With ongoing climate change water availability in the source regions of alpine streams are at stake. In particular, dry mountain regions which currently rely on glacial meltwater will need to adapt. Since rock glaciers are more resilient to climate change and occur in nearly all high‐mountain catchments around the globe with some form of glacierization, it is of interest to investigate their contribution to runoff under different climate scenarios. Three well‐monitored rock glacier sites in the Swiss Alps (Murtèl, Ritigraben, and Schafberg) have been investigated under the climate change scenarios corresponding to low, medium and high greenhouse gas emissions to determine how their runoff contribution is affected. By the end of the 21st century, runoff from permafrost melting could account for 5–12% (12.0% for Murtèl, 7.0% for Ritigraben, and 5.0% for Schafberg) of monthly catchment runoff at maximum in an average year, and up to 50% in extreme years. For the low‐emission scenario, little change in the runoff contribution from rock glaciers is found, while the medium‐emission scenario shows increased variability and a shift in the seasonal runoff peak to earlier in the year. The high‐emission scenario indicates a further increase in the variability of the permafrost runoff contribution and also the development of a secondary seasonal peak in autumn, most prominently in the late century.
{"title":"Temperature evolution and runoff contribution of three rock glaciers in Switzerland under future climate forcing","authors":"L. Pruessner, M. Huss, D. Farinotti","doi":"10.1002/ppp.2149","DOIUrl":"https://doi.org/10.1002/ppp.2149","url":null,"abstract":"With ongoing climate change water availability in the source regions of alpine streams are at stake. In particular, dry mountain regions which currently rely on glacial meltwater will need to adapt. Since rock glaciers are more resilient to climate change and occur in nearly all high‐mountain catchments around the globe with some form of glacierization, it is of interest to investigate their contribution to runoff under different climate scenarios. Three well‐monitored rock glacier sites in the Swiss Alps (Murtèl, Ritigraben, and Schafberg) have been investigated under the climate change scenarios corresponding to low, medium and high greenhouse gas emissions to determine how their runoff contribution is affected. By the end of the 21st century, runoff from permafrost melting could account for 5–12% (12.0% for Murtèl, 7.0% for Ritigraben, and 5.0% for Schafberg) of monthly catchment runoff at maximum in an average year, and up to 50% in extreme years. For the low‐emission scenario, little change in the runoff contribution from rock glaciers is found, while the medium‐emission scenario shows increased variability and a shift in the seasonal runoff peak to earlier in the year. The high‐emission scenario indicates a further increase in the variability of the permafrost runoff contribution and also the development of a secondary seasonal peak in autumn, most prominently in the late century.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2022-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44624786","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Qingfeng Wang, H. Jin, Qingbai Wu, Ting-jun Zhang, Ziqiang Yuan, Xiaoying Li, Jiao Ming, Chengsong Yang, R. Serban, Yadong Huang
Currently, we know little about accumulation of soil carbon and nitrogen in permafrost‐affected wetlands on the Qinghai–Tibet Plateau (QTP). In this study, we analyze the vertical distribution of concentrations, stocks, and apparent accumulation rates of soil organic carbon (SOC) and total nitrogen (TN) in a wetland underlain by ice‐rich permafrost in the Headwater Area of the Yellow River (HAYR) on the northeastern QTP in the context of Holocene environmental change. SOC and TN stocks at depths of 0–216 cm were 80.0 kg C m−2 and 6.7 kg N m−2, respectively. During the past 7.3 kyr, the general regional climate trend in the HAYR was cooling and drying, as indicated by the decline in chemical weathering in the soil profile. Overall, SOC and TN concentrations increased during this period. Meanwhile, an intense period of SOC and TN accumulation occurred at 1,110–720 yr BP, in contrast to much lower apparent accumulation rates of SOC and TN for the other periods during the past 7.3 kyr. This suggests that the accumulation of SOC and TN in permafrost‐affected wetlands was also affected by local environmental factors, such as soil material deposition rate, in addition to climatic controls as exerted mainly by temperature and precipitation. This study may help integrate relevant studies on plateau wetlands into global models and estimates to better simulate and predict interactions between the carbon cycle and climate changes on a global scale.
目前，我们对青藏高原多年冻土影响湿地的土壤碳氮积累知之甚少。在本研究中，我们分析了全新世环境变化背景下黄河源头富冰多年冻土湿地土壤有机碳（SOC）和总氮（TN）的浓度、储量和表观积累率的垂直分布。0–216深处的SOC和TN储量 cm分别为80.0 kg C m−2和6.7 kg N m−2。在过去的7.3 kyr期间，HAYR的总体区域气候趋势是冷却和干燥，这表明土壤剖面中化学风化的减少。总的来说，SOC和TN浓度在这一时期有所增加。同时，在1110–720时出现了SOC和TN的强烈积累期 yr BP，相比之下，在过去7.3 kyr的其他时期，SOC和TN的表观积累率要低得多。这表明，受永久冻土影响的湿地中SOC和TN的积累也受到当地环境因素的影响，如土壤物质沉积速率，以及主要由温度和降水施加的气候控制。这项研究可能有助于将高原湿地的相关研究纳入全球模型和估计，以更好地模拟和预测全球范围内碳循环与气候变化之间的相互作用。
{"title":"The vertical distribution of soil organic carbon and nitrogen in a permafrost‐affected wetland on the Qinghai–Tibet Plateau: Implications for Holocene development and environmental change","authors":"Qingfeng Wang, H. Jin, Qingbai Wu, Ting-jun Zhang, Ziqiang Yuan, Xiaoying Li, Jiao Ming, Chengsong Yang, R. Serban, Yadong Huang","doi":"10.1002/ppp.2146","DOIUrl":"https://doi.org/10.1002/ppp.2146","url":null,"abstract":"Currently, we know little about accumulation of soil carbon and nitrogen in permafrost‐affected wetlands on the Qinghai–Tibet Plateau (QTP). In this study, we analyze the vertical distribution of concentrations, stocks, and apparent accumulation rates of soil organic carbon (SOC) and total nitrogen (TN) in a wetland underlain by ice‐rich permafrost in the Headwater Area of the Yellow River (HAYR) on the northeastern QTP in the context of Holocene environmental change. SOC and TN stocks at depths of 0–216 cm were 80.0 kg C m−2 and 6.7 kg N m−2, respectively. During the past 7.3 kyr, the general regional climate trend in the HAYR was cooling and drying, as indicated by the decline in chemical weathering in the soil profile. Overall, SOC and TN concentrations increased during this period. Meanwhile, an intense period of SOC and TN accumulation occurred at 1,110–720 yr BP, in contrast to much lower apparent accumulation rates of SOC and TN for the other periods during the past 7.3 kyr. This suggests that the accumulation of SOC and TN in permafrost‐affected wetlands was also affected by local environmental factors, such as soil material deposition rate, in addition to climatic controls as exerted mainly by temperature and precipitation. This study may help integrate relevant studies on plateau wetlands into global models and estimates to better simulate and predict interactions between the carbon cycle and climate changes on a global scale.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2022-05-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46217112","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rapidly increasing air temperatures will alter permafrost conditions across the Arctic, but variation in soils, vegetation, snow conditions, and their effects on ground thermal regime complicate prediction across spatial and temporal scales. Processes that result in the emergence of new surfaces (lake drainage, channel migration, isostatic uplift, etc.) provide an opportunity to assess the factors influencing permafrost aggradation and terrain evolution under a warming climate. In this study we describe ground temperatures, vegetation, and snow and soil conditions at six drained lake basins (DLBs) that have exposed new terrain in the Tuktoyaktuk Coastlands in the last 20–100 years. We also use one‐dimensional thermal modeling to assess the impact of ecological succession and future climate scenarios on permafrost conditions in historical and future DLBs. Our field observations show that deep snow pack and shallow organic layers at shrub‐dominated DLBs promote increased thaw depth and ground temperatures compared to a sedge‐dominated DLB and two ancient DLB reference sites. Modeling of past and future drainages shows that climate warming projected under RCP 8.5 will reduce rates of permafrost aggradation and thickness, and drive top‐down thaw that could degrade permafrost in shrub‐dominated DLBs by the end of the century. Permafrost at sedge‐dominated sites was more resilient to warming under RCP 8.5, with the onset of top‐down thaw delayed until about 2080. Together, this indicates that the effects of ecological succession on organic soil development and snow drifting will strongly influence the aggradation and resilience of permafrost in DLBs. Our analysis suggests that DLBs and other emergent landscapes will be the first permafrost‐free environments to develop under a warming climate in the continuous permafrost zone.
{"title":"Impacts of ecological succession and climate warming on permafrost aggradation in drained lake basins of the Tuktoyaktuk Coastlands, Northwest Territories, Canada","authors":"T. Lantz, Yu Zhang, S. Kokelj","doi":"10.1002/ppp.2143","DOIUrl":"https://doi.org/10.1002/ppp.2143","url":null,"abstract":"Rapidly increasing air temperatures will alter permafrost conditions across the Arctic, but variation in soils, vegetation, snow conditions, and their effects on ground thermal regime complicate prediction across spatial and temporal scales. Processes that result in the emergence of new surfaces (lake drainage, channel migration, isostatic uplift, etc.) provide an opportunity to assess the factors influencing permafrost aggradation and terrain evolution under a warming climate. In this study we describe ground temperatures, vegetation, and snow and soil conditions at six drained lake basins (DLBs) that have exposed new terrain in the Tuktoyaktuk Coastlands in the last 20–100 years. We also use one‐dimensional thermal modeling to assess the impact of ecological succession and future climate scenarios on permafrost conditions in historical and future DLBs. Our field observations show that deep snow pack and shallow organic layers at shrub‐dominated DLBs promote increased thaw depth and ground temperatures compared to a sedge‐dominated DLB and two ancient DLB reference sites. Modeling of past and future drainages shows that climate warming projected under RCP 8.5 will reduce rates of permafrost aggradation and thickness, and drive top‐down thaw that could degrade permafrost in shrub‐dominated DLBs by the end of the century. Permafrost at sedge‐dominated sites was more resilient to warming under RCP 8.5, with the onset of top‐down thaw delayed until about 2080. Together, this indicates that the effects of ecological succession on organic soil development and snow drifting will strongly influence the aggradation and resilience of permafrost in DLBs. Our analysis suggests that DLBs and other emergent landscapes will be the first permafrost‐free environments to develop under a warming climate in the continuous permafrost zone.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2022-04-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49216576","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The accuracy of electrical resistivity tomography (ERT) as a method for locating frozen‐to‐unfrozen interfaces in permafrost environments was investigated systematically for simplified scenarios using forward modeling. The impacts of varying the resistivity, thickness, and lateral continuity of the frozen region, altering the thickness of the surface thaw layer, and of differing array types were evaluated in relation to the detection and positioning of frozen–unfrozen interfaces. The results from these simple scenarios show that boundaries between frozen and unfrozen ground are more accurately indicated by maximum gradients rather than a fixed threshold value based on the resistivity at the base of the surface thawed layer. The resistivity of the frozen region plays a significant role in interpreted boundary locations, with high resistivity values causing a decrease in model sensitivity at depth and increased uncertainty in the interpreted base of the frozen zone, particularly in laterally continuous permafrost. Error in the interpreted base of the frozen zone also increases for thicker permafrost bodies, while thaw layer thickness plays a less significant role. In laterally discontinuous permafrost, wider frozen bodies cause the boundary at the base of the frozen region to become less distinct. Array type affected the appearance of the inverted resistivity models and the frozen–unfrozen boundaries located using the threshold method, but boundary locations were comparable among array types when the maximum gradient method was used. This synthetic modeling showed that the boundaries between unfrozen and frozen regions in ERT images should be interpreted with caution, particularly in ice‐rich, laterally continuous permafrost where sensitivity at depth is low. We conclude that forward modeling is a useful tool for permafrost investigations, both for assessing the likelihood of achieving ERT survey goals prior to fieldwork, and as an interpretive aid after field data have been acquired.
{"title":"A systematic evaluation of electrical resistivity tomography for permafrost interface detection using forward modeling","authors":"T. Herring, A. Lewkowicz","doi":"10.1002/ppp.2141","DOIUrl":"https://doi.org/10.1002/ppp.2141","url":null,"abstract":"The accuracy of electrical resistivity tomography (ERT) as a method for locating frozen‐to‐unfrozen interfaces in permafrost environments was investigated systematically for simplified scenarios using forward modeling. The impacts of varying the resistivity, thickness, and lateral continuity of the frozen region, altering the thickness of the surface thaw layer, and of differing array types were evaluated in relation to the detection and positioning of frozen–unfrozen interfaces. The results from these simple scenarios show that boundaries between frozen and unfrozen ground are more accurately indicated by maximum gradients rather than a fixed threshold value based on the resistivity at the base of the surface thawed layer. The resistivity of the frozen region plays a significant role in interpreted boundary locations, with high resistivity values causing a decrease in model sensitivity at depth and increased uncertainty in the interpreted base of the frozen zone, particularly in laterally continuous permafrost. Error in the interpreted base of the frozen zone also increases for thicker permafrost bodies, while thaw layer thickness plays a less significant role. In laterally discontinuous permafrost, wider frozen bodies cause the boundary at the base of the frozen region to become less distinct. Array type affected the appearance of the inverted resistivity models and the frozen–unfrozen boundaries located using the threshold method, but boundary locations were comparable among array types when the maximum gradient method was used. This synthetic modeling showed that the boundaries between unfrozen and frozen regions in ERT images should be interpreted with caution, particularly in ice‐rich, laterally continuous permafrost where sensitivity at depth is low. We conclude that forward modeling is a useful tool for permafrost investigations, both for assessing the likelihood of achieving ERT survey goals prior to fieldwork, and as an interpretive aid after field data have been acquired.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2022-04-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46337395","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Majdański, W. Dobiński, A. Marciniak, B. Owoc, M. Glazer, M. Osuch, T. Wawrzyniak
Two seismic field surveys were organized in the Fuglebekken coastal catchment of Hornsund, Spitsbergen, Svalbard, to map frozen and unfrozen ground and assess the spatial and temporal state of the permafrost. Surveys were conducted during maximum thawing in September and maximum freezing in April of the following year. The obtained seismic wavefields were interpreted using three methods: the dispersion of surface waves, seismic refraction, and travel time tomography. The seismic experiments were supported by nearby boreholes with continuous thermal monitoring. In the frozen survey, a gradual increase in ice content of water‐filled sediments was found, farther from the coast. In September the shallow sensors in the boreholes validated positive ground temperatures down to 3.0 m depth, with below‐zero temperatures at greater depths. However, seismic tomography indicated that the ground was unfrozen down to 30 m. The ground probably remained unfrozen due to intrusion of high‐salinity seawater, even though it had been below 0°C. In April, in the area 300 m and farther from the coast, the ground below 3 m depth was frozen, except for a 19‐m‐deep open talik identified in a borehole at the slope of Fugle Mountain. We attribute the complex spatial extent, form, and condition of permafrost in the Fuglebekken coastal catchment to multiple factors, including variable solar energy, snow and ground cover, thermal and humidity properties of the soil, subsurface water flow, and seawater intrusion. The presented combination of seismic methods provides a new robust and precise approach to assess the spatial variability of permafrost in a coastal environment. The proposed interpretation shows deep percolation of subsurface flow into permafrost and its seasonal unfreezing at a depth of 30 m in both the zone of saltwater intrusion and the slope area.
{"title":"Variations of permafrost under freezing and thawing conditions in the coastal catchment Fuglebekken (Hornsund, Spitsbergen, Svalbard)","authors":"M. Majdański, W. Dobiński, A. Marciniak, B. Owoc, M. Glazer, M. Osuch, T. Wawrzyniak","doi":"10.1002/ppp.2147","DOIUrl":"https://doi.org/10.1002/ppp.2147","url":null,"abstract":"Two seismic field surveys were organized in the Fuglebekken coastal catchment of Hornsund, Spitsbergen, Svalbard, to map frozen and unfrozen ground and assess the spatial and temporal state of the permafrost. Surveys were conducted during maximum thawing in September and maximum freezing in April of the following year. The obtained seismic wavefields were interpreted using three methods: the dispersion of surface waves, seismic refraction, and travel time tomography. The seismic experiments were supported by nearby boreholes with continuous thermal monitoring. In the frozen survey, a gradual increase in ice content of water‐filled sediments was found, farther from the coast. In September the shallow sensors in the boreholes validated positive ground temperatures down to 3.0 m depth, with below‐zero temperatures at greater depths. However, seismic tomography indicated that the ground was unfrozen down to 30 m. The ground probably remained unfrozen due to intrusion of high‐salinity seawater, even though it had been below 0°C. In April, in the area 300 m and farther from the coast, the ground below 3 m depth was frozen, except for a 19‐m‐deep open talik identified in a borehole at the slope of Fugle Mountain. We attribute the complex spatial extent, form, and condition of permafrost in the Fuglebekken coastal catchment to multiple factors, including variable solar energy, snow and ground cover, thermal and humidity properties of the soil, subsurface water flow, and seawater intrusion. The presented combination of seismic methods provides a new robust and precise approach to assess the spatial variability of permafrost in a coastal environment. The proposed interpretation shows deep percolation of subsurface flow into permafrost and its seasonal unfreezing at a depth of 30 m in both the zone of saltwater intrusion and the slope area.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2022-04-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47158214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yan-hui You, Qihao Yu, Xinbin Wang, Lei Guo, Kun Chen, Qingbai Wu
The thermal effects of cast‐in‐place piles on the surrounding permafrost frequently induce deformation or failure of piles in permafrost regions. Because piles are directly inserted into the permafrost layer, the thermal disturbance of the piles is more straightforward than that of road embankments to the permafrost. Thermosyphons have proven to be effective in stabilizing the embankments of highways and railways in permafrost regions. However, the effects of thermosyphons on the thermal regime and stability of the cast‐in‐place piles remain unclear. The foundation soils of most piles in permafrost regions along the Qinghai‐Tibet Power Transmission Line were cooled by thermosyphons, and the results of a 7‐year‐period monitoring of ground temperature and deformation of a pile are presented in this paper. The results showed that the extent of thawed permafrost during the installation of the pile extended more than 5 m away from the pile. Thermosyphons shortened the refreezing time by more than 2 months. Thermosyphons cooled the surrounding permafrost to temperatures below the ambient ground temperature at the end of the cold seasons, and the temperature difference lasted until the end of the warm seasons owing to cold reserves formed in the cold season. The thermosyphons mitigated the thermal effects of the concrete pile owing to their higher thermal conductivity. Thermosyphons also significantly decreased the rate of active layer thickening around the pile compared to that observed in a natural field under a warming climate. Generally, thermosyphons stabilized the piles during the observation period by cooling the permafrost around the pile and producing a greater adfreeze force to counteract the frost heave force and subsequently support the tower. Additional thermosyphons or insulation measures may be necessary to ensure the long‐term stability of piles, considering a faster degradation of the ambient permafrost than expected. The results may provide insights into the design and maintenance of cast‐in‐place piles in warm permafrost regions.
{"title":"Effects of thermosyphons on the thermal regime and stability of cast‐in‐place piles in permafrost regions on the Qinghai‐Tibet Plateau","authors":"Yan-hui You, Qihao Yu, Xinbin Wang, Lei Guo, Kun Chen, Qingbai Wu","doi":"10.1002/ppp.2144","DOIUrl":"https://doi.org/10.1002/ppp.2144","url":null,"abstract":"The thermal effects of cast‐in‐place piles on the surrounding permafrost frequently induce deformation or failure of piles in permafrost regions. Because piles are directly inserted into the permafrost layer, the thermal disturbance of the piles is more straightforward than that of road embankments to the permafrost. Thermosyphons have proven to be effective in stabilizing the embankments of highways and railways in permafrost regions. However, the effects of thermosyphons on the thermal regime and stability of the cast‐in‐place piles remain unclear. The foundation soils of most piles in permafrost regions along the Qinghai‐Tibet Power Transmission Line were cooled by thermosyphons, and the results of a 7‐year‐period monitoring of ground temperature and deformation of a pile are presented in this paper. The results showed that the extent of thawed permafrost during the installation of the pile extended more than 5 m away from the pile. Thermosyphons shortened the refreezing time by more than 2 months. Thermosyphons cooled the surrounding permafrost to temperatures below the ambient ground temperature at the end of the cold seasons, and the temperature difference lasted until the end of the warm seasons owing to cold reserves formed in the cold season. The thermosyphons mitigated the thermal effects of the concrete pile owing to their higher thermal conductivity. Thermosyphons also significantly decreased the rate of active layer thickening around the pile compared to that observed in a natural field under a warming climate. Generally, thermosyphons stabilized the piles during the observation period by cooling the permafrost around the pile and producing a greater adfreeze force to counteract the frost heave force and subsequently support the tower. Additional thermosyphons or insulation measures may be necessary to ensure the long‐term stability of piles, considering a faster degradation of the ambient permafrost than expected. The results may provide insights into the design and maintenance of cast‐in‐place piles in warm permafrost regions.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2022-04-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42234143","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ice‐wedge polygon troughs play an important role in controlling the hydrology of low‐relief polygonal tundra regions. Lateral surface flow is confined to troughs only, but it is often neglected in model projections of permafrost thermal hydrology. Recent field and modeling studies have shown that, after rain events, increases in trough water levels are significantly more than the observed precipitation, highlighting the role of lateral surface flow in the polygonal tundra. Therefore, understanding how trough lateral surface flow can influence polygonal tundra thermal hydrology is important, especially under projected changes in temperatures and rainfall in the Arctic regions. Using an integrated cryohydrology model, this study presents plot‐scale end‐of‐century projections of ice‐wedge polygon water budget components and active layer thickness with and without trough lateral surface flow under the Representative Concentration Pathway 8.5 scenario. Trough lateral surface flow is incorporated through a newly developed empirical model, evaluated against field measurements. The numerical scenario that includes trough lateral surface flow simulates discharge (outflow from a polygon) and recharge (rain‐induced inflow to a polygon trough from upslope areas), while the scenario that does not include trough lateral surface flow ignores recharge. The results show considerable reduction (about 100–150%) in evapotranspiration and discharge in rainy years in the scenarios ignoring trough lateral surface flow, but less effect on soil water storage, in comparison with the scenario with trough lateral surface flow. In addition, the results demonstrate long‐term changes (~10–15 cm increase) in active layer thickness when trough lateral surface flow is modeled. This study highlights the importance of including lateral surface flow processes to better understand the long‐term thermal and hydrological changes in low‐relief polygonal tundra regions under a changing climate.
{"title":"Modeling the role of lateral surface flow in low‐relief polygonal tundra","authors":"A. Jan","doi":"10.1002/ppp.2145","DOIUrl":"https://doi.org/10.1002/ppp.2145","url":null,"abstract":"Ice‐wedge polygon troughs play an important role in controlling the hydrology of low‐relief polygonal tundra regions. Lateral surface flow is confined to troughs only, but it is often neglected in model projections of permafrost thermal hydrology. Recent field and modeling studies have shown that, after rain events, increases in trough water levels are significantly more than the observed precipitation, highlighting the role of lateral surface flow in the polygonal tundra. Therefore, understanding how trough lateral surface flow can influence polygonal tundra thermal hydrology is important, especially under projected changes in temperatures and rainfall in the Arctic regions. Using an integrated cryohydrology model, this study presents plot‐scale end‐of‐century projections of ice‐wedge polygon water budget components and active layer thickness with and without trough lateral surface flow under the Representative Concentration Pathway 8.5 scenario. Trough lateral surface flow is incorporated through a newly developed empirical model, evaluated against field measurements. The numerical scenario that includes trough lateral surface flow simulates discharge (outflow from a polygon) and recharge (rain‐induced inflow to a polygon trough from upslope areas), while the scenario that does not include trough lateral surface flow ignores recharge. The results show considerable reduction (about 100–150%) in evapotranspiration and discharge in rainy years in the scenarios ignoring trough lateral surface flow, but less effect on soil water storage, in comparison with the scenario with trough lateral surface flow. In addition, the results demonstrate long‐term changes (~10–15 cm increase) in active layer thickness when trough lateral surface flow is modeled. This study highlights the importance of including lateral surface flow processes to better understand the long‐term thermal and hydrological changes in low‐relief polygonal tundra regions under a changing climate.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2022-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46605915","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rock glaciers (RGs) are landscape features impacting the composition and magnitude of runoff and, given their ice content, they are used as indicators for past and present climate conditions. While our knowledge of RG coverage has improved over recent years in many mountainous regions, there is very little information available for RGs in Greenland. Here, we provide evidence for an active RG in West Greenland, about 230 km south of what previously has been identified as the southern limit of active RGs. We present field evidence such as bottom temperature of the snow pack and surface displacements and indicate how these results could be utilized in further studies to better assess RG distribution or their ice content.
{"title":"Challenging the southern boundary of active rock glaciers in West Greenland","authors":"J. Abermann, K. Langley","doi":"10.1002/ppp.2139","DOIUrl":"https://doi.org/10.1002/ppp.2139","url":null,"abstract":"Rock glaciers (RGs) are landscape features impacting the composition and magnitude of runoff and, given their ice content, they are used as indicators for past and present climate conditions. While our knowledge of RG coverage has improved over recent years in many mountainous regions, there is very little information available for RGs in Greenland. Here, we provide evidence for an active RG in West Greenland, about 230 km south of what previously has been identified as the southern limit of active RGs. We present field evidence such as bottom temperature of the snow pack and surface displacements and indicate how these results could be utilized in further studies to better assess RG distribution or their ice content.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2022-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49026863","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Understanding the mechanical properties of frozen flawed rock masses is fundamental to conducting safe rock engineering in frozen rock strata. However, there has been scarce research in this area, especially on key issues such as the strength and deformability of frozen flawed rock masses and failure processes under load. In this paper, frozen flawed sandstone was subjected to uniaxial compression and the cracking process was observed. The influences of flaw inclination angle and freezing temperature on the strength and cracking behavior of frozen flawed sandstone under load were determined. The results show that: (a) the strength of frozen flawed sandstone increases with increases in flaw inclination and decreases in temperature; (b) the flaw inclination has a dramatic influence on both the crack coalescence behavior and the final failure form of frozen flawed samples under compression; and (c) the significant influence of freezing temperature on the cracking behavior of frozen flawed sandstone is caused by the interaction between flaw ice and its surrounding rock. Strengthening of flawed sandstone by freezing results because (i) pore ice provides support and cohesion at the pore scale, while (ii) at the crack scale ice can support the flaw and resist its deformation during compression, and cementation of the ice–rock interface provides normal and tangential cracking resistance.
{"title":"Strength and the cracking behavior of frozen sandstone containing ice‐filled flaws under uniaxial compression","authors":"H. Jia, L. Han, T. Zhao, Q. Sun, Xian-jun Tan","doi":"10.1002/ppp.2142","DOIUrl":"https://doi.org/10.1002/ppp.2142","url":null,"abstract":"Understanding the mechanical properties of frozen flawed rock masses is fundamental to conducting safe rock engineering in frozen rock strata. However, there has been scarce research in this area, especially on key issues such as the strength and deformability of frozen flawed rock masses and failure processes under load. In this paper, frozen flawed sandstone was subjected to uniaxial compression and the cracking process was observed. The influences of flaw inclination angle and freezing temperature on the strength and cracking behavior of frozen flawed sandstone under load were determined. The results show that: (a) the strength of frozen flawed sandstone increases with increases in flaw inclination and decreases in temperature; (b) the flaw inclination has a dramatic influence on both the crack coalescence behavior and the final failure form of frozen flawed samples under compression; and (c) the significant influence of freezing temperature on the cracking behavior of frozen flawed sandstone is caused by the interaction between flaw ice and its surrounding rock. Strengthening of flawed sandstone by freezing results because (i) pore ice provides support and cohesion at the pore scale, while (ii) at the crack scale ice can support the flaw and resist its deformation during compression, and cementation of the ice–rock interface provides normal and tangential cracking resistance.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2022-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42165868","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ruiqing Shi, Z. Wen, Desheng Li, Qiang Gao, Yanjing Wei
Owing to a minor thermal disturbance to the permafrost environment, cast‐in‐place piles are widely used for building and bridge foundations in permafrost regions. However, because of the dynamic and cyclic variation in frozen ground affected by the atmosphere, the load transfer mechanism is not yet clear, and the current design is economically insufficient. To illustrate the bearing pattern of cast‐in‐place piles subjected to freeze–thaw cycles, a systematic in situ investigation was carried out. Results show that the load from the superstructure has a marginal action effect, while freeze–thaw cycles have a more significant action effect. Freeze–thaw cycles have a decisive effect on the dynamic variations of the pile's working state and action effect sharing while the mechanisms are quite different, which vary with depths. Action effect sharing of the pile shaft and tip experiences a cyclic variation and is affected by the long‐term effect of freeze–thaw cycles. The shaft takes an increasing sharing proportion gradually and has a 19% rise after two freeze–thaw cycles, while the pile tip goes the opposite way. Two years after the building is completed, the bearing capacity is almost entirely provided by shaft resistance and mainly by the upper one‐third of the pile. This research clarifies several essential issues about the bearing pattern and provides solid scientific support and novel opinions for the pile design in permafrost regions.
{"title":"Effect of freeze–thaw cycles on the performance of cast‐in‐place piles in permafrost regions: Working state and action effect sharing","authors":"Ruiqing Shi, Z. Wen, Desheng Li, Qiang Gao, Yanjing Wei","doi":"10.1002/ppp.2140","DOIUrl":"https://doi.org/10.1002/ppp.2140","url":null,"abstract":"Owing to a minor thermal disturbance to the permafrost environment, cast‐in‐place piles are widely used for building and bridge foundations in permafrost regions. However, because of the dynamic and cyclic variation in frozen ground affected by the atmosphere, the load transfer mechanism is not yet clear, and the current design is economically insufficient. To illustrate the bearing pattern of cast‐in‐place piles subjected to freeze–thaw cycles, a systematic in situ investigation was carried out. Results show that the load from the superstructure has a marginal action effect, while freeze–thaw cycles have a more significant action effect. Freeze–thaw cycles have a decisive effect on the dynamic variations of the pile's working state and action effect sharing while the mechanisms are quite different, which vary with depths. Action effect sharing of the pile shaft and tip experiences a cyclic variation and is affected by the long‐term effect of freeze–thaw cycles. The shaft takes an increasing sharing proportion gradually and has a 19% rise after two freeze–thaw cycles, while the pile tip goes the opposite way. Two years after the building is completed, the bearing capacity is almost entirely provided by shaft resistance and mainly by the upper one‐third of the pile. This research clarifies several essential issues about the bearing pattern and provides solid scientific support and novel opinions for the pile design in permafrost regions.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2022-02-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47034438","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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