Snow avalanches are frequent and destructive mountain hazards in snow-covered mountains. Accurate and timely information on avalanche occurrence is a key factor for avalanche warning, crisis management and avalanche documentation. There are two monitering means on snow avalanche: field-based approaches and remote sensing. Of the field-based approaches, three methods can be taking: snow test, long-term site observation, as well as seismic and infrasound detections. However, field-based approaches fail in creating continuous datasets on avalanche activity on inaccessible regions. The use of remote sensing instruments in avalanche science has large potential to help fill these data gaps. In this paper, we review past and current avalanche detection using ground based, air-, and space borne remote sensing data from optical, laser, and radar sensors, and analyze their advantages and disadvantages. Being a young and evolving scientific field, automatic detection and algorithm, remote sensing of large spatial avalanches is still a challenge the researchers have to be faced. Which platform-sensor combination should be deployed depends largely on the spatio-temporal scale of the monitoring purpose. Both optical time-lapse cameras and terrestrial LiDAR scanners are recommend deploying for continuous slope-scale monitoring. For regional-scale monitoring of avalanche activity, optical- and radar satellite data are the preferred technology. The Southeastern of Qinghai-Xizang (Tibet) Plateau, with a wet snow avalanche region and abundant snowfall in spring, it is recommend that radar satellites, such as RS-2U or Sentinel-1 to monitor the avalanche in this region, and validated by Very High Resolution (VHR) optical remote sensing imagery like SPOT6/7 or QuickBird under clear conditions. The Doxiongla Tunnel is an ideal site to monitering avalanche on field base.
Borehole climatology, a method for reconstructing climate from subsurface temperatures, is a valuable tool for understanding how climate conditions have responded in specific areas over time. By measuring temperature-depth profiles, the process of glacier surface temperature variation can be reconstructed based on the close relationship between glacier inner temperature and surface temperature change. The coupled heat conduction and ice-flow model and relative inversion algorithm serve as the theoretical basis and key method for studying climate reconstruction via glacier temperature-depth profiles. This study first presents a numerical experiment under ideal conditions to compare the results of the reconstructed changes in glacier surface temperature using the least square method, Tikhonov regularization method, and Monte Carlo algorithm on a century scale. Next, a simulation experiment based on borehole data from the Malan Glacier located on the northern Qinghai-Xizang (Tibet) Plateau and meteorological data from the Wudaoliang meteorological station investigates glacier surface temperature histories for the past 10 and 40 years using the three aforementioned inversion algorithms. The advantages, disadvantages, and applicability of each algorithm are also discussed. Comparison of the results of the two experiments indicates that the Tikhonov regularization method performs the best in solving the inverse problem, producing results in good agreement with the input data. Furthermore, by introducing random errors in the input data, the stability of the methods is assessed. The results demonstrate that the Tikhonov regularization method effectively filters noise interference, providing a stable solution to the inverse problem.
The ice-water phase transition in the active layer will lead to seasonal frost heaving and thawing and the melting of underground ice at the upper limit of permafrost will lead to long-term subsidence of the surface. Understanding the seasonal and long-term variation rules of surface deformation can provide a new perspective and method for remote sensing monitoring of permafrost state. Taking the northern boundary of the permafrost area of the Qinghai-Xizang (Tibet) Plateau (Xidatan-Kunlun Pass) as an example, this paper uses the C-band downorbit Sentinel-1 data and SBAS-InSAR technology to obtain the surface deformation results of the permafrost area of Xidatan-Kunlun Pass from 2014 to 2020. By analyzing the time series of surface deformation and extracting the long-term deformation rate and seasonal deformation, this paper also discusses the permafrost deformation law in this region. The results show that there are large spatial differences in the discontinuous permafrost region in the Xidatan area of the northern boundary of permafrost, and the long-term settlement rate and seasonal deformation in permafrost region are higher than those in seasonal permafrost region. In addition, the surface subsidence of high-temperature permafrost is more significant than that of low-temperature permafrost. The spatial distribution characteristics of deformation are closely related to geomorphic units. Compared with the Xidatan area, the long-term deformation rate and seasonal deformation variables in Kunlun Pass and the high plains area of Chumar River are obviously increased. At the same time, the deformation law is further studied by combining the data of the thermokarst ponds. In the early stage of the development of the thermokarst ponds, the melting of underground ice increases the regional seasonal deformation. With the expansion of the thermokarst ponds, the long-term settlement rate of the region is intensified, and the regional seasonal deformation may decrease after the further development of the thermokarst ponds.
To ensure the safety of major engineering construction in cold regions, the study of dynamic characteristics of frozen soil containing stone is essential. In order to reveal the mechanical behavior of frozen soil-rock mixtures under cyclic loading, the dynamic stress-strain relationship of frozen soil-rock mixtures was obtained by uniaxial cyclic compression tests at different low temperatures (-5 ℃, -10 ℃, -15 ℃). The influence of temperature and rock content on dynamic elastic modulus was discussed, and an evolution model was proposed to explain the laws of cumulative plastic strain. The results showed that the dynamic stress-strain curve of frozen soil-rock mixture developed from thinning to dense and then to thinning, and the hysteresis loops of frozen soil-rock mixture presented an unclosed elliptic shape first, then a scalded shape, and finally a flat and long elliptic shape as the number of cycles increased. Additionally, with the increase of gravel content and the decrease of temperature, the dynamic elastic modulus shows an increasing trend. There are obvious stages in the accumulation of plastic strain and the number of cycles, which can be divided into three stages: initial deformation, stable deformation, and rapid deformation, according to the growth rate of cumulative plastic deformation with the number of cycles. On this basis, an improved Monismith model was proposed to describe the cumulative plastic deformation and cycle number. The model was found to fit the experimental results better than the original Monismith model. In order to explore the relationship between parameters and experimental conditions, Spearman correlation analysis and deviation correlation analysis were used. The results showed that parameter “b” in the improved Monismith model had a significant positive correlation with stone content, while parameter “a” had a significant negative correlation with temperature. The findings suggest potential applications for this new model in predicting the behavior of materials under different conditions.
Based on the assessment report on “the impact of short-lived climate forcing factors (SLCFs) on Arctic climate, air quality and Human Health” issued by the Arctic Monitoring and Assessment Programme (AMAP) of the Arctic Council in 2021, this paper provided the new acknowledge on the characteristics black carbon, methane, ozone and sulfate aerosols and their impacts on Arctic climate changes. The AMAP assessment reported that black carbon, ozone and methane together promoted the Arctic rapid warming; while sulfate aerosols played a cooling effect on Arctic climate, slowing down the warming trend caused by carbon dioxide and other SLCFs. Global anthropogenic emissions and atmospheric concentrations of methane in the Arctic continued to increase. Tundra degradation, peatland melting and frequent forest fires hastened emissions of black carbon and organic carbon aerosols in the Arctic. Climate warming further resulted in wider and more frequent forest fires and permafrost degradation, forming positive feedback on the release of black carbon and methane and their potential effects on climate change. Therefore, SLCFs emission reduction would be favorable to the health and sustainability of the ecological environment in the Arctic. Meanwhile, this paper also provided the uncertainties of assessment on SLCFs in the Arctic and the perspectives in future.
The Arctic Monitoring and Assessment Program (AMAP) of the Arctic Council released “Arctic climate change update 2021: key trends and impacts” in May 2021. The report presented that near-surface air warming in the Arctic has been three times greater than the global mean over the past 49 years (1971—2019), resulting in profound changes in Arctic precipitation, sea ice, land ice, permafrost, and snow cover. Glacial ablation was intensifying. Sea ice continued to decline in the Arctic other than the Bering Sea, which is one of the causes of mid-latitude extreme weather and climate events. Extreme events (extreme precipitation, extreme heat events, extreme cold events, and extreme wildfires) occurred frequently in the Arctic, significantly affecting Arctic ecosystems and Arctic communities. The latest climate models and scenarios projected that the Arctic Ocean will be free of sea ice in September for the first time, as early as 2040, and that no sea ice in summer will be the new norm by 2050. Unfortunately, the COVID-19 epidemic has caused many Arctic studies to be postponed or canceled, resulting in gaps in datasets in 2020—2021 including some key indicators. Climate warming caused by greenhouse gas emissions has been ranked as the top global environmental problem, and the Arctic amplification of climate change makes the Arctic one of the most dramatic areas of near-surface air temperature increasing, making the Arctic more vulnerable to climate change. Based on Arctic climate change assessment report of AMAP, this paper interprets the change characteristics of climate and cryospheric elements of the Arctic, the change characteristics of Arctic extreme events, and the impacts of Arctic ecosystem and social and economic development. The results show that the Arctic climate is accelerating to a warmer and wetter state, and the instability of Arctic environmental elements is increasing, which has profound impacts on the Arctic ecosystem and economic and social development. To date, the concentration of greenhouse gases in the atmosphere continues to increase, and climate warming will continue. There is an urgent need to strengthen the monitoring and prediction of recent Arctic climate change and extreme events, and improve the ability to cope with the adverse effects of Arctic climate change. The transition towards a ecologically resilient state is the focus of Arctic climate change research in the future.
Climate change significantly affects the oceanic and terrestrial environment in the Arctic, and thus is directly and indirectly impacting the sources, transport pathways, and fate of persistent organic pollutants (POPs) and chemicals of emerging Arctic concern (CEACs). The Arctic Monitoring and Assessment Program (AMAP) recently released the report “AMAP Assessment 2020: POPs and Chemicals of Emerging Arctic Concern(CEACs): Influence of Climate Change”, which pointed out that climate warming induces the release of previously accumulated POPs from permafrost, snow and ice melt in the Arctic and the redistribution of POPs among water, sediments, snow, and air. Meanwhile, raising human activities in the Arctic under the impact of warming may result in new pollution emission sources. Global warming enhances the long-range atmospheric transport (LRAT) potential of semi-volatile POPs; while the process of “biological pump” would also be strengthened by climate change, increasing the sequestration of POPs in deep ocean and sediment. Additionally, the Arctic environment has low resilience and is sensitive to some external environmental influences due to homogeneous environmental elements and ecological scenarios. Consequently, climate change led to the changes of physical environment and ecology, which, in turn is influencing the exposure to, and potentially the effects of these contaminants on Arctic wildlife and other biota, as well as people. The assessment report revealed the high complexity of influence on POPs and CEACs in the Arctic by climate change. In the future studies, more chemicals with POPs properties need to be included in the long-term monitoring programme. Interdisciplinary efforts and cooperation among government, college, and Arctic communities needed to be strengthened.
To surmount the technical obstacles in producing alpine skiing pistes for high-level events such as the Winter Olympic, this study carried out various snow piste production experiments at the Heilongjiang Yabuli Sports Training Base, the Genting Resort Secret Garden, and the National Alpine Ski Center in Yanqing. The study discovered that a cloudless sky with a temperature of -12 ℃ is the ideal condition for icy piste production. The optimal scheme is -15~-10 ℃ (temperature)/6~9 bar (water injection pressure)/4~8 s (water injection duration). Based on experimental data, this study established the qualification standards for icy piste and the first international weather-water injection quantitative model for icy piste production. The model has the capability of being applied to alpine events in continental climate conditions and also has the potential to be expanded to other cold and dry regions. Furthermore, we discovered that the quality of the track is significantly influenced by the water content and microstructure of artificial snow. The lower the water content, the smaller the snow particles become, leading to a more uniform snow morphology and improved stability and track hardness. This achievement fills the gap in domestic ice and snow sports support technology and can provide intellectual support for China to undertake large-scale ice and snow events.
Due to the low permeability of permafrost, the seasonal freeze-thaw cycle and its accompanying hydrothermal transportation,the occurrence, storage and flow processes in the basin was changed, and water resource was affected. Over the past few decades, climate warming has caused permafrost degradation and accelerated multiphase transformations of water, which is remodeling the hydrogeological conditions in cold regions and changing the groundwater hydrothermal status. Melting of frozen soil ice affects the spatial and temporal patterns of permafrost groundwater, threatens regional water resources, ecological environment and engineering facilities; in addition, this process also releases greenhouse gases and reduces the carbon storage function of permafrost, thus accelerating climate change. Although hydrogeochemistry and numerical simulation techniques are widely used in cryosphere hydrological studies, that advancing the understanding of permafrost groundwater mechanisms, there are huge challenges in the research of groundwater in permafrost. This review compares articles on permafrost groundwater, illustrates the spatial and temporal modalities of permafrost groundwater, discusses the interaction between permafrost and groundwater, and highlights the different focuses when studying based on hydrochemical and numerical models. The scattered research results of permafrost groundwater changes due to climate warming are integrated. The characteristics of permafrost groundwater changes and the hydrological, ecological and environmental effects of these changes are systematically described in the background of climate warming, spatially from the recharge zone to the discharge zone, and temporally from the initiation of permafrost thawing to long-term degradation to its disappearance. This article provides a reference for the study of hydrology, water resources and ecology of permafrost groundwater.
Sea ice is an important component of the polar climate system. Previous observations and simulation studies have shown that the persistent anomalies of Antarctic sea ice can directly alter the thermal radiation balance in the Southern Hemisphere (SH), thereby affecting the zonal temperature and pressure gradients, and have the ability to affect the atmospheric circulation in the SH. The main mode of Antarctic sea ice variability is called the Antarctic Dipole (ADP), which is characterized by the inverse changes of sea ice anomalies on both sides of the Antarctic Peninsula. The occurrence of ADP is significantly correlated with atmospheric circulation anomalies in the SH and profoundly influenced by El Ni?o-Southern Oscillation (ENSO) events. Previous studies have shown that El Ni?o underwent a noteworthy interdecadal shift from an eastern Pacific to a central Pacific type after 2000. The correlation coefficient between ENSO in the mature stage and the subsequent cold season ADP has significantly weakened in the past two decades. With this transition, the anomalous patterns of Antarctic sea ice and its impact on atmospheric circulation in the SH have also undergone interdecadal changes. Results from the Empirical Orthogonal Function (EOF) decomposition suggest that post-2000, the principal mode of SH autumn sea ice anomalies no longer represents ADP. The impacts of Antarctic sea ice anomalies on the SH winter-spring atmospheric circulation during the two periods have also undergone interdecadal changes. The maximum covariance analysis (MCA) can be used to study the connection between two fields. The results of MCA between prior Antarctic sea ice anomalies and lagged SH winter-spring geopotential height anomalies are intriguing. Specifically, from 1979 to 1999, the persistent positive phase of ADP from austral winter to spring demonstrated a significant correlation with the austral springtime negative phase of the Southern Hemisphere Annular Mode (SAM). However, this correlation became weaker and shifted to a significant correlation between the austral autumn tri-polar sea ice anomalies and the subsequent winter SAM from 2000 to 2021. The correlation between the MCA and EOF time series of the two fields proves that the early Antarctic sea ice anomalies are related to the main modes of sea ice variability, and can significantly affect the main variability of the later austral cold seasons atmospheric circulation in the SH. The main modes of austral autumn and winter sea ice anomalies in the two stages have undergone interdecadal changes, and the traditional ADP in the second stage no longer appears as the dominant mode. This may be related to the weakening of the ENSO-ADP connection after 2000. In the first stage, ENSO has a strong connection with ADP, establishing a tropical-to-polar connection. However, in the second stage, ENSO's impact on Antarctic sea ice has weakened and its location of influence has changed, partially explaining the changes in sea ice anomaly modes. Although the main modes of sea ice anomalies that affect the later atmospheric circulation underwent interdecadal changes around 2000, the overall response of the SH atmospheric circulation during the first phase in austral spring and the second phase in austral winter to the previous sea ice anomalies presents a structure similar to SAM. Dynamical diagnosis proves that ADP and the tri-polar sea ice anomalies can trigger changes in high-frequency transient eddies, thus stimulating and maintaining SAM-like atmospheric circulation patterns. In subsequent research, numerical simulation experiments can be used to verify the impact and specific mechanism of two sea ice anomaly modes on SAM. In addition, the changes in the relationship between Antarctic sea ice and SH atmospheric circulation are likely closely related to the interdecadal changes of ENSO. The different roles of sea ice forcing factors such as ENSO in the process of Antarctic sea ice anomalies affecting SH atmospheric circulation around 2000 still need further research and confirmation.
The Qinghai-Xizang (Tibet) Plateau and adjacent mountainous areas experienced glacial events during MIS 3, and its scale was larger than that of the Last Glacial Maximum (LGM). At present, the climatic drivers of the glacial advance that occurred during different subphases of MIS 3 on the Qinghai-Xizang Plateau are still not resolved. Gurla Mandhata (30°35′~30°18′ N, 81°05′~81°35′ E) is situated towards the west of the Himalayas and lies in the southwest of the Qinghai-Xizang Plateau. During the Quaternary period, multiple glaciations occurred on the planation surface of Ronggua valley, Muguru valley and Namarodi valley of Gurla Mandhata. Therefore, they well preserved a large number of Quaternary moraines. Field investigation of glacial morphology and existing 10Be exposure age dating show that multiple glaciations occurred on Gurla Mandhata during MIS 3b and MIS 3c. The glacial history of Gurla Mandhata thus provides an opportunity to investigate the drivers of glacial advance during MIS 3b and MIS 3c. According to the reconstructed chronological framework, we used glacier reconstruction tools to reconstruct paleoglacier surfaces during MIS 3b and MIS 3c of Gurla Mandhata. In addition, the accumulation area ratio (AAR) and area altitude balance ratio (AABR) methods were used to calculate the material glacier equilibrium line altitude (ELA) during MIS 3b and MIS 3c after paleoglacial restoration, which shows that the reconstructed MIS 3b and MIS 3c ELAs were 250~253 m and 348~456 m lower than that of modern times, respectively. By the precipitation-temperature and temperature lapse-rate models, we reconstructed paleoclimatic conditions of MIS 3b and MIS 3c. Model results suggested that MIS 3b temperature was 1.38~4.91 ℃ lower than that of present, with MIS 3b precipitation amounts being 50%~100% of modern values. With a MIS 3c precipitation at 140%~200% of present, MIS 3c temperature was -1.31~1.68 ℃ higher than that of present. Combining our model results with other climatic proxy records on the Qinghai-Xizang Plateau, temperature depression was identified as the main control of MIS 3b glacial advance, and abundant precipitation induced MIS 3c glacial advance.
The Parlung Zangbo basin, located in the southeastern Tibetan Plateau, where the marine glaciers are most concentrated. However, due to global climate warming over recent years, these glaciers have experienced substantial losses. By applying the Open Global Glacier Model (OGGM), we simulated the mass balance of 1 554 glaciers within the basin from 1980 to 2019. The results show that the mass balance of the entire Parlung Zangbo basin was in a continuous state of loss from 1980 to 2019, with a rate of -0.41 m w.e.a-1. The loss was even more severe in 2000—2019, reaching -0.56 m w.e.·a-1. Spatially, the southeast and northwest parts of the basin suffer from the most severe glacier losses, while the central and western parts have relatively less. The main causes of glacier mass loss are the increase in temperature and a slight decrease in precipitation. Through sensitivity analysis of temperature and precipitation, it was found that when the temperature rises by 1 °C, the mass balance of 71.75% of the glaciers in the basin changes at a rate of -1 000 to -500 mm w.e. a-1. When precipitation decreases by 20%, the mass balance of 62.81% of the glaciers changes at a rate of -450 to -300 mm w.e.·a-1. Compared to precipitation, glaciers are more sensitive to changes in temperature. Meteorological data analysis from the National Meteorological Station and reanalysis data showed that the temperature increased by more than 1.5 °C from 1980 to 2019. Total precipitation at the Bomi Station from 2000 to 2019 was 10% lower than in the previous 20 years, and the overall precipitation in the basin showed a decreasing trend. The ongoing rise in temperature, coupled with a marginal decline in precipitation, has resulted in sustained glacier mass reduction in the Parlung Zangbo basin.
With the climate warming, glacier exhibits dramatic decline in recent decades. Analyzing spectral evolution characteristic of dissolved organic matter (DOM) in surface snow/ice of glacier plays an important role to understand the output of organic carbon and environmental indication role caused by glacier ablation. In this study, the dissolved organic carbon (DOC) concentration and spectral characteristic of DOM in snow/ice from Dagu Glacier in spring, summer, autumn and winter were analyzed. The results showed that DOC concentration of fresh snow in different seasons was at the range of 0.11~0.38 mg·L-1 with a higher value in winter and lower value in summer, which showed a significant seasonal difference. DOC concentration of firn/surface ice in different seasons was between 0.70~1.08 mg·L-1, with no significant seasonal difference. The fresh snow and surface ice samples in summer showed a significantly higher degree of DOM aromatization than other seasons. DOM in Dagu Glacier snow/ice was mainly composed of protein-like substances which was mainly an autochthonous source produced by microbial activities with the characteristics of low degree of humification. DOM in fresh snow in spring had more diverse sources, including microbial sources and terrestrial inputs, while DOM in other samples were mainly derived microbial sources. Due to the influence of photochemical process on the surface of glacier during summer, DOM in surface ice in summer have a higher humification degree than that in other seasons, and the lower humification degree of DOM in autumn and winter samples. These results revealed the endogenous sources and seasonal variations characterized DOM in the surface snow/ice of Dagu Glacier, and provide scientific basis for further research on the evolution process of DOM and its regional biogeochemical effects.
The ad-freezing force and shear mechanical behavior at the interface between piles and soil under load is pivotal in determining the bearing performance of pile foundations and the transfer of loads in frozen soil regions. Due to the significant rheological properties of ice and the widespread distribution of thick underground ice near the upper limit in ice rich permafrost areas, the shear creep characteristics of the ice-pile interface present in the upper part of pile foundations significantly affect their bearing capacity. To investigate the shear deformation characteristics of the pile-ice interface and its underlying mechanisms, a series of multi-level loads loading-unloading shear creep tests were conducted on ice-steel pipe structures at temperatures of -3 ℃ and -5 ℃. By independently decoupling the deformation curves into segments, the viscoelastic-plastic shear deformation behavior of the frozen interface was analyzed. The results reveal that the interface shear deformation can be decomposed into instantaneous elasticity (Sie ), instantaneous plasticity (Sip ), viscous plasticity (Svp ), and viscoelastic deformation (Sve ). The generalized elastic shear modulus gradually increases with increasing load level, suggesting a notable strengthening effect at the interface before accelerated structural failure during loading and unloading cycles. The shear creep characteristics of the interface transition from attenuation to non-attenuation with increasing in shear stress levels. Specifically, viscoelastic deformation and viscoplastic deformation at low shear stress levels both exhibit attenuation behavior, with greater loads leading to increased viscoelastic deformation. At high stress levels, viscoplastic deformation shows non-attenuation behavior, and the deformation rate significantly increases with higher shear stress levels. Overall, the proportion of plastic deformation at the frozen interface to the total cumulative deformation initially decreases and then increases, in view of instantaneous plastic deformation primarily occurring during the loading stages with the initial stress levels. The strengthening effect of the frozen interface during creep may be attributed to the densification of the interface contact zone under shear stress and the refreezing of the interface in minus-temperature environment.
Under the global climate change, frozen soil regions are sensitive to changes in external hydrothermal conditions, and are tend to degrade regionally, which is mainly manifested by the thickening of permafrost active layer, thinning of seasonally frozen soil layer and reduction in seasonal frozen days. As an important part of the cryosphere, the direct and indirect risks of the changes or degradation of frozen soil to the ecological environment system and the safety of human production have been gaining wide attention from scholars. The changes of surface soil in cold regions have significant impact on the evolution of the landscape pattern, and the material or energy exchange between land surface and atmosphere. Therefore, it is of great significance to monitor the distribution and spatiotemporal changes of seasonally frozen soil for carrying out natural scientific research in cold regions, or ensure the safety of ecological environment and human production activities. After several decades of development, remote sensing technology and frozen soil physics have made considerable progress. However, the application of frozen soil research results in the field of disaster risk assessment, prevention and control at regional scale is still at a low level. Aiming at the shortage of frozen soil process simulation and facing the short board in the frozen soil research results application, we focus on the systematic expression of land surface soil freeze-thaw cycle and its water and heat transfer process over the alpine canyon area and its surrounding areas on the southeastern margin of the Qinghai-Xizang (Tibet) Plateau. The dynamic balance of water and heat in various land surface processes such as meteorology, vegetation, snow cover and soil were considered comprehensively to establish a spatially distributed numerical model. Based on the simulated high-precision frozen soil characteristic parameters, the evolution process of the frozen soil system in the study area was analyzed deeply by using the methods of GIS spatial analysis and data processing technologies. The seasonal freeze-thaw cycle and its changing characteristics of surface frozen soil over the study area in the past decade have been analyzed, and the spatiotemporal evolution of the surface frozen soil in the complex geographical environments under climate change has been revealed in the present study. On this basis, a parametric characterization method of surface freeze-thaw action was developed based on various frozen soil characteristic parameters of the soil hydrothermal processes. Then, the damage coefficient of soil shear strength caused by freeze-thaw action is innovatively proposed by combining the relevant theories of soil shear strength and thawing stability of slopes. The results showed that surface frozen soil on southeastern of the Qinghai-Xizang Plateau changes sharply with the increase of temperature with strong spatial heterogeneity. In addition to the periodic freeze-thaw cycle, seasonally frozen soil showed a degradation trend overall. Degradations of frozen soil were mainly manifested by the increase of soil temperature and the increase of soil water content. Undoubtedly, it increases more uncertainties to the change of shear strength of rock and soil mass structure under freeze and thaw environment. Finally, influence degree of soil freeze-thaw action on slope stability in frozen regions were revealed from the perspectives of time variation and spatial distribution, based on the damage coefficient of soil shear strength that proposed in this study. The results indicated that the damage coefficient of soil shear strength could effectively express the hydro-thermal process of surface frozen soil and its freeze-thaw characteristics. This study can provide new ideas for the research of frozen soil, and provide data and technical support for the dynamic evolution of frozen soil system for the research of disaster risk assessment and disaster prevention in cold regions.
Because of varied topography and landscape heterogeneity, Tianshan Mountain has extremely complex hydrological processes. Considering that the climate change poses a great threat to the water security, it’s necessary to simulate the change of water elements quantitatively and systematically along with elevation. In this study, we applied the modified FLEXG-Δh model to four classic river basins in Tianshan Mountain in consideration of glacier area changes. The results suggested that: (1) FLEXG-Δh model has high simulation accuracy for the historical runoff process because the average Kling-Gupta coefficient (
Alpine meadows are one of the most important vegetation types in Qilian Mountain National Park. Quantifying soil water storage and exchange is essential to evaluating the function of regional water conservation. Based on the continuous observational hydrothermal data from August 1, 2017, to July 31, 2018, and the parameterized SHAW (simultaneous heat and water) model, this paper aimed to explore the seasonal variations of 0-100 cm soil water storage and soil water flux and their environmental controls. The results showed that the SHAW model could simulate soil hydrothermal processes reasonably. The simulation performance of soil water content was better than that of soil temperature. The daily 0-100 cm soil water storage (SWS0-100) was 274.99±19.57 mm (Mean±S.D.), which was 21.92 mm lower in the growing season from May to October than that of the nongrowing season. The seasonal variations of SWS0-100 were mainly controlled negatively by evapotranspiration and positively by leaf area index, through the effects of shallow (0-20 cm) and middle (20-60 cm) soil moisture storage. The daily 0-100 cm soil water flux (SWF0-100) exhibited downward transmission and averaged 0.16±9.52 mm·d-1. SWF0-100 migrated downward at a rate of 3.27 mm·d-1 during the growing season and converged upward at a rate of -3.23 mm·d-1 during the nongrowing season. The seasonal variations of SWF0-100 were indirectly determined by precipitation and deep soil temperature gradients, via the effects of the shallow, middle soil water flux and the deep (60-100 cm) soil water fluxes. The research results can provide data support and a theoretical basis for the scientific evaluation of the water conservation function of alpine meadows in the Qilian Mountains.
As one of the important origins of the Yangtze River, the Dongkemadi Glacier has been mainly explored for glacier climate, geological changes, and other natural geographical directions. However, there are still few reports about the diversity and community composition of culturable bacteria in the different ambient medium of Dongkemadi Glacier. In order to clarify the cultivable bacterial diversity and the relationship between the cultivable bacterial diversity and environmental factors in Dongkemadi Glacier, and explore microbial resources, investigated the three habitats of snow, ice, and melt water of Dongkemadi Glacier. The strains were isolated by the traditional culturable method, identified by 16S rRNA Gene Sequence analysis, and the diversity of culturable bacteria and its influencing factors were analyzed by statistical method. The results showed that the culturable bacteria in this study belonged to Actinobacteria, Proteobacteria, Bacteroidetes, and Firmicutes. Among them, Actinobacteria is the dominant phylum, and Kocuria, Microbacterium, and Massilia are the dominant genus. The highest number of culturable bacteria, complex community structure, and diversity was higher in ice samples compared with snow and meltwater. In addition, 8 of the 36 genera isolated from the Dongkmadi Glacier were not reported from other glaciers; therefore, 32.21% of the culturable bacteria were potential new species. The community structure of culturable bacteria was distinct across the samples; pH, Cl- and Ca2+ are the main environmental factors affecting the number and diversity of culturable bacteria. Dongkemadi Glacier contains rich microbial resources, 46 new species were isolated in this study, which could provide data support and strain resources for the developing and utilizing microbial resources in the cryosphere.
Soil water availability is affected by alpine meadow degradation, which profoundly affects soil fauna diversity and ecological function. However, little knowns about the composition of soil fauna in alpine meadow ecosystems. How changes in soil water content affect their distribution and diversity during alpine meadow degradation is still unclear. Our study area was the Shule River headwaters in the western Qilian Mountains, alpine marsh meadow (AMM), alpine meadow (AM), alpine steppe meadow (ASM) and desertification alpine meadow (DAM) formed a gradient of degradation of the Shule River headwaters. In June and October 2021, soil mesofauna was collected using the improved Tullgren funnel method in the AMM, AM, ASM, and DAM habitats of the Shule River headwaters, at the same time soil water content was also measured in four alpine meadow habitats. Further, soil mesofauna diversity, Acarina/Collembola (A/C) ratios, and the soil biological quality index (QBS-ar) in four alpine meadow habitats were calculated, and a regression analysis was performed to determine the impact of soil water content on soil mesofauna community indices during the degradation process of alpine meadows in the Shule River headwaters. Results showed that soil mesofauna communities differed considerably between the four alpine meadow habitats, degradation of alpine meadows in the Shule River headwaters strongly affected the density changes of soil mesofauna such as mites (Acarina) and springtails (Collembola), and their response patterns to alpine meadow degradation determined the assemblage of soil mesofauna community. Furthermore, the density, group richness, and Shannon-Wiener index in soil mesofauna communities in ASM habitats was significantly higher than those in AMM, AM, and DAM habitats in June and October in the Shule River headwaters, respectively. In October, the density and group richness of soil mesofauna communities in AMM habitats was significantly higher than those in AM and DAM habitats of the Shule River headwaters. Changes in soil mesofauna QBS-ar indices of four alpine meadow habitats during two sampling periods are consistent with the Shannon-Wiener index of soil mesofauna community, and A/C ratios over two sampling periods followed the opposite pattern. Alpine meadow degradation caused soil mites to respond differently, and there were seasonal and taxon-specific differences. The density of Oribatida in ASM habitats was significantly greater than those in the other alpine meadow habitats in June and October. As compared to AM or DAM habitats, ASM habitats had a significantly higher density of Mesotigmata in June and October. In June, the density of Prostigmata was significantly higher in ASM habitats than in AM and DAM habitats, and in October, it was significantly higher in ASM habitats than in AM and DAM habitats. Soil springtails responded in the same way to alpine meadow degradation in June and October, and the density of Entomobryidae and Isotomidae significantly outnumbered other alpine meadow species in ASM habitats. Alpine grassland degradation was associated with changes in soil moisture content and soil mesofauna community indices in the Shule River headwaters. During the degradation of alpine meadows, soil water content and the density, group richness, and Shannon-Wiener index of soil mesofauna community showed a significant quadratic curve relationship, and soil mesofauna community indices and soil water content first increased and then decreased. We also found a similar relationship QBS-ar index of the soil mesofauna community and soil water contents with other soil mesofauna community indices. In conclusion, the density, Shannon-wiener index, and QBS-ar index of soil mesofauna community in ASM habitats were higher during the degradation of the alpine meadow, indicating that a certain degree of declined soil water availability due to degradation of an alpine meadow could improve the diversity and ecological functions of soil mesofauna in the Shule River headwaters.
In China, ice and snow tourism is becoming the core driver of ice and snow economy. China can powerfully realize green transformation and upgrading development by means of developing ice and snow tourism. The concept of ice and snow tourism is discussed firstly in this text. After that, the authors elaborate that the formation process of “ice and snow +” all-for-one tourism development mode on the basis of analyzing the historical development of China’s ice and snow tourism. This paper analyzes the endogenous-external development mechanism of “ice and snow +” all-for-one tourism development mode according to the all-for-one tourism development thinking. A set of “ice and snow +” all-for-one tourism development mode systems are constructed based on the analyses of their regional differences. The system is composed of snow and ice industry development mode in Northeast China, ice and snow sports events mode in pan Beijing-Tianjin-Hebei region, ice and snow-silk road culture development model in Shaanxi, Gansu, Ningxia, Xinjiang Uygur Autonomous Region and western part of Inner Mongolia Autonomous Region, self-driving exploration and sightseeing model over the Qinghai-Xizang (Tibet) Plateau, glacier sightseeing resort model in big Shangri-la region, ice and snow leisure experience development model in southern China. Although the Beijing Winter Olympics and national all-for-one tourism policy have promoted Chinese snow and ice tourism to achieve the “quantity” jump and fusion development, but it is suffered from climate warming, market competition, and ice and snow technology development. In the end, the article suggests to establish planning and decision-making mechanism involved from governments, enterprises, and individuals, to balance use of ice and snow resources, to moderate exploitation of glacier tourism resources, to develop ice-snow culture resources and scientific and technological resources, to take comprehensive development path, to enhance anti-risk resilience of snow and ice tourism.
Ice core is one of the most important archives for paleoclimate reconstructions. Paleo-atmosphere is directly enclosed in bubbles when the pores in ice cores are closed. Therefore, trapped air in ice cores are direct samples to study the atmospheric compositions during the glacial-interglacial time period. Trapped air in ice cores and its isotopic and gas ratio compositions have been widely used in paleoclimate reconstructions. Due to the subtle variations in the gas compositions of paleo-atmosphere, high precision measurements of its isotopic and gas ratio compositions are required. First, extraction and purification of trapped gases from ice cores need to be proceeded under strict vacuum conditions, because modern atmosphere can contaminate the gas compositions of paleo-atmosphere. In this study, we describe the detail procedures of storage and cutting methods of ice core samples, as well as the extraction and purification of trapped gases from ice cores. We also show the structure of our lab vacuum line, which is used for removing CO2 and water vapor in the ice core gas mixtures. Isotopic and gas ratios for major gases (N2, O2 and Ar), including δ18O, δ15N, δO2/N2 and δAr/N2, are measured on a dual-inlet gas ratio mass spectrometer (Thermo Fisher Delta V Plus). However, raw data obtained from the mass spectrometer could not be directly used in paleoclimate interpretations. We perform a series of data corrections, including zero enrichment correction, chemical slope correction, air standards correction and gravitational correction, in order to reconstruct the real paleo-atmosphere isotopic compositions. These data corrections also improve the data precision and accuracy. Zero enrichment experiment and long-term observations of air standards are also useful for tracking the status of the mass spectrometer and for evaluating the data quality. Among all the data corrections, chemical slope correction is very important for studies of trapped gases from ice cores, because trapped gases from ice cores are measured as gas mixtures in the mass spectrometer. Different sample has different gas ratios, which will lead to mass interferences during oxygen and nitrogen isotopic measurements. The magnitude of mass interferences is related to the differences in gas ratios between sample gas and reference gas, filament status, and parameters of mass spectrometer. From January 2020 to October 2022, we have three analytical sessions based on three different filaments. We observe the chemical slopes for δ18O-δN2/O2 and δ15N-δO2/N2 range between 10-5~10-3 and 10-4~10-3, respectively. The isotopic variations caused by mass interferences are not negligible, especially for ice cores experiencing post-depositional alterations, such as melting and respiration. For those ice core samples affected by melting or respiratory alteration, the linear slope should be kept as low as possible in the order of 10-4 or even lower. For high linear slopes, the chemical slope can be minimized by reducing the extraction of the ion source and sacrificing some of the sensitivity, which would then improve the precision and accuracy of the corrected data after chemical slope. Therefore, chemical slope corrections are essential for studies of trapped gases from ice cores. Based on our method, we observe the long-term external precision for air standards are ±0.043‰, ±0.044‰, ±0.7‰ and ±0.7‰ for δ18O, δ15N, δO2/N2 and δAr/N2, respectively. We applied this method to the Chongce ice core, and observe a pooled standard deviation for samples above 200 m of ±0.009‰. This indicates that our method is capable for detecting subtle variations in the isotopic and gas ratios for trapped gases from ice cores. Stable isotope measurements of trapped air in ice cores and high precision δ18O data of trapped air provide a new indicator for the chronology of ice cores on the Qinghai-Xizang (Tibet) Plateau, which can provide extra information and help to solve the dating challenges for the ice cores. The δ18O of trapped air can also be used to establish the chronology for the Antarctic ice cores drilled independently by China, like the Dome A ice core. Therefore, the method described in our study has great potential to apply to the ice cores from the three polar regions.
With the intensification of global warming, glaciers at high altitudes in Asia are in an overall state of accelerated melting, the glacial lakes, which are mainly recharged by glacier meltwater, are undergoing rapid changes. As one of the important water resources in Tibet, glacial lakes play an important role in the daily life of the local people. The scale of glacial lakes in Tibet has been expanding, which may lead to natural disasters such as glacial lake outburst. Tibet is close to the Himalayas, and most of the GLOF events in Tibet originated in the glacial lakes of the Himalayan region. The current research on the factors affecting glacial lake changes basically stays on the nature of glacial lakes, using more qualitative methods.This paper is based on GIS spatial analysis, Pearson correlation analysis and Optimal Parameters-Based Geographical Detector method. All the glacial lakes with an area larger than 0.01 km2 in Tibet were counted using the open-source data of the Third Pole Glacial Lake. This study mainly analyzed the changes in the number and scale of glacial lakes in Tibet from 1990 to 2015, as well as the spatial distribution trend of glacial lakes in the region. Pearson correlation analysis and Parameters-Based Geographical Detector were used to examine the influence of seven selected environmental factors: glacial lake altitude, annual total precipitation, annual average temperature, annual relative humidity, glacier area change, GDP, and population density. The results showed that:(1) The total number of glacial lakes in Tibet increased by 303, an increase of about 2.57%; the total area of glacial lakes in Tibet increased by 59.90 km2, an increase of about 6.32%. The glacial lakes of different sizes increased significantly at different altitudes, most of which were small glacial lakes (area less than 0.1 km2), and distributed between 3 500~6 000 m. The growth direction of glacial lakes in Tibet in the past 25 years was significant, and the quantity and area distribution were highly dispersed. In 1990 and 2015, the glacial lakes in Tibet were basically distributed in the eastern and southern parts of Tibet, with the center shifting to the west. The influence of longitude was greater than that of latitude, and the growth of quantity and area of glacial lakes was slightly from southeast Tibet to southwest Tibet.(2) In Pearson correlation analysis, the glacial lake change was most correlated with the glacier area change factor, followed by the total precipitation factor, both of which showed moderate positive correlation. Then the relative humidity factor and the glacial lake altitude factor showed weak positive correlation, while the population density factor showed weak negative correlation. Finally, the glacial lake change was not correlated with the average temperature factor and GDP factor. The glacial lake change in Tibet was mainly affected by the change of glacier area and precipitation in the region. The increase of glacier area and precipitation increased, and the glacial lake expansion was more significant.(3) Parameters-Based Geographical Detector method was used to detect the influencing factors of glacial lake change in Tibet. Among them, the change of glacier area had the highest influence intensity on glacial lake change, with a value of 0.5006. The second was the annual total precipitation, with a value of 0.3106. The annual average temperature had the lowest influence intensity on glacial lake change, with a value of 0.1601. From the perspective of single factor, the change of glacier area and precipitation factor had a high influence on glacial lake change in this region. When the temperature factor and the change of glacier area interacted, they had a severe influence on glacial lake change, and the relationship was nonlinear enhancement, indicating that the two factors would affect the change of glacial lake in Tibet under the common drive. However, the influence of human factors on glacial lake change in Tibet was not high, and the dominant factors were climate change and glacier area change. It is necessary to focus on the impact of climate change and glacier retreat on glacial lake in the region.This study provides new ideas and references for exploring the driving mechanism of glacial lake changes, and provides basic information and data support for the potential risk assessment and risk analysis of GLOF in Tibet.