.
In recent years， heavy metal pollution has caused changes in the mechanical and hydraulic parameters of soils， leading to a deterioration in their engineering performance. This， in turn， has raised significant concerns regarding the stability of geotechnical structures. This paper investigates the combined application of enzyme-induced calcium carbonate precipitation （EICP） and lignin-based calcium solidification （referred to as EICP-lignin） for the remediation of copper-contaminated loess. The long-term curing effects and weather resistance of the combined treatment are evaluated through unconfined compressive strength （UCS） tests and toxicity leaching tests conducted before and after freeze-thaw cycles. Furthermore， scanning electron microscopy （SEM） is employed for microstructural analysis to explore the microscopic mechanisms underlying the EICP-lignin solidification of copper-contaminated loess under freeze-thaw conditions. The experimental results indicate that as the EICP dosage increases， the UCS of the treated soil increases and stabilizes over time. The incorporation of lignin significantly enhances the soil’s strength， with the most pronounced effect observed at a lignin dosage of 4%. However， when the lignin content is further increased， weak planes may form， leading to a decrease in compressive strength. With an increasing number of freeze-thaw cycles， the EICP-lignin treatment significantly reduces the deterioration in UCS. After 9 freeze-thaw cycles， the strength of the combined solidified soil remains at a relatively high level， with a strength loss of only 8.5%. In contrast， the strength of untreated soil， EICP-only solidified soil， and lignin-only solidified soil decreases by 41.5%， 42.4%， and 26.4%， respectively. This demonstrates that lignin combined with EICP enhances the soil’s weather resistance. In the Toxicity Characteristic Leaching Procedure （TCLP） leaching tests， the EICP-lignin combined treatment significantly reduces the copper ion leaching from loess contaminated with various concentrations of copper. The maximum solidification rate achieved is 79.54%. As the number of freeze-thaw cycles increases， the solidification rate gradually decreases. After 9 freeze-thaw cycles， the combined solidification rate of polluted soil is more than 15% higher than that achieved by EICP alone. SEM analysis reveals that lignin not only enhances the physical structure during the EICP curing process but also facilitates the uniform precipitation of calcium carbonate， thereby improving the solidification effect and weather resistance of copper-contaminated loess. This demonstrates the significant advantages of the combined strengthening mechanism. The findings of this study provide valuable scientific evidence and data to support the reinforcement and remediation of heavy metal-polluted loess sites， offering practical insights for geotechnical engineering applications.
Preferential flow （PF） is a rapid and irregular movement of water through specific channels within soil. This process is closely linked to the pore characteristics of the soil， allowing water to bypass much of the soil matrix and move swiftly along distinct pathways. In permafrost regions， PF can be triggered by rainfall， snowmelt， the formation of supra-permafrost subaerial talik （SST）， and seasonal changes in the active layer—where soil freezes and thaws each year. These dynamics make PF a complex phenomenon， influenced both by environmental factors and soil structure. In recent years， climate change and human activities have intensified the risk of permafrost degradation， leading to thawing and deformation of foundation soils in sensitive areas such as the Da Xing’anling Mountains and along the China-Russia Crude Oil Pipelines （CRCOPs）. The occurrence and behavior of PF play a critical role in the hydrothermal conditions and freeze-thaw cycles affecting pipeline foundations. As the climate continues to warm and become wetter， permafrost degradation accelerates， posing greater risks to infrastructure in these regions. To explore how PF influences freeze-thaw processes in pipeline foundation soils along the CRCOPs， this study investigated silty clay soils collected from the CRCOPs route in the Da Xing’anling Mountains. By employing methods such as indoor color tracers and comparative testing， the study visualized and measured the effects of PF within soil columns. PF was introduced to the silty clay specimens using a PF medium， and six test samples were prepared， each representing a different PF type： random irregular macroporous PF， regular macroporous PF， microfracture PF within an organic interlayer， finger PF in a sand or silty sandy clay interlayer， and funnel PF in a gravel interlayer. To analyze how each type of PF structure and distribution affected changes in temperature， volumetric water content， coloration， and PF indices （PFI） during freeze-thaw processes， these samples were compared to a control specimen of well-packed silty clay. The results showed that PF significantly influences temperature dynamics in soils. For example， the cooling time in soil columns containing microfracture PF and randomly distributed macroporous PF was extended by 65% and 87%， respectively， while the warming time increased by 57% and 39%， compared to the control. When the minimum temperatures were reached （-6.84 °C for microfracture PF and -8.43 °C for funnel PF）， the average temperatures in these PF samples were 0.4 to 2.5 °C lower than those of the control. Additionally， the time needed for these PF samples to reach stable temperatures was 1.9 to 2.4 times longer than the control， showing the insulating effect of PF on soil temperature during freeze-thaw cycles.PF also impacted volumetric water content. Minimum water content in the microfracture PF and funnel PF samples （9.4% and 10.4%， respectively） was 18% to 25% higher than in the control， indicating greater water retention in soils with PF. In terms of coloration rate， PF samples showed values 15% to 56% higher than the control， suggesting more extensive water movement through PF channels. During the first freeze-thaw cycle， the PFI values in soil columns with PF were over 48% higher than in the control， highlighting PF’s significant role in influencing water retention and distribution. Overall， the type of PF， as well as factors such as water transport capacity and connectivity of PF channels， plays a critical role in shaping the thermal and moisture characteristics of silty clay in the Da Xing’anling Mountains during freeze-thaw cycles. These findings offer valuable data for addressing operational and maintenance challenges for CRCOPs amid climate warming and permafrost degradation. They also provide essential insights for engineering and construction in similar permafrost zones， helping improve the stability and durability of foundations in a changing climate.
River is a channel for carbon transport between land and ocean and an important reactor for the metabolism of aquatic ecosystems. It plays an important role in the migration and transformation of carbon in terrestrial and marine aquatic continuums and the carbon budget of watershed ecosystems. The Qinghai-Xizang Plateau is the largest high-altitude cold region in the mid-latitude region. As an Asian water tower， it has developed many major rivers and plays an important role in the regional carbon cycle. In the context of climate change， the process of riverine carbon cycle in the Qinghai-Xizang Plateau has received extensive attention in recent years. This study focuses on the process of river carbon cycle in the Qinghai-Xizang Plateau， and systematically summarizes the progress of riverine carbon cycle in many source areas such as the Yellow River， the Yangtze River， the Lancang River， the Nujiang River and the Yarlung Zangbo River in the past decade. It is found that： （1） The dissolved carbon in the rivers of the Qinghai-Xizang Plateau is dominated by inorganic carbon， and the concentration of dissolved organic carbon is relatively low. The factors such as thawing of frozen soil， enhanced weathering， changes in hydrological processes， and increased erosion and sediment production caused by future climate change will further increase the lateral carbon transport flux in the rivers of the Qinghai-Xizang Plateau. （2） Current observations show that rivers on the Qinghai-Xizang Plateau are important sources of carbon dioxide and methane emissions， and their processes are also affected by climate change and have an increasing trend； （3）The river carbon flux in the Qinghai-Xizang Plateau has an important impact on the carbon budget of the basin ecosystem. The large river carbon horizontal and vertical carbon fluxes offset some terrestrial carbon sinks and are an important part of the ecosystem carbon process. With the warm and humid climate of the Qinghai-Xizang Plateau， its river carbon cycle process will inevitably change significantly， which in turn affects regional carbon sinks， but the extent of its impact is still unclear. In the future， in-situ observation， remote sensing inversion， machine learning and other means should be further used to accurately describe the mechanism of river carbon process， enhance the in-depth understanding of the microscopic mechanism of river carbon cycle， and develop a carbon cycle model suitable for alpine rivers on the Qinghai-Xizang Plateau based on relevant mechanisms， so as to strengthen the simulation and prediction ability of carbon cycle in plateau rivers. This study can provide a scientific basis for further understanding the role of rivers in the carbon neutrality of the Qinghai-Xizang Plateau in the context of changing environment.
The Qinghai-Xizang Plateau （Tibetan Plateau， TP）， renowned as one of the most distinctive geographical landmarks globally， stands as a critical tipping point within the climate system. As the “Asian Water Tower”， this region is highly sensitive to the effects of climate change and could significantly impact the regional climate patterns. Its influence extends profoundly， affecting the climate of East Asia and even the broader Northern Hemisphere. Therefore， it is imperative to comprehend the historical climate patterns and current dynamics of TP. As a proxy for reconstructing past climates， tree rings have been widely utilized in TP climate reconstruction studies. Dendrochronological works in TP have demonstrated a significant potential for developing long tree-ring chronologies over 1 000 years from living trees， archaeological samples， and in situ timber remnants. These records contain temperature and precipitation variability information at multidecadal scales with perfect annual resolution. While numerous literature reviews have focused on different tree-ring parameters， a comprehensive review of dendroclimatological research on TP is still lacking. Therefore， it is necessary to systematically review the research progress of tree ring climate studies in this region. This study retrieved tree-ring chronology data from 1 436 sampling sites across the TP， outlining the progress of dendroclimatology research since 1990. The analysis revealed that most studies utilized tree-ring width （TRW）， followed by maximum latewood density （MXD）， stable oxygen isotopes （δ18O）， and stable carbon isotopes （δ13C）. TRW studies were widely distributed， encompassing nearly 70 tree species， with the length of the chronologies ranging from 300 to 600 years. MXD studies were concentrated in the Hengduan Mountains， focusing mainly on Picea balfouriana， with shorter chronologies and no millennial records. MXD is predominantly used to reconstruct regional temperatures during the growing or late growing season. Studies of δ18O are primarily located in the surrounding areas of the Hengduan Mountains， Qilian Mountains， and Himalayas. The studied species is substantial， with the longest δ18O chronology dating back to 4680 B.C. δ18O mainly records hydroclimatic signals. Studies of δ13C are relatively weak， mainly concentrated near the cities of Linzhi and Chamdo and the surrounding areas of the Qilian Mountains. The species most commonly used for δ13C studies are Picea crassifolia and Sabina przewalskii. Most of the δ13C chronologies are shorter than 200 years， with the longest chronology reaching 1 171 years. Tree-ring δ13C is used to reconstruct changes in temperature and hydroclimatic signals. In the future， the accuracy of climate reconstructions can be improved by extending the length of MXD and isotope chronologies， conducting multi-parameter comprehensive analyses， and refining the detrending methods. Expanding sampling sites， particularly in the western and southern TP， is essential to address these geographic gaps. Future research should also explore the climate responses of shrubs and non-coniferous species to enhance the regional dendroclimatological database. Extending the length of tree-ring density and isotope chronologies—especially in northern and western regions—is critical. Given the current reliance of most studies on a single parameter from a single species for climate reconstruction， multi-species and multi-parameter approaches remain uncommon. Therefore， future research should prioritize integrated analyses， combining diverse dendrochronological indicators with climate models to improve the accuracy and temporal depth of multifactor climate reconstructions. Researchers can gain deeper insights into this region's changing frequency and intensity of extreme climate events by integrating tree-ring records and modern meteorological data and combining tree-ring ecology and physiology studies. This study offers a comprehensive overview of advancements in dendroclimatological research in TP， thus providing readers with a clear understanding of the latest developments and the persistent challenges in these studies. Furthermore， this review also summarizes the shortcomings of existing research and lays a theoretical foundation for future in-depth investigations in this field.
Lhasa River is one of the five major tributaries of the Yarlung Tsangpo River. Maintaining the healthy development of the Lhasa River ecosystem is of great significance to the construction of the ecological security barrier， ecological civilization highland， and sustainable development in Lhasa. In this study， we collected microbial samples from the lower Lhasa River. We determined the environmental factors， analyzed the diversity of bacterial communities， structural characteristics， and community assembly process in the lower Lhasa River by high-throughput sequencing， and explored the influence of environmental factors on the microbial diversity of the Lhasa River by combining with the physical and chemical properties of the water body. The results of bacterial amplicon sequencing at 12 sample sites within 120 km of the lower Lhasa River revealed 39 phyla， 101 orders， 289 orders， 493 families， 1 004 genera， and 1 954 species of bacteria， indicating that the bacterial communities in the lower Lhasa River had a rich bacterial diversity and that the composition of the bacterial communities in the upstream and downstream sections of the water body is highly similar， with the dominant phyla being Proteobacteria， Firmicutes， Actinobacteria， Planctomycete and Bacteroidetes ect.； the dominant genera were Limnohabitans， Exiguobacterium， etc.； Comparative analyses of the bacterial phylum and genus levels in the water body of the downstream of the Lhasa River showed that the similarity of the bacterial community compositions at the genus level was even lower. The neutral model analysis shows that the bacterial community in the water body of the downstream of the Lhasa River is affected by both stochastic and deterministic processes， but the stochastic process is dominant. Co-occurrence network analysis showed that the connectivity of bacterial communities in water bodies was mainly dominated by positive correlation edges， with the lower section of water bodies showing stronger network complexity and connectivity. Proteobacteria， Actinobacteria， and Bacteroidetes had the highest percentages in the bacterial co-occurrence networks of the upstream and downstream sections of the water body. Through the analysis of Mantel test， it can be obtained that the concentration of the water body has a significant positive correlation with the bacterial community in the upstream water， and the rest of the environmental factors do not have a significant effect on it； pH， water body temperature， salinity， light intensity， and dissolved oxygen of the water body have a significant positive correlation effect on the bacterial community in the lower section of the water body. By investigating the structure， diversity changes， and community assembly mechanisms of bacterial communities in the urban section of the lower Lhasa River， we can gain a deeper understanding of the unique microbial community structure and functions of plateau rivers， and assess the impacts of global change on river ecosystems.
In order to understand the soil fertility status and its spatial variation characteristics of the Yani Wetland， 71 soil samples were collected from the Yani Wetland. The contents of soil pH， organic matter， Total state and available state of nitrogen， phosphorus and potassium， cation exchange capacity were measured. Geostatistics and geographic information system （GIS） were used to explore the spatial distribution characteristics of fertility indicators， and using fuzzy comprehensive evaluation method to quantitatively evaluate soil fertility. The results showed that： （1） The soil pH of Yani Wetland was 7.35， which was neutral as a whole. The contents of total phosphorus and available phosphorus were at the level of grade I and grade III， respectively. The contents of total nitrogen， available potassium and cation exchange capacity were all at the level of grade IV. The contents of organic matter and total potassium were all at the level of grade V. The content of alkali-hydrolyzed nitrogen is at the level of grade VI. From the coefficient of variation， pH is a weak variation， available phosphorus is a strong variation， and the remaining fertility indicators are moderate variation intensity； （2） Total potassium shows weak spatial autocorrelation （nugget is greater than 75%）， total phosphorus shows moderate spatial autocorrelation （25%≤ nugget coefficient ≤75%）， while the nugget values of other soil fertility indicators are all below 25%， showing strong spatial autocorrelation； （3） The fuzzy comprehensive evaluation method showed that the comprehensive index value （IFI） of soil fertility in Yani Wetland ranged from 0.19 to 0.79， with an average value of 0.36， and the soil fertility was only at the level of grade IV. Among them， alkali-hydrolyzed nitrogen and total potassium were the main limiting factors of IFI. Through the IFI spatial interpolation map， the wetland soil fertility is generally low due to the influence of water erosion and thin soil layer in the study area. The high value area is mainly concentrated in the agricultural activity area， and the soil fertility is improved to a certain extent due to the intervention of human agricultural management activities.
In the post-Winter Olympics era， ski tourism has emerged as a pivotal driver for the economic revitalization and growth of Xinjiang. The global shift in tourism trends， particularly in the post-pandemic era， has seen a marked transition from mass-market tourism to more personalized and niche experiences. This evolution has placed significant demands on the tourism industry， necessitating diversification， segmentation， and innovative approaches to meet the evolving preferences of tourists. Against this backdrop， this study delves into the dynamics of ski tourism in Xinjiang， a region endowed with unique geographical and climatic advantages for winter sports.The research is grounded in data collected from 533 visitor questionnaires across five representative ski resorts in Xinjiang. Employing the K-Prototypes clustering method， the study processes the data to categorize ski tourists into distinct segments. By integrating market segmentation and customer segmentation theories， the research provides a comprehensive understanding of the diverse types of ski tourists in Xinjiang from a market perspective. Descriptive statistical analysis is further utilized to stratify customers based on three critical dimensions： skiing ability， time cost， and spending capacity. This stratification is complemented by the construction of detailed user profiles， which incorporate sociological characteristics， behavioral patterns， and preferences， thereby offering a systematic analysis of the composition of Xinjiang’s ski tourism clientele.The findings underscore the relative maturity of Xinjiang’s ski tourism industry， with “Ski Pioneers” and “Ski Elites” collectively accounting for 48.03% of visitors. These segments are identified as significant contributors to the industry， highlighting their importance in driving growth and innovation. The study categorizes ski tourists into four distinct types： （1） “Ski Novices”， characterized by weak skiing ability， minimal time cost， and low spending capacity； （2） “Ski Apprentices”， with low skiing ability， low time cost， and moderate spending capacity； （3） “Ski Pioneers”， exhibiting moderate skiing ability， moderate time cost， and low spending capacity； and （4） “Ski Elites”， distinguished by strong skiing ability， high time cost， and high spending capacity. These categories align with potential， active， potential premium， and high-end customers， respectively， with higher-tier customers demonstrating greater comprehensive value and importance to the industry.Active customers emerge as the largest segment， indicative of the robust growth trajectory of Xinjiang’s ski tourism. However， the study emphasizes the necessity of strategic relationship management with potential premium and high-end customers， alongside efforts to convert and retain novices and apprentices. Notably， all four tourist types share common traits such as high education levels and time or financial freedom， yet their preferences vary significantly. Novices prioritize safety， apprentices seek cost-effectiveness， while elites and pioneers place a premium on service quality and attitude.To address existing bottlenecks and propel the high-quality development of Xinjiang’s ice and snow tourism， the study proposes a tiered management strategy tailored to the unique needs of each customer segment. For potential customers， the focus is on designing attractive and engaging ski activities to enhance interest and satisfaction. Active customers， identified as the backbone of future consumption and a reservoir of skilled skiers， are targeted with customized services to foster loyalty and engagement. Potential premium customers， often facing a plateau in their skiing skills and preferring leisure-oriented vacations， are catered to through the creation of rest areas and the development of surrounding leisure and entertainment facilities， thereby extending their stay and enhancing satisfaction. High-end customers， characterized by advanced skiing skills and high spending capacity， are provided with professional training environments and elite coaching to ensure their retention and satisfaction.These strategies collectively aim to refine the ice and snow industry system， offering actionable insights for the sustainable growth of Xinjiang’s ski tourism. By addressing the specific needs of each customer segment， the study envisions a future where Xinjiang’s ski tourism not only thrives economically but also sets a benchmark for quality and innovation in the global tourism industry.
Focusing on the profit effect of cryosphere services is an important bridge connecting functional supply and human demand. A correct understanding of the interrelationships between cryosphere services is an important prerequisite for enhancing human well-being and promoting scientific decision-making. This article focuses on the interrelationships between ecosystem services and human well-being in the evolution of cryosphere services， such as trade-offs and mutual gains. Based on the coupling framework of human environment systems， the study investigates the relationship between ecosystem services and human well-being， and makes targeted adjustments to the characteristics of cryosphere elements， functions， and services. It attempts to construct a theoretical framework and technical path for the trade-offs， synergies， and adaptation strategies of cryosphere services， which will help to further understand their spatiotemporal heterogeneity， dynamic evolution， and scale effects. The cryosphere is one of the major layers of the global climate system， which not only has irreplaceable climate effects， but also maintains the good functioning of socio-economic and natural ecosystems in cold and arid regions. Focusing on the beneficial effects of cryospheric services is an important bridge between functional supply and human demand， and a correct understanding of the interrelationships between cryospheric services is an important prerequisite for improving human welfare and promoting scientific decision-making. Focusing on the selective preference of human beings for cryospheric services， the evolution of different cryospheric services， both in terms of their mutual benefits and their mutual reciprocal benefits， is related to the diversity of cryospheric services， the differences in spatial and temporal distributions， and the directionality of human well-being. Quantitatively assessing the classification characteristics， formation mechanisms and spatial and temporal patterns of the trade-offs and synergistic relationships between cryospheric services， especially studying the non-linear and heterogeneous spatial and temporal distribution of cryospheric services， is of great significance for the rational utilisation of cryospheric services， the promotion of the optimal overall benefits， and the avoidance of related disasters and risks. Furthermore， it is necessary to propose corresponding comprehensive adaptation strategies based on the trade-offs and synergistic relationships among the time scale， space scale and stakeholder scale， and to optimise the allocation of various resource elements of the cryosphere and the social economy horizontally， and optimise the utilisation of the current and future cryospheric services vertically from the perspective of the overall interests of the region or even the whole country， and ultimately realise that the utilisation of the cryospheric services is balanced with the socio-economic development and the ecological and environmental benefits. This not only has certain scientific value to the cryosphere science and the theory of human-earth relationship territorial system， but also is an important research field directly facing the construction of “One Belt， One Road”， sustainable development and ecological civilisation construction. This paper follows the following research logic： firstly， it clarifies and explains the conceptual connotation of the service trade-off and synergy in the cryosphere from the cascade framework， connotation definition and example analysis； secondly， it elaborates the internal logic of the service trade-off and synergy in the cryosphere through the service maximisation model and the boundary model of production possibilities； thirdly， it puts forward the quantitative exploration of the service trade-off and synergy in the cryosphere at different scales by the methods of statistical description， spatial mapping， model simulation and scenario analysis； thirdly， it proposes the method of statistical description， spatial mapping， model simulation and scenario analysis. Finally， we propose a comprehensive adaptation strategy framework that combines fine zoning and precise policymaking， proximity coupling and long-range coupling， intra- and inter-regional compensation， and water supply services and snow and ice tourism services as breakthroughs， so as to focus on the transformation of trade-offs and synergies， and put forward targeted regulatory measures. In the future， we should strengthen the research on the exploration of the driving mechanism， the exploration of multiple service relationships， and the forward-looking spatial flow evolution， etc. We need to further strengthen the research on the formation and evolution of the trade-offs and synergy of the cryosphere services and its socio-ecological dynamic mechanism， explore the coupling mode and mechanism of the trade-offs of the cryosphere services with the spatial distribution of the well-being of the inhabitants， as well as the pattern of the matching of the supply and demand of the cryosphere services， the simulation of the spatial flow of cryosphere services， and the mechanisms and models of the near- and long-distance impacts of cryosphere services. The study will also explore the pattern of matching supply and demand of cryosphere services， the simulation of the spatial flow of cryosphere services， and the mechanism and model simulation of the near- and long-range impacts of cryosphere services， so as to achieve the maximisation， optimisation， and minimisation of the risk of improving human welfare.
In the context of global climate change， the persistent reduction of Arctic sea ice has created more favorable conditions for the opening of Arctic shipping routes. The Northeast Passage， in particular， has garnered the interest of shipping companies due to its potential distance and cost benefits. However， the passage presents significant navigational safety challenges stemming from its complex and variable climatic and sea ice conditions. Therefore， there is an urgent demand for an intelligent path planning method to optimize the utilization of Arctic routes. This study introduces an intelligent route planning approach that integrates the Polar Operational Limit Assessment Risk Indexing System （POLARIS） with deep reinforcement learning. POLARIS assesses navigational risks by evaluating sea ice conditions along potential routes. The researchers integrate POLARIS with traditional A* algorithms and Deep Reinforcement Learning （DRL） to enhance the path planning process. This integration is crucial as it improves the capacity to manage dynamic environments—typical of Arctic conditions—more effectively than static algorithms such as A*. Experimental results indicate that DRL significantly surpasses the traditional A* algorithm in computational efficiency， achieving approximately 50 times faster processing. This efficiency is vital for real-time route planning， necessary to adapt to the rapidly changing Arctic environment. The article explores the mechanics of DRL， elucidating its superiority in managing complex and dynamic conditions. Unlike traditional methods that struggle with large state spaces and require predefined heuristic functions， DRL employs neural networks to learn optimal strategies through trial and error， making it adept at navigating the unpredictable Arctic environment. The study highlights DRL’s capacity for learning and adaptation， providing a practical solution for real-time decision-making in shipping route planning. Moreover， the study offers a detailed explanation of the employed methodologies. It categorizes DRL approaches into value-based， policy-based， and actor-critic methods， with the research selecting a value-based approach. The Deep Q-Network （DQN） algorithm is employed for its ability to handle large state spaces and efficiently learn optimal policies. The research describes the environmental setup， where Arctic sea ice and weather data are modeled on a grid to simulate navigational scenarios. The DQN model is trained on this data to predict optimal routes， taking into account navigational risk and efficiency. The researchers conducted case studies using historical sea ice data to validate the model， comparing the predicted routes against actual shipping paths taken by vessels such as the ship “Yong Sheng” in 2013. The results show a strong alignment， with the model’s predictions reflecting practical and safe routes that avoid areas of high ice concentration， akin to decisions made manually by ship captains. In conclusion， the article establishes that DRL serves as a suitable core algorithm for Arctic route planning systems. It provides a robust and efficient solution for managing the challenging and variable conditions of the Arctic， facilitating the development of intelligent， automated route planning systems. The study underscores the importance of integrating advanced AI techniques like DRL into maritime navigation to enhance safety， efficiency， and adaptability， thereby contributing to the development of the Arctic as a viable international shipping corridor. The findings suggest a promising future for automated decision-making in maritime logistics， particularly in regions where environmental conditions are critical and volatile.
