25 June 2022, Volume 44 Issue 3
    

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  • Hu LIU, Lei WANG
    Journal of Glaciology and Geocryology. 2022, 44(3): 737-752. https://doi.org/10.7522/j.issn.1000-0240.2022.0073
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    The Tibetan Plateau and its surrounding mountains contain the largest amount of glaciers outside the polar regions and therefore is called the “Third Pole” (TP). The TP is very sensitive to climate change. In the context of elevation-dependent warming over the mountainous TP, river runoff has changed dramatically due to the accelerated glacier melting, bringing grand challenges to integrated water resources management over the TP and its downstream regions. However, it is very difficult to quantify glacier runoff owing to very sparse in-situ glacier-hydrology observations over the TP and the inherent complexity of glacio-hydrological processes.

    This paper reviewed the major research progresses and problems of glacier runoff studies in the TP region. Comprehensive literatures indicate that the research methods of glacier runoff can be roughly classified into five categories: direct discharge measurement, remote sensing monitoring, water balance calculation, hydrochemical tracers, and glacio-hydrological modeling. The glacio-hydrological modeling can be further divided into temperature-index and energy-balance methods. The modeling approach is the most widely used since it can systematically and quantitatively describe the glacio-hydrological processes and project future changes.

    Previous studies on glacier runoff based on these methods showed that glacier runoff has generally increased since the 1990s induced by atmospheric warming over the TP, but the contribution of glacier runoff to total river runoff is influenced by both climate and glacier storage in the basin. The results of the contribution of glacier runoff to total river runoff have significant uncertainties among different studies mainly due to the following reasons, e.g., different methods used, distinct definition of glacier runoff, different meteorological inputs (especially the precipitation), and different glacier data (glacier extent, volume, and debris cover). In general, studies suggested that the contribution of glacier runoff to total river runoff in the westerlies-dominated region was greater than that in the monsoon-dominated region.

    As for the projections for future changes in the glacier runoff over the TP, the results varied widely among previous studies based on different climate change projection scenarios. The latest research indicates that glacier runoff in most basins will reach the peak before 2050 and decrease after the peak except for some basins in the westerlies-dominated region with large glacier storage (e.g., Tarim and upper Indus), based on the climate change projections in the CMIP6 (Coupled Model Intercomparison Project Phase 6) climate model ensemble.

    There are considerable uncertainties among the studies or literatures in the estimates of glacier runoff over the TP, mainly caused by sparse in-situ observations and highly-simplified models. Limited by available ground-based observations, most studies have used the temperature-index glacio-hydrological models for the TP basins, while the energy-balance models were applied to small basins. In addition, even the state-of-the-art energy-balance glacio-hydrological models do not fully consider some factors that affect glacier ablation, e.g. the glacier dynamics, debris covers, and black carbon. These factors may bring significant uncertainties to the simulated results. Therefore, we suggest that comprehensive observations and new advanced glacio-hydrological models need to be constructed and developed in the future studies; and, on the other hand, process-based multi-variable calibration/verification should be adopted in the glacio-hydrological modeling studies to improve the accuracy of glacier runoff studies over the TP. Doing so will provide a scientific basis for water resources utilization and management, flood prevention and mitigation in the downstream of TP.

  • Keqin DUAN, Peihong SHI, Jinping HE
    Journal of Glaciology and Geocryology. 2022, 44(3): 753-761. https://doi.org/10.7522/j.issn.1000-0240.2022.0074
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    Glaciers on the Asia High Mountains are melting and shrinking rapidly in a global warming condition. For a better understanding the glacier variability and its response to climate change, it is imperative to simulate the glacier variability based on the physical mechanism process. As the frontier direction and hot field of glacier change research, numerical simulation has been the core task of alpine glacier studies. In the past decades, much progress in glacier variability has been made by numerical simulations. Here, we briefly introduced the basic principles and methods of numerical simulation on mountain glaciers, and then briefly reviews the research progress of numerical simulation of glaciers in the Asian High Mountains in recent years. Finally, based on the current research and understanding, we put forward a prospect for simulating the glacier variation in future.

  • Jiansheng HAO, Lanhai LI
    Journal of Glaciology and Geocryology. 2022, 44(3): 762-770. https://doi.org/10.7522/j.issn.1000-0240.2022.0075
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    Snow avalanches are a major natural hazard in the cryosphere. It seriously threatens transportation corridors, energy transmission and communication lines, mining and touristic areas in the cold mountainous regions and often causes the destruction of infrastructure and human casualties, hindering the sustainable development of society and economy in mountainous areas. Under climate change and the expansion of human activities to alpine mountains, more population and infrastructure will expose to the risk of avalanches. In order to ensure the sustainable development in mountainous areas, the demand for the prevention and management of avalanche disasters is increasing. Based on the review of the main avalanche research progress in China since 1960 and the avalanche research results all over the world, this paper summarized the progress on the influencing factors and regional distribution of avalanche activities, avalanche formation and movement mechanism, avalanche monitoring and early warning, avalanche risk assessment and engineering prevention, as well as the frontier problems and scientific difficulties that need to be studied. In addition, the impact of climate change on avalanche activities and the interaction between human activities and avalanche activities are discussed. By looking forward to the future needs of avalanche disaster prevention and reduction, including the countermeasures, the research on avalanche in China is promoted.

  • Shimei DUAN, Shiyin LIU, Yu ZHU, Wenfei MIAO, fengze HAN, miaomiao QI
    Journal of Glaciology and Geocryology. 2022, 44(3): 771-783. https://doi.org/10.7522/j.issn.1000-0240.2022.0076
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    Snow avalanche refers to the phenomenon that the cohesion of the snow inside the slope is less than the gravity, and the friction force at the bottom is less than the shear stress, which makes it unstable slide and cause a large number of snow bodies to fall. Avalanches occur at uncertain times and can be extremely destructive when they destroy trees, sweep away roads and bridges, and destroy important infrastructure such as communications and electricity. Large-scale avalanches can also cause debris flow, landslides and other secondary disasters. The damage caused by an avalanche is incalculable and avalanches have seriously affected human productive activities and destroyed the natural environment. Therefore, snow avalanches are regarded as a serious natural disaster. Meili Snow Mountain is located in the monsoon maritime climate zone. Due to the difficult natural environment and lack of meteorological stations, there are few studies on snow avalanches, especially the necessary understanding of the reconstruction of the avalanche process. On January 3, 1991, 17 members of a Sino-Japanese mountaineering team were killed in an avalanche disaster at Meili Snow Mountain. On February 16, 2019, our field observation equipment recorded a large avalanche near the Mingyong glacier in Meili Snow Mountain. The avalanche generated a wave of air and destroyed the weather station at the end of the glacier. The trees in the path of the avalanche body were destroyed and the surrounding ecology suffered serious damage. To date, no detailed study of the avalanche process has been published. Only a good understanding and grasp of historical avalanche events can effectively avoid risks. Through the analysis of the two events, it is found that they belong to different avalanche types, which has a good indication for us to analyze the formation mechanism of avalanche, forecast and early warning. In this study, RAMMS (Rapid Mass Movement System) model was used as the main method. Firstly, the empirical values and empirical formulas were used to determine the avalanche fracture depth of the two avalanche events, and then the friction coefficient was determined by referring to the literature and model manual. On this basis, the two different avalanche disasters were reconstructed. Quantitative analysis of avalanche accumulation, range and maximum speed, et al. The simulation results show that: (1) In 1991, the avalanche lasted for 192 s. The avalanche broke at an altitude of 5 730 m, collapsed along the slope and finally accumulated in the flat area of 5 000 m above sea level, forming an accumulation body with an area of 0.6 km2 and a volume of 67×104 m3. The maximum height of the accumulation body was 13.46 m. The team’s camp 3 was completely submerged by the avalanche. The numerical simulation results show that the maximum height and velocity of avalanche flow are 16.98 m and 42.22 m·s-1, respectively. (2) In 2019, the avalanche lasted for 158 s, the maximum height of avalanche flow was 35.91m, the maximum velocity was 79.34 m·s-1, and the accumulation volume was 76.2×104 m3. The range of avalanche accumulation was consistent with that observed in the field. (3) The two avalanche events occurred in the extremely high risk area of avalanche and high risk area, which verifies the accuracy of risk assessment to a certain extent. Field observation of snow properties and meteorological conditions can determine the cause and type of avalanches, while numerical simulation can analyze and reproduce avalanche dynamics. Based on the observed avalanche accumulation range, the numerical model can give quantitative results such as avalanche path, accumulation amount and movement speed through parameter calibration. On this basis, combined with the avalanche hazard zoning map and the overlay of the actual weather process, the avalanche disaster can be predicted at fixed points and the early warning information can be issued. Therefore, the RAMMS model is an effective tool for snow avalanche modeling and prediction, which can perform avalanche process reconstruction and hazard zoning well.

  • Huan SUN, Ninglian WANG
    Journal of Glaciology and Geocryology. 2022, 44(3): 784-794. https://doi.org/10.7522/j.issn.1000-0240.2022.0077
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    Borehole paleothermometry, a reconstruction of the past ground surface temperature change from subsurface temperatures, is an important tool for understanding climate responses to conditions of a certain area in the past. Based on the close relation between glacier inner temperature and surface temperature change, glacier surface temperature variation process can be reconstructed by the borehole temperatures. Because of firnification and ice flow, the climate reconstruction from glacier borehole temperatures is more difficult than for other places such as permafrost. The coupled heat transfers and ice-flow equation and relative inversion algorithm are the theoretical basis and the key method of study on paleoclimate reconstruction by glacier borehole temperatures. In this study, we collected publications about the reconstructions of paleoclimate by glacier borehole temperatures over the last three decades, and reviewed some progresses in these areas. The advantages and disadvantages of different inversion algorithms (trial and error, control methods, Monte Carlo inverse modelling and the Tikhonov regularization method) were briefly introduced and discussed. Although the relationship between borehole temperatures and the climate may be affected by many factors (solar radiation, melt water, and so on), the cold glacier borehole temperatures in polar and high latitude regions can reflect the climate change well. At present the history of climatic changes has been reconstructed on different time scales in the world since the Last Glacial Maximum. Meanwhile, the reconstructed results using glacier borehole temperatures and the climate records in the ice core are able to confirm one another. In addition, by analyzing the glacier borehole temperatures and instrumental records, we can obtain a general understanding of the glacier-climate interactions and predict the response of glacier to climate change. However, less research has been done on the reconstruction of paleoclimate by cold glacier borehole temperatures for the middle latitude regions, and strengthening the study in these areas can help to reveal the climate change at middle latitude with high altitude.

  • Tao CHEN, Ge GAO, Deliang CHEN, Duo BIAN
    Journal of Glaciology and Geocryology. 2022, 44(3): 795-809. https://doi.org/10.7522/j.issn.1000-0240.2022.0078
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    Snow cover over the Tibetan Plateau has an important impact on the regional climate and water cycle. At present, the existing snow cover datasets have great uncertainty across this region, so the applicability assessment is indispensable in order to make best use of the advantages and bypass the disadvantages. In this study, a comprehensive quantitative evaluation of multiple variables and multiple evaluation indicators was carried out for three snow depth datasets over the Tibetan Plateau against the meteorological station observations (OBS). The three snow depth datasets include one passive microwave remote sensing dataset (CHE) and two reanalysis datasets (ERA5-Land and MERRA2). The variables are the annual mean snow depth, the annual maximum snow depth, and the annual snow cover days. In addition, the evaluation indicators are seasonal cycle, climatology, maximum value, standard deviation, interannual variation, and trend. A rank score (RS) value of 0~1 is computed for each evaluation indicator of each variable, the larger value of RS indicate relatively better performance of a snow depth dataset. Assessment results imply that, comprehensively considered, MERRA2 exhibits best agreement with OBS, followed by ERA5-Land, and finally CHE. Evaluate based on the RS of each variable, MERRA2 shows better performance on annual maximum snow depth and annual snow cover days, CHE shows better performance on annual mean snow depth. Evaluate based on the RS of each evaluation indicator, CHE shows advantages in describing trend, ERA5-Land exhibits better agreement with OBS on interannual variation, and MERRA2 show better performance on the rest of the indicators including seasonal cycle, climatology, maximum value and standard deviation. The RS statistics in terms of regional average and spatial distribution show that CHE performs better in the former, and ERA5-Land performs better in the latter. On the other hand, there are obvious deficiencies in all three snow depth datasets. MERRA2 has insufficient ability to characterize the interdecadal variation in snow cover, and its qualitative results for trend in snow cover is inconsistent with OBS, the reason for the first deficiency needs to be further studied and the second deficiency may be mainly related to its simulation capability to precipitation trend. ERA5-Land significantly overestimates the snow cover over the Tibetan Plateau, this may be mostly related to its data assimilation scheme. CHE has poor ability to characterize the spatial distribution of snow cover, coarse spatial resolution of passive microwave remote sensing may be the main reason. The conclusions are only applicable to the central and eastern part of the Tibetan Plateau due to the scarcity of meteorological station in west part of the Tibetan Plateau. Based on the remote sensing and reanalysis data, there is great uncertainty in the trend of snow cover in the western part of the Tibetan Plateau. These systematic classification evaluation of the three representative snow depth datasets provides information on data selection and data refinement.

  • Zhilan WANG, Feimin ZHANG, Chenghai WANG, Xuying SUN, Chunyan LÜ
    Journal of Glaciology and Geocryology. 2022, 44(3): 810-821. https://doi.org/10.7522/j.issn.1000-0240.2022.0079
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    Snow depth is an important parameter of surface characteristics, which has a significant impact on radiation budget, energy balance, weather and climate change. Based on the data of passive microwave remote sensing snow depth over the Tibetan Plateau (TP) from 1980 to 2019, temporal and spatial characteristics of snow depth are analyzed. The TP is divided into four regions: eastern, southern, western and central parts. The results show that the variation characteristics of snow depth in different regions at different time scales are different. The rate of snow depth accumulation and melting in eastern part is faster than that in western part, while in southern part is faster than in central part. On seasonal scale, winter snow depth in eastern part is the more, and that in central part is the less. In spring, the melting rate of snow in eastern part is the faster, while that in western part is slow, but snow depth in western part is the most. Snow still exists in western part of the TP in summer. On interannual scale, snow depth in each part decreased slowly from 1980 to 2019, but was not significant in eastern part. The interdecadal variation of snow depth in eastern part is different from the other three parts. The response of snow depth to air temperature and precipitation is different in different parts. There is significant negative correlation between snow depth and air temperature in eastern and central parts, while no significant positive correlation between snow depth and precipitation in all parts.

  • Wenxia WEI, Zhen LI, Yanan LI
    Journal of Glaciology and Geocryology. 2022, 44(3): 822-829. https://doi.org/10.7522/j.issn.1000-0240.2022.0080
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    Ice thickness distribution and ice volume are the basics of glaciological research. In order to obtain the ice thickness distribution and ice volume of this glacier, the ground-penetrating radar (GPR) was used to probe the ice thickness of Qiyi Glacier in August 2015. In this paper, we integrated GPS location data, glacier topographic data, and remote sensing data, using a co-kriging spatial interpolation algorithm, to retrieve the ice thickness distribution map and ice bed topography of the glacier. The thickness integration method was used to estimate the ice volume. The results show that the area of Qiyi Glacier in 2015 was 2.517 km2, and the average ice thickness and ice volume were 44.9 m and 0.1129 km3, respectively. The measured maximum ice thickness was 115 m. The regions within the altitude range of 4 480 to 4 600 m and altitude of 4 640 to 4 800 m have larger ice thicknesses on Qiyi Glacier, where the average ice thicknesses are 88 m and 97 m, respectively.

  • Zemin WANG, Chunxia ZHOU, Baojun ZHANG, Hong GENG, Yong LIU, Yide QIAN, Mingliang LIU, Shuang WU
    Journal of Glaciology and Geocryology. 2022, 44(3): 830-842. https://doi.org/10.7522/j.issn.1000-0240.2022.0081
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    The mass loss of the Antarctic ice sheet enters the ocean mainly via the ice shelves. Studying the dynamic changes and mass balance of Antarctic ice shelves provides significant references for revealing climate change in Antarctica. Focusing on monitoring changes in the Antarctic ice shelves, this study reviews recent research on five aspects, including surface melt, ice velocity, iceberg calving, basal melt and mass balance. It briefly summarized the observation methods and results, mechanism analysis of ice shelf change, and key problems. The development of polar observation satellites, field observation networks, multi-dimensional comprehensive analysis and numerical simulation of ice shelves, will help to further reveal the coupling effect between factors and evolution mechanism in ice shelf change, so as to deepen our understanding of the response of the Antarctic ice sheet/ice shelf to climate change.

  • Yulun ZHANG, Yetang WANG, Shugui HOU
    Journal of Glaciology and Geocryology. 2022, 44(3): 843-862. https://doi.org/10.7522/j.issn.1000-0240.2022.0082
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    With the global warming, Antarctica is increasingly becoming the attentive hotspot in global climate change research. However, there is a principal reason for our poor understanding the mechanism of climate change in Antarctica due to the inadequate meteorological observations. Polar Weather Research and Forecasting Model (Polar WRF), one of the most advanced limited-area models, is an appropriate tool available for offsetting the lack of observations. It is crucial to assess the performance of Polar WRF before application for climate change studies because of the model’s uncertainties. Simulated 2 m temperature, 10 m wind speed and near surface pressure over the Antarctic Ice Sheet for the period 2004—2013 are evaluated using 28 weather stations. Results show that there is a cold bias over coast of East Antarctica, a warm bias in the inland of East Antarctica, and both cold and warm biases exist in the Antarctic Peninsula. In addition, the simulation of wind speed and near surface pressure is overestimated in the entire ice sheet. The modeled 2 m air temperature and near surface pressure along the coast are more accurate than in the inland, but opposite for the wind speed. In general, Polar WRF shows a good skill in simulating 2 m air temperature, 10 m wind speed and near surface pressure. The trend of observed air temperature, wind speed and near surface pressure in the period of 2004 to 2013 is roughly captured by simulations. Moreover, the simulated annual mean 2 m temperature and near surface pressure simulated passed significance test of α=0.1, the seasonal and monthly errors are relative lower, and the correlation of all months are greater than 0.90 and 0.79 respectively. While some larger errors exist in costal stations for wind speed, the correlation between seasonal and monthly mean simulated wind speed and observed wind speed is greater than 0.5 and the error value is less than 4.5 m·s-1. Overall, as a weather model, Polar WRF performs well in simulating long time scale weather and climate.

  • Liyun ZHAO, Xueyuan TANG, Tong ZHANG, Wei LENG, Songtao AI, Chengyan LIU, Yuzhe WANG, Yan LIU, Chao YUE
    Journal of Glaciology and Geocryology. 2022, 44(3): 863-871. https://doi.org/10.7522/j.issn.1000-0240.2022.0083
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    Numerical simulation of ice sheets is a method to understand the physical mechanism of ice flow movement, diagnose and predict its evolution by constructing and solving the dynamic equations of ice flow based on multi-source observation data. Numerical simulation has been widely used in the study of ice sheet change. In this review, we briefly introduce the numerical simulation methods of polar ice sheets, summarize the research progress of Chinese scholars in polar ice sheets numerical simulation in the last decade, and identify the bottlenecks and key problems encountered in the field of ice sheet numerical simulation in China. We expound how to combine the advantageous areas of polar ice sheet scientific research in China, cooperate with multi-source enhanced observation and numerical simulation, develop and improve the ice sheet model, enhance the ice sheet simulation ability, and contribute to the quantitative estimation of polar ice sheets mass balance and its impact on future sea level rise. By gradually developing the research ability of ice sheet model, it is expected to make a breakthrough in the scientific understanding of key dynamic processes and mechanisms of ice sheets in the future.

  • Zhenxiang FANG, Ninglian WANG, Xiang LI, Yujie ZHANG, Xuenan TAI
    Journal of Glaciology and Geocryology. 2022, 44(3): 872-884. https://doi.org/10.7522/j.issn.1000-0240.2022.0084
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    The monitoring of the Greenland Ice Sheet is of great significance to global and Arctic climate change. As the largest Ice Sheet in the Northern Hemisphere, the Greenland Ice Sheet is critical to the climate response and has always been the focus of global attention. Based on the MODIS temperature product data, this paper analyzes the interannual trend of the Greenland Ice Sheet summer surface temperature and surface melting range from 2000 to 2020. The effect of surface temperature on the mass balance of the Greenland Ice Sheet is analyzed with IMBIE data, and the effect of atmospheric circulation on the surface temperature of the Greenland Ice Sheet is discussed. The results show that the trend of summer surface temperature and melting range of the Greenland Ice Sheet is consistent, showing a positive upward trend from 2000 to 2012, reaching a peak in 2012, and then showing a downward trend of fluctuation. The northern part of the Greenland Ice Sheet had the highest rate of warming during the study period, more than twice as fast as any other region, the south-east and south-west had the highest temperatures but the lowest growth rates; And there was a strong correlation between the Greenland Ice Sheet’s summer surface temperature, the extent of melting, and the mass balance, at the same time, an increase of 1 °C in the summer surface temperature of the Greenland Ice Sheet will lead to an increase of 74.29 Gt·a-1 in mass loss. Finally, the NAO (North Atlantic Oscillation) and GBI (Greenland blocking index) indices are analyzed, the influence of GBI on the surface temperature of Greenland Ice Sheet in summer is stronger than that of NAO. Greenland Ice Sheet surface temperature is negatively correlated with NAO (r=-0.64, P<0.05) and positively correlated with GBI (r=0.77, P<0.05).

  • Shanshan HOU, Ninglian WANG, Zhijie LI
    Journal of Glaciology and Geocryology. 2022, 44(3): 885-899. https://doi.org/10.7522/j.issn.1000-0240.2022.0085
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    Glacial meltwater is an important freshwater resource in the Caucasus and is important for regional irrigation and hydroelectricity generation. This paper analyses the spatial and temporal patterns of glacier change in the Caucasus Mountains from 1960 to 2020 based on Landsat images, coherence images from Sentinel-1 image pairs, GLIMS glacier inventory and WGMS glacier mass balance data. The results of the study show that in 2020 there were 1912 glaciers in the Caucasus Mountains, with a total area of (1 087.36±66.44) km2. The total glacier area shrank by (587.36±98.66) km2 (35.07±5.89%) between 1960 and 2020, with an average annual shrinkage rate of (0.58±0.10%)·a-1. The area shrinkage rates of Caucasian glaciers for 1960—1986, 1986—2000 and 2000—2020 are (0.44±0.20%)·a-1, (0.66±0.77%)·a-1 and (0.96±0.31%)·a-1, respectively, indicating that Caucasian glaciers in a state of accelerated retreat over the last 60 years. Analysis of mass balance information shows that both the Djankuat and Garabashi glaciers in the Caucasus have been in a strong negative equilibrium for nearly 60 years, with a significant acceleration of mass deficit after 2000. Analysis of climate data suggests that the strong warming is the main reason for the accelerated retreat of glaciers in the Caucasus mountains in recent decades.

  • Yong ZHANG, Shiyin LIU, Xin WANG
    Journal of Glaciology and Geocryology. 2022, 44(3): 900-913. https://doi.org/10.7522/j.issn.1000-0240.2022.0086
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    Debris cover is widespread over the ablation zones of glaciers in the Tibetan Plateau and surroundings. It dramatically alters melt progress and its spatial pattern through the energy and water exchange between land surface and atmosphere and albedo change, and then affects the response mechanism of mass balance, runoff generation and disaster process. Debris-covered glaciers are fundamentally different from those of debris-free glaciers. This review systematically analyzes the spatial distribution characteristics of debris cover over the Tibetan Plateau and surroundings, and comprehensively examines the influence of debris thickness and its spatial distribution on the processes of ice melt, mass balance and catchment runoff, as well as the response of these processes to climate change. Furthermore, the study progress of debris-cover effect is also systematically analyzed from the perspective of field observation and model simulation. Despite the importance of debris cover, the influence of debris cover in glacier mass balance and runoff models at different scales is still insufficient. Consequently, there remains challenges in applying these models to study the influence of debris thickness and its dynamic change under the climate change. In the future, we will focus on the understanding of the interaction and feedback mechanisms of climate-glacier-debris system, develop a dynamic model of the co-evolution of the ice-debris system considering key physical processes, and then forecast the dynamic impact and change in debris cover on regional water resources due to climate change, thus serving the regional social and economic development and the green silk road construction.

  • Junfeng WEI, Te ZHANG, Yong ZHANG, Xin WANG, Zongli JIANG, Yajie ZHENG
    Journal of Glaciology and Geocryology. 2022, 44(3): 914-929. https://doi.org/10.7522/j.issn.1000-0240.2022.0087
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    The lake-terminating glaciers, due to the effect of proglacial lakes, have experienced a greater mass loss than land-terminating glaciers, which in turn accelerated the expansion of proglacial lakes. Reconstruction of the mass change from lake-terminating glaciers could provide basic data and method references for the studies of the responses of glaciers with different types to climate change and risks of glacial lake outburst. The annual mass changes of Longbasaba Glacier during 1989—2018 were estimated, by combining the results of model-estimated surface mass balance, terminal retreat, and ice-flow velocity. The total mass loss of Longbasaba Glacier was 0.315 km3 w.e. during the past three decades (0.114 km3 w.e.?a-1), and predominantly contributed by the surface mass loss, from which the contribution decreased during the last decade. The surface mass balance of Longbasaba Glacier, with the rate of -0.26 m w.e.?a-1 on average during 1989—2018, was more sensitive to the air temperature than the precipitation, and its responses in summer were more significant than other seasons. The debris cover promoted the surface mass melt for Longbasaba Glacier, and thinner debris cover could accelerate the surface mass loss.

  • Yin ZHAO, Yong ZHANG, Shiyin LIU, Xin WANG
    Journal of Glaciology and Geocryology. 2022, 44(3): 930-945. https://doi.org/10.7522/j.issn.1000-0240.2022.0089
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    Maritime glaciers mainly concentrate in the southeastern Tibetan Plateau, including the Hengduan Mountains, central and eastern Nyainqentanglha Mountains and eastern Himalayas, which show higher mass loss and accumulation and ice temperature compared to other glacier types, with relatively fast ice velocity. Maritime glaciers show the unique sensitive to the changing climate and have experienced the most dramatic mass loss over the past decades, with important consequences for assessing regional water resource availability and glacial hazards risk. It has become a hotspot for the cryosphere change of the Tibetan Plateau. This study summarizes the spatial and temporal characteristics of mass balance of maritime glaciers, and reviews the driving factors of accelerated mass change and new features of mass change of maritime glaciers. As a consequence of continuous temperature rising, precipitation changing and spatially distributed debris cover, maritime glaciers has been expriencing dramatic mass loss since the year of 2000, on which the average mass balance varies from -0.66 to -0.61 m w.e.·a-1. In particular, these glaciers experience an accelerating trend in mass loss over the past ten years. However, the current studies on maritime glacier mass balance still suffers from insufficient observational data and uncertainties of model simulations. In particular, the existing models are oversimplification or basically missing in discribing the processes such as ice crevasse enlargement, interaction between ice cliff, supraglcail pond and debris cover, englacial and subglacial system and ice avalanche as well as the interaction between ice and water at the terminus of lake-terminating glaciers, and their mechanisms and impacts are still uncertain. This study motivates further effort to further develop the monitoring system of maritime glacier mass balance, and improve models’ ability to couple the multi physical processes of glacier mass balance through conducting integrated research based on multi-data and multi-approaches. Overall, this study draws an intergrated view of understanding the characteristics of maritime glacier mass change and associated driven factors in the southeastern Tibetan Plateau, which provides a foundation for understanding and predicting the status of maritime glaciers and their responses to climate change as well as assessing the vulnerability of regional water resources and glacier-related hazards in the southeastern Tibetan Plateau.

  • Xinyue ZHONG, Shichang KANG, Wanqin GUO, Xiaodong WU, Jinlei CHEN
    Journal of Glaciology and Geocryology. 2022, 44(3): 946-953. https://doi.org/10.7522/j.issn.1000-0240.2021.0090
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    The Working Group I report of the Sixth Assessment Report (AR6) of the Intergovernmental Panel on Climate Change (IPCC) was released in August 2021. Base on updated and expanding data, AR6 presented the improved assessment of past changes and processes of cryosphere. AR6 also predicted the future changes using the models in CMIP6. The components of cryosphere were rapid shrinking under climate warming in the last decade. There were decreasing trends in Arctic sea-ice area and thickness. Sea-ice loss was significant. The Greenland Ice Sheet, the Antarctic Ice Sheet and all glaciers lost more mass than in any other decade. Global warming over the last decades had led to widespread permafrost warming, active layer thickness increasing and subsea permafrost extent reducing. Snow cover extent in the Northern Hemisphere also decreased significantly. However, the variations of snow depth and snow water equivalent showed great spatial heterogeneity. The rapid shrinking of the cryosphere accelerated the global mean sea level rise. The impact of human activities on cryosphere will become more significant in the future. The Arctic sea-ice area will decrease, and the Arctic Ocean will likely become practically sea ice-free. The Greenland Ice Sheet, the Antarctic Ice Sheet and glaciers will continue to lose mass throughout this century. Permafrost and Northern Hemisphere snow cover extent will continue to decrease as global climate continues to warm. In addition, there are still uncertainties in the prediction of cryosphere due to the absence of observations, the poor sensitivity of models to the components and processes of cryosphere, and the inexplicit represent of the mechanism of light-absorbing impurities. More attentions should be paid on these issues in the future.

  • Wanqin GUO, Zhen ZHANG, Kunpeng WU, Shiyin LIU, Donghui SHANGGUAN, Junli XU, Zongli JIANG, Xin WANG
    Journal of Glaciology and Geocryology. 2022, 44(3): 954-970. https://doi.org/10.7522/j.issn.1000-0240.2022.0091
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    Glacier surge is a key inducing factor for many types of glacier hazards. It has become a hot spot in global and domestic glaciological studies following the increasing occurrence of recent glacier surge related hazards such as ice avalanche, glacier collapse, glacier-debris flow, etc. According to an analyses of the published literatures, there are totally ca. 1 850 surge-type glaciers all over the world, which mainly distribute around circum-Arctic and in High Mountain Asia (HMA). There are totally 146 surge-type glaciers in western China referring to recent studies. Surge-type glaciers can be identified through their unique appearance on the surface, the dramatic changes of their termini, the changes among their surface elevation and velocity before and during their surges, and also by the geomorphological and sedimentological features caused by their surges. Most recent studies on surge-type glaciers were based on different kinds of remote sensing techniques, which mainly focused on their surface changes, and speculated the possible surge mechanisms from the results. Due to the limited accuracy of remote sensing techniques as well as the frequent constraints by weather and terrain on the data acquisitions, and also because of their incapability on obtaining the key englacial and subglacial parameters and processes that are vitally important to study the surge-type glaciers, field monitoring and investigations still play an irreplaceable role. Limited by the shortages on those field observation data, major deficiencies still exist in current knowledge about the mechanisms of glacier surges, which are largely confined on the two well-known glacier surge mechanisms, i.e., the thermal and hydraulic surge-triggering theory. The major problems encountered by the two mechanisms include the difficulties to explain the co-existence of surge-type glaciers with different mechanisms in same region, and to understand the phenomena of the surge initiation on the lower part of some glaciers. Meanwhile, large knowledge gaps also exist and obstructed our understandings about the impacts of climate change on surge-type glacier as well as the modelling and forecasting of the glacier surges, which all need to be considered with high priority in future studies.

  • Kai WANG, Yongling SUN, Shijin SUN, Xiao LIU
    Journal of Glaciology and Geocryology. 2022, 44(3): 971-983. https://doi.org/10.7522/j.issn.1000-0240.2022.0092
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    Skamri Glacier is the largest glacier in China, and it is a surge-type glacier. The study on the characteristics of glacial movement is of great significance for early warning of glacial disasters caused by glacier surge. In this paper, 20 pairs of Landsat-8 images from 2018 to 2021 were selected to extract the surface velocity of Skamri Glacier using optical image feature tracking method, analyze the uncertainty of velocity, and analyze the temporal and spatial changes characteristics of velocity of the glacier. The results show that there are obvious spatial differences in the surface velocity of Skamri Glacier. During the period from January 2018 to June 2019, the velocity of the south tributary of Skamri Glacier is much greater than that of its north tributary (west), while during the period from June 2019 to November 2021, it presents completely opposite spatial characteristics, which is mainly due to the sudden increase of the velocity of the north tributary (west) in June 2019. According to the results of velocity changes from 2018 to 2021, it is found that the north tributary (west) surges in June 2019 and is still in the surge period until November 2021. The north tributary (west) glacier terminus will advance about 320 m towards the main glacier from August 2020 to September 2021; The velocity of the south tributary has been very large during the study period, and the maximum velocity reaches 441 m·a-1; The velocity of the north tributary (east) of Skamri Glacier increased sharply in July 2021, and the tributary may surge; The velocity of the main glacier of Skamri Glacier increased significantly after the confluence of the south tributary and the surge of the two north tributaries. In addition, there are temporal and spatial differences in the elevation distribution of the maximum velocity of the main glacier and its tributaries in this area.

  • Shuzhen ZHU, Farong HUANG, Ting FENG, Xin ZHAO, Lanhai LI
    Journal of Glaciology and Geocryology. 2022, 44(3): 984-997. https://doi.org/10.7522/j.issn.1000-0240.2022.0093
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    Snow mass in mountains areas is an important water source and can bring economic benefits to regional development. Therefore, the amount of snow mass has a profound impact on regional water resources and economic development. The uncertainties in the spatial and temporal distribution of snow depth, snow cover and snow density, which integrally determine the amount of snow, result in the difficulties to determine the snow mass. This paper estimated the snow mass amount during the snow season (November to March ) and its different periods (accumulation, stable and melt period) in Tianshan Mountains over the past 40 years, and analyze its spatial and temporal distributions as well as its relationship with topographic and meteorological factors, using the dataset of snow depth time series from 1979 to 2020 and the snow density retrieving from the Fengyun 3B Microwave Radiation Imager (FY-3B/MWRI). The results showed that: (1) snow mass in the Tianshan Mountains varied in different periods from 1979 to 2020, i.e. the snow mass in the stable period was the largest, followed by the ablation period and the smallest in the accumulation period. The maximum and minimum values of snow mass in snow season appeared in 1979 and 1998, respectively. The snow mass showed a slight downward trend during the study period, but a significant downward trend during the ablation period. (2) The spatial pattern of mean snow mass is consistent with snow depth and snow density during the study period, i.e. high in northwest and low in southeast. (3) The spatial distribution of snow mass is mainly affected by altitude and slope, and the snow mass is positively correlated with altitude. The higher the altitude, the higher snow mass. The slope below 15° has a great impact on snow mass, and the greater the slope within the 15° limit, the higher the snow mass. (4) The multi-year variation of snow mass in different periods is closely related to air temperature. The lower the air temperature in certain range, the greater the snow mass. The change of snow mass in the stable period is also affected by precipitation in the accumulation period, i.e. higher precipitation, and more snow mass. The results of estimated snow mass in Tianshan Mountains based on the snow depth and density retrieved from remote sensing data may provide a reference for water resources utilization and economic development in Xinjiang under the condition of climate change.

  • Xiaochong PANG, Xiaoming ZHU, Yanhu MU, Kun ZHANG, Lijie ZHANG, Bo ZHENG, Lingjie LI
    Journal of Glaciology and Geocryology. 2022, 44(3): 998-1010. https://doi.org/10.7522/j.issn.1000-0240.2022.0094
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    Thermal insulation is widely used to prevent frost related damages to tunnels in cold regions. By laying thermal insulation materials, the heat exchange process between the tunnel structure and air flow in the tunnel can be slowed down, and then the seasonal freeze-thaw of lining and surrounding rock mass can be diminished. In engineering design, the length and thickness of thermal insulation materials in the tunnel are the two critical parameters, among which the laying thickness is relatively easy to determine. However, at present, there is no uniform standard and simple and reliable method for determining the laying length, which brings difficulty and uncertainty to design of thermal insulation. This paper systematically summarizes the engineering practice, research progress and challenges in determining the length of insulation section of tunnel in cold regions, including the requirements of existing railway and highway specifications, empirical formulas, engineering analogy, theoretical analysis, numerical simulation and so on. Based on the summary, some key issues that still need attention in future engineering practice and research was proposed. These issues include the selection of meteorological data for thermal insulation design, the basis for determining thermal insulation length, the difference between tunnel entrance and exit, and the difference between tunnels in seasonally frozen ground and permafrost regions. It is hoped that this review can provide a reference for future in-depth study and engineering design of thermal insulation of tunnels in cold regions.

  • Bin WANG, Chuanxin RONG, Hua CHENG, Haibing CAI
    Journal of Glaciology and Geocryology. 2022, 44(3): 1011-1020. https://doi.org/10.7522/j.issn.1000-0240.2022.0011
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    In order to reasonably analyze the mechanical properties of the heterogeneous frozen wall induced by directional seepage, the latest closure position of the frozen wall under the action of groundwater was regarded as the “dangerous section”, combining the piecewise equivalent method with the temperature characteristic points, the temperature curve expression of the frozen wall of this section was obtained. According to the linear relationship between mechanical parameters of frozen soil and freezing temperature, the frozen wall was regarded as heterogeneous material whose property changed with temperature function. Based on the M-C criterion, D-P criterion, generalized Tresca criterion and double shear strength criterion, the stress calculation formulas of heterogeneous frozen wall induced by directional seepage were derived. Basing on the formulas and the design parameters of freezing scheme, the mechanical property of the frozen wall was calculated and analyzed. The calculation results showed that: the bearing capacity of the frozen wall decreased with the increase of flow rate. At the flow rate of 5 m·d-1, the elastic ultimate bearing capacity and the plastic ultimate bearing capacity were 2.480, 2.462, 2.741, 3.202 and 4.349, 4.318, 4.561, 5.779, which were calculated based on M-C、D-P、generalized Tresca、 double shear criterion, respectively. When the flow rate increased to 10 m·d-1, the corresponding elastic ultimate bearing capacity and plastic ultimate bearing capacity decreased to 2.087, 2.085, 2.203, 2.784 and 3.700, 3.707, 3.908, 4.939. The radial stress of the frozen wall increased with the increase of the relative radius r, while the variation law of hoop stress in different regions was different. In the elastic limit state, the maximum value of hoop stress of the frozen wall appeared near the middle of the frozen wall. While in the plastic limit state, the maximum value of hoop stress appeared at the partition boundary (r=1.685) of the frozen wall.

  • Liang JIA, Nuliyanmu Xiafukaiti, Cen CHEN, Jian GUO, Dexiang BAO
    Journal of Glaciology and Geocryology. 2022, 44(3): 1021-1028. https://doi.org/10.7522/j.issn.1000-0240.2022.0095
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    With the increase of rapid repair and construction of concrete projects, it is significant for fast hardening cement with good frost resistance in the cold regions of China. Magnesium phosphate cement has the characteristics of high early strength, short initial setting time, good compatibility with concrete, and thus is seen as an excellent material for the concrete engineering required rapid construction. However, the cement mortar or concrete made of magnesium phosphate cement often suffers from freezing and thawing cycles in winter in northern China thereby causing various degrees of degeneration in its durability and strength. In order to enhance the frost resistance of magnesium phosphate cement, a certain amount of ferro-aluminate cement was used to replace over-burning magnesium oxide to prepare magnesium phosphate-ferro-aluminate composite cement during the preparation of magnesium phosphate cement. A conclusion can be drawn based on the quality loss test, strength test, porosity test and SEM-EDS test of magnesium phosphate-ferro-aluminate composite cement mortar specimens before and after freeze-thaw cycles. When the substitution rate of ferro-aluminate cement for MgO is 30%~40%, the loss rate of mass attains the minimum, and the compressive strength and flexural strength reach the peak, and the residual rates of the compressive strength and flexural strength achieve the highest, and the porosity is lowest for the prepared magnesium phosphate-ferro-aluminate composite cement mortar specimens after freeze-thaw cycles, and thus the frost resistance of the magnesium phosphate-ferro-aluminate composite cement prepared under the above mix ratio is optimal. The SEM-EDS tests show that for the magnesium phosphate cement mortar specimen after freeze-thaw cycles, the gel materials K-struvite existing in its matrix are partly dissolved, which results in a loose structure with plenty of gaps between the crystals. Magnesium phosphate-ferro-aluminate composite cement, which is prepared by adding ferro-aluminate to magnesium phosphate cement, generates a large number of crystals during the hydration reaction to fill in the matrix of the mortar specimen, and the amorphous hydration products have a certain compensation effect for the strength, which result in a great drop in the porosity and increase in the density and thus dramatically improves the frost resistance for magnesium phosphate-ferro-aluminate composite cement. Magnesium phosphate-ferro-aluminate composite cement provides a new material for concrete construction projects required rapid completion in winter in the northern cold areas of China.

  • Jing LI, Shiyin LIU, Shiqiang ZHANG, Rensheng CHEN, Qiudong ZHAO, Wanqin GUO, Donghui SHANGGUAN, Rongjun WANG, Xinyue ZHONG, Zhengliang YIN, Hongyi LI
    Journal of Glaciology and Geocryology. 2022, 44(3): 1029-1040. https://doi.org/10.7522/j.issn.1000-0240.2022.0096
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    Snowmelt runoff is a valuable water resource in Northwest China. In the past few decades, progress has been achieved in snowmelt runoff simulation in mountainous areas, including observation and simulation of snow melt process, improvement and development of distributed snow melt runoff model, and ability for application of snow melt runoff model with temporal and spatial distribution driving data. The development of interpolation algorithm, remote sensing and data assimilation technology provides data support for the widespread application of distributed snowmelt runoff model in northwest mountainous regions of China. Climate warming and economic and social development will further aggravate the contradiction between supply and demand of water resources in the arid regions of Northwest China, which requires higher precision and detail spatial and temporal resolution of snowmelt runoff simulation. Based on the progress and challenges on snowmelt runoff simulation in mountainous regions of Northwest China, following studies need more attention: the mechanism of snow accumulation and ablation, snow cover spatial and temporal distribution monitoring and high precision of snow distribution data acquisition, quantitative climate change impact on river basin snowmelt runoff.

  • Qiong WANG, Xin WANG, Dongyu LEI, Yongsheng YIN, Junfeng WEI, Yong ZHANG
    Journal of Glaciology and Geocryology. 2022, 44(3): 1041-1052. https://doi.org/10.7522/j.issn.1000-0240.2022.0097
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    The coupling process of the glacier and glacial lake is a significant component of the cryosphere material and energy cycle, and it’s crucial for improving the theoretical system of cryosphere science and recognizing the changing pattern of glacierized region, water cycle model, and disaster effect to depict the interaction mechanism between glacier evolution and glacial lake development, systematically. Establishing the mountain glacier evolution and glacial lake development process, this paper systematically summarizes the research advance of the coupling process of the glacier and glacial lake, profiles the coupling mechanism of glaciation and glacial lake development and the application of relevant models, and analyzes and summarizes the shortcomings and challenges of the present research on the coupling mechanism of glacier evolution and glacial lake development.The results suggest that the environmental topographic factors around the glacial lake parent glacier dominate the glaciation process and glacial lake development, and constrain the characteristics of the lake basin. Glacier slope (surface slope, bottom topography) controls glacier dynamics and influences glacial lake differentiation; the surrounding rocks participate in the glaciation process and directly constitute the glacial lake basin; glacier erosion, transport, deposition, and ablation processes shape the landform and material transportation to provide multiple topographic conditions for glacial lake development.The glacial lake basin receives water from all components of the environment, which makes the depressions eventually develop into lakes. The runoff generation and concentration mechanism is closely related to the glacier runoff yield and concentration, where glacier ablation and external water sources enter the glacier hydrological system, and the glacial lake basin converges and collects water from the glacial sink path to form glacial lakes; the bottom of the glacial lake basin and the dam structure formed by different glaciation control the glacial lake storage and discharge mechanism, which determines the glacial lake dynamics and final development form.There are extensive and profound effects of glacial lake evolution on glacier dynamics. Glacial lake hydrodynamics control glacier ice flow, as manifested by the transient acceleration of ice flow under the impact of drainage events, regulation of basal friction, and migration of grounding lines; glacial lakes act on surface albedo, intra-ice heat transfer, and ice melting point to control mass balance and influence glacier thermal ablation mechanisms. The ablation of the submerged part of the ice body of the incoming glacier is also influenced by a combination of elements such as topographic radiation, buoyancy, geometry, and heat exchange in the glacial lake and its surrounding landscapes; changes in terminal morphological features caused by rapid glacial lake drainage processes, glacial lake outbursts, and water pressure differences at the ice-water interface may trigger glacial terminal disintegration.The improvement of glacier-glacial lake interaction mechanism provides support for integrated numerical simulation and promotes model performance optimization and application. The simulation of coupled glacier-glacial lake process in the background of continuous improvement of mathematical foundation and development of hardware performance gradually changes and develops from empirical model and first-order approximation model to higher-order dynamics model, and gradually takes the parameters of debris coverage, intra-ice runoff, and grounding line into consideration, and the method is gradually integrated and complicated.In summary, the glacial lake development process under glaciation is the comprehensive effect of various elements. Relatively significant progress has been made in recent years in glacier-glacial lake coupling mechanism research and numerical simulation, from single, qualitative research to higher-order, quantitative research, and the methods are gradually integrated and complicated. However, the theoretical system of glacier-glacier-lake-hazard is still not well developed, and the numerical simulations still do not reflect all components integratingly. Exploring the knowledge of the mechanism of the glacier-glacier lake coupling process will build the theoretical support for the improvement of numerical simulation and the enhancement of model accuracy and credibility, which will contribute to the enhancement of the credibility and accuracy of numerical simulation and to the provision of data and theoretical basis for assessing the impact of glacier-glacier-lake coupling process, establishing disaster monitoring and early warning system and taking adaptive measures.

  • Zijing FENG, Tianhao HE, Shaoyong WANG, Xiaobo HE, Hongkai GAO
    Journal of Glaciology and Geocryology. 2022, 44(3): 1053-1062. https://doi.org/10.7522/j.issn.1000-0240.2022.0098
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    Albedo has been considered an important factor affecting the process of glacier runoff and mass balance, but still lack of quantitative studies. In this study, albedo and incoming shortwave radiation are taken into account in the glacier hydrological model FLEXG, and tested in the Dongkemadi River Basin, in the source region of the Yangtze River. To account for spatial heterogeneity, the basin was classified into 19 elevation bands at 50 m intervals, and was divided into 3 different aspects (north facing, south facing and west/east facing) for both glacier and non-glacier regions. Observed hydrology and meteorology data from 2005 to 2009, MODIS(MOD10A1) daily albedo product and daily incoming shortwave radiation product during ablation seasons (May-September) were used to force the models, and calibrate the parameters. The hydro-meteorological data and glacier mass balance data from 2010 to 2014 were used to validate model performance. Monte Carlo sampling was used to generate 2×104 sets of parameters within the prior range. Kling-Gupta efficiency (KGE) was used as an objective function to evaluate model performance in calibration. Then the best one percent of parameter sets was regarded as behavioral ones for further analysis and generate uncertainty ranges of the simulated runoff. The results showed that consideration of the albedo and incoming shortwave radiation could increase the model realism, including daily runoff, glacier mass balance, and the glacial runoff proportion. More specifically, the runoff simulation was improved from KGE=0.49 to KGE=0.51, the glacier mass balance simulation was improved from R2=0.67 to R2=0.83; and the glacier runoff proportion was increased from 63% to 66%, which is closer to the previous result obtained by isotopic hydrograph separation. This study illustrates that considering the albedo and incoming shortwave radiation can improve the performance and model realism of the degree-day factor model.

  • Yuting LIU, Jingshi LIU, Guligena Halimulati, Namaiti Tuoheti
    Journal of Glaciology and Geocryology. 2022, 44(3): 1063-1069. https://doi.org/10.7522/j.issn.1000-0240.2022.099
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    Climate of the middle Himalayas in 2005 was warm and dry, particularly with the highest summer temperatures. Used both observed hydrometeorologic data at the Rongbuk glacier of Mount Qomolangma and discharge data at glacier-fed Karuxung watershed and meteorologic data at the Nargaze station in the Yamdrok lake basin, the meltwater flow processes were analyzed for the two studied river, and established the numerical model for ice and snow ablation. The results showed that there was good statistical correlation (r>0.8) between temperature and precipitation in the two basins, indicated that the climate processes in the two regions were similar at the regional scale. The melting intensity of Rongbuk glacier was 2 times of that of Kaluxiongqu glacier, and the glacial retreat rate was 2.5 times of that in Kaluxiongqu glacier, indicated that the water loss estimated by glacial melting temperature basically reflected the fact of glacier changed in two places. The proposed model can be used to estimate the melt water and glacier changes in the vast glacier basins between the two glacier regions, and to reconstruct the long-term hydrological processes and water resources changes in Qomolangma and other parts of the Himalayas.

  • Diyuan NIU, Jianyong LI, Ninglian WANG, Jianfeng DU, Xiaojun CHEN
    Journal of Glaciology and Geocryology. 2022, 44(3): 1070-1082. https://doi.org/10.7522/j.issn.1000-0240.2022.0088
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    Based on the pollen spectrum characteristics of 46 surface samples collected in the western Tianshan Mountains of Xinjiang and a plant community quadrat survey, we analyzed the relationship between pollen assemblages and modern climate and vegetation distribution in the region. The results showed the surface pollen assemblages were consistent with the distribution of modern vegetation. Based on the results of cluster analysis, the study area could be divided into three pollen assemblage zones (mountain steppe zone, desert vegetation zone and typical desert zone). In general, pollen assemblage can roughly reflect the main characteristics of local vegetation, but there are significant differences in the percentage of some pollen types and the coverage of related plants. The pollen of Picea and Pinus in arbor plants, Ephedra in shrub plants, Chenopodiaceae and Artemisia in herb plants were high represented due to the influence of natural wind, water flow and their own pollen yield. While Rosaceae pollen in shrubs and Poaceae in herbs were less representative in a modern plant community with its own dominant species; The Artemisia and Chenopodiaceae (A/C) ratio can distinguish the desert zone from the mountain steppe zone, and could clearly reflect the aridity level. However, when using this indicator to reconstruct the climate environment, it is necessary to combine the characteristics of pollen assemblage and the influence of changes in vegetation composition and other factors to distinguish; Altitude, average annual precipitation, and average annual temperature all affect the distribution of surface pollen in the area.

  • Lide TIAN, Mingxing TANG
    Journal of Glaciology and Geocryology. 2022, 44(3): 1083-1090. https://doi.org/10.7522/j.issn.1000-0240.2021.0100
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    Ice core is nature archives to rebuild paleo climate and environment in varying time scale with high resolution and high fidelity, while precise ice core dating is the prerequisite for such a purpose. This paper presented a review of ice core dating methods mostly used in the Tibetan Plateau ice core research, and also addressed the challenge and opportunity involved in the ice core dating. Conventional dating methods includes annual layer counting, radioactive laying marker, glacier flow modeling, comparison with other established chronology, and radioactive dating. The most reliable dating method is the annual layer counting. However, this method is limited in the middle and lower part of ice core as the annual layer become too thin to be identified as ice moves towards the bottom of glacier. The glacier flow modeling is restricted by larger uncertainty in the dating result and hard to be verified. The achievements in the ice core research require an improvement in the ice core dating precision. Therefore, we also reviewed the new technology and methods emerged in recent years made available in the ice core dating. Ice core continuous measuring technique (e g., ice core water isotope continuously measurement, laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS)), provides sub-millimeter-scale sampling resolution, and therefore, can extend the annual layer counting method to the bottom of ice core. Noble gas (85Kr、81Kr、39Ar) radioactive dating method based on ATTA (Atom Trap Trace Analysis) provided a revolutional method for absolute dating of glacier ice, as for their stability and homogeneity in the atmosphere. Dissolved organic carbon (DOC) 14C dating will make its practice in laboratory ice dating due to its less ice sample size used and showed its potential in the ice core dating. In addition, low level 3H in ice core measurement, particular prior to the nuclear test epoch, can be used to dating the ice core age in the past 1~2 centuries as for its concentration steps with the solar cycle. These new methods and technique provide the potential wide practice in the recent and future alpine ice core dating, and therefore, benefit the future ice core research.

  • LI Xubing , HUANG Xiaodong , LIU Aili
    Journal of Glaciology and Geocryology. 2022, 44(3): 1091-1099. https://doi.org/10.7522/j.issn.1000-0240.2022.0101
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    At present,passive microwave data is the main data source for snow depth retrieval,and there is large uncertainty in snow depth retrieval due to its coarser spatial resolution. Due to its high measurement accura? cy,LiDAR has a specific potential in snow depth retrieval. This study tries to extract the snow depth of the snow season from October 2018 to September 2019 in the northern Xinjiang region based on the spaceborne LiDAR ICESat-2 data. Since it is difficult to obtain snow depth observation data at the ICESat-2 footprints,thus,this study first uses ground snow depth observations to verify the current popular passive microwave snow depth prod? ucts and then obtains reliable snow depth products,which are compared with the ICESat-2 snow depth data pro? duced in this study. The results show that the AMSR2 snow depth product has a large error and overall overesti? mation in northern Xinjiang. The long-term sequence of snow depth dataset in China(CHINA_SD)is relatively reliable,and which is used as a reference data for evaluating the simulated snow depth from ICESat-2;ICESat-2 snow depth is highly consistent with the snow depth products of CHINA_SD in terms of space and change trend, but ICESat-2 snow depth changes more continuously,indicating that ICESat-2 can not only extract the snow depth in regional,but also be more sensitive to the spatial change of snow depth than passive microwave data, and can obtain more details of snow depth spatial change,providing data support for refining the spatial distribu? tion of snow depth.
  • Junfeng LIU, Rensheng CHEN, Chuntan HAN, Shuhai GUO, Zhangwen LIU, Xueliang WANG, Wenwu QING
    Journal of Glaciology and Geocryology. 2022, 44(3): 1100-1108. https://doi.org/10.7522/j.issn.1000-0240.2022.0102
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    In order to achieve 4D (time+space) multi-objective and high-precision snow monitoring, a single-camera time-lapse Structure-from-Motion (SfM) photogrammetry setup was build-up and tested at two different places of Qilian Mountains. The one test was performed to estimate snow depth, snow cover area and their distribution on slope scale at Qilian Alpine station. Another experiments was carried out next to the August-one glacier to monitor snow-surface depth and snow-surface features at plot-scale. At slope scale, the 4D SfM photogrammetry is capable to acquire snow cover area with high accuracy. Yet the accuracy of 4D SfM photogrammetry derived snow depth was poor at slop scale. At plot-scale, the 4D SfM photogrammetry can obtain continuous snow surface characteristic information and snow depth well. The absolute error between the 4D SfM photogrammetry estimated and the SR50 observed snow depth was less than 3.4 cm. The 4D SfM photogrammetry performance varies with the variation of surface condition in different season. The best performance was reached with snow surface features were abundant in winter and in melt season. It is hard for 4D SfM photogrammetry to capture high precision and alignment achievement in spring. Our results suggest that 4D SfM photogrammetry can achieve long-term, continual, multi-objective and high-precision monitor of plot scale snow processes.