2020072556 Chen Kun (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Yu Qihao; Guo Lei; Zhang Guike and Zhang Dongming. A fast-freezing system to enhance the freezing force of cast-in-place pile quickly in permafrost regions: Cold Regions Science and Technology, 179, Paper 103140, illus. incl. 4 tables, 25 ref., November 2020. Based on Publisher-supplied data.
Quick refreezing of the soils surrounding a pile in permafrost regions has been an widely concerned issue for infrastructure construction, since the bearing capacity would be quite small before a full back-freeze was finished. In order to accelerate the refreezing process of cast-in-place pile and improve its freezing force in permafrost, a fast- freezing system (FFS) using the method of artificial freezing was put forward. Field test of two piles with and without FFS was conducted in Beiluhe of the Qinghai-Tibet Plateau (QTP). A three-dimensional thermal-fluid coupling model was established to analyze the cooling effect of FFS under different conditions. The results show that FFS has a significant cooling effect, which can quickly freeze the pile foundation to -3 °C » -4 °C, effectively reducing the temperatures of the surrounding soils and increasing the cold reserves of the pile foundation. Even if the molding temperature and the size of the pile increase, it can still reduce the temperature of the pile to below the natural ground temperature. Since FFS significantly reduced the temperature of soils around the foundation and kept the foundation under a lower interface temperature and a higher freezing force for 7 months, the cooling technology can save the latency time of subsequent construction and is meaningful to solve the problem of rapid construction of cast-in-place pile in permafrost.
2020072557 Liu Minghao (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Niu Fujun; Lin Zhanju; Luo Jing; Yin Guoan and Fang Jianhong. Field investigation on thermal characteristics of a slope-cooling structure for permafrost embankment in the Qinghai-Tibet Plateau: Cold Regions Science and Technology, 179, Paper 103150, illus. incl. 2 tables, 22 ref., November 2020. Based on Publisher-supplied data.
A poor cooling effect on warm permafrost (> -1.0 °C) was observed in the crushed-rock revetment embankment (CRRE), which is widely used in the Qinghai-Tibet Railway. The filling of the porous rock layers caused by wind-blown sand and rock-weathering in the Qinghai-Tibet Plateau can further weaken the cooling capacity of the CRRE and may cause instability of the railway vehicles. This study describes a novel slope-cooling structure (NSCS), which combines a CRRE and a slope-warming prevention measure. A full-scale embankment was built using the new design in a warm permafrost region of the plateau. Ground temperatures and air speeds in the pore space of rock layer of the slopes were monitored. The thermal characteristics of the NSCS were evaluated along with its cooling performance. The results indicated that the new slope structure produced an effective cooling process on the side-slopes and the subgrade permafrost. The permafrost table was elevated and the ground temperatures at the embankment shoulders showed a decreasing trend after construction, particularly under the shady side. Asymmetrical convection process, which exhibits a significantly higher air speed and frequency in winters than those in summers, was observed to occur in the rock layers of the new structure. The NSCS decreases the heat absorption during summers and thus is beneficial for the heat-dissipating of the side-slopes. Moreover, the NSCS can reduce the sunny-shady slope temperature difference, which is induced by embankment orientation; therefore, the symmetry of the embankment temperature distribution is maintained. In general, these cooling characteristics contribute to the enhancement of thermal stability of the embankment and confirm the application of the NSCS as an effective method for the design and maintenance of embankments formed on warm permafrost.
2020070498 Du Yizhen (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Cryosphere Research Station on the Qinghai-Tibet Plateau, Lanzhou, China); Li Ren; Zhao Lin; Yang Chengsong; Wu Tonghua; Hu Guojie; Xiao Yao; Zhu Xiaofan; Yang Shuhua; Ni Jie and Ma Junjie. Evaluation of 11 soil thermal conductivity schemes for the permafrost region of the central Qinghai-Tibet Plateau: Catena (Giessen), 193, Article no. 104608, illus. incl. 10 tables, geol. sketch map, 84 ref., October 2020.
Soil thermal conductivity (l), which describes the ability of the soil to transfer heat, is critical to understand the thermal regime of ground surfaces. In this study, in situ measurements of l were conducted at two field sites in the permafrost region of the central Qinghai-Tibet Plateau (QTP) and the results were used to evaluate 11 schemes of l at depths of 10-50 cm during the freeze-thaw cycle period. Our analyses revealed that l had a remarkable seasonal variation, due to the significant effects of soil moisture content and ice-water phase changes as temperature changed during the freeze-thaw cycle period. Among the selected schemes, the Johansen scheme, its three derivatives (i.e., the He scheme, Yang scheme and Zhao scheme), and the Campbell scheme were significantly superior to others. Moreover, the Johansen scheme ranked among the top schemes for frozen soil, while the Campbell scheme gave the most accurate values for unfrozen soil. The effects of different estimation methods of quartz content (q), dry l and the Kersten number (Ke) on the predicted schemes results were also evaluated. The results showed that, the methods used for the estimation of q and Ke had the greatest influence on the calculation results for the permafrost region. Overall, this research provides insights for the development of a l scheme for the permafrost region of the central QTP.
2020072525 Gao Qiang (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Wen Zhi; Brouchkov, Anatoli; Zhang Mingli; Feng Wenjie and Zhirkov, Alexander. Effect of a ventilated open structure on the stability of bored piles in permafrost regions of the Tibetan Plateau: Cold Regions Science and Technology, 178, Paper 103116, illus. incl. 1 table, 30 ref., October 2020. Based on Publisher-supplied data.
Temperature is a key factor that affects the adfreeze strength between frozen soil and a structure. Under the influence of climate change, permafrost degradation reduces the bearing capacity of bored piles in permafrost regions. Based on the monitoring results of bored piles at a site in Beiluhe and related simulations, the effect of a ventilated open structure (VOS) on the temperature at the pile-soil interface and the bearing capacity of bored piles was discussed. The results showed that climate warming can significantly reduce the bearing capacity of bored piles. The higher thermal conductivity of concrete than frozen soil had a negligible influence on thermal stability of pile. However, the temperature at the pile-soil interface decrease drastically within a year due to the lower surface boundary temperature beneath a VOS. Numerical simulation indicated that the bearing capacity of bored piles with a VOS increases during the first 25 years and then decreased. While the bearing capacity without a VOS decreases over 50 years. A VOS can improve the stability of bored piles, delay bearing capacity degradation of bored piles for at least 50 years, and significantly reduce the design pile length.
2020072524 Huang Long (Lanzhou Institute of Technology, School of Civil Engineering, Lanzhou, China); Sheng Yu; Wu Jichun; Cao Wei; Peng Erxing and Zhang Xiyan. Experimental study on mechanical interaction between buried pipe and soil during freezing: Cold Regions Science and Technology, 178, Paper 103129, illus. incl. 2 tables, 24 ref., October 2020. Based on Publisher-supplied data.
Understanding the frost-induced pipe-soil interaction is very important to address the problem of damage to buried pipelines caused by frost heaving. Herein, a frost heaving experiment was designed to investigate the mechanism of interaction between a buried pipe and frozen soil. Based on the data collected using various sensors, the variations of the soil parameters (such as temperature, water content, soil pressure, and frost heave) and the distributions of the deformation and stress of the pipe were analyzed. Furthermore, the checking calculation of the pipe stress was carried out. The experimental results show that the interaction between the pipe and the soil under frost heaving is a process of coordinated development of various forces and deformations. The pipe is deformed by frost heaving of the soil while the pipe itself restrains the frost heaving. There is a state of dynamic equilibrium between the pipe and the soil. The uneven changes in the internal properties of the soil are related to the restraint of the pipe. For the soil closer to the pipe, when the pipe deformation is small, the pipe restraint on the frost heaving is stronger, the frost heaving force is larger, and the frost heaving is smaller. In addition, the axial stress of a pipe caused by frost heaving can be calculated approximately by the method of bending stress analysis of a beam. The influence of cross-sectional deformation should be considered in the stability calculation of the pipe when the pipe is subjected to large loads. The experimental results can be used as a theoretical reference for pipeline designs in permafrost regions, particularly in the calculation of pipe strength and selection of pipe material.
2020067288 Daout, Simon (University of Oxford, Department of Earth Sciences, Centre for Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET), Oxford, United Kingdom); Dini, Benedetta; Haeberli, Wilfried; Doin, Marie-Pierre and Parsons, Barry. Ice loss in the northeastern Tibetan Plateau permafrost as seen by 16 yr of ESA SAR missions: Earth and Planetary Science Letters, 545, Paper no. 116404, illus. incl. sketch maps, 49 ref., September 2020.
InSAR time series of surface deformation from 16 yr of Envisat (2003-2011) and Sentinel-1 (2014-2019) ESA satellite radar measurements have been constructed to characterise spatial and temporal dynamics of ground deformation over an 80,000 km2 area in the permafrost of the northeastern Tibetan Plateau. The regional deformation maps encompass various types of periglacial landforms and show that seasonal thaw effects are controlled by the sediment type and local topography. High seasonal ground movements are concentrated on shallow slopes and poor-drainage areas in unconsolidated, frost-susceptible and fine-grained sediments within glacier outwash plains, braided stream plains, alluvial deposits or floodplains. Fast subsidence due to thaw settlement takes place during June/July while frost heave is intense during December/January when two-sided freezing of pore water under pressure causes prolonged ice segregation near the permafrost table. The analysis reveals pervasive subsidence of the ground of up to ~2 cm/yr, and increasing by a factor of 2 to 5 from 2003 to today, in high-relief and well-drained areas. The findings suggest that seasonal thaw increasingly affects ice-rich layers at the permafrost table, as well as high-rates of widespread mass movements of non-consolidated sediments, the latter amplified by an increase of effects from frost heave/thaw settlement.
2020072504 Gao Siru (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Wu Qingbai; Zhang Zhongqiong and Jiang Guanli. Simulating active layer temperature based on weather factors on the Qinghai-Tibetan Plateau using ANN and wavelet-ANN models: Cold Regions Science and Technology, 177, Paper 103118, illus. incl. 3 tables, sketch map, 25 ref., September 2020. Based on Publisher-supplied data.
Active layer temperature (ALT) is an important dynamic attribute in characterization of permafrost change. Accurate simulation of the dynamic changes of ALT is essential for management and application of monitoring ALT data. This paper discusses the use of artificial neural network (ANN) and wavelet-ANN (W-ANN) hybrid models to simulate and forecast the ALT time series data based on five weather factors: air temperature, precipitation, wind speed, downward longwave radiation and downward shortwave radiation. Data are available for cold (FH1 site) and warm (CM2 site) permafrost locations on the Qinghai-Tibetan Plateau for the period 1996-2010. The ANN-based and W-ANN-based ALT models are developed using data from 1996 to 2007 and ALT forecasts are produced for the period 2008-2010 at both sites. The results demonstrate that ANN and W-ANN models can precisely simulate the ALT. The W-ANN hybrid model that uses decomposed sub-series as input provides forecasting results that are more accurate than the ANN model, which uses original time series. Moreover, the W-ANN-based ALT model is found more appropriate for modeling complicated physical relations between inputs and output.
2020072501 Kong, Xiangbing (Laval University, Department of Civil and Water Engineering, Quebec City, QC, Canada); Doré, Guy; Calmels, Fabrice and Lemieux, Chantal. Investigation on the heat extraction capacity of the heat drain for thermal stabilization of embankments on thaw sensitive permafrost: Cold Regions Science and Technology, 177, Paper 103075, illus. incl. 2 tables, sketch map, 33 ref., September 2020. Based on Publisher-supplied data.
Construction of transportation infrastructure often results in permafrost degradation and climate warming amplifies this phenomenon. Heat drains, based on wintertime natural convection, are a new mitigation technique designed to limit or avoid the thawing of permafrost. In winter, heat extraction is enhanced by the buoyancy-driven convection of the pore-air due to unstable air density in the heat drain. To monitor the efficiency of this technique, a heat drain was constructed in the shoulder of the Tasiujaq airstrip in Northern Quebec, Canada, in the summer of 2007. Thermistors were installed beneath the side slopes to measure ground temperatures. A good thermal performance was observed resulting in thermal stabilization of the underlying permafrost. A thermal model was developed based on the Tasiujaq experimental site characteristics and conditions. The model was also calibrated to the field data collected at Tasiujaq. A set of design charts were developed through the model and were successfully validated using the measured data from Salluit, Northern Quebec, Canada, where a heat drain was installed in 2012.
2020072656 Burn, Christopher R., editor (Carleton University, Department of Geography and Environmental Studies, Ottawa, ON, Canada). Transactions of the International Permafrost Association number 3: Permafrost and Periglacial Processes, 31(3), p. 343-453, illus., July 2020. Individual papers are cited separately.
2020072665 Angelopoulos, Michael (Alfred Wegener Institute Helmhotz Centre for Polar and Marine Research, Potsdam, Germany); Overduin, Pier P.; Miesner, Frederieke; Grigoriev, Mikhail N. and Vasiliev, Alexander A. Recent advances in the study of Arctic submarine permafrost: in Transactions of the International Permafrost Association number 3 (Burn, Christopher R., editor), Permafrost and Periglacial Processes, 31(3), p. 442-453, illus., 118 ref., July 2020.
Submarine permafrost is perennially cryotic earth material that lies offshore. Most submarine permafrost is relict terrestrial permafrost beneath the Arctic shelf seas, was inundated after the last glaciation, and has been warming and thawing ever since. As a reservoir and confining layer for gas hydrates, it has the potential to release greenhouse gases and impact coastal infrastructure, but its distribution and rate of thaw are poorly constrained by observational data. Lengthening summers, reduced sea ice extent and increased solar heating will increase water temperatures and thaw rates. Observations of gas release from the East Siberian shelf and high methane concentrations in the water column and air above it have been attributed to flowpaths created in thawing permafrost. In this context, it is important to understand the distribution and state of submarine permafrost and how they are changing. We assemble recent and historical drilling data on regional submarine permafrost degradation rates and review recent studies that use modelling, geophysical mapping and geomorphology to characterize submarine permafrost. Implications for submarine permafrost thawing are discussed within the context of methane cycling in the Arctic Ocean and global climate change. Abstract Copyright (2020), John Wiley & Sons, Ltd.
2020072660 Ensom, Timothy (Wilfrid Laurier University, Department of Geography and Environmental Studies, Waterloo, ON, Canada); Makarieva, Olga; Morse, Peter; Kane, Douglas; Alekseev, Vladimir and Marsh, Philip. The distribution and dynamics of aufeis in permafrost regions: in Transactions of the International Permafrost Association number 3 (Burn, Christopher R., editor), Permafrost and Periglacial Processes, 31(3), p. 383-395, illus. incl. 1 table, sketch map, 87 ref., July 2020.
Aufeis, also known as an icing or naled, is an accumulation of ice that forms primarily during winter when water is expelled onto frozen ground or ice surfaces and freezes in layers. Process-oriented aufeis research initially expanded in the 20th century, but recent interest in changing hydrological conditions in permafrost regions has rejuvenated this field. Despite its societal relevance, the controls on aufeis distribution and dynamics are not well defined and this impedes projections of variation in aufeis size and distribution expected to accompany climate change. This paper reviews the physical controls on aufeis development, current broad-scale aufeis distribution and anticipated change, and approaches to aufeis investigation. We propose an adjustment to terminology to better distinguish between the formation process and resulting ice bodies, a clarification of the aufeis classification approach based on source water, and a size threshold for broad-scale aufeis inventory to facilitate collaborative research. We identify additional objectives for future research including advancing process knowledge at fine spatial scales, describing broad-scale distribution using current remote sensing capabilities, and improving our understanding and predictive capacity over the interactions between aufeis and landscape-scale permafrost, hydrogeological, geotectonic, and climate conditions. Abstract Copyright (2020), John Wiley & Sons, Ltd.
2020072659 Holloway, Jean E. (University of Ottawa, Department of Geography, Ottawa, ON, Canada); Lewkowicz, Antoni G.; Douglas, Thomas A.; Li Xiaoying; Turetsky, Merritt R.; Baltzer, Jennifer L. and Jin Huijun. Impact of wildfire on permafrost landscapes; a review of recent advances and future prospects: in Transactions of the International Permafrost Association number 3 (Burn, Christopher R., editor), Permafrost and Periglacial Processes, 31(3), p. 371-382, illus. incl. 1 table, sketch map, 98 ref., July 2020.
Changes in the frequency and extent of wildfires are expected to lead to substantial and irreversible alterations to permafrost landscapes under a warming climate. Here we review recent publications (2010-2019) that advance our understanding of the effects of wildfire on surface and ground temperatures, on active layer thickness and, where permafrost is ice-rich, on ground subsidence and the development of thermokarst features. These thermal and geomorphic changes are initiated immediately following wildfire and alter the hydrology and biogeochemistry of permafrost landscapes, including the release of previously frozen carbon. In many locations, permafrost has been resilient, with key characteristics such as active layer thickness returning to pre-fire conditions after several decades. However, permafrost near its southern limit is losing this resiliency as a result of ongoing climate warming and increasingly common vegetation state changes. Shifts in fire return intervals, severity and extent are expected to alter the trajectories of wildfire impacts on permafrost, and to enlarge spatial impacts to more regularly include the burning of tundra areas. Modeling indicates some lowland boreal forest and tundra environments will remain resilient while uplands and areas with thin organic layers and dry soils will experience rapid and irreversible permafrost degradation. More work is needed to relate modeling to empirical studies, particularly incorporating dynamic variables such as soil moisture, snow and thermokarst development, and to identify post-fire permafrost responses for different landscape types and regions. Future progress requires further collaboration among geocryologists, ecologists, hydrologists, biogeochemists, modelers and remote sensing specialists. Abstract Copyright (2020), John Wiley & Sons, Ltd.
2020072657 O'Neill, H. Brendan (Natural Resources Canada, Geological Survey of Canada, Ottawa, ON, Canada); Roy-Leveillee, Pascale; Lebedeva, Liudmila and Ling Feng. Recent advances (2010-2019) in the study of taliks: in Transactions of the International Permafrost Association number 3 (Burn, Christopher R., editor), Permafrost and Periglacial Processes, 31(3), p. 346-357, illus. incl. 2 tables, 103 ref., July 2020.
Taliks are bodies or layers of unfrozen ground in permafrost areas. Recent research on taliks has been driven largely by the potential for release of greenhouse gases as taliks expand, and engineering challenges associated with thawing permafrost. Observations of talik configuration and development have been assisted by advances in geophysical techniques that complement mechanical and thermal measurements. Suprapermafrost taliks have been observed in a range of settings associated with disturbance from wildfire and infrastructure. These features are included in a revised talik classification scheme presented in this paper. Observations of methane release have renewed interest in lake talik initiation and development, resulting in substantial efforts to model thaw lake expansion. Hotspots of methane release have also been identified at saline springs. Recent simulations indicate that groundwater flow can significantly accelerate talik expansion and that incorporating heat advection may be required for accurate transient simulations. Ongoing global warming is expected to exacerbate the effects of surface disturbances on talik development and limit the ability of permafrost to recover in marginal permafrost areas. Abstract Copyright (2020), John Wiley & Sons, Ltd.
2020072658 Tank, Suzanne E. (University of Alberta, Department of Biological Sciences, Edmonton, AB, Canada); Vonk, Jorien E.; Walvoord, Michelle A.; McClelland, James W.; Laurion, Isabelle and Abbott, Benjamin W. Landscape matters; predicting the biogeochemical effects of permafrost thaw on aquatic networks with a state factor approach: in Transactions of the International Permafrost Association number 3 (Burn, Christopher R., editor), Permafrost and Periglacial Processes, 31(3), p. 358-370, illus., 131 ref., July 2020.
Permafrost thaw has been widely observed to alter the biogeochemistry of recipient aquatic ecosystems. However, research from various regions has shown considerable variation in effect. In this paper, we propose a state factor approach to predict the release and transport of materials from permafrost through aquatic networks. Inspired by Hans Jenny's seminal description of soil-forming factors, and based on the growing body of research on the subject, we propose that a series of state factors-including relief, ice content, permafrost extent, and parent material-will constrain and direct the biogeochemical effect of thaw over time. We explore state-factor-driven variation in thaw response using a series of case studies from diverse regions of the permafrost-affected north, and also describe unique scaling considerations related to the mobile and integrative nature of aquatic networks. While our cross-system review found coherent responses to thaw for some biogeochemical constituents, such as nutrients, others, such as dissolved organics and particles, were much more variable in their response. We suggest that targeted, hypothesis-driven investigation of the effects of state factor variation will bolster our ability to predict the biogeochemical effects of thaw across diverse and rapidly changing northern landscapes. Abstract Copyright (2020), John Wiley & Sons, Ltd.
2020072662 Wang Shuangjie (State Key Laboratory of Road Engineering Safety and Health in High-altitude Regions, Shaanxi, China); Niu Fujun; Chen Jianbing and Dong Yuanhong. Permafrost research in China related to express highway construction: in Transactions of the International Permafrost Association number 3 (Burn, Christopher R., editor), Permafrost and Periglacial Processes, 31(3), p. 406-416, illus. incl. 2 tables, sketch map, 81 ref., July 2020.
Express highways are roads of high speed, large capacity, and transportation flexibility. The network of express highways in China has been developed over the last 30 years to accommodate the needs of a growing population and to facilitate economic development. Part of the network is in permafrost regions, where the construction and maintenance of these roads present significant engineering challenges due to permafrost degradation induced by climate warming and by construction. This paper summarizes the engineering problems encountered in the construction and maintenance of these express highways, and the mitigation techniques used to overcome them on new transportation projects in permafrost regions. Ten types of engineering problems along the Qinghai-Tibet Highway, the oldest and longest highway in the permafrost regions of China are identified. Their main cause is related to permafrost degradation in the subgrade beneath the road subbase. Settlement of the highway embankment due to thaw consolidation of degrading permafrost is the dominant mechanical distress observed. Mitigation techniques, mainly for enhancing heat convection beneath express highways, are discussed along with their effects. Research in China related to transportation projects may provide a reference for future express highway design and construction in permafrost regions around the world. Abstract Copyright (2020), John Wiley & Sons, Ltd.
2020072663 Wu Qingbai (Chinese Academy of Science, Northwest Institute of Eco-Environment and Resource, State Key Laboratory of Frozen Soil Engineering, Lanzhou, China); Sheng Yu; Yu Qihao; Chen Ji and Ma Wei. Engineering in the rugged permafrost terrain on the Roof of the World under a warming climate: in Transactions of the International Permafrost Association number 3 (Burn, Christopher R., editor), Permafrost and Periglacial Processes, 31(3), p. 417-428, illus. incl. 1 table, 110 ref., July 2020.
Permafrost is sensitive to both climate warming and engineering disturbance on the Qinghai-Tibet Plateau (QTP). These factors degrade the stability of infrastructure built on permafrost and reduce its service life. To counter these effects, cooling of the subgrade to lower permafrost temperature forms part of the engineering design on the QTP. Proactive cooling of the subgrade has been used in construction of the Qinghai-Tibet Railway (QTR), the Chaidaer-Muli Railway, the Qinghai-Tibet DC Power Transmission Line, and the Gonghe-Yushu Express Highway. As a consequence, there has been significant ground cooling and little permafrost thaw beneath these infrastructure projects. However, the QTR has experienced some problems, such as in the stability of transitions at bridge abutments, reductions to the convective capacity of crushed rock structures from infilling by eolian sand, and freeze-thaw damage. A monitoring network has been established to examine the influence of climate change for engineering stability on the QTP. Climate warming on the plateau will present significant challenges for engineering of proposed oil and gas pipelines, express highways and the high-speed railway from Golmud to Lhasa. Abstract Copyright (2020), John Wiley & Sons, Ltd.
2020072661 Zhao Lin (Nanjing University of Information Science & Technology, School of Geographical Sciences, Nanjing, China); Zou Defu; Hu Guojie; Du Erji; Pang Qiangqiang; Xiao Yao; Li Ren; Sheng Yu; Wu Xiaodong; Sun Zhe; Wang Lingxiao; Wang Chong; Ma Lu; Zhou Huayun and Liu Shibo. Changing climate and the permafrost environment on the Qinghai-Tibet (Xizang) Plateau: in Transactions of the International Permafrost Association number 3 (Burn, Christopher R., editor), Permafrost and Periglacial Processes, 31(3), p. 396-405, illus. incl. 4 tables, sketch map, 75 ref., July 2020.
Permafrost on the Qinghai-Tibet Plateau (QTP) has undergone degradation as a result of recent climate change. This may alter the thermo-hydrological processes and unlock soil organic carbon, and thereby affect local hydrological, ecological, and climatic systems. The relationships between permafrost and climate change have received extensive attention, and in this paper we review climate change for permafrost regions of the QTP over the past 30 years. We summarize the current state and changes in permafrost distribution and thickness, ground temperature, and ground ice conditions. We focus on changes in permafrost thermal state and in active-layer thickness (ALT). Possible future changes in ground temperature and ALT are also discussed. Finally, we discuss the changes in hydrological processes and to ecosystems caused by permafrost degradation. Air temperature and ground temperature in the permafrost regions of the QTP have increased from 1980 to 2018, and the active layer has been thickening at a rate of 19.5 cm per decade. The response of permafrost to climate change is not as fast as in some reports, and permafrost degradation is slower than projected by models that do not account for conditions deep in permafrost. Abstract Copyright (2020), John Wiley & Sons, Ltd.
2020072252 Qin Yanhui (Qingdao University of Technology, iSMART, Qingdao, China); Zhang Peng; Liu Wenfeng; Guo Zonghe and Xue Shanbin. The application of elevation corrected MERRA2 reanalysis ground surface temperature in a permafrost model on the Qinghai-Tibet Plateau: Cold Regions Science and Technology, 175, Paper 103067, illus. incl. 2 tables, 22 ref., July 2020. Based on Publisher-supplied data.
There is an urgent need to evaluate the accuracy of reanalysis datasets to improve the reliability of climate research, hydrology, ecology, engineering work, and so on. The ground surface temperature (GST) is also regarded as a significant upper boundary condition when simulating permafrost distribution. In this study, the newest Modern-Era Retrospective Analysis for the Research and Applications Version 2 (MERRA2) reanalysis GST from the National Aeronautics and Space Administration's (NASA) Global Modeling and Assimilation Office (GMAO) is compared with GST data from 69 meteorological stations over the Qinghai-Tibet Plateau (QTP). Then, elevation correction of the MERRA2 GST was performed for different altitudes on seasonal scales. The correction indicates that the accuracy of raw MERRA2 GST data has been greatly improved after the elevation calibration. The decreased proportions of root mean square error (RMSE) for calibrated GST in winter, autumn, summer, and spring are 88.4, 92.8, 95.7, and 92.8%, respectively. The improvements in the mean bias error (MBE) in winter, autumn, summer, and spring are 88.4, 92.8, 95.7, and 92.8%, respectively. Most of the QTP presents a statistically increasing tendency of 0.2 to 0.5 °C/10a for GST at a significance level of 0.01 from 1980 to 2013. Then, the elevation corrected MERRA2 GST was applied in the surface frost number semi-physical permafrost model. The simulated results show that the permafrost area on the QTP is approximately 1.02 ´ 106 km2 in the early 21st century, excluding lakes and glaciers. The permafrost degradation was characterized by the disappearance of permafrost which mainly occurred in the eastern QTP.
2020072250 Wang Tao (China University of Mining and Technology, State Key Laboratory for Geomechanics and Deep Underground Engineering, Xuzhou, China); Zhou Guoqing; Wang Jianzhou and Chen Tuo. Statistical characteristics and probabilistic analysis of uncertain settlement of subgrade in permafrost regions: Cold Regions Science and Technology, 175, Paper 103079, illus. incl. 4 tables, 22 ref., July 2020. Based on Publisher-supplied data.
The settlement characteristics of permafrost subgrade are uncertain on account of the random thermal regime and mechanical parameters. This can affect the stability of permafrost foundation. In this study, the uncertain settlement behaviors of permafrost subgrade under global warming conditions are computed by Monte Carlo (MC) method. After that, the distributing fitting inspection of the samples of uncertain settlement characteristics are carried out. A probabilistic analysis methodology of the uncertain settlement of subgrade in permafrost regions is presented. The statistical characteristics and reliability of uncertain settlement for the subgrade center and shoulder are analyzed and predicted. This study presents a novel approach to estimate the stability of uncertain roadbed settlement. The results indicate that the uncertain settlement characteristics of embankment follow a normal distribution on the condition that significance level is 0.1. The reliability of subgrade center and subgrade shoulder varies with time, which imply railway operation have different risk in different seasons. The global warming can promote the thawing of permafrost foundations and it reduces the reliability. This study clearly clarifies the statistical characteristics and reliability of uncertain settlement characteristics of permafrost subgrade and the results can provide a reasonable basic data for the stability evaluation of permafrost subgrade.
2020068951 Glazer, Michal (University of Silesia, Faculty of Natural Sciences, Sosnowiec, Poland); Dobinski, Wojciech; Marciniak, Artur; Majdanski, Mariusz and Blaszczyk, Malgorzata. Spatial distribution and controls of permafrost development in non-glacial Arctic catchment over the Holocene, Fuglebekken, SW Spitsbergen: Geomorphology, 358, Paper no. 107128, illus. incl. sects., sketch map, 2 tables, geol. sketch map, 100 ref., June 2020.
This article presents the distribution and properties of the permafrost based on electrical resistivity tomography (ERT) and multichannel analysis of surface waves (MASW) data collected at the Fuglebekken coastal catchment area in SW Spitsbergen. This work summarizes the development of permafrost in this area during the Holocene, from the mountain environment through to the system of elevated marine terraces found around the coast. The ERT models were analysed taking into consideration the non-unique nature of the data inversion process and the physical limitations of this method. Comparing the ERT and the MASW results allows a zonal characterization of the occurring ice-bearing permafrost and its correlation with the evolution history of the catchment area. Maritime transgression as well as intensive watercourses during past degradation episodes have altered the permafrost presence and ice-accumulating abilities of different sediment zones. Permafrost development depends greatly on the presence of surface watercourses in talus slopes. The youngest elevated uplifted marine terrace did not develop an ice-rich permafrost, but the presence of permafrost in a cryotic form is possible. The significant range of the fjord water infiltration found within the sedimentary cover have influenced the development of the coastal permafrost. The current structure of ice-bearing permafrost found in the research area seems to be very sensitive to the climatic changes. Based on these results, we propose a model for the formation of the current permafrost in the studied area.
2020064811 Albers, Britt M. C. (Wageningen University and Research, Wageningen, Netherlands); Molson, John W. and Bense, Victor F. Parameter sensitivity analysis of a two-dimensional cryo-hydrogeological numerical model of degrading permafrost near Umiujaq (Nunavik, Canada): Hydrogeology Journal, 28(3), p. 905-919 (French, Spanish, Chinese, Portuguese sum.), illus. incl. 4 tables, sketch maps, 45 ref., May 2020. Part of the topical collection Hydrogeology of a cold-region watershed near Umiujaq (Nunavik, Canada), prefaced by Lemieux, Jean-Michel, et al.
A calibrated field-scale numerical model of groundwater flow and permafrost degradation has been used in a sensitivity analysis of permafrost thaw on thermal and hydraulic parameters. The two-dimensional cryo-hydrogeological model was developed using the HEATFLOW-SMOKER code applied to the Umiujaq field site in Nunavik, Quebec, Canada, and includes coupled groundwater flow and advective-conductive heat transport with latent-heat and temperature-dependent thermal and hydraulic properties. Model sensitivity was evaluated by using the PEST code to systematically vary selected thermal and hydraulic parameters, and was quantified with respect to three system output variables or 'targets': subsurface temperature, groundwater velocity and ground-surface heat flux. PEST-derived model sensitivities were similar for all targets which contained subsurface temperature profiles, while sensitivities were slightly higher when only summer conditions were considered as the target compared to a full year of data. This trend was attributed to greater heat exchange at the ground surface during the summer months, leading to a more active groundwater flow system and greater feedback to the thermal regime. For all targets, the hydraulic and thermal parameters of the shallow layers (fine sand and marine silt, respectively) as well as the parameters defining the ground-surface heat exchange layer, were more sensitive compared to the deeper layers (coarse sand and gravel, and unfractured bedrock). Sensitivities were also among the highest for the ground-surface heat flux target. High model sensitivity to these parameters highlights the importance of detailed site characterization in the near-surface zone for more realistic simulations of permafrost dynamics.
2020064808 Cochand, Marion (Université Laval, Département de Géologie et de Génie Géologique, Laval, QC, Canada); Molson, John; Barth, J. A. C.; Van Geldern, R.; Lemieux, Jean-Michel; Fortier, Richard and Therrien, Rene. Rapid groundwater recharge dynamics determined from hydrogeochemical and isotope data in a small permafrost watershed near Umiujaq (Nunavik, Canada): Hydrogeology Journal, 28(3), p. 853-868 (French, Spanish, Chinese, Portuguese sum.), illus. incl. 1 table, sketch maps, 72 ref., May 2020. Part of the topical collection Hydrogeology of a cold-region watershed near Umiujaq (Nunavik, Canada), prefaced by Lemieux, Jean-Michel, et al.
Hydrogeochemical data are used to better understand recharge dynamics and to support a hydrogeological conceptual model in a 2-km2 watershed in a discontinuous permafrost zone in Nunavik, Canada. The watershed contains an upper (surficial) and lower aquifer within Quaternary deposits, above and below a marine silt layer containing ice-rich permafrost mounds. The analysis is based on water samples from precipitation, groundwater monitoring wells, ground ice in permafrost mounds, thermokarst lakes and a perennial stream. Groundwater geochemistry in both aquifers reflects young, poorly evolved waters, with mainly Ca-HCO3 water types and low mineralisation ranging from 11 to 158 mg/L total dissolved solids (TDS), implying short pathways and rapid travel times of a year or less. While relatively low, TDS signatures in groundwater and surface water show increasing values downgradient. Groundwater isotope values (d18OH2O and d2HH2O) are often strongly influenced by snowmelt, while those of thermokarst lakes show evidence of evaporation. Recharge along the cuesta contributes to a transverse component of groundwater flow within the valley with higher TDS and d13CDIC values influenced by open-system weathering. Even where permafrost-free, the marine silt unit has a strong confining effect and plays a more important role on recharge dynamics than the discontinuous permafrost. Nevertheless, the vulnerability of these types of hydrogeological aquifer systems is expected to increase due to rapid recharge dynamics associated with the gradual loss of the confining effect of permafrost. This hydrogeochemical data set will be useful as a baseline to document impacts of permafrost degradation on the hydrogeological system.
2020064810 Dagenais, S. (Université Laval, Département de Géologie et de Génie Géologique, Quebec City, QC, Canada); Molson, John; Lemieux, Jean-Michel; Fortier, Richard and Therrien, Rene. Coupled cryo-hydrogeological modelling of permafrost dynamics near Umiujaq (Nunavik, Canada): Hydrogeology Journal, 28(3), p. 887-904 (French, Spanish, Chinese, Portuguese sum.), illus. incl. 4 tables, sketch maps, 60 ref., May 2020. Part of the topical collection Hydrogeology of a cold-region watershed near Umiujaq (Nunavik, Canada), prefaced by Lemieux, Jean-Michel, et al.
A two-dimensional (2D) cryo-hydrogeological numerical model of groundwater flow, coupled with advective-conductive heat transport with phase change, has been developed to study permafrost dynamics around an ice-rich permafrost mound in the Tasiapik Valley near Umiujaq, Nunavik (Quebec), Canada. Permafrost is degrading in this valley due to climate warming observed in Nunavik over the last two decades. Ground temperatures measured along thermistor cables in the permafrost mound show that permafrost thaw is occurring both at the permafrost table and base, and that heat fluxes at the permafrost base are up to ten times higher than the expected geothermal heat flux. Based on a vertical cross-section extracted from a 3D geological model of the valley, the numerical model was first calibrated using observed temperatures and heat fluxes. Comparing simulations with and without groundwater flow, advective heat transport due to groundwater flow in the subpermafrost aquifer is shown to play a critical role in permafrost dynamics and can explain the high apparent heat flux at the permafrost base. Advective heat transport leads to warmer subsurface temperatures in the recharge area, while the cooled groundwater arriving in the downgradient discharge zone maintains cooler temperatures than those resulting from thermal conduction alone. Predictive simulations incorporating a regional climate-change scenario suggest the active layer thickness will increase over the coming decades by about 12 cm/year, while the depth to the permafrost base will decrease by about 80 cm/year. Permafrost within the valley is predicted to completely thaw by around 2040.
2020064806 Fortier, Richard (Université Laval, Département de Géologie et de Génie Géologique, Quebec City, QC, Canada); Banville, David-Roy; Lévesque, Richard; Lemieux, Jean-Michel; Molson, John; Therrien, René and Ouellet, Michel. Development of a three-dimensional geological model, based on Quaternary chronology, geological mapping, and geophysical investigation, of a watershed in the discontinuous permafrost zone near Umiujaq (Nunavik, Canada): Hydrogeology Journal, 28(3), p. 813-832 (French, Spanish, Chinese, Portuguese sum.), illus. incl. strat. cols., 2 tables, sketch maps, 53 ref., May 2020. Part of the topical collection Hydrogeology of a cold-region watershed near Umiujaq (Nunavik, Canada), prefaced by Lemieux, Jean-Michel, et al.
Among the few positive impacts of climate warming in cold regions, permafrost degradation can increase the availability of groundwater as a potential source of drinking water for northern communities. Near the Inuit community of Umiujaq in Nunavik, Canada, a watershed in a valley in the discontinuous permafrost zone was instrumented to monitor the impacts of climate change on permafrost and groundwater, and assess the groundwater availability and quality. Based on Quaternary chronology, knowledge of periglacial processes, and an investigation carried out in the valley (including mapping of Quaternary deposits and ice-rich permafrost distribution, drilling and sampling of deposits, and geophysical surveys), a three-dimensional (3D) geological model of the watershed was built into GoCAD to assess the hydrogeological context in this degrading permafrost environment. In total, six units were identified within the watershed including an upper aquifer in marine sediments, a lower aquifer at depth in glaciofluvial and glacial sediments, and the bedrock acting as a low-permeability boundary. An aquitard, made of frost-susceptible silty sand and discontinuously invaded by ice-rich permafrost, confines the lower aquifer. This 3D geological model clarifies the local stratigraphic architecture and geometries of Quaternary deposits, especially the stratigraphic relationship between the two aquifers, aquitard, and bedrock, and the extent of ice-rich permafrost within the watershed. It is the cornerstone to understand the groundwater dynamics within the watershed and to carry out numerical modelling of coupled groundwater flow and heat transfer processes to predict the impacts of climate change on groundwater resources in this degrading permafrost environment.
2020064809 Jamin, Pierre (Liège Université, Département Urban and Environmental Engineering, Liege, Belgium); Cochand, M.; Dagenais, S.; Lemieux, Jean-Michel; Fortier, Richard; Molson, John and Brouyère, S. Direct measurement of groundwater flux in aquifers within the discontinuous permafrost zone; an application of the finite volume point dilution method near Umiujaq (Nunavik, Canada): Hydrogeology Journal, 28(3), p. 869-885 (French, Spanish, Chinese, Portuguese sum.), illus. incl. sects., 2 tables, sketch map, 46 ref., May 2020. Part of the topical collection Hydrogeology of a cold-region watershed near Umiujaq (Nunavik, Canada), prefaced by Lemieux, Jean-Michel, et al.
Permafrost thaw is a complex process resulting from interactions between the atmosphere, soil, water and vegetation. Although advective heat transport by groundwater at depth likely plays a significant role in permafrost dynamics at many sites, there is lack of direct measurements of groundwater flow patterns and fluxes in such cold-region environments. Here, the finite volume point dilution method (FVPDM) is used to measure in-situ groundwater fluxes in two sandy aquifers in the discontinuous permafrost zone, within a small watershed near Umiujaq, Nunavik (Quebec), Canada. The FVPDM theory is first reviewed, then results from four FVPDM tests are presented: one test in a shallow supra-permafrost aquifer, and three in a deeper subpermafrost aquifer. Apparent Darcy fluxes derived from the FVPDM tests varied from 0.5´10-5 to 1.0´10-5 m/s, implying that advective heat transport from groundwater flow could be contributing to rapid permafrost thaw at this site. In providing estimates of the Darcy fluxes at the local scale of the well screens, the approach offers more accurate and direct measurements over indirect estimates using Darcy's law. The tests show that this method can be successfully used in remote areas and with limited resources. Recommendations for optimizing the test protocol are proposed.
2020064805 Lemieux, Jean-Michel (Université Laval, Département de Géologie et de Génie Géologique, Quebec City, QC, Canada); Fortier, Richard; Molson, John; Therrien, René and Ouellet, Michel. Hydrogeology of a cold-region watershed near Umiujaq (Nunavik, Canada): Hydrogeology Journal, 28(3), p. 809-812 (French, Spanish, Chinese, Portuguese sum.), illus. incl. sketch maps, 23 ref., May 2020. Introduction to the topical collection Hydrogeology of a cold-region watershed near Umiujaq (Nunavik, Canada).
A cold-region watershed located in the discontinuous permafrost zone near Umiujaq (Nunavik, Canada) was studied in order to increase understanding of the subarctic water cycle and permafrost dynamics. This essay gives an overview of the research, summarised in a collection of six papers that: respectively characterize the physical three-dimensional cryo-hydrogeological system, present a detailed water balance of the watershed, characterize groundwater and surface-water hydrogeochemistry, describe the application of a tracer method to determine groundwater fluxes, develop a two-dimensional numerical model identifying impacts of groundwater flow on permafrost dynamics, and present a parameter sensitivity analysis. The work serves as a guide for developing site characterization plans at similar permafrost-impacted sites and for evaluating their groundwater resource potential.
2020064807 Lemieux, Jean-Michel (Université Laval, Département de Géologie et de Géie Géologique, Quebec City, QC, Canada); Fortier, Richard; Murray, Renaud; Dagenais, Sophie; Cochand, Marion; Delottier, Hugo; Therrien, René; Molson, John; Pryet, Alexandre and Parhizkar, Masoumeh. Groundwater dynamics within a watershed in the discontinuous permafrost zone near Umiujaq (Nunavik, Canada): Hydrogeology Journal, 28(3), p. 833-851 (French, Spanish, Portuguese sum.), illus. incl. block diag., 5 tables, sketch map, 49 ref., May 2020. Part of the topical collection Hydrogeology of a cold-region watershed near Umiujaq (Nunavik, Canada), prefaced by Lemieux, Jean-Michel, et al.
Groundwater distribution and flow dynamics were studied in a small watershed located in the discontinuous permafrost zone near Umiujaq in Nunavik (Quebec), Canada, to assess the seasonal variations and perform a quantitative analysis of the water cycle in a subarctic watershed. Due to the complexity of the subsurface geology within the watershed, an integrated investigation was instrumental to provide a detailed understanding of the hydrogeological context as a basis for the water balance. Based on this water balance, for the two studied hydrological years of 2015 and 2016, the average values are 828 mm for precipitation, 337 mm for evapotranspiration, 46 mm for snow sublimation, 263 mm for runoff, 183 mm for groundwater exchange (losses with other aquifers outside the watershed), and 0 mm for change in water storage. Although these values likely have significant uncertainty and spatial variability, this water balance is shown to be plausible. It was also found that permafrost influences surface water and groundwater interaction, even if located in low-permeability sediments. It is expected that permafrost degradation will likely increase stream baseflow, especially in winter.
2020069002 Zhang Liwei (Beijing Normal University, School of Environment, Beijing, China); Xia Xinghui; Liu Shaoda; Zhang Sibo; Li Siling; Wang Junfeng; Wang Gongqin; Gao Hui; Zhang Zhenrui; Wang Qingrui; Wen Wu; Ran Liu; Yang Zhifeng; Stanley, Emily H. and Raymond, Peter A. Significant methane ebullition from alpine permafrost rivers on the east Qinghai-Tibet Plateau: Nature Geoscience, 13(5), p. 349-354, illus. incl. geol. sketch map, 42 ref., May 2020.
2020072049 Wang Zunce (PetroChina Pipeline R&D Center, CNPC Key Laboratory of Oil & Gas Storage and Transportation, Langfang, China); Lu Zhaohong; Zhang Dong and Liu Haishui. Stress effect of the interface between buried pipeline and sandy soil layer in a cold environment: Cold Regions Science and Technology, 172, Paper 102981, illus. incl. 2 tables, April 2020.
The interaction between buried pipe and soil is an important aspect of disaster prevention and mitigation. In this paper, interfacial stress tests between room-temperature or frozen sand and pipeline were performed to study the interfacial stress problems experienced by a buried pipeline in sand. According to the basic assumptions, a calculation model for the mechanical stress of the buried pipeline was established. The experimental data were used to verify the correctness of the theoretical calculation model and the stress-displacement formula of the buried pipeline interface was fitted. The stress-displacement curve of the interface between the pipe and the room-temperature soil was compared with the stress-displacement curve of the interface between the pipe and the frozen soil. The results show that the interfacial stress value calculated by the theoretical model of pipe-soil interfacial stress is consistent with experimental values. The stress at the pipe-soil interface after the sand was frozen is much larger than the stress at the pipe-soil interface when the sand is at room temperature. Frozen soil has a great influence on the pipe-soil interaction. This theoretical formula can be used to analyze the interfacial stress problem for the pipe-soil coupling and lay a foundation for further studies of the influence of the permafrost-pipeline interaction on the stress and strength of the pipeline.
2020070221 Pan Haojie (Research Institute of Petroleum Exploration and Development, Beijing, China); Li Hongbing; Chen, Jingyi; Zhang Yan; Cai Shengjuan; Huang Yucheng; Zheng Ying; Zhao Yi and Deng Jian. A unified contact cementation theory for gas hydrate morphology detection and saturation estimation from elastic-wave velocities: Marine and Petroleum Geology, 113, Paper no. 104146, illus. incl. 4 tables, 77 ref., March 2020.
Good knowledge of hydrate morphology and accurate quantification of hydrate saturation are significant for reservoir characterization, resource exploitation and geohazards assessment. Although many of empirical or theoretical models have been developed to detect hydrate morphology and predict hydrate saturation from elastic-wave velocities, they either fail to hold true for complex morphologies or cannot provide accurate hydrate saturation estimate. In this study, we propose a unified contact cementation theory by applying the modified Hashin-Shtrikman upper and lower bounds to an extended cementation theory. By merging the cementation theory and effective medium theory, it can be used to account for four types of hydrate morphologies. Numerical modeling results provide some new insights into effects of normalized thickness of hydrate layer, friction coefficient and effective pressure on elastic-wave velocities for different morphologies, which will be helpful for analyzing the borehole stability and determining optimum production-related strategies. In addition, we propose a hydrate morphology-based inversion method by introducing the ratio of multiple hydrate morphologies from statistical analyses and apply it to the acoustic logs from the Mallik 5L-38 permafrost-related gas hydrate research well in Mackenzie Delta and other three marine wells in Nankai Trough and Hikurangi margin. The velocity-based gas hydrate saturation estimations are in good agreement with those predicted from resistivity log and Nuclear Magnetic Resonance measurement, as well as core data, confirming feasibility and applicability of our theory and inversion method, and indicating its potential in seismic characterization of gas hydrate reservoirs.
2020071717 Yu Wenbing (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Zhang Tianqi; Lu Yan; Han Fenglei; Zhou Yuanfu and Hu Da. Engineering risk analysis in cold regions; state of the art and perspectives: Cold Regions Science and Technology, 171, Paper 102963, illus. incl. 10 tables, 25 ref., March 2020. Based on Publisher-supplied data.
Climate change and anthropic activities increase the engineering risk in cold regions. This paper reviews the risk assessment of permafrost and constructions. Permafrost temperature, permafrost type, topography and geomorphology and vegetation were considered in former works. Permafrost risks and disaster zones were classified in Tibet Plateau and the arctic regions. Engineering risk assessment in cold regions is mainly divided into frost heave risk and thaw settlement risk according to difference mechanism. The present risk evaluation of constructions (tunnel, bridge, roadbed etc.) focuses on the thermal and mechanical stability, and then the probability and risk of structural instability under multi-factors with traditional risk assessment method, such as the expert scoring method, the analytic hierarchy process, the fuzzy comprehensive evaluation method etc. But there are some shortcomings of these methods. They need large historical data and some of them are subjective. The key of risk evaluation of infrastructures in cold regions is to improve the understanding of the interaction between the infrastructure and ambient factors, especially the climate warming and humidifying. A general coupled model of hydro-thermo-salt-mechanical need to be founded to establish a relatively objective and reliable risk assessment method, combined with numerical simulation and traditional methods.
2020071681 Li Fanghua (Guangxi University, College of Civil Engineering and Architecture, Nanning, China); Qin Yinghong; Wu Bo and Wang Tianyu. Experimental study on the cooling performance of shading boards with different emissivities at the underside: Cold Regions Science and Technology, 169, Paper 102902, illus., 25 ref., January 2020. Includes appendix.
The settlement of roadways in permafrost regions is sensitive to the warming of the permafrost under the roadbeds. Various measurements have been proposed to cool the roadbeds for preserving the underlying permafrost. One of these measurements is to install shading boards over the side slope of the roadway embankment for sheltering the side slope from solar insolation. Under the board, an air gap with a 30-50 cm thickness is left for draining the heat from the side slope via the stack effect. However, boards over such an air gap are rendering to the risk of wind damages, which have limited the application of the shading boards as a popular roadway-cooling method. Here we investigated if the heat gain of the embankment soil can be curtailed by reducing the emissivity of the board's underside (eu). A group of shading boards with different eu was placed side by side in a permafrost region for testing the temperature of the soils under the boards. It is found that the board with a lower eu retains the solar absorption at the board and curtails the heat radiating to the underlying soils. As a result, soils under shading boards with a lower emissivity at the underside stay cooler. Further studies are called to measure the soil temperature under boards with different eu in a long period and to understand how the condenser and icing on the board's underside influence the temperature of the embankment soils.
2020071674 Li Qiang (Zhejiang Ocean University, Department of Civil Engineering, Zhoushan, China); Shu Wenli; Duan Weiwei and Cao Lu. Vertical vibration of a pile in a double-layered stratum under the freezing and thawing processes of saturated porous media: Cold Regions Science and Technology, 169, Paper 102891, illus. incl. 3 tables, 26 ref., January 2020. Includes appendix.
In permafrost or seasonally frozen regions, due to seasonal factors or engineering factors, an active layer is produced at the upper part of the stratum to form a double-layered foundation which has an effect on pile integrity test. The theories of Leclaire's frozen porous medium and Biot's porous medium are used to simulate permafrost and unfrozen soil, respectively. A simplified model for studying the vertical vibration of a pile embedded in double-layered soil is established. The double-layered stratum is divided into four types of cases, according to the freezing or thawing of the upper active layer in the permafrost or seasonally frozen regions, and the analytical solutions of the dynamic responses at the pile head are obtained. The result shows that the simplified double-layered model is in good agreement with the monolayer solution and can meet the needs of engineering research. The effect of stratification caused by freezing and thawing processes on the vertical vibration of a pile is studied via the parametric analysis method. The results show that the freezing and thawing processes of permafrost or seasonally frozen soil have an obvious influence on the reflected wave curves of the pile.
2020071679 Zhang Zhongqiong (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Wu Qingbai; Jiang Guanli; Gao Siru; Ji Chen and Liu Yongzhi. Changes in the permafrost temperatures from 2003 to 2015 in the Qinghai-Tibet Plateau: Cold Regions Science and Technology, 169, Paper 102904, illus. incl. 2 tables, sketch maps, 23 ref., January 2020.
Alterations in the permafrost due to a warming climate increases the risk of permafrost thawing, accelerates carbon release, lowers super-permafrost groundwater, strengthens desertification, and destroys infrastructure. The permafrost temperature in six boreholes up to 40 m depth was measured from 2003 to 2015 along the Qinghai-Tibet Railway. Results showed an increase in the permafrost temperature, with an average of 0.14 °C decade-1 at 10 m depth. The deep permafrost showed significant warming with average rates of 0.11 and 0.09 °C decade-1 at 20 m and 30 m depth, respectively. At 40 m depth, the cold permafrost showed significant warming trend, but no evident warming trend was observed in the warm permafrost. With the ground temperature increases, the depth of the zero annual amplitude of the ground temperature of the warm permafrost slightly increased, whereas that of the cold permafrost decreased. Permafrost thickness was <30 m at the BL1 and TT1 sites and was thinner by 2.1 and 0.8 m from 2003 to 2015. Such changes in the permafrost temperature may have been driven by the long-term increase in the air temperature and precipitation on the Qinghai-Tibet Plateau (QTP). In the high-middle mountain areas of the QTP, the thermal effect of warming climate on the cold permafrost reached a depth of >40 m. In the high plain and basin of the QTP, the thermal effect of the warming climate on the warm permafrost reached a depth of 30 m.
2020064369 Bakker, Pepijn (Vrije Universiteit Amsterdam, Department of Earth Sciences, Amsterdam, Netherlands); Rogozhina, Irina; Merkel, Ute and Prange, Matthias. Hypersensitivity of glacial summer temperatures in Siberia: Climate of the Past, 16(1), p. 371-386, illus. incl. 3 tables, 57 ref., 2020.
Climate change in Siberia is currently receiving a lot of attention because large permafrost-covered areas could provide a strong positive feedback to global warming through the release of carbon that has been sequestered there on glacial-interglacial timescales. Geological evidence and climate model experiments show that the Siberian region also played an exceptional role during glacial periods. The region that is currently known for its harsh cold climate did not experience major glaciations during the last ice age, including its severest stages around the Last Glacial Maximum (LGM). On the contrary, it is thought that glacial summer temperatures were comparable to the present day. However, evidence of glaciation has been found for several older glacial periods. We combine LGM experiments from the second and third phases of the Paleoclimate Modelling Intercomparison Project (PMIP2 and PMIP3) with sensitivity experiments using the Community Earth System Model (CESM). Together, these climate model experiments reveal that the intermodel spread in LGM summer temperatures in Siberia is much larger than in any other region of the globe and suggest that temperatures in Siberia are highly susceptible to changes in the imposed glacial boundary conditions, the included feedbacks and processes, and to the model physics of the different components of the climate model. We find that changes in the circumpolar atmospheric stationary wave pattern and associated northward heat transport drive strong local snow and vegetation feedbacks and that this combination explains the susceptibility of LGM summer temperatures in Siberia. This suggests that a small difference between two glacial periods in terms of climate, ice buildup or their respective evolution towards maximum glacial conditions can lead to strongly divergent summer temperatures in Siberia, allowing for the buildup of an ice sheet during some glacial periods, while during others, above-freezing summer temperatures preclude a multi-year snowpack from forming.
2020072641 Euskirchen, Eugenie S. (University of Alaska Fairbanks, Institute of Arctic Biology, Fairbanks, AK); Timm, Kristin; Breen, Amy L.; Gray, Stephen; Rupp, T. Scott; Martin, Philip; Reynolds, Joel H.; Sesser, Amanda; Murphy, Karen; Littell, Jeremy S.; Bennett, Alec; Bolton, W. Robert; Carman, Tobey; Genet, Helene; Griffith, Brad; Kurkowski, Tom; Lara, Mark J.; Marchenko, Sergei; Nicolsky, Dmitry; Panda, Santosh; Romanovsky, Vladimir; Rutter, Ruth; Tucker, Colin L. and McGuire, A. David. Co-producing knowledge; the integrated ecosystem model for resource management in Arctic Alaska: Frontiers in Ecology and the Environment, 18(8), p. 447-455, illus. incl. sketch map, 41 ref., 2020.
Assessments of climate-change effects on ecosystem processes and services in high-latitude regions are hindered by a lack of decision-support tools capable of forecasting possible future landscapes. We describe a collaborative effort to develop and apply the Integrated Ecosystem Model (IEM) for Alaska and northwestern Canada to explore how climate change influences interactions among disturbance regimes, permafrost integrity, hydrology, and vegetation, and how these dynamics in turn influence resource management decisions. This process emphasizes co-production of knowledge among decision makers, scientists, major funders, partners, and stakeholders. We highlight research findings based on IEM applications in Arctic Alaska, as well as successes and challenges of the co-production process. The overall framework and lessons from our work with the IEM are relevant to other collaborative efforts outside the Arctic that aim to develop a decision-support tool or an undertaking of equivalent scope.
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