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.
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.
Antarctic continent is in the southernmost part of the earth. The climate conditions there is special， and has the largest glacier in the world. Nowadays， more evidences show that Antarctic climate change plays an important role on global climate change. Therefore， Antarctic meteorological monitoring is of great significance to the study of global climate change. In recent years， countries have paid much more attention to the monitoring of Antarctic meteorology， and there are many automatic weather stations established in the Antarctic especially in the inland area. For the harsh climate of Antarctic continent and long-term unattended running conditions of the stations， it has high requirements of the structural strength and stability of the meteorological tower. In this paper， the structural strength of meteorological tower and its influence on wind speed measurement are studied. Guyed mast structure， the structure of the meteorological tower， is sensitive to wind. Unfortunately， Antarctic continent has the strongest wind on earth. The high wind-speed in the Antarctic region would cause the tower to vibrate violently. Under long-term dynamic load， the tower may have serious wind-induced fatigue damage， which may lead a shortened life of the tower. So we have to analyze the wind-induced fatigue under cyclic wind loads. The extreme wind in Antarctic continent may break down the meteorological tower， rendering it inoperable， so analysis of the tower’s buckling stability is also necessary. Base on the concurrence of solid and fluid， fluid-solid coupling analysis is a good method for the simulation in this paper. On the one hand， the strength of the meteorological tower can be discussed in the actual size， and on the other hand， this method is more suitable for long-term dynamic load simulation. Using the 24-hour meteorological data of the larger wind day of the Antarctic Taishan Station on July 17， 2017， the fluid-solid coupling analysis was carried out. In the case of a calculated scale factor of 20， the minimum safety factor for one-month circulation is still 1.065 by using rain-flow method， which indicates that the current structure of the meteorological tower has a good fatigue life. Through the buckling stability analysis， it is found that the minimum safety factor is still 3.8016 under the wind-speed of 50 m·s-1， which indicates that the meteorological tower can remain stable in the Antarctic. Wind speed measurement is an important work of the meteorological tower. However， the structure of the tower would affect the measurement of wind speed. In order to ensure the accuracy of the wind speed， we should analyze how the structure of the tower affects the wind speed measurement. The working conditions of the meteorological tower under different wind-speed are simulated， and the maximum average deviation from the original wind speed is only 1.37%. It shows that the structure of the meteorological tower has little influence on the measurement data of the wind speed sensor， which ensures the reliability of the Antarctic meteorological data monitored by the meteorological tower. The result of the analysis prove that the structure of the meteorological tower has a reliable structure strength and can provide a reliable data of Antarctic wind-speed.
Iron （Fe） is an important marine micronutrient， which is considered as one of the key factors affecting the growth of marine phytoplankton and carbon output. The Southern Ocean accounts for 20% of the global ocean area， is the world’s largest “high nutrient， low chlorophyll” sea area， playing an irreplaceable role in global biogeochemical processes. Due to perennial iron deficiency， macronutrients （such as nitrogen， phosphorus， and silica） in the Southern Ocean are high but primary productivity is relatively low. Therefore， new bioactive iron sources can alleviate the limitation of iron deficiency in the Southern Ocean， thus improving marine productivity， promoting the absorption of atmospheric CO2 and indirectly affecting global climate change. On the basis of summarizing the research progress on aerosol iron over the Southern Ocean and the Antarctic in recent years， this article focuses on the following parts： （1） Discuss the chemical forms， the concentration distribution of atmospheric aerosol iron， fractional iron solubility and the factors affecting solubility. Total iron can be divided into bioactive iron and insoluble iron， and bioactive iron includes two forms： soluble iron and unstable iron. During field observations， the concentration of atmospheric aerosol iron ranged from 0.1 to 150 ng·m-3. The mass concentration of total iron has obvious seasonal variations， with the peak in austral summer （mainly in January and February）， and the lowest in austral winter. The main oxidation states of iron include the Fe（II） and Fe（III）， which have significant concentration differences and are affected by seasonal variation. The fractional iron solubility ranges from 0.01% to 90%， which is affected by the atmospheric aging process （includes acid dissolution， organic complexation， photo-reductive dissolution and cloud processing） and the characteristics of aerosol iron （such as particle size， specific surface area） and air mass sources. （2） Summarize sources of iron in aerosols， including mineral dust sources， anthropogenic emissions （biomass burning and fossil fuel burning）， and local sources in the Antarctic. Among them， mineral dust sources are the main source of iron in the atmosphere， providing natural iron nutrients for the Southern Ocean， and contributing up to （33±15）% to the annual net production of phytoplankton communities in the Southern Ocean. Compared with mineral dust iron， anthropogenic aerosol iron is the more important source for dissolved iron， due to its high solubility and is thought to be more bioavailable. With the intensification of human activities and the development of industry， the contribution of anthropogenic emissions of atmospheric dissolved iron in the Southern Ocean is becoming increasingly important. With the accelerated melting of sea ice leading to the expansion of the open sea ice-free area， the dust iron source from the Antarctic continent needs more attention. （3） Explore the deposition flux of atmospheric aerosol iron and evaluate the response of the Southern Ocean to the atmospheric deposition process. The atmospheric deposition process includes dry and wet deposition and the range of the total iron deposition flux is 1.31×10-6~297.33×10-6 g·m-2·a-l. The feedback of the Southern Ocean to atmospheric deposition of aerosol iron is quite sensitive， experiments such as “iron fertilization” confirmed that the change of soluble iron significantly affected the growth of marine phytoplankton， and then affected the annual net production of phytoplankton communities. The significant increase of soluble iron in aerosols caused by the Australian wildfires and stimulated phytoplankton rapid growth in the ocean， resulting in the algal bloom phenomenon. In addition， this paper also puts forward some suggestions based on the current research status of aerosol iron over the Southern Ocean and the Antarctic， in order to provide a basic reference for further research on atmospheric aerosol iron over the Southern Ocean and the Antarctic in the future.
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.
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 （Tmax） and minimum temperature （Tmin） 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 Tmax events occurring with and without the influence of human activities was 3.67% and 0.012%， respectively. The contribution of human activities to extreme Tmax events in summer 2022 was estimated to be 1.26 ℃ （90% CI： 0.86~1.68 ℃）. The probability of extreme Tmin events occurring with and without human activities is 23.5% and 0， respectively. The contribution of human activities to extreme Tmin 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 Tmax and Tmin events similar to those in 2022 occurring on the Qinghai-Xizang Plateau in the future is increasing.
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.
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.
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.
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.
In order to study the freezing characteristics of soil under different temperature modes， the unidirectional freezing test of silty clay in Changchun area was carried out by using the freezing test device. By changing the temperature and temperature change rate of the roof of the test device， the temperature change of the soil during the test， the water content change of the soil before and after the test， the cold structure and vertical frost heave displacement of the sample after the test were studied and analyzed. The test results show that the soil temperature change is roughly divided into four stages： sudden drop， rebound or slow drop， continuous cooling， constant. At the same cooling rate， the greater the temperature gradient of the roof and floor， the greater the temperature recovery in the second stage； When the temperature gradient of the roof and floor is the same， the greater the cooling rate， the smaller the temperature recovery in the second stage. After the test， reticular cracks appeared on the outer surface of the soil and widened along the depth direction. The width of the reticular structure was proportional to the temperature gradient. There is obvious water crystallization inside the soil， and the continuous segregated ice wraps the soil to form a honeycomb-like structure， in which there is a certain amount of unfrozen water visible to the naked eye， and the smaller the cooling rate， the less the unfrozen water content visible to the naked eye. The water content of the soil near the temperature control roof （cold end） increases significantly， and the water content of the soil near the temperature control floor （warm end） decreases or remains basically unchanged， and the cooling rate is the same， The greater the temperature gradient， the more obvious the increase of soil moisture content near the cold end. At the same freezing temperature， the lower the cooling rate， the greater the water content increment near the cold end. The vertical frost heave of the soil is proportional to the temperature gradient. Under the condition of 30 min cooling time， the cold end temperature decreases from 0 °C to -15 °C， and the frost heave increases greatly. When the cooling time is 60 min， the frost heave in the temperature range of -10~-15 °C has the largest change trend.
Earthquake-induced liquefaction occurs frequently in frozen soil regions. Taking the earthquake records in China as an example， the earthquake in Bachu County， Xinjiang in 2003， the Ms7.1 earthquake in Yushu， Qinghai in 2010， the Mw6.6 Akto earthquake in the northwest Pamir Plateau in 2016， and the Menyuan 6.9 earthquake in Qinghai in 2022 all showed seismic liquefaction. At the same time， there are 5~10 m thick silt soil layer， fine sandy soil layer， medium-coarse sandy soil layer and other soil layers in the alluvial areas in the eastern part of the river valley around the Qinghai-Xizang Plateau and some debris flow accumulation areas in the middle and western ends of the Qinghai-Xizang Plateau. The perennial saturated area is also in the high-incidence area of earthquakes， and the possibility of liquefaction damage is extremely high， which needs urgent attention from researchers. The influence of overlying frozen soil on sand liquefaction characteristics is complex. The soil temperature， moisture content， confining pressure， loading frequency and the coupling of various factors will affect the dynamic performance of frozen soil. Freeze-thaw cycles， the content and type of fine-grained sand， poor drainage before freezing and other factors will affect the liquefaction resistance of sandy soil. In order to study the seismic liquefaction characteristics of sandy soil covered with frozen soil layer and clarify the variation law of dynamic parameters of frozen soil and sandy soil under different seismic waves， a shear model box of soil freezing system was designed and shaking table test of seismic liquefaction characteristics of sandy soil covered by frozen soil layer was carried out. The variation of acceleration， pore water pressure， soil pressure， interlayer and top displacement of the model under different seismic waves was analyzed. The results show that under the condition of frozen soil coverage， the sandy soil layer will begin to liquefy locally from the bottom， and the liquefaction height will gradually increase with the increase of the peak value of the input ground motion. The variation law of acceleration amplification coefficient after liquefaction of sandy soil layer is consistent with that of frozen soil layer， which increases first and then decreases with the increase of peak value of input ground motion. However， the amplification effect of sandy soil layer on input seismic wave is greater than that of frozen soil layer， and different soil layers have different amplification sensitivity to ground motion. When the sandy soil layer is partially liquefied， the peak horizontal displacement increases with the increase of the height of the soil below the liquefaction surface. However， because the friction between the particles of the sandy soil layer above the liquefaction surface is higher than that of the liquefiable soil layer， the peak horizontal displacement will decrease abruptly after exceeding the liquefaction surface. The maximum vibration subsidence value at the top of the model soil reaches 5.16 mm. In addition， the seismic subsidence and slip phenomenon appear in the frozen soil layer. The upward migration of water caused by seismic liquefaction gathers at the frozen-sandy soil interface， which aggravates the slip of the frozen soil layer. The friction between the soil layers is reduced， and the sliding displacement is related to the degree of liquefaction. It reaches the maximum when the sandy soil layer is completely in the critical state of liquefaction. After the soil is completely liquefied， the slip value of the frozen soil layer relative to the sandy soil layer will decrease. Therefore， the seismic checking of the structure in the liquefiable site of the overlying frozen soil layer should focus on the frozen soil-sandy soil interface and the liquefaction height. This study can provide data support for the changes in mechanical behavior of soil in liquefiable sites overlying frozen soil layer.
The strength of frozen soil plays an important role in evaluating the stability and safety of structures in frozen soil areas. However， due to the complex four-phase medium system of frozen soil， there are no mature means to monitor the mechanical properties of soil in real time. Based on the piezoelectric ceramic test technology and the low-temperature triaxial test， the mechanical properties of the soil under different negative temperature conditions are quantitatively studied by taking the silty sand in a project site in northeast China as the object. The results show that with the decrease of temperature， the failure strength， elastic modulus and cohesion of soil show a trend of rapid growth first and then slow growth. At the same time， the time domain image of the piezoelectric signal received by the sensor is extended and expanded， and the main signal frequency range gradually moves to the high frequency direction. The energy of the piezoelectric signal is very sensitive to the change of soil strength. Based on the decomposition signal energy obtained by wavelet packet analysis， the strength strengthening index of silty sand is established， which can well reflect the relationship between negative temperature and soil strength. The research results can provide reference for the engineering application of piezoelectric ceramic testing technology.
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.
Soil organic carbon （SOC） in permafrost regions of the Northern Hemisphere is an important part of the global carbon pool and plays an important role in the global carbon balance process. With global climate change， forest fires occur frequently in mid-high latitudes permafrost regions， which induces rapid degradation of permafrost， leading to a large loss of SOC， and forming a positive feedback effect on climate warming. Therefore， it is of great significance to study the changes of SOC and carbon fraction in permafrost regions with varied fire severities for the management of SOC pool. In this paper， the burned area in 2009 in the permafrost area of Alongshan Town， Da Xing’anling Mountains was selected as the research object in 2023. The SOC content， density and fraction were analyzed at depths of 0~1 m at different fire severity sites by the adjacent sample plot comparison method. The results showed that： （1） In the unburned plots， with increasing soil depth， SOC content and density， free particulate organic carbon （fPOC）， occluded particulate organic carbon （oPOC） and particulate organic carbon （POC） contents decreased. Compared with 0~10 cm， the SOC content， SOC density， fPOC， oPOC and POC contents at depth of 90~100 cm decreased by 84.75%， 2.78%， 99.82%， 91.86% and 98.97%， respectively； the content of mineral-associated organic carbon （MAOC） increased by 830.93%. （2） Compared with the unburned plots， the SOC content and density at the lightly burned plots decreased by 9.78% and 9.30% at the depth of 0~1 m， respectively. The contents of fPOC， oPOC， POC and MAOC increased by 5.03%， 39.95%， 11.19% and 15.98%， respectively. The SOC content， SOC density， fPOC， POC and MAOC contents at the severely burned plots decreased by 65.11%， 68.48%， 72.53%， 54.29% and 81.81%， respectively. The content of oPOC increased by 30.84%. （3） The effects of fire severity， soil depth and their interaction on SOC content， density and its fractions contents were extremely significant. In conclusion， forest fire has a significant impact on SOC and its fractions， resulting in a large loss of SOC and its fractions， changing the distribution pattern of SOC pool， and reducing the quality and stability of soil carbon pool. The results of this study can provide basic data support for the post-fire soil carbon dynamics in the permafrost region of the Da Xing’anling Mountains.
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.
Terrestrial cosmogenic nuclide （TCN） surface exposure dating is the most mainstream and significant methods of determining the age of local or regional Quaternary glaciation. Intense geomorphologic processes often cause samples to be affected by pre-exposure or incomplete exposure， which leads to dating results that are not indicative of the true age of glaciation， and the dispersion of the chronological data can even be very high when their influence is large. Several statistical analyses of moraine exposure dating have been proposed by scholars to reduce their influence. However， the results are often highly variable， which have even become the source of controversy over the asynchronous temporal and spatial patterns of glacial evolution and its driving mechanism. What’s more， there is a lack of systematic review and assessment of these methods， both nationally and internationally. In this paper， we aim to review the existing analytical strategies and methods， as well as their possible limitations， and propose a better analytical method. The P-PDE method proposed in this paper is not only reliable， but also fulfils the requirements for establishing glacial evolution sequences on a millennial time scale. In addition， the summary of the strategies and methods of chronological data in this paper is also important for improving the reliability and accuracy of exposure dating for applications in other related fields.
