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.

Based on a review of existing studies and recent work， this paper collects and organizes research findings on glacier mass balance from 2013 to 2023. It summarizes the current methods and models commonly used in glacier mass balance research and reviews the status of such research in China. The results indicate the following： The commonly used methods for glacier mass balance research can be classified into three categories： traditional glaciological methods， geodetic imaging methods， and satellite gravity monitoring methods. Additionally， glacier balance models， which focus on the relationship between glacier mass balance （the algebraic sum of accumulation and ablation） and meteorological variables， have been developed. These models are based on energy balance equations and can be further divided into three subcategories： semi-empirical glacier balance models—degree-day models， energy-balance models， and coupled glacier flow and mass balance models， such as the Open Global Glacier Model （OGGM）. Under the influence of global warming， glaciers in China exhibit an overall negative mass balance trend with significant regional variations. Specifically： The No.12 Glacier in Laohugou， Qilian Mountains， experienced a severe mass deficit， with a cumulative loss of -71 760 mm w.e. between 1991 and 2020. The Kunlun Mountains initially showed relatively stable mass balance， but a negative trend has emerged in recent years. For example， glaciers in the eastern Malan Mountains lost -300 to -180 mm w.e. from 2000 to 2020. Glaciers in the Tianshan Mountains are significantly affected by temperature changes， showing a pronounced negative mass balance trend. For instance， glaciers in the Manas River basin lost -9 811.19 mm w.e. from 2000 to 2016， while the Urumqi Glacier No.1 lost -17 351.5 mm w.e. from 1956 to 2016. Glaciers in the Tanggula Mountains exhibit changes in mass balance similar to those in the Kunlun Mountains but with a more pronounced negative trend. Glaciers in the Dongkemadi River basin lost -7 550 mm w.e. from 1966 to 2015. In the Himalayas， glaciers show a slight negative mass balance. For example， glaciers in the Yamdrok Lake basin experienced a cumulative loss of -930 mm w.e. from 1987 to 2021. Glaciers in the Altai Mountains also exhibit a negative mass balance， with greater losses observed during 2000—2010 compared to the post-2010 period.

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.

In seasonally frozen ground region landslides are become a more common geological disaster， which has attracted widespread attention in the world. Whether the physical processes of snow ablation and soil freezing and thawing in seasonally frozen ground region， as opposed to the non-monsoon freezing zone， have an impact on landslides deserves further study. A giant loess landslide group （Galamput landslide group） occurred on May 9， 2002 in the Ili region of China provides an ideal case study. By using field survey， remote sensing image identification， meteorological data analysis and loess characteristic test， we attempt to explore the formation process and failure mode， and further reveal the instability mechanism of Galamput landslide group. The results show that the Garamput loess landslide group is composed of three landslides with a total volume of approximately 17.355 million m³. The formation and development of the landslide group was a multi-stage and multiple sliding failure process. The Galamput landslide was the coupling triggering result of early snowmelt and post rainstorm. The snowmelt infiltration and soil freeze-thaw cycle in spring played an important role in the evolution process of slope deformation. The rapid infiltration of extreme rainstorm was the ultimate triggering factor of the landslide. In addition， special slope structures and stratigraphic combinations provide a material structural basis for the occurrence of loess landslides. Combined with the slope deformation process we established a deformation failure model for loess slopes considering the effects of precipitation infiltration and freeze-thaw cycles， and proposed that the combination of static liquefaction on the slip surface and sliding liquefaction at the foot of the slope is an important mechanism inducing the occurrence of loess landslides. In the future， the risk of large-scale landslides in the Ten-zan’s seasonally frozen ground region is extremely high with climate warming. This study can provide a new perspective on the formation process and failure mechanism of loess landslides， and is of great significance for understanding the early warning and risk assessment of landslide disasters in seasonally frozen ground region.

The Svalbard Archipelago is one of the most climate-sensitive areas in the world. Affected by the Arctic amplification effect， most of glaciers there have been undergoing significant shrinkage. Previous studies indicated that mass loss of glaciers in Svalbard accelerated in the past decades， but the ice mass loss caused by surge-type glaciers in the region remains unclear. Based on the high-precision observations from ICESat-2 laser altimetry， this study utilizes an improved classification method to investigate the elevation changes of the Svalbard’s glacier during the period from March 2019 to June 2022. The results show that， from 2019 to 2022， the elevation change of glaciers in the Svalbard shows a declining trend， with an average elevation change rate of （-0.94±0.23） m·a^-1， corresponding to a volume change rate of （-31.62±7.73） km³·a^-1. Among them， the surging glaciers occupy about 22% of the area， with a volume change rate of -13.23 km³·a^-1， accounting for 42% of the total volume change in the glacial area. Therefore， changes in surging glaciers are one of the main factors leading to the whole ice volume reduction in the region. As the largest surging glacier in the Svalbard， Storisstraumen Glacier has expanded its surge area by about 284 km² in the past 20 years， with a volume change rate of -5.67 km³·a^-1， accounting for 18% of the total ice volume loss in the area. Further analysis suggests that the increase in temperature may play a dominant role in triggering the surging of Storisstraumen glacier. This study not only reveals the elevation change characteristics of glaciers in Svalbard during the span from 2019 to 2022， but also quantifies the contribution from surge-type glaciers to the total ice mass loss in Svalbard， which may provide a reference for deep understanding the varying elevation change of glaciers in the region.

In the water cycle， water bodies show different characteristics of stable hydrogen and oxygen isotopes （δ¹⁸O and δ²H） in different processes of evaporation， transport， convection， and condensation due to the influences of isotope fractionation. Therefore， δ¹⁸O and δ²H is widely used in the study of paleoclimate and modern hydrological processes. Previous studies mainly focused on the variations of precipitation stable isotopes in the low-altitude regions in the Lhasa River basin， a critical area for the studies of the progressing and evolution of monsoon and westerly wind systems. In contrast， studies on δ¹⁸O and δ²H data obtained from the alpine regions are largely lacking. In this study， we analyzed 347 event scale precipitation samples collected at three sampling sites in the Kuoqionggangri Glacier region from July 2020 to July 2023. The spatial and temporal variations of precipitation δ¹⁸O， the local meteoric water lines， the relationship between precipitation δ¹⁸O and meteorological factors， and the relationship between precipitation δ¹⁸O and convective activity are investigated to understand the influences of the Indian monsoon and westerly wind on the precipitation δ¹⁸O and δ²H in the Kuoqionggangri Glacier region at the source of the Lhasa River of the southern Qinghai-Xizang Plateau. Besides， the backward trajectory of water vapor was further demonstrated through correlation analysis and cluster analysis， so as to reveal sources of water vapor. The results showed that there was little difference in temperature， relative humidity， and precipitation among the three fixed points located in different altitudes in this study area from July 2020 to July 2023 （the glacier terminus （5 544.5 m a.s.l.）， the basin source （5 374.0 m a.s.l.） and the basin export （4 941.3 m a.s.l.））. In addition， the precipitation δ¹⁸O and local meteoric water lines were similar among these three sampling sites from July 2020 to August 2020. This suggested that the climate conditions remained relatively identical within the Kuoqionggangri glacier region. According to the above results， we put emphasis on data of the precipitation δ¹⁸O collected at the basin export from July 2020 to July 2023. The results revealed a two-stage pattern of changes in daily precipitation δ¹⁸O： a higher value before mid-June followed by a lower value. The monthly precipitation δ¹⁸O shows the highest value in June and the lowest value in September. The slope and intercept of the local meteoric water line during the monsoon period （8.12， 11.78） were obviously smaller than those during the non-monsoon period （8.79， 23.18）， indicating that the water vapor source of the precipitation during the monsoon period possessed a higher relative humidity compared with that during the non-monsoon period. The slope and intercept of the local meteoric water line around the year （8.27， 15.10） were more similar to those in the monsoon period. This phenomenon might be due to the large contribution of precipitation in the monsoon period around the year in this region. Monthly precipitation δ¹⁸O exhibited a significant dependence on temperature in the monsoon period. Specifically， the monthly precipitation δ¹⁸O and temperature are positively correlated. Daily precipitation δ¹⁸O were significantly dependent on precipitation amount around the year. Specifically， the daily precipitation δ¹⁸O and precipitation amount are negatively correlated. The convection activity taking place 1~6 days before the precipitation event would deplete the precipitation δ¹⁸O. This influence on the precipitation δ¹⁸O was mainly concentrated in the monsoon period. Results of the backward trajectory tracking analysis indicated that water vapor transported by the Indian monsoon contributed the most to the precipitation of the region throughout the year， which depleted the precipitation δ¹⁸O. This study preliminarily reveals the spatial and temporal variations of precipitation δ¹⁸O and its main influencing factors in the alpine mountains of the southern Qinghai-Xizang Plateau. Results of the current work can provide basic data for the study of water cycle in the alpine regions.

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.

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 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.

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.

The warming of the Qinghai-Xizang Plateau has led to glacier retreat， permafrost melting， and an increase of meteorological and derived disasters， capturing widespread attention across society. In recent years， the warming of the Qinghai-Xizang Plateau has intensified further. In 2022， the summer was the warmest since 1961， with the average summer maximum temperature （T_max） and minimum temperature （T_min） in the central and eastern Qinghai-Xizang Plateau being 2.37 ℃ and 2.51 ℃ higher than that during the period of 1961—1990. The attribution technique， combining model evaluation and reconstruction， was employed to detect and analyze the anthropogenic influence on the extreme temperature events of the summer 2022 over the Qinghai-Xizang Plateau， utilizing CMIP6 model simulation data. The results indicated that greenhouse gases emissions from human activities significantly heightened the probability of maximum temperature extreme events during the summer 2022 over the Qinghai-Xizang Plateau. The probability of extreme T_max events occurring with and without the influence of human activities was 3.67% and 0.012%， respectively. The contribution of human activities to extreme T_max events in summer 2022 was estimated to be 1.26 ℃ （90% CI： 0.86~1.68 ℃）. The probability of extreme T_min events occurring with and without human activities is 23.5% and 0， respectively. The contribution of human activities to extreme T_min events in summer 2022 was estimated to be 2.35 ℃ （90% CI： 1.89~2.81 ℃）. The CMIP6 model underestimated the observed temperature changes over the Qinghai-Xizang Plateau. The simulation deviation of the model is calibrated based on the attribution constraint method， and the projected summer maximum and minimum temperature over the Qinghai-Xizang Plateau are expected to continue to increase in the future under the medium emission SSP2-4.5 scenario of shared socioeconomic path. The risk of extreme T_max and T_min events similar to those in 2022 occurring on the Qinghai-Xizang Plateau in the future is increasing.

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.

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.

The warming and humidifying climate on the Qinghai-Xizang Plateau of China is causing permafrost degradation at a faster rate， which is affecting the stability of infrastructure such as highways and railways on it. To resolve this problem， thermosyphons have been widely applied to protect the degrading permafrost in Northeast China and the Qinghai-Xizang Plateau. The thermosyphon has the characteristic of active unidirectional cooling. Existing researches often use numerical simulation or borehole temperature measurement methods to analyze its cooling effect on permafrost foundations. With the development of geophysical exploration technology， ground penetrating radar （GPR） technology provides a new research method for frozen soil engineering， which can obtain continuous data without causing damage to structures. The section of the Qinghai-Xizang Highway from Tuotuo River to Tanggula Mountain Pass was selected as the research area， and GPR technology is used to study the cooling effect of thermosyphons. Based on the investigation of road problems， three typical road sections were selected， where double-sided and single-row vertical thermosyphons， single-sided and single row oblique thermosyphons， and adjacent non-thermosyphons were placed， respectivley. GPR technology was used to detect and analyze structural damage and underlying permafrost distribution. Meanwhile， combined with on-site investigations， the impact of different thermosyphon placement methods on the cooling effect of frozen soil embankment was evaluated. The results indicate that the cooling effect is as follows： double-sided and single row vertical thermosyphons have better cooling effect， followed by single-sided and single row oblique thermosyphons and non-thermosyphon. The distribution of the permafrost layer beneath the double-sided and single-row vertical thermosyphon embankment had good continuity， with an increase of 0.47 m in the upper limit of permafrost compared to the natural surface near the road， and the road structure was entire. The permafrost layer under the single-side and single-row inclined thermosyphon embankment had general continuity， and its permafrost table was close to that of the natural surface. There were areas where structures loosened and cracks happened in the embankment structure. The continuity of the permafrost layer under the non-thermosyphon embankment was lower， and the degradation of permafrost was significant， its permafrost table has degraded by 0.80 m compared to the natural surface. The embankment structure showed large areas of looseness and cracks， and there was water accumulation in some areas. Meanwhile， permafrost degradation can trigger road engineering damages. Comparison showed that the single-sided and single-row oblique thermosyphon embankment and the adjacent non-thermosyphon embankment with permafrost degradation showed loose embankment structures and developed some cracks， and were prone to uneven settlement， cracks， potholes， and other problems. GPR testing can effectively present the distribution of permafrost beneath roads and the characteristics of embankment structural damage. Furthermore， it can used to analyze the mechanism of road surface problems and to provide scientific basis for highway maintenance. Analysis shows thermosyphons can effectively slow down the degradation rate of permafrost， but different placement methods have a certain impact on the cooling effect， the single-sided layout of thermosyphon for high embankments does not cool the warming permafrost. Therefore， it is necessary to scientifically and reasonably carry out the correct design， standardized construction， and effective operation and maintenance of thermosyphon embankments based on the thermal state and structural characteristics of the roads. This can raise the permafrost table under the embankment and reduce or slow down engineering problems caused by permafrost degradation. This study has important practical significance for promoting thermosyphon to be widely used and for improving the serviceability of highways in permafrost regions.

Ice and snow tourism， as a unique form of tourism， not only has significant economic value but also exerts profound impacts on regional ecological environments and social cultures. Due to its unique geographical and climatic conditions， Northeast China has become an important destination for ice and snow tourism in China. On the one hand， ice and snow tourism has brought significant economic benefits to Northeast China. It has promoted local economic development， increased employment opportunities， and improved infrastructure. This influx of tourism-related activities has stimulated various sectors， creating a ripple effect that boosts the overall economy of the region. The economic gains have allowed for better services， enhanced public facilities， and an improved quality of life for the residents. On the other hand， ice and snow tourism faces several challenges， including ecological and environmental pressures as well as social and cultural impacts. Without effective management， these challenges can lead to environmental degradation， resource depletion， and cultural homogenization. The natural landscapes that attract tourists are at risk of being damaged by overuse， and the local culture may become diluted as it adapts to cater to tourists. Currently， the development of ice and snow tourism in Northeast China is also encountering several difficulties and bottlenecks. One major issue is the regional imbalance in tourism development. While some areas， particularly those along the coast， have advanced rapidly， inland areas lag behind， resulting in uneven distribution of tourism benefits. Another significant challenge is the lack of scale efficiency， which hampers the overall effectiveness of the tourism industry in the region. Many areas struggle with unstable resource development， where inconsistent investment and planning lead to sporadic growth and underutilization of tourism potential. These problems not only constrain the sustainable development of ice and snow tourism but also affect the overall competitiveness of the region’s tourism industry. To address these issues， this paper uses the three-stage super-efficiency SBM model to measure the efficiency of ice and snow tourism development in Northeast China. Combined with the pressure-state-response theory， the panel Tobit model is used to analyze the influencing factors of efficiency. The main conclusions are as follows： （1） Analyzing the temporal characteristics， the development efficiency of ice and snow tourism in Northeast China from 2015 to 2023 shows an overall fluctuating upward trend. However， the main cause of inefficiency is identified as scale efficiency. Despite the upward trend， the fluctuations indicate periods of both progress and setbacks， reflecting the complex dynamics of tourism development in the region. （2） From the perspective of spatial characteristics， the efficiency of ice and snow tourism development in Northeast China from 2015 to 2023 exhibits a spatial distribution pattern of “decreasing from coastal to inland areas”. This spatial gradient highlights significant regional disparities in tourism development. The formation of two major ice and snow tourism circles centered around Shenyang and Harbin underscores the concentration of tourism activities and resources in these areas. The average efficiency values follow a descending order from Liaoning Province， Jilin Province， Heilongjiang Province， to the eastern part of Inner Mongolia Autonomous Region. Most cities have not reached the ideal state， revealing prominent issues of regional imbalance and instability in the development of ice and snow tourism resources. （3） The results of the influencing factors calculation show that the development efficiency of ice and snow tourism in Northeast China is affected by various factors related to urban pressure， state， and response. Specifically， the pressure exerted by increasing tourist numbers and activities， the current state of tourism infrastructure and environmental conditions， and the response measures implemented by local governments and communities all play crucial roles. When developing the ice and snow tourism industry， it is essential to balance social pressures with ecological pressures. Strengthening social response mechanisms is vital to mitigate these pressures. This highlights the necessity of addressing regional disparities and promoting balanced development across different areas.

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

The 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.

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.

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.

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.

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.

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.

This study investigates the mechanical properties of silty soil in seasonally frozen regions， stabilized using lignin fibers in conjunction with microbially induced carbonate precipitation （MICP）. A series of experiments were conducted， including assessments of calcium carbonate production influenced by lignin fibers， unconfined compressive strength tests， direct shear tests， and scanning electron microscopy （SEM） analysis of lignin fiber-MICP stabilized samples subjected to freeze-thaw cycles. The results indicate a linear increase in calcium carbonate content with increasing fiber content， with the calcium carbonate content in the SF2M sample exhibiting a 426.6% increase compared to the SF0M sample. With an increase in freeze-thaw cycles， both the unconfined compressive strength and shear strength of all samples diminished， eventually stabilizing. Among the samples， the SF1.5M， containing 1.5% lignin fiber， demonstrated the highest resistance to freeze-thaw degradation. After 10 freeze-thaw cycles， its unconfined compressive strength decreased by only 45.9%， whereas the SF0M and SF0 samples showed reductions of 63.4% and 80.0%， respectively. Furthermore， after 10 freeze-thaw cycles under a normal stress of 400 kPa， the shear strength of the SF1.5M sample increased by 76.4% and 184% compared to the SF0M and SF0 samples， respectively. Cohesion in the SF1.5M sample also improved significantly， with increases of 46.5% and 126.0% over the SF0M and SF0 samples. At a fiber content of 1.5%， a denser cemented structure formed between soil particles， calcium carbonate crystals， and fibers， enhancing soil stabilization. However， when the fiber content reached 2.0%， calcium carbonate crystals intertwined with the fibers， forming aggregates that impeded the effective cementation between soil particles， thereby diminishing the stabilization effect. In conclusion， this research offers important data and theoretical guidance for soil reinforcement in cold regions， particularly under the influence of freeze-thaw cycles. The findings contribute to the understanding of soil stabilization mechanisms and provide practical insights for improving the mechanical properties of silty soils in seasonally frozen environments.

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.

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.

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 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.

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.

With the rapid advancement of China’s economy and accelerating urbanization， the proportion of subways in urban transportation networks is steadily increasing. The artificial ground freezing method is an essential construction technique for tunneling through soft， water-saturated soil layers. The frost heave-induced deformation of the ground surface resulting from this method may adversely affect adjacent existing engineering structures. In extreme scenarios， it could lead to significant economic losses and pose a threat to human safety. Therefore， considering the crucial factor of ground surface deformation caused by soil frost heave becomes imperative during the horizontal freezing construction of shallow buried tunnels. The investigation into the redistribution of the soil layer displacement field induced by artificial ground freezing and its resulting ground surface uplift deformation has garnered significant attention among scholars； however， certain limitations are present. To overcome the limitation of previous studies that overlook the spatial variability in frost heave ratio resulting from a non-uniform temperature field， the article proposes an innovative methodology for quantifying ground surface deformation induced by frost heave during underground tunnel construction. The proposed method integrates the principles of superposition and the theory of random media within the framework of thermo-elasticity mechanics， utilizing the concept of an equivalent thermal expansion coefficient. The presented approach was employed to calculate ground surface deformation induced by soil frost heave due to single-loop distribution freezing pipes， based on an engineering case study. The rationality and applicability of the presented method were demonstrated through a comparison with observed values. The calculation results obtained from this method demonstrate a markedly higher degree of agreement with the observed values compared to those achieved by conventional approaches and finite element method （FEM）. Conventional approaches typically assume a constant frost heave ratio and estimate stress and deformations using the principles of thick-walled cylinders. The FEM is based on the principles of “cold expansion and hot contraction” and employs thermal-mechanical coupling to simulate frost heave phenomena induced by artificial ground freezing. In contrast to the presented approach， the conventional model fails to consider the reduction in soil frost heave ratio near the outer side of a frozen soil wall due to higher temperatures， leading to an overestimation of computational results. Compared to FEM， the approach proposed in this study is more straightforward and practical， while also providing deeper insights into underlying mechanical principles. In addition， the investigation focused on the distribution of ground surface frost heave deformation induced by the artificial ground freezing， taking into account the influences of refrigerant medium temperature， burial depth of the tunnel center， and freezing front extension coefficient ε. The results indicate that as the refrigerant medium temperature decreases， there is a notable overall increase in ground surface deformation， with particularly pronounced effects observed above the center of the tunnel. The appropriate selection of coolant medium temperature is crucial for ensuring the safety and stability of adjacent existing structures. The central buried depth of the tunnel， to some extent， reflects the average embedment depth of freezing pipes and serves as a critical factor influencing ground surface frost heave deformation. With an increase in the burial depth of the tunnel， both the maximum deformation caused by ground frost heave and its influence range gradually diminish. The distribution of ground surface frost heave deformation is closely correlated with the depth of the tunnel center， which in turn governs the magnitude and extent of ground surface deformation. The maximum ground surface frost heave deformation and the affected area exhibit a slight increase as ε increases， although this increment is not significant. This study can provide reference for the application of artificial ground freezing technology in high-risk underground engineering projects.

Frozen soil is a critical type of porous medium that is widespread in high-latitude and high-altitude regions around the world. This soil type is characterized by the freezing of pore water in cold environments， which leads to significant changes in the soil’s particle structure and pore configuration. These alterations can compromise the structural integrity of the soil， potentially resulting in severe damage or even complete failure of soil-based engineering systems. As such， understanding the mechanical properties and deformation behaviors of frozen soil is crucial for the stability and safety of infrastructure in cold climates. The accurate modeling of temperature fields within frozen soils is essential， as these fields directly affect the soil’s deformation and mechanical properties. Heat conduction in frozen soil is complicated by phase transitions， particularly the conversion of liquid pore water to solid ice at temperatures below the freezing point. This phase transition introduces substantial nonlinearity and discontinuity into the heat conduction problem， which poses significant challenges for traditional modeling approaches. Conventional heat transfer models， which rely on continuity assumptions and local partial differential equations （PDEs）， frequently encounter computational singularities， leading to inaccuracies or instability in predictions. To address these challenges， this paper introduces an innovative numerical approach known as the Differential Operator of Near-Field Dynamics （PDDO）. PDDO is a sophisticated non-local operator derived from partial differential （PD） non-local theory and the orthogonality of PD functions. Unlike traditional local PDE methods， PDDO defines the local derivative of any order for a material point as a non-local integral expression within the local space or time domain. This transformation of partial differential equations into non-local integral forms effectively resolves the singularity issues associated with phase transitions， enhancing the accuracy and stability of numerical simulations. The research applies the PDDO method to develop a phase transition heat transfer model based on the enthalpy approach. This model is used to conduct detailed numerical simulations of heat conduction processes in one-dimensional and two-dimensional frozen soil scenarios. Various near-field ranges are systematically tested to identify the optimal range for achieving high precision in simulations. The results indicate that PDDO significantly outperforms traditional methods， providing more accurate and stable solutions to the nonlinearity and discontinuity challenges inherent in phase transition problems. Additionally， the study extends the application of PDDO to simulate heat conduction in two-dimensional phase change materials， successfully capturing temperature variations and phase transition behaviors. The accuracy of these simulations validates PDDO’s effectiveness in predicting temperature changes during phase transitions， demonstrating its robustness and applicability in handling complex material behaviors.Moreover， the paper investigates the freezing process in two-dimensional soil under various freezing temperatures. The simulations accurately capture the phase transition temperature and highlight the distinctive plateau characteristics of the phase transition temperature， which is critical for understanding soil behavior under freezing conditions. This aspect of the research underscores the reliability and practical applicability of the PDDO-based simulation method in predicting frozen soil behavior across a range of temperature conditions. In conclusion， the frozen soil heat conduction simulation method based on PDDO presented in this paper represents a significant advancement in the analysis and modeling of frozen soil and phase transition phenomena. This method offers both theoretical and practical improvements， providing a robust tool for accurately predicting the behavior of frozen soils in cold environments. By overcoming the limitations of conventional approaches， PDDO enhances the precision and stability of simulations， thereby improving the design， safety， and stability of engineering projects in challenging frozen soil conditions. The findings and advancements from this research are expected to make a substantial contribution to the development of more reliable and effective engineering solutions for managing and utilizing frozen soils， ultimately benefiting a range of applications from infrastructure development to environmental management in cold regions.

Under the influence of Huang-Huai cyclones， two heavy snowstorm events hit northeastern China on 7—9 and 21—23 November 2021， respectively. In search of monitoring indicators and improved forecasting techniques， this paper uses conventional observation data， FY-4A infrared cloud images， combined with the 0.25°×0.25° hourly ERA5 reanalysis data from the European Center or Medium-Range Weather Forecasts （ECMWF） to make a comparative analysis of the two snowfall events. The results show that： （1） in the former， the Huang-Huai cyclone moved northward alone， with the cyclone track more westerly， and stayed in northeastern China for a long time， with a wide range of heavy snowfall， and complex precipitation phases， such as rain， sleet， and snow； whereas， in the latter， the Huang-Huai cyclone merged with the Mongolian cyclone， with the cyclone track easterly， and stayed in northeastern China for a short time， and with a small extent intense snowfall， with pure snow as the primary precipitation phase. （2） The cloud evolution of the two cyclones both show a Shapiro-Keyser development model with the back-bent warm front and wrapping occlusion characteristics， with the former broad warm frontal cloud controlling eastern Inner Mongolia and northeastern China， causing widespread heavy snowfall， while the latter warm frontal cloud is in the eastern part of northeast China， resulting in a small range of heavy snowfall. Snowfall intensity is strongly correlated with the intensity and duration of mesoscale precipitation areas with reflectivity greater than 30 dBZ. （3） The water vapor and thermodynamic conditions of the two snowstorms are very different： the former is affected by the transport of water vapor from the periphery of tropical disturbances， with two water vapor channels transporting water vapor from the Sea of Japan， the Yellow Sea and the East China Sea， whereas the latter has only one water vapor channel transporting water vapor from the Sea of Japan， and the water vapor convergence， warm advection and frontogenesis of the former are stronger than the latter， and thus there is stronger precipitation than that of the latter. （4） The latter and the former in the western part of northeastern China of the whole layer of temperature has been below 0 ℃， to mainly snowfall， while the surface temperature of the 7—9 snowstorm event of eastern Jilin and eastern Liaoning is higher before the cold air affected， for the rainfall， some areas of the surface temperature is below 0 ℃， but there is a warm layer between 900~800 hPa， the ice crystals melt， causing sleet and freezing rain， the precipitation type turns to snow after the main force of cold air comes down. In this paper， two Huang-Huai cyclone snowstorm processes were compared， and the reanalysis data was used， which was slightly insufficient. The next step is to use high-resolution numerical simulation data for detailed analysis. For the individual cases of phase transition of rain and snow， there are often large errors in the forecast. For example， due to the incorrect prediction of the phase state of precipitation in some areas of Liaoning before “11·7” process， the forecast of the snowfall area is much farther north than the actual situation， and the heavy snow in Anshan is misestimated. Therefore， it is necessary to pay attention to the water vapor and thermal dynamic conditions in the short term forecast of snowstorm to see whether it is conducive to the formation of the mesoscale rainfall region. In addition， do not only focus on the 0 ℃ line on the ground， but also consider the warm layer at the lower level. In the future， we will make statistical study on the cyclones and snowstorms in Huang-Huai so as to provide reliable reference for the forecast of this kind of precipitation.