In order to explore the characteristics of winter temperature changes and extreme cold weather in Heilongjiang Province， cope with extreme climate events， daily temperature data and ERA5 reanalysis data from 84 national meteorological stations in Heilongjiang Province during 1961/1962—2022/2023 were selected， and the spatio-temporal distribution characteristics of multi-year temperature in Heilongjiang Province were analyzed by means of synoptic and statistical methods. the atmospheric circulation during extreme temperature was discussed， and the atmospheric circulation index which had better indication of winter temperature was selected. The results show that the winter mean temperature and extreme minimum temperature in Heilongjiang Province are higher in the south and lower in the north， and both show a warming trend， and the extreme cold weather shows a decreasing trend， but the longest duration and maximum influence range of the extreme cold weather have no obvious decreasing trend. The extreme cold weather mainly occurred in the north of Heilongjiang Province， where the Greater Khingan Mountains accounted for 68.7% of the total extreme cold days， followed by the Lesser Khingan Mountains 27.6%， and other regions only 3.7%. Most of the extreme cold weather occurred in January， accounting for 56.9% of the total number of extreme cold weather in winter， followed by December （24.5%）， and February （18.6%）. The abrupt changes in winter mean temperature and extreme cold station occurred in the 1980s， while the abrupt changes in extreme minimum temperature occurred in the 1990s， which are more consistent with the abrupt changes in the Arctic Oscillation， the East Asian trough intensity， and the Arctic sea ice area in autumn. The winter temperature in Heilongjiang Province is mainly affected by the polar circulation， and the southerly polar vortex may lead to a long duration of extremely cold weather in Heilongjiang Province. The Kuroshio Current SST Index， East Asian Trough Intensity Index and Scandinavian Pattern have good correlation with winter temperature in Heilongjiang Province， which have good indication for predicting future extreme temperature changes.

The rapid formation， expansion， and outburst of glacial lakes are the prominent consequences of global warming and glacier recession. Large-scale glacial lake mapping， glacial lake outburst flood （GLOF） compilations， and risk assessments are essential for understanding regional environmental changes and implementing effective disaster prevention and management strategies. Centered on the Tibetan Plateau， the Asian Water Tower is one of the major global glacial lake regions and has experienced rapid glacial lake expansion and significant disaster impacts over the past few decades. This study focuses on glacial lake changes， outbursts， and associated risks in the Asian Water Tower and summarizes recent advances in glacial lake research. The results show that： （1） The overall rate of glacial lake area expansion in the Asian Water Tower from 1990 to 2018 ［（31.6±4.0） km²·（5a）^-1］ exceeded the average rate observed during 2018—2022 ［（22.7±8.5） km²·（5a）^-1］. Proglacial lakes， accounting for 83% of the total area increase during 2018—2022， emerge as the primary contributor to the current expansion of glacial lakes in the Asian Water Tower， with changes mainly concentrated in the eastern Himalayas and southeastern Xizang. Under the future ice-free scenarios， a total of 15 826 potential glacial lakes with areas exceeding 0.02 km² are projected to emerge， covering an area of （2 253.95±1 291.29） km² with a water volume of （60.49±28.94） km³. The western glacier-rich region is projected to experience a greater emergence of new and rapidly expanding lakes， although with a time lag compared to eastern regions such as the eastern Himalayas and southeastern Xizang， due to different climate patterns. （2） From 1900 to 2020， 145 credible moraine-dammed GLOFs were recorded in the region， with a marked increase in frequency after the 1980s. Specifically， the average annual number increased from 1.5 GLOFs during 1981—1990 to 2.7 GLOFs during 2011—2020. Spatially， GLOF activity has intensified in southeastern Xizang and China-Nepal border area. Additionally， 183 GLOFs stemming from ice-dammed lakes are documented， mainly concentrated in the Karakoram and western Tianshan Mountains， demonstrating watershed-scale clustering and periodic outbursts. （3） The ongoing expansion and frequent outbursts of glacial lakes have significantly increased disaster risk across the region. A systematic hazard assessment has identified 1 499 glacial lakes classified as high or very high hazard level， potentially affecting a flood inundation area of 6 353 km². In terms of disaster-bearing bodies， approximately 55 808 buildings， 105 existing or planned hydropower projects， 194 km² of farmland， 5 005 km of roads， and 4 038 bridges are vulnerable to potential GLOFs. Approximately 190 000 peoples are directly exposed along GLOF-prone pathways. Subsequently， 85 lakes are classified as very high risk level and 113 as high risk level. The eastern Himalaya and southeastern Xizang exhibit the highest levels of GLOF hazard， exposure， and risk. This situation is exacerbated by the rapid expansion of glacial lakes， the increased frequency of GLOFs， the density of dangerous glacial lakes， and the significant potential disaster volume in the Asian Water Tower. These findings highlight the urgent need for more proactive GLOF prevention and mitigation efforts and the necessity of constructing a regionally coordinated and dynamic disaster management system. Overall， while glacial lake research in the Asian Water Tower has progressed rapidly over the past decade， critical challenges remain. These include the need for standardized and high-precision lake mapping， improved understanding of GLOF-climate relationships， and more refined and watershed-scale risk assessments.

The Qinghai-Xizang Plateau （Tibetan Plateau， TP）， renowned as one of the most distinctive geographical landmarks globally， stands as a critical tipping point within the climate system. As the “Asian Water Tower”， this region is highly sensitive to the effects of climate change and could significantly impact the regional climate patterns. Its influence extends profoundly， affecting the climate of East Asia and even the broader Northern Hemisphere. Therefore， it is imperative to comprehend the historical climate patterns and current dynamics of TP. As a proxy for reconstructing past climates， tree rings have been widely utilized in TP climate reconstruction studies. Dendrochronological works in TP have demonstrated a significant potential for developing long tree-ring chronologies over 1 000 years from living trees， archaeological samples， and in situ timber remnants. These records contain temperature and precipitation variability information at multidecadal scales with perfect annual resolution. While numerous literature reviews have focused on different tree-ring parameters， a comprehensive review of dendroclimatological research on TP is still lacking. Therefore， it is necessary to systematically review the research progress of tree ring climate studies in this region. This study retrieved tree-ring chronology data from 1 436 sampling sites across the TP， outlining the progress of dendroclimatology research since 1990. The analysis revealed that most studies utilized tree-ring width （TRW）， followed by maximum latewood density （MXD）， stable oxygen isotopes （δ¹⁸O）， and stable carbon isotopes （δ¹³C）. TRW studies were widely distributed， encompassing nearly 70 tree species， with the length of the chronologies ranging from 300 to 600 years. MXD studies were concentrated in the Hengduan Mountains， focusing mainly on Picea balfouriana， with shorter chronologies and no millennial records. MXD is predominantly used to reconstruct regional temperatures during the growing or late growing season. Studies of δ¹⁸O are primarily located in the surrounding areas of the Hengduan Mountains， Qilian Mountains， and Himalayas. The studied species is substantial， with the longest δ¹⁸O chronology dating back to 4680 B.C. δ¹⁸O mainly records hydroclimatic signals. Studies of δ¹³C are relatively weak， mainly concentrated near the cities of Linzhi and Chamdo and the surrounding areas of the Qilian Mountains. The species most commonly used for δ¹³C studies are Picea crassifolia and Sabina przewalskii. Most of the δ¹³C chronologies are shorter than 200 years， with the longest chronology reaching 1 171 years. Tree-ring δ¹³C is used to reconstruct changes in temperature and hydroclimatic signals. In the future， the accuracy of climate reconstructions can be improved by extending the length of MXD and isotope chronologies， conducting multi-parameter comprehensive analyses， and refining the detrending methods. Expanding sampling sites， particularly in the western and southern TP， is essential to address these geographic gaps. Future research should also explore the climate responses of shrubs and non-coniferous species to enhance the regional dendroclimatological database. Extending the length of tree-ring density and isotope chronologies—especially in northern and western regions—is critical. Given the current reliance of most studies on a single parameter from a single species for climate reconstruction， multi-species and multi-parameter approaches remain uncommon. Therefore， future research should prioritize integrated analyses， combining diverse dendrochronological indicators with climate models to improve the accuracy and temporal depth of multifactor climate reconstructions. Researchers can gain deeper insights into this region's changing frequency and intensity of extreme climate events by integrating tree-ring records and modern meteorological data and combining tree-ring ecology and physiology studies. This study offers a comprehensive overview of advancements in dendroclimatological research in TP， thus providing readers with a clear understanding of the latest developments and the persistent challenges in these studies. Furthermore， this review also summarizes the shortcomings of existing research and lays a theoretical foundation for future in-depth investigations in this field.

Soil carbon pools are among the largest carbon reservoirs in the Earth’s surface ecosystems and play a key role in the global carbon cycle due to their large storage capacity. This study took the northern Xizang （Tibet Autonomous Region） as the study area and obtained measured data of soil organic carbon stock and physicochemical properties in the 0~30 cm soil layer through field experiments. Combined with meteorological station data in the study area and meteorological and soil data from sampling points from 2014 to 2023， the DNDC model was driven， calibrated， and validated. Subsequently， the model was employed to simulate soil organic carbon stocks across the study area of northern Xizang. Statistical methods including the coefficient of variation， spatial interpolation， correlation analysis， and partial least squares regression analysis were used to analyze the spatiotemporal characteristics of soil organic carbon stocks in different soil layers of northern Xizang， and quantitatively assess the influence of climatic and environmental factors on soil organic carbon stocks. The results showed that： （1） Based on the results of previous studies and the actual data of the grasslands on the Qinghai-Xizang Plateau， the model parameters were iteratively adjusted through repeated experiments. The R² value between the simulated and measured values from the DNDC model was greater than 0.8， with a root-mean-square error （RMSE） of 5.16 and a Nash-Sutcliffe efficiency coefficient （NSE） of 0.61. The localized DNDC model demonstrated strong applicability for simulating soil organic carbon stocks in the grasslands on the Qinghai-Xizang Plateau， though its simulation results required simple correction. （2） On the time scale， from 2014 to 2023， the soil organic carbon stock in the 0~10 cm soil layer in northern Xizang showed a fluctuating decline trend. The soil organic carbon stock in the 10~20 cm soil layer remained relatively stable， with a slight increase in 2023. In the 20~30 cm soil layer， the soil organic carbon stock was stable from 2014 to 2022 but declined significantly in 2023. On the spatial scale， the soil organic carbon stock exhibited a distribution pattern characterized by low values in the central area and high values around the periphery. The soil organic carbon stock was concentrated in the eastern part of the study area， such as Baqen County， Sêni District， and Lhari County， while it was lower in the central and western parts of the study area， such as Nyima County， Xainza County and Gar County. （3） Average precipitation and soil water content were the main factors positively correlated with carbon storage. In contrast， soil bulk density， pH value， sand-to-gravel ratio， and elevation were negatively correlated factors， and the annual average temperature had a weak influence on the soil organic carbon stocks in northern Xizang. The results of partial least squares （PLS） regression showed that elevation， soil bulk density， sand-to-gravel ratio， and soil water content had relatively strong explanatory importance for the dependent variable （soil organic carbon stocks）. This study holds significant implications for grassland management and ecosystem conservation in northern Xizang. In future carbon pool management， attention should be paid to environmental factors， land use， and ecological restoration measures， especially the importance of precipitation and elevation in the dynamic changes of soil organic carbon. This will promote the stabilization or growth of soil organic carbon stocks. This study provides data support for the carbon cycling processes of grassland ecosystems and offers a practical basis for ecological environmental protection and construction in northern Xizang.

Dust microparticles， as key components of atmospheric aerosols， have significant impacts on climate change and atmospheric environments. Based on continuous observations from November 2022 to January 2024， this study systematically analyzed the deposition characteristics of dust microparticles in snow and ice， glacial meltwater， as well as atmospheric precipitation and meltwater-fed Mingyong river water in the Mingyong Glacier， Meili Snow Mountain， southeastern Qinghai-Xizang Plateau. The results showed that： （1） The number concentration of microparticles in glacier meltwater runoff had pronounced seasonal variations， and the monsoon season was higher than in the non-monsoon season. （2） During the period of intense glacier melting （May—October）， the number concentration of microparticle in the Mingyong river water showed notable diurnal variations， nighttime concentrations were higher than daytime values. This phenomenon was mainly attributed to a decrease in the rate of glacier ablation at night， which slowed down meltwater runoff and thus prolonged the retention time of suspended particles in the river water. Through the continuous observation of meltwater runoff during day-night， it was found that the peak concentration of microparticles appeared around 20：00 CST， which further proved that there was a responsive relationship between the diurnal variation of microparticles in meltwater runoff and the strong ablation process of the glacier. （3） Fine particles （0.57~2 μm in diameter） dominated the number concentration of microparticles in water bodies. The volume-diameter distribution of microparticles in different water bodies generally exhibited a unimodal pattern， with small median particle sizes， indicating that dust microparticles in this glacier region predominantly originated from long-range atmospheric transport and deposition. This study revealed the deposition characteristics of dust microparticles in snow， ice and water bodies in the Meili Snow Mountain glacier area， providing significant insights for analyzing the mechanisms of the rapid ablation of the cryosphere and its response to regional climate change in the context of global warming.

River is a channel for carbon transport between land and ocean and an important reactor for the metabolism of aquatic ecosystems. It plays an important role in the migration and transformation of carbon in terrestrial and marine aquatic continuums and the carbon budget of watershed ecosystems. The Qinghai-Xizang Plateau is the largest high-altitude cold region in the mid-latitude region. As an Asian water tower， it has developed many major rivers and plays an important role in the regional carbon cycle. In the context of climate change， the process of riverine carbon cycle in the Qinghai-Xizang Plateau has received extensive attention in recent years. This study focuses on the process of river carbon cycle in the Qinghai-Xizang Plateau， and systematically summarizes the progress of riverine carbon cycle in many source areas such as the Yellow River， the Yangtze River， the Lancang River， the Nujiang River and the Yarlung Zangbo River in the past decade. It is found that： （1） The dissolved carbon in the rivers of the Qinghai-Xizang Plateau is dominated by inorganic carbon， and the concentration of dissolved organic carbon is relatively low. The factors such as thawing of frozen soil， enhanced weathering， changes in hydrological processes， and increased erosion and sediment production caused by future climate change will further increase the lateral carbon transport flux in the rivers of the Qinghai-Xizang Plateau. （2） Current observations show that rivers on the Qinghai-Xizang Plateau are important sources of carbon dioxide and methane emissions， and their processes are also affected by climate change and have an increasing trend； （3）The river carbon flux in the Qinghai-Xizang Plateau has an important impact on the carbon budget of the basin ecosystem. The large river carbon horizontal and vertical carbon fluxes offset some terrestrial carbon sinks and are an important part of the ecosystem carbon process. With the warm and humid climate of the Qinghai-Xizang Plateau， its river carbon cycle process will inevitably change significantly， which in turn affects regional carbon sinks， but the extent of its impact is still unclear. In the future， in-situ observation， remote sensing inversion， machine learning and other means should be further used to accurately describe the mechanism of river carbon process， enhance the in-depth understanding of the microscopic mechanism of river carbon cycle， and develop a carbon cycle model suitable for alpine rivers on the Qinghai-Xizang Plateau based on relevant mechanisms， so as to strengthen the simulation and prediction ability of carbon cycle in plateau rivers. This study can provide a scientific basis for further understanding the role of rivers in the carbon neutrality of the Qinghai-Xizang Plateau in the context of changing environment.

Reconstructing glacier retreat from the Last Glacial Maximum （LGM） to the early Holocene using cosmogenic ¹⁰Be exposure dating of moraines is essential for understanding the climatic transition between glacial and interglacial periods. This period， spanning approximately 26.5~10 ka， is marked by major reorganizations in the global climate system， including rapid temperature shifts， fluctuations in atmospheric CO₂， changes in ocean circulation， and variations in orbital forcing. These processes collectively shape ice sheet dynamics and influence cryospheric feedbacks in the Northern Hemisphere. However， the fragmented preservation of moraine sequences at individual sites has hindered efforts to resolve the spatiotemporal patterns of glacier retreat on a continental scale. Single-site records often fail to capture the timing and magnitude of broader deglacial trends. To overcome this limitation， this study compiled a comprehensive dataset of 4 003 published ¹⁰Be exposure ages from 802 well-dated moraines spanning the period between 26.5 and 10 ka. The dataset encompassed a wide range of glacial settings and climates， offering a rare opportunity to conduct integrated regional and hemispheric-scale analyses. The moraines were grouped into four major regions—Asia， Europe， North America， and Greenland—to enable comparative analysis. All ¹⁰Be exposure ages were recalculated using a consistent， globally averaged ¹⁰Be production rate and the LSDn （time-dependent） scaling scheme. This recalibration ensured inter-study comparability and minimized biases caused by inconsistent production rates or scaling methods across different studies. To resolve the temporal distribution of glacier retreat events， the Probabilistic Cosmogenic Age Analysis Tool （P-CAAT） was employed based on probability density estimation （PDE） of exposure ages. This method identified statistically significant clusters of moraine ages by fitting the composite age distribution with multiple Gaussian components， enabling the identification of peak periods of moraine formation or abandonment. Gaussian component analysis was conducted independently for each region and for a combined Northern Hemisphere dataset excluding Greenland. The Greenland moraines were analyzed separately due to preservation patterns heavily constrained by the spatial extent and temporal evolution of the ice sheet margin， differing from other regions. This analytical framework enabled the identification of eight statistically significant hemispheric-scale glacier retreat episodes， centered at （23.9±1.0） ka， （20.5±1.3） ka， （18.3±0.7） ka， （16.6±0.8） ka， （14.7±0.8） ka， （13.0±0.7） ka， （11.4±0.4） ka， and （10.3±0.6） ka. The first two episodes occurring before 19 ka were primarily attributed to increases in Northern Hemisphere summer insolation due to orbital forcing. In contrast， the third through seventh episodes occurred after 19 ka and broadly coincided with abrupt increases in atmospheric CO₂， indicating that greenhouse gas forcing became the dominant driver of glacier retreat. The final retreat episode around 10.3 ka aligned with the peak in summer insolation during the early Holocene. Regional comparison showed a high degree of synchronicity in retreat timing， although the earliest phase （~24 ka） was absent from the Greenland and North American records， likely due to differing responses between ice sheet and mountain glacier systems. Some variability in the number or prominence of retreat episodes across regions could also be attributed to differences in sample density and uncertainties in exposure ages. This study represents one of the most extensive syntheses of ¹⁰Be moraine chronologies in the Northern Hemisphere to date. By integrating a large， globally distributed dataset and applying a standardized analytical workflow， this study improves the temporal resolution of deglacial patterns and provides critical geological constraints for climate-cryosphere interaction models. The findings enhance the understanding of the timing and drivers of glacier retreat and have implications for refining ice sheet reconstructions， glacial isostatic adjustment models， and past sea-level estimation. Moreover， the observed regional differences highlight the importance of glacier type， geographic context， and climate forcing in shaping the heterogeneous responses of ice masses to global climate change.

The accelerated glacier melting under the intensification of global warming has significantly altered glacial erosion and weathering processes within the cryosphere， with unprecedented enhancement observed in recent decades. In warm glacier catchments， these enhanced processes may exert substantial impacts on the global carbon balance and climate change. Specifically， chemical weathering regulates the carbon cycle by consuming atmospheric CO₂， playing a crucial regulatory role in global climate change over geological timescales. However， with the accelerated melting of glaciers， the chemical weathering rate may change， and its specific impact on the carbon cycle requires further investigation. Mingyong Glacier catchment， located on the southeastern margin of the Qinghai-Xizang Plateau， was selected as the research area. A two-year monitoring campaign （from October 2018 to October 2020） of river water hydrological indicators and daily sampling was conducted， ultimately acquiring 731 river water samples. Multiple analytical approaches were employed， including mass balance calculations， Gibbs diagram analysis， mathematical statistics， and hydrochemical characterization. The hydrochemical characteristics of the river water in Mingyong Glacier catchment were investigated， and the chemical weathering rate of rocks and the carbon sink/source rate in the catchment were quantified. The results showed that river water exhibited significant seasonal variations in Mingyong Glacier catchment， with higher anion and cation concentrations in river water during the non-monsoon periods and lower values during the monsoon periods； the water hydrochemical type was classified as HCO₃-Ca. The anions and cations were predominantly derived from carbonate rock weathering， with participation of sulfuric acid in carbonate weathering contributing the largest proportion （62.1%） to chemical composition in river water. Other sources include carbonic acid in carbonate rock weathering （32.4%）， silicate weathering （4.5%）， and atmospheric deposition （1.0%）. Quantitatively， the silicate weathering rate and atmospheric CO₂ consumption flux averaged 0.16 t·km^-2·a^-1 and 0.31×10³ mol·km^-2·a^-1， respectively. In contrast， sulfuric acid-driven carbonate weathering exhibited higher rates （3.34 t·km^-2·a^-1） and corresponding CO₂ release （4.00×10³ mol·km^-2·a^-1）， yielding a net carbon source flux of 3.70×10³ mol·km^-2·a^-1. This indicated that CO₂ release rates through chemical weathering in the study area exceeded its consumption rates by up to 13 times， exhibiting pronounced seasonal variability with monsoon periods showing significantly higher values than non-monsoon periods. Further analysis of the influencing factors for the above characteristic changes revealed that runoff was identified as the primary controlling factor affecting chemical weathering rates in the Mingyong Glacier catchment， with air temperature exerting greater impact than precipitation. The carbon fluxes in the Mingyong Glacier catchment were directly controlled by chemical weathering rates， while runoff and rainfall indirectly controlled these fluxes by modulating the weathering processes. In conclusion， chemical weathering in warm glacier catchments plays a pivotal role in regulating both local hydrochemical characteristics and ecosystems， as well as global carbon balance and climate change. Consequently， research in this field holds substantial scientific and social value， and deserves widespread attention. Future research should focus on the interaction mechanism between chemical weathering process and climate change to provide a scientific basis and decision-making support for addressing global climate change.

The Qinghai-Xizang Railway （QXR）， a crucial strategic corridor and vital support for Xizang’s economic development in China， extensively employed bridges instead of embankments to protect permafrost during its construction. A total of 156 kilometers of the railway consists of bridges rather than conventional embankments， with 447 bridges constructed， including 125 kilometers of dry bridges， leading to a higher proportion of embankment-bridge transition sections （EBTSs） compared to ordinary railways. However， with global warming and increasing human engineering activities， numerous engineering distresses have emerged in the EBTS in permafrost regions， such as differential embankment settlement， subsidence of wing walls， and bridge structure deformation. Addressing these issues is crucial for ensuring the safe and sustainable operation of this vital infrastructure. This paper reviews and summarizes the current research on engineering distress of the EBTS along the QXR from four aspects： distress types， causes， existing treatment measures， and analysis of faced problems. Additionally， it integrates the latest observations from the QXR’s experimental project on integrated treatment technologies， proposing future directions and recommendations for engineering distress treatment in EBTSs. Research findings indicate that the non-uniform degradation of permafrost induced by the thermal effects of bridge structures is the primary cause of differential settlements in EBTS， contributing up to approximately 50% of the observed settlement. For the numerous dry bridges along the QXR， foundation settlement constitutes the main source of embankment settlement in EBTSs， accounting for over 80% of the total settlement. Bridge structural deformation primarily results from decreased bearing capacity of permafrost foundations and seasonal frost heaving of backfill. Given the lower elevation of EBTSs， protection-cone slopes are subjected to substantial groundwater thermal erosion and intense frost heave， leading to subsidence and cracking deformations. With ongoing warm and rainfall increases on the Qinghai-Xizang Plateau， EBTSs along the QXR face increased risks of distress occurrence in the future. Traditional reinforcement measures are inadequate to address future challenges. The integrated treatment technology has shown promising results in addressing engineering distresses in EBTSs. This technology employs a multi-faceted approach， utilizing innovations such as horizontal thermosyphons， ventilated slope and targeted thermosyphon arrays to achieve comprehensive cooling and regulation of embankment slopes， cone slopes， and foundations. Field monitoring data indicate that this technology has successfully transformed warm permafrost into cryogenic permafrost within a year， concurrently achieving rapid enhancement in structural stability. This technology holds practical significance for enhancing the engineering quality and promoting sustainable development of the railway.

Snow cover is the main controlling factor of the freeze-thaw cycle of seasonally frozen ground in northern Xinjiang， and seasonally frozen ground affects the infiltration of snowmelt water by changing the freeze-thaw phase of shallow soil. However， the freeze-thaw state of shallow soil in the thawing snowmelt season in this region is not clear， making it difficult to accurately assess the synergistic regulation of snow cover and frozen soil on soil moisture from the mechanism level. Therefore， based on the monitoring data of snow cover and frozen ground at six meteorological stations in the Altai Mountains from 1961 to 2011， this study applied the Gaussian model and the Boltzmann model to analyze the basic characteristics of snow cover and seasonally frozen ground in northern Xinjiang on the basis of dividing high snowfall years， low snowfall years and normal years， and discussed the freeze-thaw state of shallow soil during the melting period in detail. The results show that the average duration of snow cover is 123.2 days and the average maximum depth of snow is 29.7 cm. The average annual freezing period of seasonal frozen soil is 150.9 days， and the average maximum freezing depth is 120.3 cm. In general， the snow cover showed an increasing trend， mainly manifested as an increase in snow depth. On the other hand， the frozen soil shows a degradation trend， which is mainly reflected in the shortening of the freezing period and the decrease in maximum freezing depth. The comparative analysis of the end time of the frozen soil melting and the end time of snow melt in different types of snow cover years shows that the end time of frozen soil melting in 70% snowy years and 60.5% normal years is 8.2 and 5.5 days earlier than the end time of snow melt， respectively. The end time of frozen soil melting in the year with low snowfall is 13.2 days later than the end time of snow melting. Overall， the results indicate that as snowfall increases， the probability of seasonally frozen ground being in a thawed state during the snowmelt period also increases significantly. The snowmelt water can recharge soil moisture， which leads to a longer retention time of snowmelt water in the soil. This snow-frozen soil synergistic mechanism significantly affects the infiltration of snowmelt water and alters the snow hydrology runoff process. This process can facilitate more snowmelt water replenishing the soil and strengthens the exchange between meltwater and groundwater， contributing to the effective utilization of snowmelt water in arid regions.

High-altitude glacial ecosystems serve as sensitive indicators of global climate change. Within these systems， aquatic microbial communities， acting as core carriers of biodiversity and ecological function， are crucial for maintaining ecosystem stability. Selin Co， the largest glacier-fed endorheic lake on the Qinghai-Xizang Plateau， provides a unique environment that serves as an ideal platform for investigating the ecological patterns of microbial communities under extreme conditions. This study focused on analyzing the diversity patterns and assembly mechanisms of bacterial communities in the waters of Selin Co Lake and assessing their potential response dynamics to environmental changes. Systematic sampling was conducted in June 2022 at the south shore， north shore， and main inflow of Selin Co. Key physicochemical parameters， including pH， total dissolved solids （TDS）， turbidity （TUR）， and nutrients， were measured concurrently. Using 16S rRNA gene high-throughput sequencing， the bacterial community composition and structure were deeply analyzed， yielding a total of 1 327 612 high-quality sequences clustered into 8 587 operational taxonomic units （OTUs）， spanning 28 phyla and 98 genera， thereby revealing exceptionally high taxonomic diversity. Community structure analysis showed that Proteobacteria， Bacteroidota， and Actinomycetota were the absolutely dominant phyla， with Loktanella， Belliella， and Aquiluna as the predominant genera at the genus level. Although α-diversity indices exhibited no statistically significant differences among sampling regions， richness and diversity showed an increasing spatial trend from the south shore to the north shore and inflow， indicating potential influence of local environmental heterogeneity or hydrological inputs. β diversity decomposition （based on Bray-Curtis dissimilarity） demonstrated that differences in bacterial community composition across the regions in Selin Co were primarily driven by species turnover rather than nestedness， reflecting strong environmental filtering or dispersal limitation. Microbial co-occurrence network analysis showed that bacterial taxa were mainly significantly positively correlated， indicating widespread cooperative interactions or niche overlap within the community. This pattern suggested that implementing “a simultaneous multi-region conservation strategy without prioritization” might be more effective for protecting aquatic microbial diversity than prioritizing specific areas. To further analyze community assembly mechanisms， this study applied both the neutral community model （NCM） and checkerboard score （C-score） test. The results showed that deterministic processes predominated in structuring bacterial communities in Selin Co， while stochastic processes played a relatively minor role. Further linear regression modeling of the relationship between bacterial OTU niche breadth and environmental factors identified pH， TDS， and TUR as key drivers significantly influencing bacterial niche breadth. Using multiple community ecological analytical approaches， this study systematically revealed the high diversity， spatial pattern characteristics， and assembly mechanisms of bacterial communities in Selin Co， Qinghai-Xizang Plateau. The findings provide an important case for understanding microbial biogeography in high-altitude glacial lakes， highlighting the central role of environmental selection in shaping microbial communities within extreme aquatic environments. More importantly， the identified key environmental driving factors （pH， TDS， TUR） are highly susceptible to regional climate changes （e.g.， accelerated input of debris from glacial retreat， altered precipitation patterns， and rising water temperatures）. Therefore， the community-environment relationship model established in this study provides a solid scientific foundation for predicting the dynamic responses of microbial community structure and function in Selin Co and similar high-altitude glacial lake ecosystems under future climate change scenarios. This study holds significant scientific value for assessing the impact of global change on vulnerable alpine aquatic ecosystems and for formulating conservation strategies.

With global warming and increasing human activities， slope geohazards such as landslides， thaw collapse， and gelifluctions have become increasingly frequent on the Qinghai-Xizang Plateau. A large number of slope geohazards have developed along the Gongyu High-grade Highway on the eastern edge of the Qinghai-Xizang Plateau， posing serious threats to infrastructure construction and safe operation in the region. However， the distribution patterns and factors influencing unstable slopes along the entire highway remain unclear， which severely constrains the construction and development of highways. Using IPTA-InSAR technology， this study conducted surface deformation monitoring， early-stage identification of unstable slopes， and field validation along the Gongyu High-grade Highway. Then， the spatial distribution and types of unstable slopes were summarized， and their influencing factors of deformation were analyzed. The results showed that the surface deformation rate along the radar line-of-sight direction in the study area ranged from -249 to 335 mm·a^-¹. The overall area remained relatively stable， with significant surface uplift observed near the Duogerong Basin and Bayan Har Mountains. Based on the InSAR deformation monitoring results， a total of 974 unstable slopes were identified. Unstable slopes were widely distributed in the study area， mainly concentrated in the Heka Mountain to Wenquanxiang segment and Qingshuihe County to Yushu segment， with minor distributions near Maduo County and Yeniugou. Types of unstable slopes included creep， colluvial landslides， and bedrock landslides. Among them， one large-scale bedrock landslide was located along the Qinggenhe in Wenquanxiang. The development of this landslide was structurally controlled. Under the influence of rainfall and river erosion， the slope experienced sliding. In the future， it may block the Qinggen River， potentially triggering disaster chain effects such as barrier lake and dam break. One colluvial landslide was located in the mountainous area of Heka Mountain， mainly influenced by rainfall and temperature. The persistent and cyclic freeze-thaw actions caused extensive cracks on the slope surface. Precipitation infiltrated through cracks， altering the thermal state at the base of the colluvium and promoting ground-ice melting on the bedrock interface. This process formed a sliding surface. Meltwater and rainwater further eroded and transported the colluvium， triggering sliding. Additionally， the sliding of the lower gully channel at the slope’s toe exerted a retrogressive pull， causing the middle section of the slope to slide. There were 972 creep slopes distributed along the entire highway. One typical creep slope was located near the Heka Mountain. This slope was located in a small watershed catchment area with consistently high water or ice content. Under the influence of road construction and excavation disturbances， the underground ice layer was exposed and gradually melted. As the underlying materials became saturated with water， the soil structure was damaged， leading to an increase in pore water pressure and a reduction in shear strength. This resulted in the formation of a weak sliding surface， triggering slope failure. In the future， this landslide may gradually evolve into other types of geohazards. The deformation of unstable slopes in the study area is primarily controlled by the loose soil characteristics of grassland and desert areas. Increased rainfall and temperature variations serve as the direct driving factors for slope deformation. This study reveals the development characteristics and influencing factors of slope geohazards along the Gongyu High-grade Highway， providing scientific support for risk prevention， hazard control， and the safe operation of the Gongyu High-grade Highway.

In the context of global climate change， the persistent reduction of Arctic sea ice has created more favorable conditions for the opening of Arctic shipping routes. The Northeast Passage， in particular， has garnered the interest of shipping companies due to its potential distance and cost benefits. However， the passage presents significant navigational safety challenges stemming from its complex and variable climatic and sea ice conditions. Therefore， there is an urgent demand for an intelligent path planning method to optimize the utilization of Arctic routes. This study introduces an intelligent route planning approach that integrates the Polar Operational Limit Assessment Risk Indexing System （POLARIS） with deep reinforcement learning. POLARIS assesses navigational risks by evaluating sea ice conditions along potential routes. The researchers integrate POLARIS with traditional A* algorithms and Deep Reinforcement Learning （DRL） to enhance the path planning process. This integration is crucial as it improves the capacity to manage dynamic environments—typical of Arctic conditions—more effectively than static algorithms such as A*. Experimental results indicate that DRL significantly surpasses the traditional A* algorithm in computational efficiency， achieving approximately 50 times faster processing. This efficiency is vital for real-time route planning， necessary to adapt to the rapidly changing Arctic environment. The article explores the mechanics of DRL， elucidating its superiority in managing complex and dynamic conditions. Unlike traditional methods that struggle with large state spaces and require predefined heuristic functions， DRL employs neural networks to learn optimal strategies through trial and error， making it adept at navigating the unpredictable Arctic environment. The study highlights DRL’s capacity for learning and adaptation， providing a practical solution for real-time decision-making in shipping route planning. Moreover， the study offers a detailed explanation of the employed methodologies. It categorizes DRL approaches into value-based， policy-based， and actor-critic methods， with the research selecting a value-based approach. The Deep Q-Network （DQN） algorithm is employed for its ability to handle large state spaces and efficiently learn optimal policies. The research describes the environmental setup， where Arctic sea ice and weather data are modeled on a grid to simulate navigational scenarios. The DQN model is trained on this data to predict optimal routes， taking into account navigational risk and efficiency. The researchers conducted case studies using historical sea ice data to validate the model， comparing the predicted routes against actual shipping paths taken by vessels such as the ship “Yong Sheng” in 2013. The results show a strong alignment， with the model’s predictions reflecting practical and safe routes that avoid areas of high ice concentration， akin to decisions made manually by ship captains. In conclusion， the article establishes that DRL serves as a suitable core algorithm for Arctic route planning systems. It provides a robust and efficient solution for managing the challenging and variable conditions of the Arctic， facilitating the development of intelligent， automated route planning systems. The study underscores the importance of integrating advanced AI techniques like DRL into maritime navigation to enhance safety， efficiency， and adaptability， thereby contributing to the development of the Arctic as a viable international shipping corridor. The findings suggest a promising future for automated decision-making in maritime logistics， particularly in regions where environmental conditions are critical and volatile.

The stability of permafrost subgrades is closely related to the surrounding hydrothermal environment. Under the influence of climate warming and humidification on the Qinghai-Xizang Plateau， the extensive scale and segmented design of permafrost subgrades in expressways lead to significant ponding issues. Based on long-term field investigations， unmanned aerial vehicle image modelling， and ground-penetrating radar surveys of Gonghe-Yushu Expressway （GYE）， combined with ground temperature and moisture monitoring in typical ponding sections， this study analyzed the spatial distribution of permafrost subgrade distress and their relationship with roadside ponding in the 340-km section from Elashan to Qingshuihe of the GYE. Additionally， it revealed how roadside ponding affected the development of large-scale permafrost subgrade distress. The results showed that subgrade distress in the permafrost sections of the GYE were primarily classified into three types： uneven settlement （77.3%）， transition settlement （13.5%）， and cracks （8.6%）. In the 340-km study section， more than 60% of the sections showed signs of subgrade distress， which were mainly distributed in the high plains and intermountain basins from Changshitoushan to Duoqinankelang and from Yeniugou to Qingshuihe. The distress rate reached up to 60% in permafrost regions with high temperatures and high ice content. The distress rate of the entire study section was 8.4%， while the distress rate in the permafrost section was significantly higher， reaching 18.05%. A strong correlation was observed between roadside ponding and the development of subgrade distress. Approximately 31% of the permafrost sections exhibited roadside ponding， which was mainly distributed in flat terrain. About 66.1% of subgrade distress was associated with roadside ponding. The severity of these distress increased with larger ponding area， greater ponding depth， and shorter distance to the subgrade slope foot. In the ponding sections， moisture content and temperature at the subgrade foot were significantly higher than those in the non-ponding sections， and the permafrost table beneath the subgrade was notably lower than that in the non-ponding sections. Roadside ponding served as a long-term heat source， continuously transferring heat to the permafrost layer beneath the subgrade. During the warm season， ponding absorbed external heat and stored it internally， while simultaneously transferring heat to the permafrost layer. In the early-to-mid cold season， the ponding surface froze， forming an ice layer that acted as a barrier to heat exchange with the external environment. However， due to the high salt content of ponding water， the freezing point was lowered， enabling continued heat transfer from the bottom of the ponding to the permafrost layer. This resulted in a shorter cold season for the soil beneath the ponding area， reducing the amount of cold absorbed by the soil. As a result， the ground temperature in the ponding area increased significantly， leading to asymmetric temperature distribution in the permafrost subgrade area. This process， coupled with increased moisture content， ultimately led to partial thawing of the permafrost layer beneath the subgrade， disrupting the subgrade and inducing various types of subgrade distress. The findings of this study provide valuable insights into the relationship between roadside ponding and subgrade distress in permafrost regions. The results provide a scientific basis for formulating preventive measures and maintenance strategies to mitigate ponding-induced distress in permafrost subgrades. Additionally， the study contributes to a deeper understanding of hydrothermal dynamics affecting subgrade stability and offers practical guidance for future construction and maintenance of subgrades in water-rich permafrost areas. Furthermore， the study highlights the critical role of roadside ponding in the management of permafrost subgrades.

The changes in Qilian Mountain glaciers are not only a direct reflection of climate change， but also has an important impact on fresh water resources. In recent years， the glaciers in Qilian Mountain have been in a state of retreat and instability， to deeply understand the response of the glaciers in the Qilian Mountain to climate change in the 21st century and the magnitude of the change， clarify the characteristics of the Qilian Mountain glaciers change， the process and the reasons， and further predict the trend and magnitude of glacier change， and analyze the Qilian Mountain glaciers destabilization and imbalance in the climate warming background of the mechanism， we selected the Qiyi Glacier， which is strongly influenced by the westerllies， and the Lenglongling No.2 Glacier， which is strongly influenced by the monsoon as examples by analyzing remote sensing images and numerical simulation， it is found that the two glaciers show obvious retreat at the end of the glacier in 1990 to 2022， with the area reduced by 10.28% and 19.04% respectively， and the retreat rate of Lenglongling No.2 Glacier is obviously larger than that of Qiyi Glacier， which is attributed to the fact that the eastern part of the Qilian Mountain is warmer than the western part， and the eastern part of the glacier has decreased in precipitation. To explore the future changes of the two glaciers， the OGGM model considering glacier flow was driven by CMIP6 model data.The relative errors were within 2.5% by comparing the glacier area of the two glaciers simulated by the model and the visually interpreted area from 2008 to 2022. The simulated values of the mass balance of the Qiyi Glacier were more in line with the observed values， with an average difference of 88 mm w.e. Between the two mass balances， the difference between the two is 88 mm w.e.， which indicates that the OGGM model can simulate the glacier changes better.The simulation results show that under the high-emission scenario （SSP5-8.5）， the area and volume of the Qiyi Glacier will decrease by 77% and 94%， and the area and volume of the Lenglongling No.2 Glacier will decrease by 93% and 99% by 2060， and by the 21st century 80s， the air temperature in the area of the Qiyi Glacier will increase by 4.1 ℃ compared with that of the period of 1990 to 2015， while the increase in precipitation will not be obvious， and the glacier will be completely extinguished by that time. In contrast， temperatures in the eastern section of the Qilian Mountain will rise even faster， and it is predicted that the Lenglongling No.2 Glacier will be completely extinct around 2075. Even under the most optimal carbon emission scenario （SSP1-2.6）， a temperature increase of 1.0 ℃ in the Qilian Mountain by 2050 compared with the 1990 to 2015 prognosis will lead to the retreat of both glaciers into ice buckets by 2080 when the area and volume of Qiyi Glacier will be only 22% and 8% of that of 2020， and the Lenglongling No.2 Glacier will be only 17% and 6%. The rapid ablation of glaciers will cause changes in glacier runoff， and the runoff of the Qiyi Glacier and the Lenglongling No.2 Glacier will peak in 2035 and 2024， respectively， and the runoff of the two glaciers will be reduced by 28.98% and 41.82% by the end of the century under the SSP5-8.5 scenario， respectively. Therefore， regardless of climate scenarios， Qilian Mountain glaciers will retreat significantly in the 21st century， or even disappear， due the temperature， precipitation atmospheric circulation， and other influences， which will also make the eastern Qilian Mountain glaciers than the western glaciers retreat faster. Clarifying the trend and magnitude of glacier changes， and understanding the process mechanism of Qilian Mountain glaciers imbalance and destabilization in the context of climate change will deepen our understanding of the current and future glacier changes in the Qilian Mountain region， so as to cope with the environmental and water resource problems caused by the glacier changes， which require us to plan in advance.

Ice and snow tourism is increasingly emerging as a vital and rapidly expanding sector within the global tourism industry. The presence and effective utilization of ice and snow resources form the essential bedrock upon which this niche tourism thrives. As a prominent example of this development， the Northeast region of China stands out as a national leader and pioneer in ice and snow tourism. This region has been proactive in enlarging its resource base and strategically optimizing the spatial configuration of its offerings to maximize appeal and economic benefits. Consequently， a comprehensive understanding of the spatial and temporal dynamics of ice and snow tourism resources is crucial to advancing the sustainable and high-quality development of this sector. This study adopts a geographical spatio-temporal framework to scrutinize the evolution and distribution of ice and snow tourism resources across the three northeastern provinces of China， Heilongjiang， Jilin， and Liaoning， from 1990 to 2022. Through the application of advanced tools such as ArcGIS spatial analysis and geographic detectors， the research investigates the patterns of resource distribution and the underlying drivers of change across four critical dimensions： temporal evolution， spatial configuration， clustering characteristics， and influencing factors. The study’s findings present several key insights： （1） Growth Phases and Regional Specialization： the development trajectory of ice and snow tourism in the three northeastern provinces over the period from 1990 to 2022 can be delineated into four distinct phases： “initial emergence”， “steady expansion”， “adjustment phase”， and “rapid development”. Each phase reflects a unique period of growth and transformation in the region's tourism landscape. Heilongjiang Province， with its rich ice resources， has established itself as a dominant hub for “ice” tourism. Jilin Province， on the other hand， has gained recognition for its specialization in “snow” tourism， leveraging its unique geographical and climatic conditions. Meanwhile， Liaoning Province has differentiated itself by offering a combination of “ice and hot springs” tourism， creating a diverse and complementary tourism product that appeals to a broader market. （2） Spatial Distribution and Correlation Patterns： the spatial distribution of ice and snow tourism resources within these provinces demonstrates a significant positive correlation， indicating a high degree of clustering. Over time， there has been a discernible shift in the spatial concentration of these resources， moving from hot spots in the southeastern areas to cold spots in the northwestern regions. This migration reflects both natural and socio-economic factors that influence where and how tourism resources are developed and utilized. （3） Evolution of Distribution Patterns： from 1990 to 2022， the spatial distribution pattern of ice and snow tourism resources in the three northeastern provinces has evolved through several stages， reflecting broader trends in regional development and planning. Initially， the distribution was more “dispersed”， followed by a phase of “agglomeration”， which then transitioned into a stage characterized by “agglomeration and diffusion”. The final stage saw a process of “re-agglomeration”， leading to the emergence of a diagonal “T”-shaped distribution pattern. This structure is anchored around two core axes： Daqing-Harbin-Mudanjiang and Harbin-Changchun-Shenyang. The general trend of this spatial distribution is along a “northeast-southwest” axis， with the gravitational center initially shifting northeast before moving southwest. As a result， disparities in the distribution of high-quality ice and snow tourism resources among the three provinces have decreased， signaling a trend towards more balanced and equitable regional development. （4） Influencing Factors and Underlying Drivers： the spatial and temporal distribution of ice and snow tourism resources in Northeast China is shaped by a complex interplay of various factors， including the natural environment， socio-economic conditions， the level of tourism development， and the quality and extent of transportation infrastructure. Among these， the most significant influences are exerted by domestic and international tourism revenue and road mileage. These findings highlight the “tourism-dependent” and “transportation-driven” characteristics that are pivotal to understanding the spatial dynamics of ice and snow tourism in this region. The correlation between transportation infrastructure and tourism growth suggests that improved accessibility and connectivity are crucial for future development strategies. By employing a spatio-temporal perspective， this study aims to broaden the scope of research on ice and snow tourism and enrich the understanding of its spatial and temporal structure. It advocates for a more rational and strategic distribution of ice and snow tourism resources across the three northeastern provinces， aiming to foster regional integration and leverage the complementary advantages of each province. Ultimately， the insights derived from this research are intended to support the sustainable and high-quality development of ice and snow tourism in the post-Winter Olympics era， ensuring.

This study investigates the significant role of Antarctic sea ice in the global climate system， with a specific focus on the contribution of coastal polynyas， particularly in the Ross Ice Shelf region. Polynyas， areas of open water within the sea ice cover， are known to be critical sites for sea ice production， influenced predominantly by wind-driven processes. The Ross Ice Shelf polynya， a prominent feature in the Southern Ocean， is one of the most important regions for understanding the mechanisms of sea ice production and its implications for global climate dynamics. The primary aim of this research is to accurately determine the extent of the polynya and the volume of sea ice produced within it， under the influence of wind. Traditional methods for estimating sea ice volume often do not account for the contributions of polynyas， leading to an incomplete understanding of their role in sea ice dynamics. This study addresses this gap by using advanced remote sensing techniques to identify the spatial extent of the polynya， measure the frequency of sea ice production events， and calculate the corresponding volume of sea ice produced. By achieving this， the research provides more accurate estimates of sea ice production in the Antarctic and contributes to a better understanding of its role in the global climate system. To achieve these objectives， the study employs a combination of Sentinel-1 Synthetic Aperture Radar （SAR） data and Advanced Microwave Scanning Radiometer 2 （AMSR2） data. The Sentinel-1/SAR data is used to determine the spatial extent of the polynya during wind-driven events. This high-resolution data allows for precise detection of open water areas within the sea ice cover， which are crucial for understanding the dynamics of polynyas. In parallel， the AMSR2 data is used to measure the thickness of the sea ice that forms within the polynya and is subsequently blown away by wind. By integrating these two datasets， the study is able to accurately identify the boundaries of the polynya during wind events and quantify the volume of sea ice produced. The research focuses on the period from 2019 to 2021 in the Ross Sea region， identifying each wind-driven polynya event and the resulting sea ice production. Additionally， the study analyzes the intra-annual and inter-annual variations in the area， thickness， and volume of ice produced by these events from 2017 to 2021. This comprehensive analysis provides insights into the temporal variability of sea ice production in the Ross Sea polynya and its potential impact on the broader climate system. The findings of the study reveal that wind-driven polynya events in the Ross Sea predominantly occur between mid-March and mid-November each year， with the peak of sea ice production happening in July， August， and September. The average ice thickness during these events ranges from 1 to 30 cm， with the annual frequency of events varying between 72 and 114 occurrences. The volume of sea ice produced in these events ranges from 196 to 284 cubic kilometers， showing a trend of initial increase followed by a decline over the five-year study period. This research makes a significant contribution to the field of polar studies by presenting a novel approach to precisely identify and quantify the extent and impact of polynyas on sea ice production in the Antarctic region. The use of advanced satellite data， combined with a detailed analysis of wind-driven processes， provides new scientific evidence that enhances the understanding of the role of Antarctic sea ice in global climate change. The findings underscore the importance of considering polynyas in sea ice dynamics and highlight their potential impact on climate models and predictions of future changes in the Antarctic environment. This study not only advances the understanding of polar processes but also offers valuable insights into the broader context of global climate variability and change.

The chain reaction of glacial lake outburst floods in the alpine and high altitude mountains area poses a significant threat due to its extensive impact range， large flood scale， and high flow velocity. Traditional prevention and control measures downstream of the disaster chain are often difficult to implement and economically unfeasible. Moreover， the primary triggering factors， such as ice collapses， are usually located at altitudes above 5，000 m， making access and engineering interventions extremely challenging. To address these issues， this study proposes a novel prevention and control approach focusing on the overflow outlet of the moraine dam， based on field investigations and statistical analysis. A new integrated protective system， combining rigid and flexible reinforcement layers， is developed to enhance the stability of the moraine dam’s armor layer at the overflow section. The system consists of scaffold steel pipes， high-strength metal flexible nets， and anchor rods， forming a “rigid-flexible integrated plate-like” protective structure. Laboratory physical model experiments were conducted to verify its effectiveness under simulated flood conditions. The results indicate that as protection measures are strengthened， the initiation flow velocity of the armor layer increases significantly. Compared to the unprotected state， a single-row rigid connection provides a minimal increase in stability， whereas a double-row rigid connection increases the initiation flow velocity by approximately 2%， a triple-row rigid connection by about 5%， and the combined rigid-flexible system by approximately 8%. The effectiveness of the protection system improves with an increase in the protected area， demonstrating its potential for mitigating moraine dam breaches. This research provides a feasible and technically viable solution for preventing moraine dam failures in high-altitude， cold environments. The proposed system offers advantages in terms of adaptability， cost-effectiveness， and ease of implementation in remote mountainous regions. It has the potential to serve as an effective first line of defense against glacial lake outburst floods and contribute to disaster risk reduction in alpine and high-altitude areas.

The Qilian Mountain National Nature Reserve in Gansu and the Important Water Source Recharge Ecological Functional Area of Yellow River in Gannan are two major ecological functional areas in Gansu. Establishing a scientific and effective ecological compensation mechanism is crucial for ensuring ecological security and promoting sustainable development in the region. To address this issue， this study selected data from four prefecture-level cities in the Qilian Mountain National Nature Reserve in Gansu and the Important Water Source Recharge Ecological Functional Area of Yellow River in Gannan from 2010 to 2023， and analyzed their ecological compensation performance， main obstacle factors， and the coupling coordination among economic， social， and ecological performance using the entropy-weighted TOPSIS method， obstacle factor diagnostic model， and coupling coordination degree model. The results showed that： （1） the comprehensive ecological compensation performance of the Qilian Mountain National Nature Reserve in Gansu increased from 0.234 to 0.701， improving from a poor level to a good level， while that of the Important Water Source Recharge Ecological Functional Area of Yellow River in Gannan fluctuated from 0.349 to 0.606， shifting from a qualified level to a good level. （2） Among the four prefecture-level cities， the ecological compensation performance of the three cities under the jurisdiction of the Qilian Mountain National Nature Reserve in Gansu showed regional heterogeneity. Among them， Jinchang ranked highest， Zhangye was in the middle， and Wuwei ranked the lowest. （3） The main obstacle factors affecting the ecological compensation performance of the Qilian Mountain National Nature Reserve in Gansu included the value of production of ecological material products in economic performance， the number of people covered by unemployment insurance in social performance， and the daily treatment capacity of urban wastewater in ecological performance. For the Important Water Source Recharge Ecological Functional Area of Yellow River in Gannan， main obstacle factors included the green coverage rate of built-up areas in social performance and the total water consumption in ecological performance. The results indicated regional heterogeneity in the ecological compensation performance across the cities. （4） The coupling coordination degree of ecological compensation performance in the Qilian Mountain National Nature Reserve in Gansu increased from 0.466 to 0.844， improving from borderline imbalance to good coordination. In the Important Water Source Recharge Ecological Functional Area of Yellow River in Gannan， the coordination degree fluctuated from 0.530 to 0.785， shifting from barely coordinated to moderately coordinated. Therefore， it is recommended to improve the ecological compensation mechanism by refining laws and regulations， standardizing compensation criteria， clarifying compensation subjects and targets， diversifying funding sources， and strengthening performance evaluation， so as to provide a basis for strengthening the ecological security barrier in western China and promoting the positive interaction between ecological protection and economic development in the important water source recharge area of the upper reaches of the Yellow River.

Wildfire activities， an important part of natural ecosystems， are strongly influenced by climate change and vegetation types. As one of the best proxies for reconstructing wildfire history and wildfire occurrence mechanisms， the quantitative statistics and morphological analysis of charcoal can not only recover the frequency， intensity and changes of wildfire activities over geologic historical periods， but also understand the types of vegetation （woody and herbaceous plants） in which wildfires occurred. In addition， different sizes of charcoal can reflect the distance between the wildfire site and the depositional area. The Qinghai-Xizang Plateau with its high-altitude is very sensitive to the environment changes. However， there are few reliable charcoal records in the Qinghai-Xizang Plateau， and the research results mainly focused on macroscopic charcoal anatomy and the charcoal records in the late Holocene archaeological sites. In this study， a Holocene sedimentary profile with the complete sedimentary sequences was founded in the Zoîgé Basin on the eastern Qinghai-Xizang Plateau through extensive field investigations. The history of Holocene wildfire activities and climate changes in the Zoîgé Basin were reconstructed using a variety of paleoclimate proxies （charcoal， magnetic susceptibility and total organic carbon）， and the relationship between Holocene environment change and wildfire activities was revealed. The results showed that the wildfire activities in the Zoîgé Basin were dominated by regional wildfire activities during the Holocene， and local wildfire activities were dominated by burning woody plants， regional wildfire activities were dominated by burning herbaceous plants. However， the low magnetic susceptibility （mean 7.9×10^-8 m³/kg） and TOC （mean 0.23%） of the aeolian sand layer in the early Holocene （before 8.5 ka） were presented indicated that the temperature has increased， but the climate was still dry and cold， with frequent dust storms and weak biopedogenesis. The lowest value of total charcoal concentration （mean 33 390 grains/g） was presented in the aeolian sand layer， indicating that there was less vegetation and low coverage， limited plant biomass limited the occurrence of wildfire activities， and the occurrence frequency of regional and local wildfires was low. In the middle Holocene （from 8.5 to 3.1 ka）， under the moist and warm climate， the paleosol layer developed. The magnetic susceptibility of paleosol layer reached the highest value （mean 7.9×10^-8 m³/kg）， and the TOC value was also high （0.23%）， indicating that the increase of temperature and precipitation in the middle Holocene led to lush vegetation in the Zoîgé Basin. The value of total charcoal concentration （mean 45 315 grains/g） was relatively high in the paleosol layer， reaching the highest level in the middle Holocene， reflecting the frequent occurrence of wildfire activities in the middle Holocene. However， due to the increase of temperature and precipitation， the plant biomass in the Zoîgé Basin increased， leading to the frequent occurrence of regional and local wildfire activities related to the increase of plant biomass. In the late Holocene （after 3.1 ka）， The magnetic susceptibility （mean 16.6×10^-8 m³/kg） and TOC （mean 0.55%） of the modern meadow soil layer in the late Holocene decreased compared with that in the mid-Holocene. It was inferred that under the condition of lower temperature and precipitation in the late Holocene， weathering and soil formation in the Zoîgé Basin weakened， and vegetation decreased， Vegetation coverage decreased. The total carbon concentration was relatively stable and low in the late Holocene， with an average of 34 615 grains /g， indicating that the intensity of wildfire activities in the Zoîgé Basin was relatively stable and the frequency of wildfire activities was low， which may be due to the decrease of plant biomass during this period， and the lack of combustible biomass led to the decline of wildfire activities. However， the intensification of local wildfires activities during this period may also be caused by human activities. The results of this study will contribute to the in-depth understanding of wildfire history and climate evolution in the Zoîgé Basin.

Ice thickness and glacier topography data are the basis of glacial dynamics simulation. The analysis of ice thickness distribution and terrain features is important to understand the characteristics of glacier flow velocity， stress and its change. In September 2021， a ground penetrating radar system was used to probe the ice thickness of the Ningchan River Glacier No.3 in the Qilian Mountains， then using Ordinary Kriging interpolation method to process ice thickness and glacier surface elevation data， and based on the processed data we analyzed the glacier’s profile and whole characteristics of ice thickness distribution and glacier topography， and also studied glacier’s changes in recent years. The results showed that： the thicker parts of the Ningchan River Glacier No.3 were mainly located in the areas where the bed terrain was relatively flat， and broadly the ice thickness value decreased from the center to the edge， and increased first and then decreased with the rise in altitude； compared with glacier surface， the bed terrain of the Ningchan River Glacier No.3 fluctuated more strongly， and the shape of glacier bed in each transverse section appeared in various forms， such as slope， double trough valley and V-shaped valley； the glacier area， maximum ice thickness， mean ice thickness and ice volume of the Ningchan River Glacier No.3 in 2021 were respectively about 1.08 km²， 60 m， 24.1 m and 0.026 km³， and the glacier area， mean ice thickness and ice volume had respectively reduced about 0.123 km²， 3.3 m and 0.007 km³ from 2009 to 2021， and their mean annual change rate were respectively about -1.03×10^-2 km²·a^-1 （-0.86%）， -0.28 m·a^-1 （-1.00%） and -5.83×10^-4 km³·a^-1 （-1.77%）， compared with the period 1972—2009， the glacier shrunk faster， and its primary cause was the rise of mean summer （June-August） air temperature； the change of ice volume was in the form of thickness thinning all the time from 1972 to 2021.

Supraglacial debris comprising rock fragments， soil， and gravel， accumulates on glacier surfaces primarily due to processes such as mountain collapses， glacial erosion， and the exposure of englacial debris. It influences sub-debris ablation patterns through energy exchange and albedo variations， resulting in distinctive mass balance responses， hydrological effects， and hazard processes in debris-covered glaciers compared to debris-free glaciers. The impact of debris on underlying glacier melt is predominantly determined by the unique thermal processes driven by variations in debris thickness. When debris thickness is below a threshold （approximately 2~3 cm）， the absorbed heat is efficiently transferred to the sub-debris ice， accelerating glacial melt and generating basal meltwater that facilitates glacier movement. In contrast， thicker debris layers impede heat transfer， reducing melt rates， and potentially leading to over- or underestimation of glacier runoff. The spatially heterogeneous distribution of debris thickness results in differential melting across the glacier surface， giving rise to ice cliffs and supraglacial lakes. Ice cliffs absorb more solar radiation， intensifying localized melt and posing risks of collapse， while expanding supraglacial lakes can lead to glacial lake outburst floods （GLOFs）， threatening downstream populations and ecosystems. The thickness of supraglacial debris is thus a key factor in simulating glacier melt and accurately quantifying glacier runoff. It provides essential data support for research on dynamics， mass balance， and hydrological modeling of debris-covered glaciers， contributing to enhanced disaster risk management and water resource planning in downstream areas. The Langtang basin， located in the central Himalayas， is characterized by extensive supraglacial debris cover. Its unique geographical setting and glacial features make it a critical area for studying Himalayan glaciers and their responses to climate change. However， current research on supraglacial debris in this region remains predominantly focused on field measurements， with limited investigations into debris thickness and its spatial distribution at the watershed scale. It significantly impedes a comprehensive understanding of glaciers with debris coverage within this area. In response to the above questions， using Landsat 8 remote sensing imagery and high temporal resolution meteorological station data， this study calculated surface temperature， sensible heat flux， and net radiation flux in the Langtang region to solve the energy balance equation. Based on this approach， the spatial distribution of supraglacial debris thickness across glaciers in the Langtang region was retrieved. The study further analyzed the spatial distribution characteristics of debris thickness in representative glaciers and investigated the factors contributing to the heterogeneity in supraglacial debris thickness distribution. The study yielded the following findings： （1） The average thickness of supraglacial debris in the Langtang Basin glaciers was （0.25±0.02） m. Specifically， Lirung glacier had a thickness of （0.55±0.02） m， Shalbachum glacier （0.48±0.02） m， Langshisha glacier （0.31±0.02） m， and Langtang glacier （0.25±0.02） m. （2） Along the longitudinal profiles， the supraglacial debris thickness increased from the upper to the lower parts of the ablation zones. For Lirung， Shalbachum， and Langtang glaciers， the debris accumulation rates first decreased and then increased along the longitudinal profiles， whereas Langshisha glacier showed a continuous decrease. In terms of the transverse profiles， the thickness of the supraglacial debris was greater on the right side of the glacier movement direction for Lirung， Shalbachum， and Langtang glaciers， while Langshisha glacier exhibited thicker debris on both sides and thinner debris in the middle. （3） The variation in debris accumulation rates along the longitudinal profiles was primarily attributed to differences in surface flow velocities in the lower ablation zones. （4） The uneven distribution of debris thickness along the transverse profiles near the glacier termini was mainly due to differences in surface flow velocities， melt rates， and topographic features.

Slope instability and collapse due to freeze-thaw cycles are significant challenges in infrastructure development in permafrost regions. To explore and analyze the causes and stability variation patterns of slope instability in seasonally frozen soil areas in Southwest China， this study focuses on the slopes of the Batang region. A research approach combining theoretical analysis， numerical simulation， and laboratory experiments is employed. A permeability coefficient model for the negative temperature zone， considering the unfrozen water and pore ice states， is applied within a soil hydrothermal coupling model. Through direct shear tests， the variation patterns of shear strength parameters for remolded slope soils were further obtained. Using the COMSOL finite element software， a customized slope stability model was developed. The slope height was set to 10 m with a gradient of 1∶1.5， and both the slope top and bottom extended 50 m and 60 m， respectively， with the slope base extending 10 m downward. This model was used to analyze the changes in temperature and seepage fields， as well as the slope instability mechanisms induced by freeze-thaw cycles affecting the soil’s shear strength parameters. Results show that the modified hydrothermal model， which incorporates the adjusted permeability coefficient， has higher accuracy， as verified by comparing the calculated values with those from one-dimensional soil column experiments. Temperature fluctuations within 1 m of the slope surface are significant. From January to March， air temperatures remain low， with deeper soil temperatures being relatively high， and soil temperature increases monotonically with depth. Between April and September， surface soil temperatures rise faster than the deeper layers， which maintain relatively high temperatures. From October to December， surface temperatures decrease more rapidly than in deeper layers， where temperatures remain relatively stable. The seepage field shows minimal variation beyond 2.5 m depth. From November to March， the slope surface freezes first， leading to a decrease in water content， although internal moisture migration is limited. Water content initially decreases with depth， then increases. Between April and June， during the thawing period， shallow soil melts， with water content decreasing with depth. From July to October， the water content initially increases with depth before decreasing again. In March， water content variation with depth is most pronounced， and due to the surface thawing while the subsurface remains frozen， excess water above the frozen layer cannot drain effectively， resulting in the lowest slope stability with a safety factor of only 1.59. The mechanism of slope failure in seasonally frozen regions is attributed to saturation above the thaw-freeze interface during the thawing period， where water cannot drain， reducing soil friction and leading to slope collapse. By dynamically adjusting the soil strength parameters to calculate slope stability， it is determined that the most significant strength degradation occurs at the thaw-freeze interface， primarily resulting in shallow slides within 1.2 m of the surface. The sliding surface is relatively flat and arc-shaped， with the primary failure mode being slumping collapse. This study provides valuable insights for slope design and disaster prevention in Southwest China， particularly for engineering projects in seasonally frozen regions， offering significant practical implications.

As an important water conservation area of the upper Yellow River， the Zoige Wetland is crucial in maintaining the stability of the plateau ecosystem and regional climate. Under the background of climate warming， the water resources in Zoige Wetland has changed significantly， which has caused a series of ecological and environmental problems， and further threatened the ecological security and economic development of the middle and lower reaches of the Yellow River. At present， the water resource status of Zoige Wetland has been widely concerned. However， many scientific problems about the water resources in this region have not been solved yet. For example， what are the law of climate change and water resources change in Zoige Wetland in recent decades？ What are the impact process and impact mechanism of the climate change on the water resources in this region？ To solve these problems systematically， based on the observation data at meteorological stations and the hydrological stations in Zoige Wetland， and the ERA-Interim monthly mean reanalysis dataset from 1981 to 2015， this paper research on the regional climate response characteristics and their impact on runoff in Zoige Wetland， by adopting the following research methods， including observation analysis and theoretical research. For the first step， this paper analyze the basic climate change characteristics of runoff in Zoige Wetland. On this basis， we explore the impact process of climate change on runoff in Zoige Wetland. The research work can provide theoretical support for water resources protection and coping strategies of climate change in Zoige Wetland. The results show that， the annual and seasonal average runoff in Zoige Wetland showed a downward trend before 2008 and showed an increased trend after 2008， and the monthly average runoff showed a “bimodal” distribution， with the runoff mainly concentrated in the flood season during 1981 to 2015. Precipitation is the main factor to impact the runoff in Zoige Wetland， and summer precipitation having the most significant impact. The precipitation decreased before 2008 and then increased after 2008， while the continuous rise of temperature， the snowmelt water and evaporation also increased significantly in Zoige Wetland. The evaporation in summer and autumn had the most significant impact on runoff. The annual and seasonal average water vapor flows in via the western and northern boundaries and flows out via the eastern boundary in Zoige Wetland. However， the annual / spring / summer / autumn average water vapor flows in via the southern boundary， and the winter average water vapor flows out via the southern boundary. The inflow from the western boundary is more than from the southern boundary. The net water vapor budget is positive for the whole year and spring/summer/autumn， which is the largest in summer. It is indicated that summer is the season with the most active water vapor transport. Therefore， the Zoige Wetland is an obvious water vapor sink for the whole year and in spring， summer， and autumn， while water vapor is exported from Zoige Wetland in winter. The annual （summer） precipitation is significantly positively correlated with the water vapor inflow at the southern， western boundary and net water vapor budget of the Zoige Wetland in the same period. Southwest wind water vapor transport is an important water vapor transport that causes precipitation anomalies in Zoige Wetland. When the anticyclonic circulation on the southern side of the plateau are strengthened （weakened）， while the anticyclonic circulation in South China and the Western Pacific region are strengthened （weakened）， the southwesterly water vapor from the South China Sea， Western Pacific， and Bay of Bengal transport along the south edge of the Qinghai-Xizang Plateau are strengthened （weakened）， the anomalous southwesterly （easterly） airflow and water vapor convergence （divergence） persist in Zoige Wetland， resulting in more （less） precipitation in summer， and eventually leading to more （less） runoff in Zoige Wetland. We hope this paper can provide a theoretical basis and scientific support for water security and water resources management in the Yellow River basin. Furthermore， the future climate change of Zoige Wetland will be predicted based on the CMIP6 global climate model， and the variation characteristics of water resources in this region under the background of future climate change will be studied. Finally， we try to explore the coping strategies and technical measures of water resources in Zoige Wetland to adapt to climate change.

Under the influence of climate warming， the flood risk of rivers in arid regions has increased significantly. In order to study the future flood risk of Fuyun County on the banks of the Irtysh River， this paper uses SRM to predict runoff in the upper reaches of Fuyun County， and couples the MIKE 11 and MIKE 21 FM models in Fuyun County to explore the flood risk of Fuyun County under future climate scenarios. In this study， the SRM model parameters of the runoff area were calibrated by using the measured data of three hydrological stations in the upper reaches of the Irtysh River， the measured snow area data and the temperature and precipitation data to calibrate the SRM model parameters of the runoff area， the DEM data and the measured river section data to construct the MIKE 11 hydrodynamic model of the evolution area， the MIKE 11 coupled MIKE 21 FM model in the oasis area by using the dem data， the measured river section data and the underlying surface roughness， and the three climate models of CMIP6 and two future climate change scenarios （SSP2-4.5， SSP5-8.5） data-driven model， which completed the simulation of future flood elements in Fuyun County， and finally made a flood risk zoning map. The results show that： （1） The flood risk prevention and control scope of Fuyun County in the Irtysh River Basin is mainly on the north bank of the river. The south side of the river is high and the north side is low， and the width of the river channel in three areas in the central and western regions of the county is significantly smaller than before， and the river runoff is prone to inundation when the river runoff increases. The simulation results of the coupled model show that from 2025 to 2065， the once-in-a-century flood under two different scenarios will be inundated on the north bank of the river. Among the inundation areas， more than 90% of the areas have a maximum water depth of more than 1 m， more than 60% of the areas have been inundated for more than half of the time， and more than 75% of the areas have reached the high-risk level. （2） The flood risk of the Irtysh River gradually decreases from southeast to northwest in the inundation area. The central part of the county is low-lying， the ground is mostly cement surface， the roughness is low， the inundation depth and flow rate are high， and the flood risk is high. There is a certain slope in Northwest China， the ground is mostly low trees， the roughness rate is high， and the depth and flow velocity of flood inundation gradually decrease from the river channel to the northwest， and the flood risk decreases accordingly. （3） The flood risk under the SSP5-8.5 scenario is more severe than that under the SSP2-4.5 scenario. Under the SSP5-8.5 scenario， there were 7.2% more high-risk areas than SSP2-4.5， and 7.7% fewer medium-risk areas than SSP2-4.5. The main difference between the two is reflected in the central part of the county， where the area is high-risk under the SSP5-8.5 scenario and medium-risk under the SSP2-4.5 scenario. The reason is that the maximum water depth in this area is 1-2 m in the SSP5-8.5 scenario and 0.5~1 m in the SSP2-4.5 scenario. The analysis of flood inundation elements shows that the average water depth of the inundation area under the SSP5-8.5 scenario is 0.19 m deeper than that of the SSP2-4.5 scenario， the average flow velocity is 0.49 m·s^-1， and the average duration is 0.20 days longer than that of the SSP2-4.5 scenario. The reason is that the runoff output of the SRM model under the SSP5-8.5 scenario is 15.77 m³·s^-1 more than that in the SSP2-4.5 scenario. This study provides a basis for flood control measures and has practical significance for the development planning and disaster prevention work of the county.

Variations in the characteristics of Arctic vortex and their impact on snowfall in mid- to high latitudes， especially extreme snowfall events， are of great significance for understanding extreme weather or climate events. This study used the climate system index dataset released by the Institute of Atmospheric Physics， Chinese Academy of Sciences， along with meteorological station observation data. Statistical methods such as trend analysis and correlation analysis were employed to analyze the variation characteristics of the polar vortex area and intensity， as well as the variation characteristics of snowfall amounts and days in the Songhua River Basin （SRB） from 1961 to 2021， thereby revealing the correlation between polar vortex indices and snowfall in the SRB. The results showed that： （1） The polar vortex characteristics changed significantly from 1961 to 2021. Specifically， the polar vortex area reduced remarkably， polar vortex intensity enhanced markedly， and polar vortex central intensity weakened considerably， at rates of -0.807·（10a）^-1， -33.291·（10a）^-1， and 5.576·（10a）^-1， respectively， while the polar vortex center location showed no significant change. （2） From 1961 to 2021， although the annual snowfall amounts and light snowfall amounts showed no significant trends， substantial changes were observed in annual snowfall days and snowfall amounts/days at various intensity levels across the SRB. Among them， annual snowfall days and light snowfall days decreased significantly， while the amounts and days of moderate/heavy snowfall increased significantly. （3） Except for light snowfall amounts， which had no significant correlation with the polar vortex， variations in polar vortex central intensity， polar vortex intensity， and polar vortex area all showed significant correlations with snowfall indicators in the SRB. The weakening of the polar vortex central intensity and the strengthening of the polar vortex are the main influencing factors leading to the increases in total snowfall， as well as the amounts and days of moderate/heavy snowfall in the SRB.

Glazed hollow bead thermal insulation concrete （GHBC） exhibits excellent thermal insulation and frost resistance performance. To explore the characteristics of long-term mechanical performance degradation of GHBC as a self-insulating material after freeze-thaw damage， comprehensive analyses were conducted after 0 to 60 freeze-thaw cycles， including surface morphology observations， uniaxial compression tests， splitting tensile tests， graded compression creep tests， and scanning electron microscopic （SEM） analyses. The results indicated that with increasing freeze-thaw cycles， surface spalling and pitting corrosion of the concrete intensified， apparent porosity increased， and pore size expanded. After 0， 20， 40， and 60 freeze-thaw cycles， the total apparent porosity of GHBC was 8.32%， 12.83%， 14.28%， and 15.21%， respectively， while that of normal concrete （NC） was 9.05%， 11.62%， 13.39%， and 20.78%， respectively. After 60 cycles， the compressive strength and tensile strength of NC decreased by 22.87% and 23.53%， respectively， while those of GHBC decreased by 20.69% and 21.67%， demonstrating the beneficial effect of glazed hollow beads in enhancing concrete’s resistance to freeze-thaw damage. GHBC creep test results indicated that with increasing freeze-thaw cycles and stress levels， creep strain and rate continuously increased， leading to continuous performance degradation until failure at critical stress. After 60 freeze-thaw cycles， creep strength decreased by 20.19%， and total creep duration was reduced by 0.33 hours. The test data were well fitted by the Burgers model. Comparison of microscopic morphology between the two types of concrete revealed that after freeze-thaw cycles， internal damage worsened， porosity increased， and microcracks gradually connected， cement matrix structure loosened， ultimately resulting in the loss of load-bearing capacity. The unique closed-cell honeycomb structure of glazed hollow beads effectively released frost heave forces during the initial stage of freeze-thaw damage， providing an internal curing effect and maintaining macroscopic stability. However， with increasing numbers of freeze-thaw cycles， this closed-cell structure failed， and the interfacial bonding strength between the cement matrix and glazed hollow beads decreased， leading to a sharp decline in the mechanical strength. This study provides valuable references for the application of GHBC in cold-region engineering projects.

The Tianshan Mountains are the most extensive in the global arid zone， with glaciers developing at high altitudes. The glacial meltwater of the Tianshan Mountains provides valuable freshwater resources for the ecological and socio-economic development of downstream oases. Significant warming has intensified the ablation of Tianshan glaciers， altering their morphology and profoundly changing the regional water allocation. Therefore， quantitative assessment of glacier changes in the Tianshan region was critical. In this paper， focusing on all glaciers in the Tianshan region， we simulated the glacier mass balance and glacier runoff by driving a monthly-scale mass balance model using temperature and precipitation data from ERA5. At the same time， the glacier area data of the Tianshan region from two glacier inventories and the mass balance results from ASTER were used to calibrate and validate the model parameters of individual glaciers. The results showed that the glacier mass balance in the Tianshan region was in a state of deficit from 1961 to 2020， with a multi-year average value of -0.36 m w.e.·a^-1. With 1990 as the boundary， the average annual glacier mass balance after 1990 was -0.43 m w.e.·a^-1， which was 0.15 m w.e.·a^-1 less than before 1990. The Tarim Basin had the most minor glacier mass loss due to the lowest mean annual temperature at the basin scale. In contrast， the Turpan-Hami Basin had the most severe loss of glacier mass balance due to the highest mean annual temperature and lowest annual precipitation. Regarding spatial changes in the glacier mass balance， most areas of the Tianshan region were below 0 m w.e.·a^-1， i.e.， most of the Tianshan region was in a state of mass deficit in the past. However， glacier mass accumulation and smaller deficits were concentrated in the western and central parts of the Tianshan region， while the eastern part faced more severe deficits. Glacier runoff in the Tianshan region increased throughout the study period， with a multi-year average value of 58.86×10⁸ m³. However， driven by a higher mass deficit， resulting in an increase in the average annual glacier runoff after 1990 by 5.91×10⁸ m³ （10.58%）. Among the four basins， the Tarim Basin had the largest glacier runoff， while the Turpan-Hami Basin had the smallest glacier runoff due to the relative minimum of glaciers. Sensitivity analysis of glacier changes in the Tianshan region found that for every 0.5 ℃ increase in temperature， the glacier mass balance decreased by an average of 0.16 m w.e.·a^-1. In contrast， for every 10% increase in precipitation， the glacier mass balance increased by an average of 0.03 m w.e.·a^-1. Although the climate of the Tianshan region showed a warming and humidification trend， a comprehensive analysis of the value of changes in temperature and precipitation revealed that the effect of increasing temperature on glacier change was significantly more significant than that of increasing precipitation. Finally， the effect of atmospheric circulation transition on the glacier mass balance in the past 60 years was discussed. It was found that the Tianshan glacier mass balance was mainly controlled by high-altitude cyclones before 1990， with the adiabatic rise of the air and the decrease of the surface temperature， which led to a relatively small deficit. After 1990， the control of high-altitude anticyclonic circulation exacerbated the adiabatic warming of the sinking airflow， resulting in a sustained and larger deficit of glacier mass in the Tianshan region. By calibrating and validating the parameters of a single glacier and accurately modelling the glacier mass balance and runoff across the entire Tianshan region， we not only deepened our understanding of the overall characteristics of glacier changes in the Tianshan region but also provided methodological references for regional water resource management and future prediction studies.

The cold region of northwest China is covered with a large area of loess layer. The structure of loess is loose and the porosity is large. Moreover， due to the influence of periodic freeze-thaw cycles， the loess subgrade is prone to frost heave and thaw settlement damage， which seriously affects the serviceability of road engineering in similar areas. In order to reduce the freeze-thaw disease of loess， the commonly used prevention and control method is to use cement and lime modified loess as roadbed filler. However， this improvement is not only costly but also not conducive to the sustainable development of the environment. The current green and economical and effective improvement methods are still insufficient， and related research is urgently needed. In recent years， the use of biopolymers to improve soil has become a research hotspot in the field of rock and soil improvement because of its natural， environmentally friendly， easy to obtain and cheap. Biopolymers are environmentally friendly materials with high yield， so they have broad application prospects in soil improvement. Among them， xanthan gum and guar gum are the most widely used in engineering， so we try to use biopolymer to improve the loess in the northwest cold region. In order to explore the freeze-thaw characteristics of biopolymer modified loess， the most representative xanthan gum and guar gum in biopolymer were selected to improve loess respectively， and the indoor freeze-thaw cycle test combined with electron microscope scanning test was carried out to study and analyze the loess improved by xanthan gum and guar gum. The results show that： （1） Both xanthan gum and guar gum modified loess can reduce the temperature fluctuation and temperature difference during the freeze-thaw cycle， and slow down the rate of temperature change. The test results show that the temperature control effect of modified loess is the best when 1.5% xanthan gum and 2.0% guar gum are added alone， and the temperature control effect of xanthan gum modified loess is better than that of guar gum modified loess. （2） After adding xanthan gum and guar gum， it can effectively reduce the water supplement and water migration of the improved loess， and alleviate the water redistribution caused by the freeze-thaw cycle. Among them， single-doped 1.5% xanthan gum and single-doped 0.5% guar gum have the best control effect on soil moisture. The water migration of the modified loess decreased by 91% and 75%， respectively， indicating that guar gum can achieve the best improvement effect at a smaller dosage. （3） Both xanthan gum and guar gum can inhibit the frost heave and thaw settlement deformation of loess， thereby reducing the frost heaving ratio and thaw settlement coefficient during the freeze-thaw cycle. Among them， 0.5% xanthan gum and 0.5% guar gum alone have the best effect， reducing the average frost heaving ratio and the average thaw settlement coefficient by 21.4%， 14.3% and 40%， 60%， respectively. （4） Biopolymer not only improves the microscopic pore structure of loess， but also enhances the anti-deformation ability of loess by means of cementation and encapsulation. Both xanthan gum and guar gum can improve the water and heat transfer and pore structure of loess， thereby reducing the frost heave and thaw settlement deformation of the improved loess. Combined with the improvement effect of two biopolymers on soil temperature， moisture and deformation， the results show that the improvement effect of xanthan gum is better than that of guar gum. The above research results can provide reference for the prevention and control of loess freeze-thaw diseases and loess improvement research in the cold region of Northwest China.

The western Sichuan region is rich in mineral resources and is one of the areas with the most abundant resources of hard-rock lithium ores in China. Most mines in this region are located in seasonally frozen soil zones of alpine regions， characterized by large temperature fluctuations， intense rainfall， and high annual evaporation. The ecological and geological environment in the region is fragile， making the balance between resource development and environmental protection a major challenge. Open-pit mining exposes slope rocks to intense evaporation and significant temperature fluctuations over prolonged periods， creating conditions for dry-wet and freeze-thaw cycles. These cycles alter the internal pore structure and the permeability of rocks， further affecting slope stability and groundwater systems. Therefore， investigating the evolution of rock pore structure and permeability under different environmental conditions is critical. This study selected slate samples from an open-pit mine slope in the alpine region of western Sichuan. The samples underwent cyclic tests under three conditions， including dry-wet cycles， freeze-thaw cycles in air， and freeze-thaw cycles in water. Additionally， multiple experimental techniques were employed， including nuclear magnetic resonance （NMR） testing， permeability testing， and scanning electron microscopy （SEM）. NMR could nondestructively detect the porosity and pore size distribution of samples under different numbers of cycles and different working conditions. Permeability tests could directly measure changes in permeability， thereby investigating the influence of the number of cycles on the permeability of samples. SEM was used to observe microstructural changes， such as internal cracks and pores of the samples. To analyze and reveal the variation patterns among the number of cycles， porosity， and permeability under different working conditions， a damage variable based on porosity was introduced. The results showed that the porosity of slate samples gradually increased with the number of cycles under all conditions. After 40 cycles， porosity increased from 0.28% to 0.33% （dry-wet cycles）， 0.64% （freeze-thaw cycles in air）， and 0.66% （freeze-thaw cycles in water）， indicating that freeze-thaw cycles had a significant influence on the increase in porosity， with an especially pronounced influence on the internal small pore structure of the slate samples. Compared with freeze-thaw cycles in air， freeze-thaw cycles in water more easily induced the formation of microcracks. This was because the continuously supplied external water during freeze-thaw cycles promoted an increase in rock porosity and the formation of new cracks. Meanwhile， the permeability of the rock samples increased gradually with the number of cycles. After 40 cycles， permeability increased from 2.7×10^-3 mD （1 mD=0.987×10^-15 m²） to 2.9×10^-3 mD （dry-wet cycles）， 4.2×10^-3 mD （freeze-thaw cycles in air）， and 6.4×10^-3 mD （freeze-thaw cycles in water）， indicating that freeze-thaw cycles had a greater influence on permeability than dry-wet cycles. Permeability and damage variables exhibited a nonlinear positive correlation. However， under the three different working conditions， the R² between permeability and damage variable varied slightly， with the highest R² for freeze-thaw cycles in air， followed by those of freeze-thaw cycles in water and dry-wet cycles. This study provides practical engineering guidance for future mining activities and offers a scientific basis and theoretical support to assess slope stability and ecological environmental impact in the open-pit mines of alpine regions.

Microencapsulated phase change materials （MPCM） exhibit excellent temperature regulation capabilities. Their integration into grouting materials for surrounding rock reinforcement can effectively alleviate freezing damage of tunnels. Due to periodic and drastic environmental temperature fluctuations， tunnels in cold regions are prone to freeze-thaw damage including water leakage， ice formation， and cracking during operation. The freezing of groundwater is a prerequisite for these damages to occur. The use of grouting materials to reinforce the surrounding rock layers has been proven to effectively reduce groundwater infiltration and mitigate freeze-thaw damage in tunnel projects. However， conventional cement-based grouting materials demonstrate limited durability under freeze-thaw conditions， highlighting the need for the development of new grouting materials to control surrounding rock heave in tunnels. Phase change materials （PCM）， with their thermal energy storage and temperature regulation capabilities， have attracted considerable attention. MPCMs demonstrate excellent dispersibility and compatibility in cement-based materials， offering a novel approach to enhancing the freeze-thaw resistance of grouting materials. However， incorporating MPCM significantly deteriorates the workability and mechanical properties of cement-based materials. Therefore， it is essential to optimize the MPCM dosage to prevent adverse effects on material performance， offering valuable insights for freeze-thaw damage prevention in cold-region tunnels. Current research on MPCM predominantly focuses on concrete structures， whereas grouting materials require specific performance characteristics， including fluidity， bleeding rate， setting time， and gelation rate. To address these issues， a four-factor， four-level orthogonal experiment was conducted to systematically investigate the effects of water-to-binder ratio， MPCM dosage， silica fume dosage， and accelerator content on the fluidity， bleeding rate， setting time， compressive strength， flexural strength， and freeze-thaw resistance of composite cement-based grouting materials. Range analysis was used to assess the effect of each factor on material performance， and a multiple linear regression model was established to determine the optimal mix ratio for achieving superior workability and mechanical properties. This research could establish an experimental basis for the preparation and application of MPCM-based cementitious grouting materials with dual functionality in thermal insulation and load-bearing capacity. The experimental results showed that： （1） as the water-to-binder ratio increased from 0.6 to 0.9， the fluidity of the grouting material improved by 87.25%. When the silica fume content was 15%， the bleeding rate decreased by 91.07%， significantly improving the slurry stability. With 1.5% accelerator content， the initial and final setting times were shortened by 22.35% and 27.55%， respectively. The incorporation of MPCM negatively affected the workability of the material. A 15% MPCM dosage resulted in a 30.86% decrease in fluidity， a 57.25% increase in bleeding， and a 24% extension in setting time， collectively compromising the material’s injectability. （2） Prior to freeze-thaw cycling， increasing the water-to-binder ratio and MPCM content significantly reduced the compressive and flexural strengths， with maximum reductions of 34.10% and 41.67%， respectively. The compressive and flexural strengths peaked with 10% silica fume content， showing increases of 27.81% and 41.87%， respectively， compared to the non-silica fume group. The accelerator contributed to strength enhancement only at the 7-day curing period. After 100 freeze-thaw cycles， the optimal freeze-thaw resistance was observed in the group with 10% MPCM content， with a compressive strength to 28-day strength ratio reaching 0.93—representing an increase of 86.02% compared to the non-MPCM group. （3） MPCM particles formed strong interfacial bonds with the surrounding binder materials， promoting the formation of dense hydration products. However， numerous small-sized MPCM particles tended to aggregate， increasing porosity. The thermal regulation capability of MPCM helped preserve the structural integrity of the hydration gel under freeze-thaw cycles， thereby enhancing the freeze-thaw resistance. （4） The optimal comprehensive performance of the grouting material was achieved with a water-to-binder ratio of 0.7， 10% silica fume， and 1.5% accelerator content. The inclusion of MPCM in the range of 0%~15% ensured compliance with required standards for material performance. These findings provide scientific evidence and practical guidance for the prevention of freeze-thaw damage in cold-region tunnels.

The alpine mountainous regions at medium and low latitudes are abundant in freshwater resources， which are vital for ensuring water supply to downstream areas. The loose sediments in the seasonally frozen soil regions serve as vital channels connecting the mountains to rivers. The interplay between groundwater and surface water significantly affects the availability of water resources and the stability of ecosystems in these regions. To investigate the interaction mechanism between groundwater and surface water in the seasonally frozen soil region of an alpine watershed， this paper took the seasonally frozen soil region of the Hulugou catchment in the Qilian Mountains as the research object. Based on the hydrogeological conditions and groundwater level monitoring data of the region， a three-dimensional groundwater flow numerical model was constructed using GMS software to simulate and analyze groundwater-surface water exchanges under seasonal freeze-thaw conditions. The results showed that： （1） During the cold season （January to March， October to December）， the frozen state of the seasonally frozen layer hindered the water supply to the tributary streams. However， due to its discontinuous distribution， there were still some unfrozen areas under the riverbed of the tributaries， allowing groundwater to contribute to streamflow in the east and west tributaries， with total conversion amounts of 4 927 m³ and 4 796 m³， respectively. These conversion amounts were positively correlated with the hydraulic gradient between recharge and discharge zones of the alluvial-proluvial porous aquifer. （2） During the warm season （April to September）， tributary streams received more water from rainfall and snowmelt， and the interaction shifted to surface water recharging groundwater， with total conversion amounts of 120 060 m³ and 141 208 m³， respectively. （3） During the thawed period， the seasonally frozen soil layer had completely thawed， and the alluvial-proluvial porous aquifers exhibited strong hydraulic conductivity and water storage capacity. The interaction between groundwater and surface water was characterized by stream water in the east and west tributaries recharging groundwater， with total conversion amounts of 505 283 m³ and 889 461 m³， respectively. （4） During the refreezing period， with the seasonally frozen soil layer gradually freezing and precipitation events being relatively sparse， the water replenishment to the east and west tributaries decreased. The interaction between groundwater and surface water in the east and west tributaries was characterized by groundwater discharging into surface water， with total conversion amounts of 272 261 m³ and 100 394 m³， respectively. Additionally， the interaction between groundwater and surface water in the mainstream throughout the hydrological year was characterized by groundwater discharging to surface water， with the total contribution amount and ratio of 9 235 476 m³ and 70.84%， respectively. Moreover， the contribution amount and contribution ratio of groundwater varied with the seasons. Compared with the other three periods， groundwater contribution was higher during the thawed period， although its proportion was lower （62%）. However， the accuracy of this study in examining the spatiotemporal scales of groundwater and surface water interaction processes in seasonally frozen soil regions remained limited. Throughout the year， groundwater remained the primary contributor to streamflow at the catchment outlet， with seasonal variations in contribution volume and proportion. Compared to the cold season （90.12%）， the warm season had a higher groundwater contribution volume but a lower proportion （65.76%）. The research results provide a theoretical basis for studying the runoff formation mechanism in alpine mountainous areas and its response to climate change. They have important practical significance for the scientific management， rational development and utilization of water resources in cold regions， and sustainable socio-economic development.