As a significant ecological barrier in northwest China， the Qilian Mountains， it is crucial to clarify the spatial-temporal variation of its ecosystem services （ESs） and evolution mechanism for regional ecological protection and restoration and sustainable development. Using the InVEST （Integrated Valuation of Ecosystem Services and Trade-offs） and CASA （Carnegie-Ames-Stanford Approach） models， we have quantified six critical ESs between 2000 and 2020 including water yield， carbon sequestration， soil retention， nutrient retention， carbon storage， and habitat quality in Qilian Mountains and then analyzed their spatial-temporal variability and spatial distribution characteristics at various scales， and the hotspots of ESs were identified. According to the results， since 2000， the six ESs in Qilian Mountains have been increasing in the region as a whole as well as in different land types， with the mountainous areas being the high value areas and the hotspot areas of category III and IV in the hotspot analysis showing an increasing trend； The six ESs in Qilian Mountains are spatially characterized as being “high in the east and low in the west”， with high values of supply per unit area for forest and grassland， and large differences in the supply capacity of ecosystem services in different topographic gradients， mostly peaking above 3 100 m above sea level， with category V hotspots in the hotspot analysis mainly located in the eastern mountainous areas. The results of the study identify the spatial-temporal variability of six ESs in the Qilian Mountains and explore the natural and anthropogenic factors affecting their spatial and temporal variability， which can provide the basis and suggestions for the formulation of targeted ecological conservation strategies and high-quality sustainable development policies in the Qilian Mountains.

Vegetation phenology is an important indicator of vegetation response to changes of the natural environment. As an important component of the cryosphere， permafrost is extremely sensitive to climate change. Accurate monitoring of vegetation phenology in permafrost areas is important for studying the response of cold-zone ecosystems to climate change. The Greater Khingan Mountains permafrost zone is the only high-latitude perennial permafrost in China， and studying the vegetation phenology in this zone can improve our understanding the response of cold-zone ecosystems to global climate changes. In order to investigate the impact of climate change on vegetation in the permafrost zone of the Greater Khingan Mountains， this paper assesses the spatial and temporal characteristics of vegetation phenology in the study area over the past 20 years and its response to climate change based on MODIS EVI time series data， with a view to enriching the study of vegetation phenology in cold-zone ecosystems. This study firstly compares the differences and adaptability of Normalized Difference Vegetation Index （NDVI）， Enhanced Vegetation Index （EVI） and Solar-induced Chlorophyll Fluorescence （SIF） in phenology studies of the permafrost zone， and the results show that EVI is more effective than the other two indices. Secondly， combines MODIS EVI time series data and meteorological data from 2000 to 2019， key phenological parameters， the beginning （SOS）， end （EOS） and length （LOS） of vegetation growing season， were extracted using Savitzky-Golay （S-G） filter and dynamic threshold approaches to analyze the spatial and temporal variation of vegetation phenology in the study region and its response to climate changes. In this case， the NDVI and EVI have a spatial resolution of 250 m and a temporal resolution of 16 d. Data processes such as mosaicking， masking and projection transformations were performed on each period of data to obtain time series data of NDVI and EVI for the study area from 2000 to 2019. The 16 d of SIF data were combined into one period according to MODIS data synthesis rules， with 23 periods of data per year. And the mean value of SIF for the study area was calculated to obtain time series data for SIF from 2015 to 2019. Monthly mean temperature and monthly total precipitation in growing seasons were selected and used the method of partial correlations analysis to analyze how climate factors affect vegetation phenology. The results show that： （1） the time series of NDVI， EVI and SIF can reflect the seasonal changes of vegetation growth in the study area， and the change curves of EVI and SIF are more consistent than those of NDVI； （2） the variation of SOS in the study area from 2000 to 2019 ranged from 96 to 144 d in chronological days， with a mean value of 129.46 d； the variation of EOS ranged from 272 to 320 d， with a mean value of 295 d and the LOS was concentrated between 128 and 224 d， with a mean value of 165.65 d. Due to the existence of the inversion phenomenon and the differences of vegetation types， the LOS in the continuous multi-year permafrost area was greater than that in the island thaw zone； （3） the mean values of SOS and EOS trends in the study area were -1.23 d·（20a）^-1 and -0.46 d·（20a）^-1， respectively， both showing early trends and the mean value of LOS trend was 2.39 d·（20a）^-1， showing an extended trend. Vegetation SOS in the study area was negatively correlated with the mean temperature of March to May （P<0.05）， and EOS was positively correlated with the mean temperature and precipitation August to October （P<0.05）. The extent and trend of significant changes in vegetation phenology were greater in the continuous permafrost zone than that in the island thaw zone permafrost zone， indicating that continuous permafrost zone is more sensitive to climate change. This research improve our understanding of vegetation phenology characteristics of permafrost region under the background of climate change.

Glacial lakes are important indicators of climate change. Against the backdrop of global warming， the continuous monitoring of glacial lakes is of significant importance for regional water resource management and disaster prevention and mitigation in alpine regions. Affected by glacier melt and climate influences， the boundaries of glacial lakes undergo seasonal and inter-annual variations. Existing glacial lake mapping researches often first identify the location of each lake on remote sensing images， and then capture its detailed boundary. In recent years， glacial lake inventories of different regions have been growing， offering a wealth of historical boundaries for glacial lakes. Monitoring these glacial lakes with known locations only requires the extraction of their current boundaries， and the historical boundaries can serve as the starting point for glacial lake boundary iteration， accelerating the update of glacial lake inventories. This study takes 488 glacial lakes with favorable imaging conditions， and another 80 glacial lakes affected by snow， ice， clouds， and mountain shadows in the Himalayas as the research subjects. The former is categorized into three classes based on their area size. Using historical boundary information provided by the 1990 glacial lake inventory， we compared the glacial lake extraction results on post-2014 Landsat-8 OLI images using manual thresholding， OTSU thresholding， U-NET， bimodal iterative method， OTSU iterative method， and C-V iterative method. The results showed： OTSU iterative method and C-V iterative method can effectively utilize the statistical information within the glacial lake buffer zones， achieving F1 scores as high as 88.89% and 89.30% respectively， which are significantly better than manual thresholding， OTSU thresholding， and bimodal iterative method. They can also extract frozen and cloud-covered glacial lakes more completely. For glacial lakes covered by snow， the C-V iterative method achieved the highest extraction accuracy. The U-NET model achieved an F1 score of 89.80%， accurately extracting glacial lakes connected to mountain shadows. This research offers methodological support for the long-term monitoring of glacial lakes with known historical boundaries.

Glacier is an important part of the cryosphere and is known as the "indicator" and "early warning device" of climate change. Under the influence of its own gravity， the glacier will move from the high-altitude area to the low-altitude direction to form the glacier ice flow. The maximum flow trajectory of the glacier ice is called the glacier mainstream line. The centerline of the glacier is the center line of the main stream line of the glacier and one of the key parameters to reflect the geometric shape of the glacier. It has important significance in measuring the change of the glacier length with time， analyzing the change characteristics of the glacier movement speed， estimating the glacier volume and building a one-dimensional glacier model. Based on the Tyson Polygon method， combined with the shortest distance formula and Dijkstra algorithm， according to the topographic characteristics of the glacier surface， this paper proposes a new method for automatic and rapid extraction of glacier centerlines in mountain glaciers from the perspective of morphology. This method encrypts the glacier vector boundary line according to the area of different glacier’s using empirical parameters， and combines the digital elevation model data to extract the glacier center line using the Tyson Polygon method with the lowest point and the local highest point on the glacier vector boundary line as the end point and the starting point. At the same time， the extracted local highest point is screened using the shortest distance formula， and only the point with the highest elevation is reserved as the starting point of the glacier centerline， In order to avoid the problem of multiple starting points of the glacier centerlines， the Dijkstra algorithm is used to filter the extracted glacier centerlines with the distance between the starting point and the end point as the weight， and only the shortest distance between the starting point and the end point is retained as the final center glacier centerline extraction result. This method was applied to 1 014 mountain glaciers in the Qinghai Tibet Plateau， and 2 114 corresponding glacier centerlines in glaciers were automatically generated， with an average length of 3.13 km and an extraction success rate of 100%. By comparing the proposed method with the methods of Kienholz et al.， Zhang et al.， it is found that the extraction results of the proposed method and the method of Kienholz et al.， Zhang et al.， have little difference for the simple structure of the single valley glacier. For compound valley glaciers and slope glaciers with more complex structures， the number of glacier centerlines extracted by the proposed method is more than that by Kienholz et al.， but less than that by Zhang et al.， and for ice cap glaciers， the number of glacier lines extracted by the proposed method is more than that by Kienholz et al.， Zhang et al. The results show that the glacier centerline extracted by this method has a more complete coverage， and the average length ratio of the glacier centerline extracted by this method and Kienholz's method is 0.98， which has a high consistency. This paper proposes a method of extracting the glacier centerline based on Tyson Polygon method， which takes the data of the digital elevation model and the boundary line of the glacier vector in the glacier catalog data as the input， can realize the automatic and rapid extraction of the glacier centerline without manual participation， and can also accurately extract the centerline in the tributaries of the glacier. This method solves the problem that only a single center line can be extracted based on the glacier axis method， and improves the extraction efficiency of glacier centerline.

Snow cover is an important indicator of global climate change， and its surface high reflection and rapid ablation change characteristics affect the energy and water vapor exchange between the earth’s land surface and the atmosphere. Therefore， accurate identification of snow ablation information is crucial for local climate research and water resources management. The traditional methods of snow cover monitoring at meteorological stations and field measurements are not only time-consuming and laborious， but also limited in observation range， which cannot fully reflect the characteristics of snow cover at regional scale. Nowadays， satellites images with large-area simultaneous observation capabilities have become an important data source for snow cover monitoring. Optical remote sensing can reliably extract snow coverage， but it is easily affected by weather factors such as clouds and fog， and is not sensitive to dry/wet snow distinction， making it difficult to identify wet snow information. Synthetic aperture radar （SAR） not only overcomes the influence of atmospheric conditions， but also is sensitive to changes in dielectric constant caused by snow ablation， and can accurately identify wet snow. However， the common microwave wavelength is much larger than the particle size of dry snow， making it difficult to directly identify dry snow cover.In this paper， a snow cover ablation recognition method is proposed by combing SAR and optical remote sensing data. Taking Babao River basin as the research area， firstly， Sentinel-2 simulation data simultaneously with Sentinel-1 were obtained to extract the snow cover range by using the ESTARFM fusion model with MODIS and Sentinel-2 images. Wet snow cover was extracted based on a multi temporal and multi polarization SAR change detection algorithm. Then， by making a difference between the wet snow extracted from SAR and the snow cover extracted from Sentinel-2 simulation data， the distribution of wet and dry snow was obtained during the ablation period （February to May） in 2020. And the uncertainty of dry and wet snow obtained is corrected through two methods： （1） the wet snow outside the snow coverage area is divided into snow free pixels based on the snow cover extracted by Sentinel-2； （2） by calculating the average elevation of wet snow on semi-shady slope， semi-sunny slope and sunny slope， all the dry snow below this elevation was corrected as wet snow. Finally， the distribution of dry and wet snow in 18 days during the ablation period in Babao River basin was obtained. At the same time， GF-2 images was used to verify the accuracy of the snow cover range， and the Sentinel-2 image during the severe ablation period were used to verify the accuracy of the wet snow distribution. The results show that the method can quickly identify the characteristics of snow ablation in Babao River basin， and the overall classification accuracy OA is as high as 99%， and the Kappa coefficient is as high as 0.86.Experiments show that the spatial distribution of dry and wet snow cover changes drastically with time in the Babao River basin during the ablation period in 2020. In the initial stage of ablation the wet snow at the is mainly concentrated in the low-altitude area of the valley， while dry snow is mainly distributed in surrounding high altitude mountainous areas. Subsequently， the wet snow area extracted from the descending orbit and ascending orbit data shows an increasing trend， while the snow cover area is basically stable. As the temperature further increases， the snow cover in high-altitude areas begains to melt. And due to the difference in satellite transit time， the area of wet snow extracted from descending orbit data is smaller than that extracted from ascending orbit data during the entire ablation period. This method can fully utilize the advantages of SAR and optical remote sensing images to quickly monitor snow cover ablation changes except for forest cover areas， and provide reliable basic data for research on climate change， water resource management， and other related fields.

With the general improvement of the national living standard， the ice and snow industry are developing rapidly， which brings many benefits to the social and economic development. Understanding the correlation between ice and snow industry and social economic development is the basis for rational development and management of ice and snow industry. In this study， based on the main components of the ice and snow industry that ski industry in Xinjiang， the research establishes the relationship between the snow and ice industry and the main economic industries， combining input-output relationship between regions， evaluating the economic and social effects of the snow and ice industry with the input-output analysis method. The results show that the production capacity of ice and snow industry in Xinjiang is about 34.5 billion and 181.9 billion RMB in 2012 and 2017， and capacity of other economic industries driven by the total output value is can reach 80.9 billion and 415.1 billion RMB. And the ice and snow industry influence coefficient are 2.28 and 2.33 in 2012 and 2017， which is larger than the that of most major economic industries； The largest four industries driven by the ski industry include the transportation， warehousing and postal services； Petroleum， coking products and nuclear fuel processing products； Wholesale and Retail； Accommodation and catering industry. Among them， the relative impact of wholesale and retail， accommodation and catering increased significantly， and the impact of petroleum and coking product departments decreased relatively. Through decomposition of economic structure found， the economic pull effect of ski industry is further strengthened. In particular， with the rise of ice and snow industry the accommodation and catering output value increased 259%. At the same time， the ski industry can provide more local employment opportunities. In a word， Xinjiang， relying on the advantages of the natural endowment of the ski industry， can bring opportunities for social and economic development. In order to maximize the economic leverage of the snow and ice industry， it is not only necessary to have a reasonable economic structure as the basis， but also to develop other closely related industries as support. In addition， in order to provide enough space for the development of the ski industry， the four major industries that are most driven by the ski industry should also be the key industries to promote their development， and fully absorb the economic dividends of the development of the ice and snow industry， so as to obtain more economic and social benefits.

The data provided by MODIS V006 version is the Normalized snow cover Index （NDSI）， but the majority of users are often concerned with the intuitive snow cover classification results， including snow cover extent or snow cover rate. The National Snow and Ice Data Center （NSIDC） recommended 0.4 is the best NDSI threshold for the global snow cover. However， the Qinghai-Tibet Plateau has complex and diverse terrain and obvious snow patch characteristics， so a single NDSI threshold of 0.4 cannot accurately distinguish the snow cover on different underlying surfaces. The Qinghai-Tibet Plateau， known as the third pole of the earth， is one of the three stable snow areas in China and contains a large amount of fresh water resources. With global warming， the Tibetan plateau ahead of time， the snow is melting glaciers， increase， affect the rivers of water， causing floods， and thus affect the normal production of human life， so determining different underlying surface threshold， improve the traditional threshold value of snow overestimated underestimate phenomenon， improve the identification accuracy of snow， and then more accurate study of the Tibetan plateau snow conditions， Is particularly urgent. In this study， This paper takes the Qinghai-Tibet Plateau as the research object. Firstly， MODIS daily cloud-free NDSI sequence is generated and its reliability is verified. Secondly， the underlying surface is forested and non-forested areas， and the NDSI sequence of cloud removal has a good corresponding relationship with the snow depth at the site. NDSI can accurately reflect the snow melting phenomenon of the pixel where the station is located. Determine the optimal threshold range of different underlying surface； Finally， the optimal threshold was determined by confusion matrix within the optimal threshold range. When NDSI=0.03， the highest overall accuracy was 94.02%. Under this NDSI， the overestimation error OE and underestimation error UE were 1.21% and 4.6%， respectively. When NDSI=0.26 for non-forestland， overall accuracy （OA） is 94.27%. Under this NDSI， he overestimates error （OE） and underestimate error （UE） are 0.51% and 5.03%， respectively. Therefore， the optimized threshold of forestland is NDSI=0.03， and that of non-forestland is NDSI=0.26. Because snow cover is a large scale phenomenon， the conventional observation data are mostly point scale observations. In order to avoid the limitations in the scale of conventional ground observation data， this paper uses the high-precision Landsat 8 OLI satellite data identification results as the “truth value” and the snow discrimination results of the optimized threshold and the snow discrimination results of the traditional threshold to verify the “pixel to pixel” level. In quantitative verification， the overall accuracy （OA） of the optimized NDSI threshold to MOD10A1 V006 snow discrimination results is 84.21%， the overestimation error OE is 5.33%， and the underestimation error （UE） is 10.46%. The overall accuracy （OA） of the traditional threshold for the snow discrimination results of MOD10A1 V006 is 82.86%， the overestimation error （OE） is 1.48%， and the underestimation error （UE） is 15.66%. It can be seen that in the quantitative verification， the snow discrimination accuracy of the optimized threshold is higher. At the same time， it can be seen from the qualitative verification that the new threshold and the traditional threshold are relatively good at snow recognition in the area with large area of concentrated snow. In the region with relatively scattered and broken snow， the optimized threshold can identify a large number of snow， while the traditional threshold cannot identify the same number of threshold. These results indicate that NDSI threshold optimization considering different land cover types can effectively improve the accuracy of snow discrimination on the Qinghai-Tibet Plateau， which provides a strong support for the application of NDSI in snow recognition. It is helpful to understand the snow distribution in this area more accurately.

China， two-thirds of which is cold area， has an extensive network of roads， airports， towns and other artificial pavement systems. The research and development of snow melting and de-icing technology is important in road safety and security. In order to comprehensively understand the research status and trends in the field of road snow melting and de-icing technology in China， the research documents of Chinese scholars in the field since 2010 were obtained through the core set of commonly used databases in China and abroad. The information regarding the amount， sources and keywords of documents is analyzed with CiteSpace. The results show that domestic road engineering field has paid more and more attention to snow melting and de-icing technology， which is reflected in the increase in the number of published research papers in this field in China since 2010. At the same time， it is found that technical journals published in Chinese by scholars in the field account for a large proportion of the research papers. The results show that Chang’an University， Harbin Institute of Technology and other universities are the main research forces， the international cooperation of scholars in China needs to be enhanced. In terms of research focus， domestic road engineering scholars are reducing the research on snow de-icing salt， and pay more attention to new snow melting and de-icing technologies such as hydronic heating pavement and electric heating pavement. The high co-citation literature since 2010 was analyzed and found that for the technical advantages， the snow melting and de-icing technology of electric heating， microwave heating and salt-storage pavement are more likely to attract the attention of scholars， but there are obvious shortcomings in engineering application. Through the literature review， it is found that the field of snow melting and de-icing technology in domestic road engineering urgently needs to solve several key issues such as energy consumption， process， cost， snow melting effect and road performance balance of the above-mentioned new snow melting and de-icing technology.

The glacial lake outburst floods （GLOFs） in the Yarkand River Basin （YRB） may cause severe disasters. In the context of global warming， establishing a GLOF database and understanding the variation characteristics of GLOFs are the basis for glacier lake research and the flood risk assessment and management. Based on the hydrological runoff data， scientific expedition data and flood disaster data， a database of Kyagar GLOFs in the YRB from 1961 to 2021 is established. Then， the frequency and peak discharge variations of GLOFs are analyzed by using statistical methods such as linear trend analysis， rescaled range analysis， accumulated anomaly analysis， Mann-Kendall test and Morlet wavelet analysis. In addition， the peak discharges under different return period scenarios are estimated by using the Multi-Distribution Fitting Tool software， and the corresponding risk assessment is conducted. The results show that the frequency and peak discharge of Kyagar GLOFs in the YRB both exhibit a unimodal pattern on the monthly timescale. The risk of GLOFs is the highest in August and September. The frequency of Kyagar GLOFs from 1961 to 2021 does not show an obvious linear trend but exhibits a decadal oscillation. The peak discharge， however， shows a significant linear decreasing trend with a rate of 15.5 m³·s^-1·a^-1， indicating that the benefits outweigh the drawbacks when utilizing floodwater resources. On the quasi-19-year period， the frequency of Kyagar GLOFs is at a low level in conjunction with a relatively low risk in the short term. It will continue to decline until around 2027， after which it will enter the next rising phase. Although there was a short-lived high-frequency period of Kyagar GLOFs due to global climate change in the early 21st century， this cannot alter the long-term oscillatory decrease trend. The Kyagar GLOFs pose a certain level of disaster risk under the 5-year return period scenario， while the disaster risk is extremely high under the 10-year or above return period scenarios. Therefore， we recommend strengthening the dynamic monitoring and risk assessment of the Kyagar Glacier Lake in the Yarkand River， as well as the research on the mechanisms of GLOFs. Additionally， we need to accelerate the construction of water conservancy projects and enhance the flood control and disaster reduction capabilities.

Land-bridge of 1401 milestone in the Qinghai-Tibet Railway is located in the permafrost area of Tanggula Mountains. After the railway official operation， serious settlement disease occurs in the bridge and serious endangers the line. Settlement data from 2009 to 2018 show that the pile foundation had stabilized after a series of treatment in 2009， 2011—2012， and 2017. The further analysis shows that the rise of permafrost temperature and base resulting from warm season， climate warming and leakage of deep artesian sub-permafrost groundwater were the main reasons of settlement problems. Complicated and long treatment process implied that thermal disturbance from countermeasures must be considered before it was put into practice. It is suggested that the land-bridge settlement should be monitored periodically. Earlier detection， earlier prevention and earlier treatment should be more welcome.

Glacial lake outburst floods are characterized by wide range， long duration， high hazard and often accompanied by debris flow. At present， there is a lack of quantitative studies on the dynamic evolution characteristic of glacial lake outburst floods. To this end， the evolutionary characteristics of Cirenmaco glacial lake outburst flood disaster are studied based on field survey and multi-period remote sensing images， and the sediment transport model and hydrodynamic model coupling method are used to reveal the evolutionary characteristics of glacial lake outburst flood erosion. The model is based on the digital elevation model （DEM） topographic data with an accuracy of 12.5 m， simulating the inversion of the 1981 Cirenmaco glacial lake outburst flood dynamics evolution process， comparing with the actual measurement results， verifying the applicability and feasibility of the model， and conducting prediction analysis of the glacial lake outburst again， to quantitatively evaluate the characteristics of flow depth， flow velocity， erosion and deposition of glacial lake outburst flood in the evolution process. The outburst flood scours erosion on the moraine deposit of the Zhangzangbu branch ditch and the loose colluvium of the downstream ditch bank during the evolution， and the high sediment concentration flood gradually evolves into turbulent debris flow. At the 707 landslide， the flow depth is 8~10 m， the maximum flow velocity is 13.7 m·s^-1， and the erosion depth is 8~9 m. The turbulent debris flow formed a barrier dam at the main ditch deposition， with a dam height of 9~11 m， which briefly blocked the Boqu River. turbulent debris flow to the downstream landslide group of Zhangmu port for scouring side erosion， erosion depth of about 10~13 m， easy to trigger large-scale secondary disasters， turbulent debris flow reaches the hydropower station， siltation buried hydropower station intake， resulting in the failure of the hydropower station. On the whole， outburst flooding in the evolution process， the flood water to the upstream ditch bed and ditch bank for strong erosion entrainment， flood peak flow enhanced. In the midstream， turbulent debris flow laterally erodes the gully bank， and the flow velocity increases in the narrow part of the gully， and undercut erosion is enhanced. In the wide part of the channel， low velocity decreases， solid materials deposition， overall reach the balance of flushing and siltation， flood peak flow gradually decay with distance， to the downstream， channel topography open， flow velocity slows down， turbulent debris flow gradually deposition， while the lateral erosion on both sides of the channel， overall for deposition. The model can well reveal the evolutionary dynamics of glacial lake outburst flood disaster erosion characteristics.

Canals are damaged by frost heaving， thawing， and soil erosion in seasonal frozen soil areas. In this study， a canal lining cushion was proposed， composed of polystyrene foam board， ceramic， and epoxy resin， to alleviate the damage to the canal. In this study， the test method used was the alternating dry-wet and freeze-thaw test to investigate the degradation law of thermal insulation and bond strength of the composite liner. Also， this study investigated the protective effect of the multi-layered combined bedding on the concrete slab. Finally， this study determined the optimum admixture of ceramic sand by combining statistical methods. The test results show that ceramic can reduce the thermal conductivity of multilayer cushions. The thermal insulation of the cushion deteriorates， caused by the polystyrene foam board and concrete， and decreases linearly with the increase of test times. The ceramic content did not affect the bond strength of the polystyrene foam board interface. However， it greatly influenced the strength of the concrete interface， and the content was inversely proportional to the strength. Multilayer cushions had a better protection effect on concrete. Compared with ordinary concrete， EP-concrete reduced the loss of quality and compressive strength by 1.04% and 8.58%， respectively. The thermal insulation of the cushion and the bonding strength of the contact surface of the polystyrene foam board were taken as the control objectives， and the calculation method of the optimal amount of ceramic sand was established. The research results of this experiment can provide a certain reference for the design of the canal cushion.

The formation and growth of ice interlayers in rock fractures are significant characteristics and causes of rock frost weathering. Fractured rock masses consist of fractures and rock matrix， which differ greatly in properties and can be considered as a porous medium. Water is typically the primary storage and transport channel in the rock mass， while unsaturated fractures often involve both gas-phase and liquid-phase migration， making it difficult to directly explain the formation and growth process of ice layers in the fractures using existing in-situ frost heave and frost segregation mechanisms. To investigate the occurrence and distribution of ice layers in unsaturated rock mass fractures， the authors conducted a unidirectional freezing test on two cement test blocks with a single vertical fracture under warm-end water replenishment conditions. After the test， three horizontal fractures and one vertical fracture appeared in the test block， with thin ice layers forming in the fractures. The negative temperature zone of the sample showed significant frosting， and the total amount of water migration during the entire process reached 221 mL， primarily in the gas phase. Based on the fundamental principles of heat transfer， the authors established a frost model for a single fracture wall surface under natural convection conditions. The frost surfaces were divided into classes I~Ⅲ based on the characteristics of different cold surfaces of the test samples， and the thickness， density， and unit mass of frost layer on the three types of cold surfaces were calculated over time. The experimental results validated the calculation results， demonstrating the reliability of the frost model on a single wall surface. Based on the frost model and relevant literature analysis， the direct factors affecting the amount of frost on the negative temperature zone wall surface of rock fractures include the convective heat transfer conditions in the fracture， the relative humidity of the air， and the size of the negative temperature zone wall surface area. The greater the values of these three factors， the more frost will form on the fracture wall surface within a certain time， and the more significant the ice formation in the fractures. The temperature gradient along the fracture is the essential reason， as the greater the temperature gradient， the stronger the convective heat transfer in the rock fracture， and the larger the negative temperature zone wall surface area， the more frost will form within a certain time.

Snow is the main form of atmospheric solid precipitation， and is a good medium to reflect the chemical composition of the atmosphere. However， different ways of treatment and storage for snow samples after collection may influence the measurement of the original information they reserved. The impacts of different filtration treatments， storage time， and storage temperature （i.e.， room temperature ~25 ℃， cold ~4 ℃， and freezing ~-18 °C） on the cationic concentrations of snow collected from the Nam Co basin， central Tibetan Plateau， were explored in this study. The results show that the non-filtration treatment will make the cationic concentrations significantly deviate from their initial values after the third day of storage. The filtration treatment could efficiently avoid the enrichment of Ca²⁺， Mg²⁺， and Sr²⁺ by decreasing carbonate mineral dissolution. Hence， filtration could reduce the overestimation of the contribution from continental dust. Nevertheless， the alteration of K⁺ and Na⁺ concentration is mainly governed by the ion exchange between clay particles and solution. This process will decrease the concentration of K⁺ but increase Na⁺. Thus non-filtration treatment may underestimate the contribution of biomass burning but overestimate the inputs from marine salt dissolution. As for filter membranes with different pore sizes， the filtration effect of 0.20 μm membrane is better than 0.45 μm membrane. Most of the ion concentrations in the filtered liquid have displayed a slight change in the first ten days of cold or room temperature storage （less than 10%）. To sum up， it is recommended that snow samples should be filtered on the day after melting and using an aperture of 0.20 μm membrane to filter the solution according to our research. Besides， the filtered fluid can be cold storage in a fridge or at room temperature for the measurement of cations. In the end， the test for cationic concentration should be finished within 10 days or less after the filtration.

In Northeast China， the annual temperature difference is relatively large， and the subgrade soil presents freeze-thaw cycle with the change of temperature， belonging to seasonal frozen soil， which is easy to cause serious deformation of subgrade in Northeast China during service， the occurrence of subgrade diseases such as frost heave， frost heave and mud heave leads to the change of soil structure， the reduction of subgrade stiffness， and the deterioration of bearing capacity. The stress-strain relationship can effectively represent the law of stress and deformation of soil， and the establishment of a reasonable freeze-thaw damage model has guiding significance for the structural design of seasonally frozen soil subgrade. Consequence， in order to explore the stress strain relationship and damage mechanism of subgrade soil in seasonal frozen area under different water content under different freeze-thaw cycles and confining pressure，choosing a highway section in Fuxin City， Liaoning Province as the test section， using the ring knife method to select the subgrade soil sample of the test section and freeze-thaw cycle and triaxial compression test， the experiment obtained the relation of the stress-strain curves of subgrade soil under different freeze-thaw cycles and confining pressures. According to the damage mechanics and statistics principles， the Weibull distribution is combined with Lemaitre effective stress principle to establish a damage constitutive model of subgrade soil in the seasonal freezing zone. The results show that the optimum moisture content of subgrade soil in seasonally frozen area is the limit moisture content of its stress-strain curve from strain softening to strain hardening. When the moisture content is less than the optimum moisture content， the peak stress of the curve increases with the decrease of the moisture content， and decreases with the increase of the number of freeze-thaw cycles. When the moisture content of the test piece is greater than the optimum moisture content， the curve has no peak stress with the increase of the moisture content， showing obvious strain hardening characteristics. When the number of freeze-thaw cycles is small and the confining pressure is low， the stress-strain curve of the specimen shows a peak stress， and the curve shows a strain softening feature with the increase of confining pressure， the strength of the specimen increases. Strain hardening is easy to occur when there are many freeze-thaw cycles and large confining pressure. Through comparative analysis， the established damage constitutive model is in good agreement with the test stress-strain curve. It can reflect that the stress-strain curve of subgrade soil in the seasonally frozen area shows a change rule of first increasing and then tending to be stable. And the parameters required by the model can be obtained through triaxial tests， which shows that the model can better describe the stress-strain relationship of subgrade soil in seasonal frozen area， and is practical. In addition， it can be seen from the test results that in order to reduce the impact of freezing and thawing cycles on the subgrade strength in the seasonal freezing area in Northeast China， it is very important to do a good job in the waterproof and drainage of the subgrade in advance for the prevention and treatment of subgrade freezing and thawing diseases.

Alpine glacier areas have unique glacial microclimates due to the characteristics of high albedo， glacier wind， inversion layer and high-value precipitation， especially high-value precipitation is an important factor influencing the change of runoff. Based on the in-situ meteorological observations on the Bailanghe Glacier No. 21 from 2nd September 2020 to 28th August 2021， the micrometeorological characteristic analysis was carried out， and the similarities and differences were compared with the simultaneous precipitation observations at different elevations and underlying surfaces in the vicinity and the precipitation observations in typical glacier areas of Qilian Mountains. Furthermore， the circulation mechanism of different types of precipitation events was analyzed. The study shows that the number of days that the daily mean temperature exceeded 0 ℃ is 84 days， only occurring from May to September. Bailanghe Glacier No. 21 is dominated by glacier wind all year round， unlike the valley wind cycle in other glacier areas； the weather is mainly cloudy； the monthly maxima of incident and reflected shortwave radiation are in May and April， respectively. Precipitation in this region is mainly concentrated in April-August， and both the frequency and intensity of precipitation increase with the increase of cloudiness. A typical precipitation process （July 25-27， 2021） was selected to analyze the circulation drive. It was found that this precipitation process belongs to local convective precipitation in mountainous areas. The northwest-southeast-oriented water vapor transport belt from high latitude to mid-latitude provides water vapor. Moreover， low-level convergence and high-level dispersion， stratification instability and strong upward motion induce the warm air rising and the precipitation area is located in front of the ridge behind the trough with constant cold air input， and then the cold and warm convergence prompt precipitation to occur.

In the context of climate warming， fencing is a common management method for grassland ecosystems. Understanding the effects of warming and fencing on soil organic carbon accumulation is very important to evaluate the carbon source and sink roles of grassland ecosystems. In this study， using the amino sugars as biomarkers， we investigated the effects of long-term warming and fencing on necromass accumulation in an alpine grassland. We collected soil samples from plots after 15 years treatment of warming and fencing. The results showed that： （1） Compared to the control， there was no significant difference in the carbon source derived from bacteria and fungi between the warming + enclosure and enclosure treatments， but bacterial residual carbon contributed more to soil organic carbon than fungal residual carbon. （2） Compared to the control， there was no significant effect on the total amount of amino sugars between the warming + enclosure and enclosure treatments， but significantly reduced the long-term turnover of microbial carbon in the soil， and the short-term turnover was not significant. （3） Total amino sugars， fungal necromass carbon and bacterial necromass carbon were significantly positively correlated with conductivity， moisture content， soil organic carbon （SOC）， and total nitrogen （TN）. In summary， bacterial necromass carbon contributed higher proportions to soil organic carbon than fungal necromass carbon， while 15 years warming and fencing had no significant effects on microbial necromass carbon in soils.

Time-lapse photography is widely used in glacier monitoring due to its advantages of reliability， high efficiency and low cost， especially for obtaining continuous change information of glacier surface. Based on the photos of the Mingyong Glacier terminus in Meri Snow Mountain taken by the phenological camera from March 2020 to September 2021 and multi-period UAV images， this study uses ground photogrammetry technology and cross-correlation algorithm to extract the daily glacier surface velocity. The results show that the resolution of glacier surface motion velocity obtained by phenological images is high. From the altitude of 2 880~3 150 m a.s.l.， the total displacement of glaciers is （129.38±7.76） to （669.95±247.88） m， and the average annual surface motion velocity is （79.14±4.74） to （412.86±152.75） m·a^-1， showing a spatial distribution characteristic of slowing down from the middle to both sides. The surface velocity of the glacier varies with the seasons. The velocity in summer ［（0.13±0.06） to （1.99±0.37） m·d^-1］ is faster than that in winter ［（0.07±0.06） to （1.35±0.37） m·d^-1］. Compared with the winter current velocity， the summer current velocity is unstable due to the increase of precipitation and temperature. According to the results of velocity separation， the bottom of the Mingyong Glacier terminus is in a state of melting or pressure melting throughout the year， and the contribution of basal sliding to the surface velocity of the glacier is between 76%~93%. The basal sliding accounts for 82% of the surface velocity in winter， and the basal sliding plays an absolutely dominant role in glacier movement in summer. The techniques used in this study provide a reference for further study of the mechanism of monsoon ocean-type glacier movement.

Based on the ERA-Interim monthly mean reanalysis data from 1979 to 2016， the climate variation characteristics and causes of water vapor budget over the Tibetan Plateau are further researched by means of statistical analysis and diagnostic method. The results show that the annual and seasonal average water vapor flows in the Tibetan Plateau via the southern， western and northern boundaries， while it flows out via the eastern boundary. The Tibetan Plateau is a significant water vapor sink in spring， summer and autumn， while water vapor is exported from the plateau in winter. Summer is the most active season for water vapor transport over the plateau. The water vapor transport and water vapor budget are greater over the eastern （southern） part of the plateau than those over the western （northern） part of the plateau. The Tibetan Plateau has a gradual wetting trend in years and summer， because of the significant reduction of water vapor outflow from the eastern boundary. The net water vapor budgetexhibits an increasing trend over the eastern and the western part of the plateau， and the increasing trend values over the western part of the plateau is larger than those over the eastern part. The decrease of the water vapor outflowing via the eastern boundary is the main reason for the increase of the net water vapor inflow in the eastern part of the plateau， and the obviously increase of the water vapor inflowing via the southern boundary is the main reason for the increase of the net water vapor inflow in the western part of the plateau. The interannual variation of water vapor budget over the northern part of the plateau is more obvious than those over the southern part. There is an obvious humidification trend over the northern part of the plateau， but there is no obvious humidification trend over the southern part. The variation of water vapor budget via the southern boundary over the Tibetan Plateau in summer is mainly affected by the southerly airflow in the monsoon controlled area over the area east and south of the plateau， and is also closely related to the variation of the Western Pacific Subtropical High. The variation of water vapor budget via the western boundary is mainly affected by the water vapor transport in the middle latitude westerly belt. The variation of water vapor budget via the northern boundary is mainly affected by the teleconnection wave train of “the Silk Road”. The less water vapor inflow via the eastern boundary is related to the anticyclone anomaly from the northeast of the plateau to the vicinity of Baikal Lake and the cyclone anomaly over South China. In short， the climate change of the water vapor budget over the Tibetan Plateau has significant regional and local characteristics. Consequently， it is necessary to investigate the climate variation characteristics and causes of water vapor budget over the Tibetan Plateau. The Tibetan Plateau is a special area for responding to climate change. Under global warming， the water vapor transport and water vapor budget in this region will change significantly， which will further result in abnormal changes of rainfall. The research results can further understand the process of water cycle， reveal the mechanism of water vapor budget change over the Tibetan Plateau， and provide a scientific basis for the change of water resources over the Tibetan Plateau. We hope this research can provide a theoretical basis and scientific support for water security and water resources management over the Tibetan Plateau.

With the construction of highway developing in cold mountain regions， it will inevitably face the roadbed sunny-shady slope problems， and the sunny-shady slope effect has an important impact on the subgrade stability in frozen ground area. Taking the seasonally frozen soil subgrade of the mountainous area as an example， based on in-situ ground temperature and deformation monitoring data of two highway test sections along a highway between Tanchang County and Diebu （Tewo） County in southern Gansu Province， the ground temperature difference and deformation difference between the shady and sunny slopes of highway subgrade was studied firstly. In order to control the sunny-shady slope effect， two new measures were put forward， which included Measure A （laying 10 cm thick XPS insulation board in half width range of road with shady slope and 6 cm thick in half width range of road with sunny slope） and Measure B （laying 6 cm thick XPS insulation board in shady slope side and in full width range of road）. The effectiveness of measures was analyzed through numerical simulation secondly. The results show that： （1） The traditional location of sunny and shady slopes of road subgrade would be changed due to be shadowed by the mountains， the obvious difference of solar radiation resulted in asymmetric thermal regime in subgrade. The maximum difference of ground temperature between shady shoulder and sunny shoulder of roadbed was 6 ℃ in the south mountainous area in Gansu. （2） The asymmetric thermal regime resulted in the unevenly transverse maximum frozen depth and deformation. The maximum differences of frozen depth of two test sections between road center and sunny shoulder were also about 0.8 m and 0.9 m in the first and second freezing period. The maximum difference of the frost heaving peak between shady shoulder and sunny shoulder in the section of K18+180 was 2.8 mm， and it appeared on February 5 （belong to early spring thawing period）. （3） While embankment height is 1.0 m and 2.0 m， the Measures A and B can all effectively reduce the roadbed difference of ground temperature between shady shoulder and sunny shoulder， and by comparison， the new two measures have better prevention effect than ordinary measures （laying 6 cm and 8 cm thick XPS insulation board in full width range of road） in the same condition. Therefore， the influence of local factor of the mountain shelter reaction on freeze-thaw state of subgrade soil should be adequately considered in seasonally frozen ground mountain regions. And in order to reduce freezing damage of road， the embankment constructional form with differential designed sunny and shady slopes should be adopted. The research results have reference significance for understanding the subgrade sunny-shady slope effect and its prevention in seasonally frozen ground mountain regions， and further studying the frost damage in other similar regions.

Thermal conductivity of frozen soil near transition point is a key physical parameter which affects the thermal stability of geotechnical engineering in cold regions. To accurately measure the thermal conductivity of frozen soil in this temperature range， a testing method for obtaining thermal conductivity by steady-state heat flux method and approximating the qualitative temperature by quantum particle swarm optimization algorithm was proposed in present work. Nuclear magnetic resonance （NMR） technology was used to determine unfrozen water content of fine sandy soil near transition point and its relationship with thermal conductivity was analyzed. Based on the testing results， distribution characteristics and parameter influence laws of thermal conductivity of fine sandy soil in the negative temperature zone were investigated， and corresponding thermal conductivity prediction models of different temperature zones were also established. The results show that： Variation curve of unfrozen water content and thermal conductivity of fine sandy soil in the negative temperature region exhibits a similar pattern， and temperature-thermal conductivity curve can be divided into near phase transition zone and stable phase transition zone with the limit of -3.2 ℃. The increase of thermal conductivity mainly occurs in near phase transition zone， and the increment accounts for about 50% of total thermal conductivity increase in the entire negative temperature zone. Meanwhile， the increment of thermal conductivity decreases gradually with temperature decrease. The average error and relative error within ±10% of predict results are 4.14% and 94.7%， and coefficients of determination （R²） in stable and near phase transition zone are 0.892 and 0.883 respectively， which proves the reliability of proposed model. The research results can provide basic physical properties for temperature field calculation and analysis of engineering in cold regions， and also offer data support for major infrastructure refined design and frozen soil risks prevention and control.

Permafrost degradation induced by global climate warming in Qinghai-Tibet Plateau has drawn great attention of researchers. Meanwhile， the Qinghai-Tibet Plateau is prone to frequent seismic activities in recent years. In order to study the influence of permafrost degradation on the seismic vulnerability of the bridge pile foundation along Qinghai-Tibet Railway， a pile-frozen soil interaction model was established， and its rationality was verified by the quasi-static test. The pile-frozen soil interaction model can simulate the deformation and mechanical behaviors of the bridge pile foundation under lateral loading， and thus it can be used to analyze the seismic response of bridge pile foundation in permafrost regions. Considering the effect of permafrost degradation， the curvature ductility ratio of the pile foundation was taken as the damage index， the ground peak acceleration （PGA） was taken as the ground vibration intensity parameter， and 80 seismic waves which are consistent with the site characteristics were selected for seismic vulnerability analysis. Nonlinear seismic damage analysis of the bridge pile foundation under different permafrost active layer thickness and axial compression ratio in permafrost region were carried out. The results of quasi-static test and numerical simulation showed that the top of pile foundation is the weak part of the pier-pile-soil system. It is found that when the active layer thickness increased， the damage probability of the pile foundation under different failure states decreased， especially in the case of severe damage. Specifically， when the PGA is 0.6g， compared with the pile foundation with 1 m active layer thickness，the damage probability of the pile foundation with the 2 m active layer thickness was reduced by 8.53% and 3.16% under severe damage and collapse states， respectively. The damage probability of the pile foundation with the 3 m active layer thickness was decreased by 13.54% and 4.66% under severe damage and collapse states， respectively. The results showed that the permafrost degradation weakened the soil constraint on pile foundation， then reduced the damage probability of the pile foundation under seismic action， but increased the displacement of the pier top. This will lead to the beam falling failure caused by excessive beam displacement if earthquake occurs. It can be seen that with the increase of axial compression ratio of the bridge pier， the damage probability of the pile foundation under different failure states increased， and the change was more obvious in the case of severe damage and collapse states. Specifically， when the PGA was 0.6g and the axial compression ratio was 4%， 5% and 6%， the damage probability of the pile foundation was 10.80%， 41.19% and 66.70%， respectively. Since it is difficult to repair the damaged bridge pile foundation， the seismic performance evaluation of the Qinghai-Tibet Railway bridge under permafrost degradation condition should also consider the adverse effect of the change of the axial compression ratio of the high pier on the seismic vulnerability of the pile foundation.

Coal is an important energy source in China， and large-scale mining activities have seriously damaged the surrounding ecological environment. However， the spatial and temporal effects of coal mining in plateau and alpine regions on land surface temperature （LST） require further in-depth research. As an important surface parameter， LST is important for the study of surface energy and water balance， and can also reflect the changes of regional ecological environment. In this paper， we use Landsat 5/8 images as the data sources to obtain 7 periods of land use/cover data and LST data using object-oriented methods and single-channel algorithm， respectively， to study the spatial and temporal characteristics of LST changes from mining to ecological restoration in the Juhugeng mining area of the Muli Coalfield from 1990 to 2021. The results showed that： The 7-period land use/cover data obtained by using the object-oriented method well reflect the several stages of the Juhugeng mining area： slow mining period （1990， 2002）， fast mining period （2005， 2009）， slow recovery period （2015， 2019） and fast-fix period （2021）. The LST of coal mine land types such as open pits， slag， built-up areas and coal pile is the highest， followed by the LST of alpine meadows， and alpine swamp meadows have lower LST. The water body has the lowest LST. Bare ground is distributed in ultra-high LST and low LST. The order of explanatory power of the influencing factors of LST in the meadow area is： NDVI > albedo> slope aspect > elevation > slope gradient， and the order of explanatory power of the influencing factors of LST in the mining area is： slope aspect > albedo > NDVI > elevation > slope gradient. The order of explanatory power of the influencing factors of LST in the restoration area is： NDVI > albedo > elevation > slope aspect > slope gradient. This research work helps to understand the spatial and temporal variation of LST in the plateau mining area， and has important reference value for evaluating the ecological restoration effect of the Muli Coalfield.

The study of heat transfer mechanism of gravel layer is of great significance to the application of subgrade improvement technology in cold regions and the interpretation of “abnormal” frozen soil distribution in nature. Many researchers have carried out experimental research on the gravel layer， but there is no unified standard for the temperature setting in the test. Compared with fine-grained soil， the influence of moisture in coarse-grained material is smaller， so the temperature setting in the test plays a key role in the test results. In order to compare the influence of different temperature settings on the three-dimensional heat transfer process of gravel， different roof temperatures， floor temperatures and ambient temperatures are combined， and COMSOL software is used to simulate different combinations under the condition of considering the heat transfer of porous media in gravel layer. The results show that even when the insulation is wrapped， the ambient temperature can still have a significant impact on the temperature profile and the heat flux in the vertical direction. When the ambient temperature is consistent with the average temperature of the gravel layer， the heat flux in the vertical direction reaches the minimum， and the heat transfer efficiency is the lowest. Therefore， in the subsequent indoor gravel layer test design， if it is necessary to reduce the impact of heat exchange in the horizontal direction， the ambient temperature should be set near the average temperature of the gravel layer as far as possible. In the project， the heat exchange inside and outside the gravel layer can be enhanced by reducing the side boundary temperature of the gravel layer， so as to enhance the heat exchange efficiency of the gravel layer.

With implementation of the large-scale development of the western region in China and the Belt and Road Initiative， engineering construction in cold regions is increasing， and the stability problem of the interface between soil-rock mixture and concrete structure is becoming increasingly prominent. Affected by periodic freeze-thaw cycles， the water in the pores of the interface between soil-rock mixture and concrete structure repeatedly freezes and melts， causing changes in the connection and arrangement of soil and stone particles， resulting in loose particle skeleton. It induces cracking of the macroscopic mechanical strength of the interface， and then the occurrence of deformation， dislocation， settlement and other disasters， and keeps safe operation of the project in the cold regions is a difficult problem. The key to solve this problem is to analyze the strength behavior of the interface under the influence of freeze-thaw action， and reveal the mutual feedback effect between the interface strength and pore structure and particle skeleton. In this paper， the indoor direct shear test of soil-rock mixture-concrete interface under different working conditions is carried out to explore the change characteristics of interface shear stress-strain curve， and clarify the influence of freeze-thaw action on the shear strength and strength parameters of soil-rock mixture-concrete interface with different rock content. Then， the NMR layering test and PFC numerical simulation are carried out to obtain the shear strength parameters and pore structure evolution characteristics of the interface area， and to clarify the characteristics of particle rotation and migration at the interface. Based on the fractal dimension theory， quantitatively evaluate the change of interface pore structure， and explain the mechanism of interface strength deterioration under freeze-thaw action： that is， at the stage of strength collapse， the orderly arrangement of the earth and rock particles at the interface is disturbed by the freezing and swelling extrusion， and the coupling and interlocking functions are weakened. At this time， the pore volume and fractal dimension are increased， and the interface integrity is decreased. In the anti-warping stage， the large soil particles at the interface split and recombined， and the skeleton collapsed， forming an inclusion structure with the block stone as the core and the clay covered outside. The reduction in the complexity of the pore interior led to a small increase in the shear strength. With the increase of numbers of freeze-thaw cycles， the soil particles outside the crushed stone peel off， the pore volume and particle rotation in the interface area slowly increase， and the interface gradually debonds and degrades. The interface of low rock content sample is mainly dominated by soil. With the increase of pore volume due to freeze-thaw action， the interface damage and deterioration， the cohesion between soil and concrete decreases， and the shear strength decreases. The shear force is mainly provided at the interface of the high rock sample through the friction and occlusion between the crushed stone and the concrete. Due to the increase of pore volume of the interface layer under freeze-thaw action， the soil-rock mixture becomes loose as a whole， and the cohesion between the crushed stone and the concrete decreases during shearing， and the shear strength shows a downward trend. With the increase of stone content， the interlocking and locking action of the crushed stone at the interface is strengthened， and the shear plane presents an irregular shear band， and the shear strength of the interface increases. The research results have guiding value for the disaster prevention mechanism of engineering structures.

The dynamic properties of frozen soil are closely related to the designing， operating， and maintaining of many infrastructure projects in permafrost areas. The dynamic parameters of permafrost are obtained from the hysteretic curve of frozen soil. Therefore， a comprehensive investigation of the morphological characteristics of frozen soil hysteretic curves is important to clarify the dynamics of frozen soil and its influencing factors. The morphological characteristics of the hysteretic curve of frozen soil can be described by four parameters： the axial dynamic stress amplitude， the degree of non-closure， the width and the area of the hysteretic curve. The specific dynamic characteristics of frozen soil reflected by these four parameters are as follows： the curve enclosed by axial dynamic stress amplitude and dynamic strain amplitude of frozen soil is called the backbone curve， which reflects the magnitude of equivalent deformation， nonlinear effect， and dynamic elastic properties of frozen soil； the degree of non-closure of frozen soil hysteretic curve reflects the plastic deformation property of frozen soil； the width of the frozen soil hysteretic curve reflects the viscous hysteretic property of frozen soil； the area of the frozen soil hysteretic curve reflects the energy dissipation capacity of frozen soil. To this end， a negative temperature dynamic triaxial test was carried out on silty clay in the seasonally frozen soil area of Northwest China. The experiment included ten testing conditions， which composed of four soil temperatures （-0.3 ℃， -1 ℃， -3 ℃， -5 ℃）， three soil water contents （14%， 16%， 18%）， three confining pressures （0.1 MPa， 0.2 MPa， 0.3 MPa） and three loading frequencies （1 Hz， 2 Hz， 4 Hz）. According to the test results， the variation trends of four morphological characteristic parameters describing hysteretic curves with vibration cycle number， confining pressure， soil temperature， water content， loading frequency， and dynamic strain amplitude are analyzed. The results show that the effect of vibration cycle number on the morphological characteristics of the hysteresis curves of frozen silty clay is small. With increasing the dynamic strain amplitude， the growing mode of the backbone curve of frozen silty clay gradually changes from an approximate linear mode to an obvious nonlinear mode. And the degree of no-closure and area of the hysteretic curve increase in a concave curve shape， while the width increases in a convex curve shape. With the increase of confining pressure， water content， loading frequency and the decrease of temperature， the backbone curve of frozen silty clay become steeper and the nonlinear effect is weaker， while the degree of no-closure， the width and area of the hysteretic curve tend to decrease in varying degrees. When the confining pressure is below 0.2 MPa， the water content is below 16% and the temperature is below -3 ℃， the morphological characteristics of the hysteretic curve of frozen silty clay change more obviously with these factors. The degree of non-closure and width of the hysteretic curve is more balanced by the loading frequency， and there is no optimal influence range. Among the four influencing factors， loading frequency and soil temperature have a greater influence on the area of the hysteretic curve， and the water content has the latter influence， while the overall influence of the confining pressure on the area of the hysteretic curve is small. The area of hysteretic curve-dynamic strain amplitude relationship curves of frozen silty clay under the three kinds of confining pressure used in this test almost coincide.

For fixing Duncan-Chang model and making it suitable for unconsolidated and undrained （UU） tests， establishing the modal which can describes saline-alkali soil strength curve of saline soil after freezing and thawing cycles and guide the engineering construction of saline-alkali soil area. In this paper， GDS triaxial was used to conduct UU tests on saline-alkali soil taken from the place in Heilongjiang Province under different confining pressures and different freeze-thaw cycles. The relationship between soil sample strength index c and φ， model parameters K and n， break ratio R_f and the number of freezing-thawing cycles N were obtained by curve fitting. The tangent modulus E_i was modified according to the error comparison between model prediction results and the real value， so the modified Duncan-Chang model was established considering the number of freezing-thawing cycles N of saline-alkali soil. The results show that the undrained stress-strain curve of saline-alkali soil is strain hardening after freeze-thaw， and the strength of saline-alkali soil decreases the most after three freeze-thaw cycles， accounting for more than 71% of the whole strength deterioration process. After freezing and thawing， the internal friction angle φ， cohesion c and parameter K decrease gradually， and the break ratio R_f decreases firstly and then increases， while parameter n increases firstly and then decreases. The modified Duncan-Chang model considering the number of freezing-thawing cycles was established in this paper， and the predicted results are in good agreement with the experimental results.

The freeze-thaw cycle has certain affect on the soil structure and properties. According to the previous research， the shear strength of different types of soil under freeze-thaw cycles show different change patterns. In order to investigate the mechanical laws of Tibetan clay， the representative samples on the Qinghai - Tibet Plateau are taken to study the shear strength changes of remolded soil under different initial water contents and different freeze-thaw cycles by means of piezoceramic monitoring experiments. The results show that the shear strength， cohesion and internal friction angle of Qinghai-Tibet clay decrease in steps with the increase of water content. Under the same water content， the deterioration curves of shear strength and cohesion can be divided into two stages： rapid deterioration stage and stability stage， in which the internal friction angle decreases first and then increases. It is also noticeable that the first freeze-thaw cycle has the most obvious influence on the shear strength. Analyzed by wavelet packet method， the stress wave signal obtained by piezoelectric ceramics monitoring are converted to the real signal amplitude and stress wave energy， both of which could reflect the deterioration trend of the shear strength of Qinghai-Tibet clay. In summary， the strength deterioration index proposed in this paper can well reflect the deterioration degree of shear strength， which has certain reference in the future engineering practices.

In order to reveal the influence of groundwater and soil properties on the water migration pattern during the freezing process of subgrade， water migration tests of unidirectional freezing conditions were conducted for open systems and closed systems of silty clay and sandy soil. By setting a gravel layer in the soil column， blocking the liquid water migration path， monitoring the hydrothermal changes of the soil column during the freezing process， and combining the frozen depth， freezing rate curve， water content distribution curve， and water replenishment time-varying curve of the soil column， the effect on the water accumulation and freezing characteristics of the top of the soil column when only water vapor was replenished was analyzed. The experimental study found that the freezing zone can be divided into a fast freezing zone， a transition freezing zone， and a stable freezing zone. The change in unfrozen water content was closely related to the change in the temperature field. At the beginning of the test， the temperature in the unfrozen zone was gradually decreasing， and the unfrozen water migrated to the cold end under the action of the water driving force， and the decrease in unfrozen water content meant that the water migrated into the frozen zone. When the freezing front gradually moved down， the unfrozen zone in the upper soil layer transformed into the frozen zone， and the unfrozen water underwent a freezing phase change and decreased rapidly. Subsequently， the unfrozen water content showed a slow decreasing trend with the negative temperature. On the other hand， there was a difference in the change of unfrozen water content below the gravel layer between the silty clay and sandy soil columns. Due to silty clay having smaller pores compared with sandy soils， a small accumulation of unfrozen water occurred in the soils below the gravel layer. At the same time， unfrozen water also migrated downward by the gravitational potential. The sandy soil has a weaker water-holding capacity compared to the silty clay and was more significantly influenced by the gravitational potential. Therefore， unlike the silty clay， the unfrozen water content of the sandy soil in the range of 50~60 cm was large compared to the initial water content. In both closed and open systems， silty clay and sandy soil columns formed two water aggregation zones in the frozen zone. The first water aggregation zone was the bottom of the temperature-controlled plate， which was aggregated in the form of frost， mainly formed by the water vapor migration and condensation phase change of the top soil of the soil column. The second water aggregation zone was formed by the liquid-vapor mixing migration in the freezing zone： with the downward push of the freezing front， the interface of disconnected pores was formed， liquid water migrates and aggregated toward the 0 ℃ ice front and turned into ice， and the migration path of water vapor was blocked and condensed into ice， resulting in a significant increase of water content in this area. The open system resulted in greater water gain in the two water aggregation zones compared to the closed system. In addition， the open system increased the latent heat of phase change from water vapor migration， which increased the temperature gradient in the freezing zone and in turn caused the first water accumulation zone to have a stronger pumping effect on the top soil water. The water supplement rate of the specimen with time can be divided into two stages： rapid recharge stages I （0~10 d） and slow recharge stage II （10~30 d）. The water supplement rate of the silty clay column gradually decreased with time and tended to be stable. However， the water supplement rate of the sandy clay column showed a sharp decrease with time and gradually decreased slowly. Compared with the silty clay， the sandy soil had larger pores， and the effect of water vapor recharge on the water aggregation area was more obvious during the test time； however， the water vapor recharge rate gradually decreased with time due to the weakened water holding capacity of the sandy soil.

In order to explore the fracture evolution characteristics of rocks under freeze-thaw cycles， CT scanning technology was used to obtain three-dimensional images of rocks with different freeze-thaw cycles， and quantitative characterization was carried out by pore network model parameters to study the evolution process of rock fracture morphology with freeze-thaw cycles and the change of pore structure with freeze-thaw cycles. The results show that： the complete rock freeze-thaw microfracture are mainly concentrated in the periphery of the rock， showing annular flake； the microfracture generated by freeze-thaw action of fractured rock mainly exist around prefabricated cracks and rock bridge areas， and the distribution range is wider. After the freeze-thaw cycles， the characteristics of various pores in PNM of intact and fractured rocks are different： the number of pores in the former decreases， the proportion of small pores decreases gradually， the proportion of medium and large pores increases， and the pore location distribution is uniform； the number of pores in the latter increases， but the proportion of mesopores decreases， and the proportion of macropores increases rapidly and is mainly concentrated in the upper and lower end faces of the core. During the freeze-thaw process， the main parameters of rock pore structure show an increasing trend， and the pore throat network of fractured rock is more intense， At the end of freeze-thaw process， the maximum throat radius increases by about twice that of intact rock. In the early stage of freeze-thaw process， the main effect of freeze-thaw cycles is to promote the connectivity of rock pores， and in the later stage， the main performance is the accelerated expansion of pore throats， and the porosity growth rate of fractured rock is greater than that of intact rock. The research results can provide reference for rock failure mechanism and disaster prevention in cold region.

As a porous medium with high porosity and large particle size， crushed rock is widely used in Qinghai-Tibet Railway project to reduce the impact of climate warming and engineering disturbance on permafrost foundation because it can cool the permafrost foundation by auto-adjusting its internal convection seasonally. Therefore， it is very important to accurately describe the heat transfer mechanism of the crushed rock embankment and simulate its long-term thermal protection effect. In some fields， it has been proven that can improve the calculation accuracy of porous media by using of local thermal non-equilibrium （LTNE）， but it is still seldom used in the calculation of heat transfer efficiency at the pore scale as large as crushed rock skeleton. The heat transfer coefficient （h_sf ） among the fluid and solid in the porous medium is a key parameter in the LTNE energy equation， and rationality of the selection for this coefficient also determines the accuracy of the calculating result. In this paper， taking the crushed rock based embankment as an example， the numerical simulation results of the traditional used local thermal equilibrium （LTE） model and the LTNE model are validated with the measured data. Besides， the influence of different classical h_sf on the heat transfer of the crushed rock embankment are also analyzed. The results show that LTNE effects in the crushed rock embankment is apparent. For example， temperature of the crushed rock skeleton and the air are not equal at the same time， and the maximum temperature differences between the air and the rock is as large as 1.54 ℃ and 0.80 ℃ in summer and winter， respectively. What’s more， simulation results of the LTNE model are closer to the monitored data， while cooling rate of the LTE model is slightly higher than expected. Difference for the averaged annual error percentages of the two models at 2 m， 5 m and 10 m researched by 6%， 1%， and 8%， respectively. Calculating result of h_sf obtained by different researchers （Achenbach， Wakao， Dixon et al.， Pallares Dixon et al.） has similar varying trend， and the averaged value and the corresponding peak differences of them are obvious， but it has little effect on the soil temperature under the crushed rock embankment.

The strength of frozen soil is a key mechanical parameter in the construction of artificial ground freezing and the safety assessment of structures on frozen soils. However， the strength characteristics of frozen soil are complex and influenced by multiple factors， such as environmental temperature， soil type， water content， and strain rate. At present， there is still a lack of unified conclusions. In view of this， this paper conducts a comprehensive review of the relevant experimental results on frozen soil strength and summarizes the influence of various factors on frozen soil strength and the underlying mechanisms. Based on the literature review， it is revealed that： （1） The strength of frozen soil increases with decreasing temperature and exhibits a linear trend within the common temperature range. The increase in ice strength and the decrease in unfrozen water content caused by temperature decrease are the main reasons for the increase in frozen soil strength. However， after the temperature drops below a certain threshold （e.g.， -80 ℃）， the strength of frozen soil reaches its maximum value and no longer changes. （2） The compressive strength of unsaturated frozen soil increases with the increase of water content， as the degree of saturation of ice rises with increasing water content. For saturated frozen soil， the increase in water content will lead to a decrease in the dry density of frozen soil， and therefore its strength will decrease with the increase of water content. （3） A strong correlation exists between the tensile and compressive strengths of frozen soil， and the ratio of compressive strength to tensile strength varies substantially with soil type， ranging from 3 to 12. Overall， there are many factors that affect the strength of frozen soil. However， current studies are mostly based on single influencing factors， and investigations on the combined effect of multiple factors， the influence of strain rate， and the tensile strength are still limited. Further research is necessary to gain a deeper understanding of these areas.

The constitutive models of frozen soil are crucial for analyzing the safety and stability of geotechnical engineering in cold regions. The cryogenic suction theory can physically explain the mechanism of the influence of temperature on the mechanical properties of frozen soil， and the constitutive models based on this theory can unify the constitutive relationships of both thawed soil and frozen soil. Therefore， the cryogenic suction theory is being paid more and more attention recently. In this paper， firstly， by analyzing the surface tension on the ice-water interface in saturated frozen soil， the concept of cryogenic intergranular suction was proposed based on the cryogenic suction theory. The function between cryogenic intergranular suction and temperature as well as the effective stress formula of saturated frozen soil were established in light of the Clapeyron equation. Secondly， some temperature-controlled confined compression tests and triaxial compression tests were conducted on various frozen saturated soils， obtaining that the effect of cryogenic intergranular suction on the mechanical properties of frozen soil can be attributed to its effect on the apparent overconsolidation of frozen soil， i.e.， the degree of apparent overconsolidation increases with the increase of cryogenic intergranular suction. According to the experimental results， the formulae for the apparent pre-consolidation pressure and shear strength of frozen soil were established. Finally， the above established formulae of frozen soil， including the effective stress formula， pre-consolidation pressure formula， and shear strength formula were combined with the unified hardening constitutive model （UH model） of overconsolidated thawed soil， and a novel thermo-mechanical elastoplastic constitutive model for frozen soil was proposed. The model was then used to simulate the confined， triaxial and uniaxial compression tests on frozen soil， and found to be able to describe the stress-strain relationship of frozen soil under different temperatures and confining pressures， with good agreement with experimental data.

The emission load of VOCs and PM in China is huge， and the atmospheric environment in northwest China is characterized by high sand and dust volume and low humidity， and the level of secondary pollution has been increasing in recent years， and the scientific understanding of the characteristics and effects of atmospheric pollution in this region needs to be improved urgently. In this paper， volatile organic compounds （VOCs）， PM （PM₁₀， PM_2.5 and PM₁） and their fractions （water-soluble inorganic ions， carbonaceous aerosols and inorganic elements） were sampled and analyzed in the atmosphere of thirteen cities in Gansu Province and Xinjiang Uyghur Autonomous Region （Gansu-Xinjiang region） based on proton transfer reaction mass spectrometry （PTR-MS） and particulate matter （PM） collection and analysis techniques. The pollution characteristics and health risks of VOCs and PM in the urban atmosphere of Gansu-Xinjiang region were investigated. The main results were： （1） The pollution characteristics analysis showed that the average total VOCs （TVOCs） concentration was （41.84±7.56） ppbv， oxygenated VOCs （OVOCs） were the important components of VOCs， and the total concentration of VOCs components was higher than that of other cities at home and abroad， mainly methanol， while aromatic hydrocarbons were lower than that of other cities. the average concentrations of PM₁₀， PM_2.5 and PM₁ had average concentrations of （139.39±32.63） μg·m^-3， （77.66±25.39） μg·m^-3 and （44.76±17.59） μg·m^-3， respectively， and water-soluble inorganic ions （WSIIs） were important components of PM in the region. （2） Health risk assessment showed that the non-carcinogenic risk of VOCs in the region was significant and the carcinogenic risk of VOCs was at an acceptable level； The non-carcinogenic risk and carcinogenic risk of heavy metals in PM were both significant. The non-carcinogenic risk of acetaldehyde and the carcinogenic risk of naphthalene are high， and the non-carcinogenic risk of Mn and the carcinogenic risk of As are high， so the control of acetaldehyde， naphthalene， Mn and As elements should be strengthened to reduce the risk of air pollution to human health.

Strain localization is the precursor of the failure of frozen soil. So far， the research on strain localization of frozen soil is relatively weak. A micropolar elastoplastic numerical framework is established to simulate the strain localization of frozen soil by considering the effect of temperature. Through numerical simulation of plane strain test of frozen sand， it is found that the process of the generation， development and formation of shear bands of frozen soil can be simulated by the established numerical framework， and the stress-strain curve and shear band are in good agreement with the test results. Besides， the effects of temperature， end restraints and initial defects on the shear band are investigated. The angle and the width of the shear band increase with the decrease of temperature， and the specific failure mode and location of the shear band are closely related to the initial defects and end restraints. Through the simulation analysis for different finite element mesh， it can be observed that the simulation results obtained based on the coarse mesh are consistent with the fine mesh， which indicates that the mesh-dependent problem can be basically avoided.

The “lake-glacier” interaction of glacial lake contacted glaciers is significant， and they act together on the water cycle process in alpine areas， playing an important role in water conservation， runoff regulation， and ecological diversity maintenance in mountainous areas. Based on Landsat remote sensing images and ERA5-Land reanalysis data， this paper discusses the evolution of glacial lakes and the mass balance of glaciers in the glacier area of Ulugh Muztagh in eastern Kunlun Mountains. The results show that the glacial lakes in the glacier area of Ulugh Muztagh are mainly distributed at an altitude of 5 275~5 400 m a.s.l.， and they are mainly glacial blocking lakes. From 1990 to 2020， there were 16 glacial lakes. Among them， the two glacial lakes formed by the blocked lakes of glaciers 5Y624E0022 and 5Y624F0020， which had three and two events of the glacial lake outburst， respectively. Both lakes are periodically collapsing glacial lakes. The former had large-scale glacial lake bursts in 1999 and 2001， respectively. The former had large-scale glacial lake bursts in 1999 and 2001， with an area of （0.250±0.044） km² and （0.500±0.097） km² before glacier lake outburst flood （GLOF）， corresponding to a volume of （0.014±0.003） km³ and （0.026±0.006） km³， respectively； the latter is a glacier-blocked lake ［（0.110±0.030） km²］ formed in 2000， which burst in that year with a water volume of （0.006±0.002） km³. During this period， the number of glacial lakes has increased， while the area and reserves have decreased. However， the accumulative mass balance of glaciers showed an increasing trend from 2000 to 2010， and a decreasing trend from 2010 to 2020， and the average annual mass balance of glacial lake contacted glaciers showed a significant decreasing trend （-0.024 m w.e.·a^-1） slightly greater than that non-glacial lake contacted glaciers （-0.022 m w.e.·a^-1）. In addition， due to glacial thermal erosion and glacier avalanche， the locations where Binglinchuan and Muztag glacial lakes are connected to the glacier have accelerated their retreat by 0.65 km and 0.28 km， respectively. In short， the number of glacial lakes in this region is increasing and the space of glacial lakes is expanding， which accelerates the material loss of parent glaciers.

Hailuogou Glacier， located on the southeast edge of Tibetan Plateau， is a typical monsoonal maritime glacier， which is extremely sensitive to climate change. It is of great practical significance to recognize the present situation and changing trend of glaciers. In this paper， Landsat series remote sensing images are used as data sources， based on remote sensing and geographic information technology， band ratio threshold method and visual interpretation method are used to extract the glacier boundaries of five periods in 1974， 1991， 2000， 2009 and 2020. Combined with digital elevation data， the variation characteristics of glacier length， total area，coverage of debris and glacier cover units in different directions in Hailuogou in recent 46 years are analyzed. The results showed that： （1） From 1974 to 2020， the glacier length shortened by 1 087.10 m， and the average annual retreat rate was 0.15%， among which the retreat rate at the end of the glacier accelerated continuously after 2000. （2） From 1974 to 2020， the area of glaciers in the study area decreased by 0.55 km²， with the area change rate of -0.52% and the annual average retreat rate of 0.03%， among which from 2000 to 2009， the largest decrease was about 0.23 km²， the area change rate of -0.93% and the annual average retreat rate of 0.10%. （3） Glaciers in different directions are also shrinking in different degrees， and the area of glaciers in the east direction is shrinking fastest. The distribution of glaciers is characterized by more in the east and less in the south and less in the north， and there is a positive correlation between the area distribution of glaciers in each orientation and the total shrinkage of corresponding orientation areas from 1974 to 2020. （4） Through comparative analysis， it is found that the debris in the northwest， northeast and southwest of Hailuogou Glacier increases after 2000 and further increases after 2009. It is predicted that the debris cover of Hailuogou Glacier will continue to expand in the future.

The water temperature of glacial lakes is the basis for studying the physical， chemical， biological and hydrodynamic processes of glacial lakes， as well as the material and energy exchange among glaciers， glacial lakes and moraine dams. In addition to the influence of solar radiation on the water temperature of the glacial lake， the melt water impounded by the glacial lake aggravates the complexity of the temporal and spatial variation of the water temperature of the glacial lake. Moreover， the change of the lake water temperature affects the temperature field and water field of the moraine dam through the heat exchange interaction between the lake water and the dam body， and therefor affects the stability of the dam body. Thus， it is of great significance to study the ablation of lake-terminal glaciers and the stability of moraine dams by establishing long-term field monitoring of lake water temperature and deeply analyzing the characteristics of water temperature changes in glacial lakes. Based on the data of preglacial lake temperature， solar radiation and water temperature at 10~200 cm depth obtained by the automatic observation station of Longba Saba Lake （27°57′17″ N， 88°04′55″ E， 5 499 m a.s.l.） from 2012 to 2021， this paper discussed the characteristics and influencing factors of water temperature change in preglacial lake. The results show that the changes of water temperature and annual freezing period of Longbasaba Lake is the result of many factors， such as air temperature， solar radiation intensity and glacier meltwater， among which the inflow of glacier meltwater has the most significant influence on the variation of water temperature of glacial lakes. In summer， due to the influence of a large amount of glacier meltwater， the water temperatures at different depths are not much different， and the average temperature is about 4 ℃. The water temperature of the observed 10~200 cm water depth varied little （the temperature difference is less than 0.2 ℃）， and there is no obvious stratification in the mixed state. The maximum water temperature appeared in August or September， and the temperature peak had a lag of 1-2 months to the peak of air temperature. In general， the solar radiation is reduced and the water temperature decreases at night. However， due to the influence of hydrodynamic mixing caused by glacier meltwater or floating ice on lake， it is found that at about 12 p.m.， the observed temperature rises at 10~200 cm depth （about 1~2 ℃） or hinders the cooling process of the lake water， forming the phenomenon of inverse stratification at night. Moreover， the frequency of this reverse stratification phenomenon at night also increases with the increase of water temperature. When the water temperature is > 4 ℃ throughout the day， the water temperature of the glacial lake is mainly affected by the solar radiation intensity and weather conditions of daytime， so that the surface water is stratified in days （the temperature difference between the lake water at a depth of 10 cm and 100 cm is greater than 1 ℃）， generally lasting for 2~6 h. In winter， the temperature of lake water at different depths varies greatly， and the temperature difference between 10 cm and 100 cm depths is about 1~7 ℃， and the lake water temperature shows obvious stratification feature. The annual freezing period of Longbasaba Lake is mainly affected by summer water temperature and glacier meltwater recharge. It is about 200 days from late October to late May of the next year. The thickness of lake ice changes significantly， and the thickness of lake ice is the thickest in February， generally between 100 cm and 200 cm. The inflow of glacier meltwater in summer inhibits the rise of lake water temperature to a certain extent， reducing the daily temperature difference of lake water temperature， and affecting the internal temperature field of dam body through the heat exchange between lake water and dam body， consequently affecting the melting process of buried ice and frozen soil in dam body.

In the Tibetan Plateau， many lakes have shoreline， erosion terraces and high-level lake sediments. These geomorphologic and sedimentary units are direct geomorphologic and lithologic evidence for the changes of lake surface in geological history. These landforms and sediments not only reflect the hydrological history of the lake， but also serve as important archives to reveal regional and global environmental changes. Lake Nam Co is the most typical and representative lake system on the Tibetan Plateau. The highest abandoned lacustrine sediments along Lake Nam Co coast lie about 150 m above the modern present lake level and 123 m above the present topographic threshold. A series of scientific issues， such as the times of the abnormally high lake-level， the transgression and regression processes of lake， the drivers of the extreme high-level events， and the hydrologic connection with other lakes， remain ambiguous or controversial. Here， we focus on the the abandoned high-level lacustrine sediments along Lake Nam Co coast. The issues of characteristics， ages， processes and driving mechanisms of lake-level changes at Nam Co were commented. Furthermore， the focuses of researches in future were presented. Finally， based on our preliminary investigations， we suggest that the high-level lake sediments around the Nam Co coast may be formed during the middle to late Holocene， indicating one transgression and regression process. The anomalous oscillation of the India-Burma Trough and relevant high snowfall may be the main driver of lake-level variation.

Climate warming has an important effect on Arctic permafrost and vegetation. Community Land Model （CLM） is one of the most widely used land surface models. However， the complex boundary conditions and parameterization process lead to uncertainty of the simulated results. In this study， we evaluated the simulation performance of the surface soil temperature and carbon cycle in Alaskan permafrost region using the CLM5.0. The results showed that CLM5.0 could capture the seasonal changes of surface soil temperature. At the tundra and needleleaf forests sites， the change of gross primary productivity （GPP） with time simulated by CLM5.0 on both daily and monthly scales were well simulated. The simulated net ecosystem exchange （NEE） has certain uncertainty. This study demonstrates that CLM5.0 can simulate the seasonal changes of soil temperature in high latitudinal permafrost region， but the model may be necessarily improved in the structure， parameterization scheme to improve the simulation accuracy for the carbon cycle.