Aufeis is a common phenomenon in cold regions of the Northern Hemisphere that develops during winter by successive water overflow and freezing on ice‐covered surfaces. Most studies on aufeis occurrence focus on regions in North America and Siberia, while research in High Mountain Asia (HMA) is still in an exploratory phase. This study investigates the extent and dynamics of icing processes and aufeis in the Tso Moriri basin, eastern Ladakh, India. Based on a combination of 235 Landsat 5 TM/8 OLI and Sentinel‐2 imagery from 2008 to 2021 the occurrence of icing and aufeis was classified using a random forest classifier. A total of 27 frequently occurring aufeis fields with an average maximum extent of 9 km2 were identified, located at a mean elevation of 4,700 m a.s.l. Temporal patterns show a distinct accumulation phase (icing) between November and April, and a melting phase lasting from May until July. Icing is characterized by high seasonal and inter‐annual variability. Successive water overflow mainly occurs between January and March and seems to be related to diurnal freeze–thaw‐cycles, whereas higher daytime temperatures result in larger icing areas. Aufeis feeding sources are often located within or in close vicinity to wetland areas, while vegetation is largely absent on surfaces with frequent aufeis formation. These interactions require more attention in future research. In addition, this study shows the high potential of a machine learning approach to monitor icing processes and aufeis, which can be transferred to other regions.
Aufeis是北半球寒冷地区的一种常见现象，在冬季，由于水连续溢出和冰层表面结冰而形成。大多数关于aufeis发生的研究集中在北美和西伯利亚地区，而亚洲高山地区的研究仍处于探索阶段。本研究调查了印度拉达克东部措莫里里盆地结冰过程和aufei的范围和动力学。基于2008年至2021年235幅Landsat 5 TM/8 OLI和Sentinel‐2图像的组合，使用随机森林分类器对结冰和aufeis的发生进行了分类。共确定了27个频繁出现的aufeis油田，平均最大面积为9km2，位于平均海拔4700 m a.s.l.时间模式显示，11月至4月之间有一个明显的积累阶段（结冰），5月至7月为融化阶段。结冰的特点是季节性和年际变化较大。连续的水溢流主要发生在1月至3月之间，似乎与白天的冻融循环有关，而白天温度越高，结冰面积越大。Aufeis的食物来源通常位于湿地内或附近，而Aufeis频繁形成的表面基本上没有植被。这些相互作用需要在未来的研究中给予更多关注。此外，这项研究表明，机器学习方法在监测结冰过程和aufeis方面具有很高的潜力，可以转移到其他地区。
{"title":"Spatial and temporal dynamics of aufeis in the Tso Moriri basin, eastern Ladakh, India","authors":"Dagmar Brombierstäudl, S. Schmidt, M. Nüsser","doi":"10.1002/ppp.2173","DOIUrl":"https://doi.org/10.1002/ppp.2173","url":null,"abstract":"Aufeis is a common phenomenon in cold regions of the Northern Hemisphere that develops during winter by successive water overflow and freezing on ice‐covered surfaces. Most studies on aufeis occurrence focus on regions in North America and Siberia, while research in High Mountain Asia (HMA) is still in an exploratory phase. This study investigates the extent and dynamics of icing processes and aufeis in the Tso Moriri basin, eastern Ladakh, India. Based on a combination of 235 Landsat 5 TM/8 OLI and Sentinel‐2 imagery from 2008 to 2021 the occurrence of icing and aufeis was classified using a random forest classifier. A total of 27 frequently occurring aufeis fields with an average maximum extent of 9 km2 were identified, located at a mean elevation of 4,700 m a.s.l. Temporal patterns show a distinct accumulation phase (icing) between November and April, and a melting phase lasting from May until July. Icing is characterized by high seasonal and inter‐annual variability. Successive water overflow mainly occurs between January and March and seems to be related to diurnal freeze–thaw‐cycles, whereas higher daytime temperatures result in larger icing areas. Aufeis feeding sources are often located within or in close vicinity to wetland areas, while vegetation is largely absent on surfaces with frequent aufeis formation. These interactions require more attention in future research. In addition, this study shows the high potential of a machine learning approach to monitor icing processes and aufeis, which can be transferred to other regions.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2022-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42343097","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}
Current climate change in the Arctic is unprecedented in the instrumental record, with profound consequences for the environment and landscape. In Arctic Sweden, aeolian sand dunes have been impacted by climatic changes since their initial formation after the retreat of the last glacial ice sheet. Dune type, location and orientation can therefore be used to explore past wind patterns and landscape destabilisation in this sensitive area. However, knowledge of the full spatial extent and characteristics of these dunes is limited by their inaccessibility and dense vegetation cover. Geographic object‐based image analysis (GEOBIA) permits the semi‐automatic creation of reproducible parameter‐based objects and can be an appropriate means to systematically and spatially map these dunes remotely. Here, a digital elevation model (DEM) and its derivatives, such as slope and curvature, were segmented in a GEOBIA context, enabling the identification and mapping of aeolian sand dunes in Arctic Sweden. Analysis of the GEOBIA‐derived and expert‐accepted polygons affirms the prevalence of parabolic dune type and reveals the coexistence of simple dunes with large coalesced systems. Furthermore, mapped dune orientations and relationships to other geomorphological features were used to explore past wind directions and to identify sediment sources as well as the reasons for sand availability. The results indicate that most dune systems in Arctic Sweden were initially supplied by glaciofluvial and fluvial disturbances of sandy esker systems. Topographic control of wind direction is the dominant influence on dune orientation. Further, our approach shows that analysing the GEOBIA‐derived dune objects in their geomorphological context paves the way for successfully investigating aeolian sand dune location, type and orientation in Arctic Sweden, thereby facilitating the understanding of post‐glacial landscape (in)stability and evolution in the area.
{"title":"Geographic object‐based image analysis (GEOBIA) of the distribution and characteristics of aeolian sand dunes in Arctic Sweden","authors":"Melanie Stammler, T. Stevens, D. Hölbling","doi":"10.1002/ppp.2169","DOIUrl":"https://doi.org/10.1002/ppp.2169","url":null,"abstract":"Current climate change in the Arctic is unprecedented in the instrumental record, with profound consequences for the environment and landscape. In Arctic Sweden, aeolian sand dunes have been impacted by climatic changes since their initial formation after the retreat of the last glacial ice sheet. Dune type, location and orientation can therefore be used to explore past wind patterns and landscape destabilisation in this sensitive area. However, knowledge of the full spatial extent and characteristics of these dunes is limited by their inaccessibility and dense vegetation cover. Geographic object‐based image analysis (GEOBIA) permits the semi‐automatic creation of reproducible parameter‐based objects and can be an appropriate means to systematically and spatially map these dunes remotely. Here, a digital elevation model (DEM) and its derivatives, such as slope and curvature, were segmented in a GEOBIA context, enabling the identification and mapping of aeolian sand dunes in Arctic Sweden. Analysis of the GEOBIA‐derived and expert‐accepted polygons affirms the prevalence of parabolic dune type and reveals the coexistence of simple dunes with large coalesced systems. Furthermore, mapped dune orientations and relationships to other geomorphological features were used to explore past wind directions and to identify sediment sources as well as the reasons for sand availability. The results indicate that most dune systems in Arctic Sweden were initially supplied by glaciofluvial and fluvial disturbances of sandy esker systems. Topographic control of wind direction is the dominant influence on dune orientation. Further, our approach shows that analysing the GEOBIA‐derived dune objects in their geomorphological context paves the way for successfully investigating aeolian sand dune location, type and orientation in Arctic Sweden, thereby facilitating the understanding of post‐glacial landscape (in)stability and evolution in the area.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2022-10-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42847007","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 Antarctic continent is a crucial area for ultimate determination of permafrost extent on Earth, and its solution depends on the theoretical assumptions adopted. In fact, it ranges from 0.022 × 106 to 14 × 106 km2. This level of inaccuracy is unprecedented in the Earth sciences. The novelty of the present study consists in determining the extent of Antarctic permafrost not based exclusively on empirical studies but on universal criteria resulting from the definition of permafrost as the thermal state of the lithosphere, which was applied for the first time to this continent. The area covered by permafrost in Antarctica is ca. 13.9 million km2, that is its entire surface. This result was also made possible due to the first clear determination of the boundaries and area of the continent. The Antarctic area includes (a) rocky subsurface with (b) continental ice‐sheets and (c) shelf glaciers, which, due to their terrigenous origin and belonging to the lithosphere, belongs to the continent in the same way. Antarctica is covered by continuous permafrost, either in a frozen or in a cryotic state. This also significantly influences delimitation of the global extent of permafrost, which can therefore be defined much more accurately. The proposed ice reclassification and its transfer from the hydrosphere to the lithosphere will allow the uniform treatment of ice in the Earth sciences, both on Earth and on other celestial bodies.
{"title":"Area and borders of Antarctic and permafrost—A review and synthesis","authors":"W. Dobiński, J. E. Szafraniec, Bartłomiej Szypuła","doi":"10.1002/ppp.2170","DOIUrl":"https://doi.org/10.1002/ppp.2170","url":null,"abstract":"The Antarctic continent is a crucial area for ultimate determination of permafrost extent on Earth, and its solution depends on the theoretical assumptions adopted. In fact, it ranges from 0.022 × 106 to 14 × 106 km2. This level of inaccuracy is unprecedented in the Earth sciences. The novelty of the present study consists in determining the extent of Antarctic permafrost not based exclusively on empirical studies but on universal criteria resulting from the definition of permafrost as the thermal state of the lithosphere, which was applied for the first time to this continent. The area covered by permafrost in Antarctica is ca. 13.9 million km2, that is its entire surface. This result was also made possible due to the first clear determination of the boundaries and area of the continent. The Antarctic area includes (a) rocky subsurface with (b) continental ice‐sheets and (c) shelf glaciers, which, due to their terrigenous origin and belonging to the lithosphere, belongs to the continent in the same way. Antarctica is covered by continuous permafrost, either in a frozen or in a cryotic state. This also significantly influences delimitation of the global extent of permafrost, which can therefore be defined much more accurately. The proposed ice reclassification and its transfer from the hydrosphere to the lithosphere will allow the uniform treatment of ice in the Earth sciences, both on Earth and on other celestial bodies.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2022-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43390481","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}
Lingxiao Wang, Lin Zhao, Huayun Zhou, Shibo Liu, G. Hu, Zhibin Li, Chong Wang, Jianting Zhao
The thawing of ice‐rich permafrost has attracted considerable attention in recent years. In this study, we analyzed both the ground surface deformation time series spanning 6 years, derived through the SBAS‐InSAR technique on the Qinghai‐Xizang (Tibet) Plateau (QTP), and the long‐term active layer soil temperature and moisture in situ observations and their relationships. The results showed that long‐term subsidence velocity directly represents the melting of ground ice instead of the thickening rate of the active layer by a quantitative analysis of both terrain subsidence velocity and active layer thickening rate and the increase in liquid water at the bottom of the active layer. Ice‐poor permafrost thawing does not result in distinct subsidence, although the active layer deepening rate can be very high. The spatial analysis reveals that long‐term deformation velocities are large in the foothills and on gentle slopes (1–5 degrees) and are closely related to geomorphological conditions, which could regulate the soil properties and ground ice content. These findings improve the understanding of the thawing degradation of icy permafrost and promote method developments for the automated mapping of ground ice melting in permafrost environments.
{"title":"Evidence of ground ice melting detected by InSAR and in situ monitoring over permafrost terrain on the Qinghai‐Xizang (Tibet) Plateau","authors":"Lingxiao Wang, Lin Zhao, Huayun Zhou, Shibo Liu, G. Hu, Zhibin Li, Chong Wang, Jianting Zhao","doi":"10.1002/ppp.2171","DOIUrl":"https://doi.org/10.1002/ppp.2171","url":null,"abstract":"The thawing of ice‐rich permafrost has attracted considerable attention in recent years. In this study, we analyzed both the ground surface deformation time series spanning 6 years, derived through the SBAS‐InSAR technique on the Qinghai‐Xizang (Tibet) Plateau (QTP), and the long‐term active layer soil temperature and moisture in situ observations and their relationships. The results showed that long‐term subsidence velocity directly represents the melting of ground ice instead of the thickening rate of the active layer by a quantitative analysis of both terrain subsidence velocity and active layer thickening rate and the increase in liquid water at the bottom of the active layer. Ice‐poor permafrost thawing does not result in distinct subsidence, although the active layer deepening rate can be very high. The spatial analysis reveals that long‐term deformation velocities are large in the foothills and on gentle slopes (1–5 degrees) and are closely related to geomorphological conditions, which could regulate the soil properties and ground ice content. These findings improve the understanding of the thawing degradation of icy permafrost and promote method developments for the automated mapping of ground ice melting in permafrost environments.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2022-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46694421","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 mechanism of formation of ground ice and the freeze–thaw history of permafrost is essential when assessing the future of permafrost in a changing climate. High‐resolution ground ice records, integrating stable isotopes (δ18O, d‐excess, and δ13C), hydrochemistry (EC and pH) data, and cryostratigraphy at a depth of 4.8 m from two contrasting permafrost profiles (P‐1, P‐2) in the Source Area of the Yellow River (SAYR) on the northeastern Qinghai–Tibet Plateau (QTP), were investigated. The results suggested significant depth variations in the stable isotopes and hydrochemistry of the ground ice. The near‐surface ground ice (NSGI) and deep‐layer ground ice (DLGI) were characterized in terms of variations in stable isotopes and known modern active layer data. By synthesizing the measured δ18O and the modeled isotopic fractionation processes during freezing, we suggest that both the NSGI and DLGI in P‐1 were mainly formed by the segregation mechanism during permafrost aggradation. The NSGI in P‐2, however, exhibited quick freezing origins compared with the predominant ice segregation processes for the DLGI. By combining the evolution of various stable isotopes and hydrochemistry with 14C age data, four historical freeze–thaw stages were identified. Specifically, one thawing–refreezing stage (2.8–2.2 m), one freezing aggradation stage (2.2–1.6 m), and two permafrost aggradation–degradation cycle stages (4.8–2.8 m; 1.6–0.7 m) were differentiated, which emphasize the importance of climate‐induced freeze–thaw transitions and differing permafrost aggradation processes on ground ice formation and resultant isotope hydrochemical behaviors. This study is the first to use high‐resolution data in ground ice to interpret the freeze–thaw history of permafrost in the SAYR. These findings are important for further understanding of past permafrost evolution and projected future permafrost degradation trends on the QTP, and provide an alternative method to explore permafrost history.
{"title":"High‐resolution stable isotopic signals of ground ice indicate freeze–thaw history in permafrost on the northeastern Qinghai–Tibet Plateau","authors":"Yuzhong Yang, Qingbai Wu, Huijun Jin","doi":"10.1002/ppp.2172","DOIUrl":"https://doi.org/10.1002/ppp.2172","url":null,"abstract":"Understanding the mechanism of formation of ground ice and the freeze–thaw history of permafrost is essential when assessing the future of permafrost in a changing climate. High‐resolution ground ice records, integrating stable isotopes (δ18O, d‐excess, and δ13C), hydrochemistry (EC and pH) data, and cryostratigraphy at a depth of 4.8 m from two contrasting permafrost profiles (P‐1, P‐2) in the Source Area of the Yellow River (SAYR) on the northeastern Qinghai–Tibet Plateau (QTP), were investigated. The results suggested significant depth variations in the stable isotopes and hydrochemistry of the ground ice. The near‐surface ground ice (NSGI) and deep‐layer ground ice (DLGI) were characterized in terms of variations in stable isotopes and known modern active layer data. By synthesizing the measured δ18O and the modeled isotopic fractionation processes during freezing, we suggest that both the NSGI and DLGI in P‐1 were mainly formed by the segregation mechanism during permafrost aggradation. The NSGI in P‐2, however, exhibited quick freezing origins compared with the predominant ice segregation processes for the DLGI. By combining the evolution of various stable isotopes and hydrochemistry with 14C age data, four historical freeze–thaw stages were identified. Specifically, one thawing–refreezing stage (2.8–2.2 m), one freezing aggradation stage (2.2–1.6 m), and two permafrost aggradation–degradation cycle stages (4.8–2.8 m; 1.6–0.7 m) were differentiated, which emphasize the importance of climate‐induced freeze–thaw transitions and differing permafrost aggradation processes on ground ice formation and resultant isotope hydrochemical behaviors. This study is the first to use high‐resolution data in ground ice to interpret the freeze–thaw history of permafrost in the SAYR. These findings are important for further understanding of past permafrost evolution and projected future permafrost degradation trends on the QTP, and provide an alternative method to explore permafrost history.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2022-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48718921","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}
Jambaljav Yamkhin, Gansukh Yadamsuren, Temuujin Khurelbaatar, Tsogt‐Erdene Gansukh, Undrakhtsetseg Tsogtbaatar, S. Adiya, Amarbayasgalan Yondon, Dashtseren Avirmed, S. Natsagdorj
This study presents the results of permafrost mapping in Mongolia based on the TTOP (temperature‐on‐top‐of‐permafrost) approach, which were validated against in situ measurements at various locations. In situ measurements indicated that the mean annual ground temperature (MAGT) ranged from 0.6 to 2.2°C interannually, showing the greatest variability when furthest from 0°C. The differences between the modeled and measured MAGTs exceeded ±1°C in locations where permafrost was in a nonequilibrium state and was controlled predominantly by local factors. It was estimated that permafrost occupies one‐third of Mongolia. We divided the extent of the permafrost into five zones: continuous, discontinuous, sporadic, isolated, and seasonally frozen ground. In total, the permafrost zones cover ~462.8 × 103 km2, accounting for 29.3% of Mongolia. Of this total area, continuous permafrost accounted for 118.3 × 103 km2 (7.5%), discontinuous permafrost 127.7 × 103 km2 (8.1%), sporadic permafrost 112.4 × 103 km2 (7.1%), and isolated permafrost 104.4 × 103 km2 (6.6%).
{"title":"Spatial distribution mapping of permafrost in Mongolia using TTOP","authors":"Jambaljav Yamkhin, Gansukh Yadamsuren, Temuujin Khurelbaatar, Tsogt‐Erdene Gansukh, Undrakhtsetseg Tsogtbaatar, S. Adiya, Amarbayasgalan Yondon, Dashtseren Avirmed, S. Natsagdorj","doi":"10.1002/ppp.2165","DOIUrl":"https://doi.org/10.1002/ppp.2165","url":null,"abstract":"This study presents the results of permafrost mapping in Mongolia based on the TTOP (temperature‐on‐top‐of‐permafrost) approach, which were validated against in situ measurements at various locations. In situ measurements indicated that the mean annual ground temperature (MAGT) ranged from 0.6 to 2.2°C interannually, showing the greatest variability when furthest from 0°C. The differences between the modeled and measured MAGTs exceeded ±1°C in locations where permafrost was in a nonequilibrium state and was controlled predominantly by local factors. It was estimated that permafrost occupies one‐third of Mongolia. We divided the extent of the permafrost into five zones: continuous, discontinuous, sporadic, isolated, and seasonally frozen ground. In total, the permafrost zones cover ~462.8 × 103 km2, accounting for 29.3% of Mongolia. Of this total area, continuous permafrost accounted for 118.3 × 103 km2 (7.5%), discontinuous permafrost 127.7 × 103 km2 (8.1%), sporadic permafrost 112.4 × 103 km2 (7.1%), and isolated permafrost 104.4 × 103 km2 (6.6%).","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2022-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43795060","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}
Xusheng Wan, W. Pei, Jianguo Lu, Enxi Qiu, Zhongrui Yan, Nima Pirhadi, Jishuai Zhu
The variation in unfrozen water content with temperature substantially affects coupled heat and water transport in frozen soil, causing frost heave and thaw settlement owing to the ice and water phase change and influencing soil stability in cold regions. Thus, analyzing the mechanism of water freezing and building a predictive model for the unfrozen water content of soils is paramount. In this study, an analytical model based on equivalent contact angle was developed to predict the unfrozen water content. The relationship between the equivalent contact angle and temperature was obtained based on the assumption that the heterogeneous nucleation rate nonlinearly decreased with temperature. The proposed analytical model was validated using existing unfrozen water content data at various temperatures for a silty clay soil material from the Qinghai–Tibet Plateau, and compared to several existing numerical models which predict unfrozen water content in soil materials. The results revealed a close relationship between the unfrozen water content and equivalent contact angle, and the equivalent contact angle increased as the temperature decreased. Meanwhile, the pore water in the soil first froze when the contact angle was smaller. Moreover, the values predicted by the analytical model for the unfrozen water content agreed well with the experimental results, especially under low‐temperature conditions and during the early stage of water freezing.
{"title":"Analytical model to predict unfrozen water content based on the probability of ice formation in soils","authors":"Xusheng Wan, W. Pei, Jianguo Lu, Enxi Qiu, Zhongrui Yan, Nima Pirhadi, Jishuai Zhu","doi":"10.1002/ppp.2167","DOIUrl":"https://doi.org/10.1002/ppp.2167","url":null,"abstract":"The variation in unfrozen water content with temperature substantially affects coupled heat and water transport in frozen soil, causing frost heave and thaw settlement owing to the ice and water phase change and influencing soil stability in cold regions. Thus, analyzing the mechanism of water freezing and building a predictive model for the unfrozen water content of soils is paramount. In this study, an analytical model based on equivalent contact angle was developed to predict the unfrozen water content. The relationship between the equivalent contact angle and temperature was obtained based on the assumption that the heterogeneous nucleation rate nonlinearly decreased with temperature. The proposed analytical model was validated using existing unfrozen water content data at various temperatures for a silty clay soil material from the Qinghai–Tibet Plateau, and compared to several existing numerical models which predict unfrozen water content in soil materials. The results revealed a close relationship between the unfrozen water content and equivalent contact angle, and the equivalent contact angle increased as the temperature decreased. Meanwhile, the pore water in the soil first froze when the contact angle was smaller. Moreover, the values predicted by the analytical model for the unfrozen water content agreed well with the experimental results, especially under low‐temperature conditions and during the early stage of water freezing.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2022-09-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41925821","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}
Coarse sand‐sized (0.5–1.0 mm) grains of vein quartz were subjected to frost‐induced stress under controlled laboratory conditions. A total of 1,000 freeze–thaw (FT) cycles, simulated under different (low, high) water mineralization conditions in the temperature range from −5°C up to +10°C, were used to test effects on collected samples. Scanning electron microscopic (SEM) microtextural analysis of grain surfaces was performed at 0 (start) and after 50, 100, 300, 700, and 1,000 FT cycles. The results indicate that variable frost‐induced microtextural imprints encountered on quartz grain surfaces prior to and following analysis depend largely on the mineralization (dissolved solute content) of water involved in the weathering process. The higher the water mineralization, the greater the intensity of mechanical weathering. Two predominant outcomes in the course of these micro‐scale frost weathering tests have been identified: a physical (mechanical) aspect manifested by the occurrence of conchoidal fractures and breakage block microtextures dominating up to 300 FT cycles, and a chemical aspect resulting in the occurrence of precipitation crusts and obliteration of grain microrelief. Moreover, three additional stages of microtexture development may be distinguished with the evolution of frost‐induced microrelief on the surface of quartz grains: (i) initial cracks of large‐sized conchoidal fractures, (ii) increasing frost cycles yielding additional small‐sized conchoidal fractures, and (iii) advanced breakage blocks. Frost‐induced exposure of fresh, unweathered grain surfaces leads to refreshing of the grain surface.
{"title":"Multi‐stage evolution of frost‐induced microtextures on the surface of quartz grains—An experimental study","authors":"M. Górska, B. Woronko","doi":"10.1002/ppp.2164","DOIUrl":"https://doi.org/10.1002/ppp.2164","url":null,"abstract":"Coarse sand‐sized (0.5–1.0 mm) grains of vein quartz were subjected to frost‐induced stress under controlled laboratory conditions. A total of 1,000 freeze–thaw (FT) cycles, simulated under different (low, high) water mineralization conditions in the temperature range from −5°C up to +10°C, were used to test effects on collected samples. Scanning electron microscopic (SEM) microtextural analysis of grain surfaces was performed at 0 (start) and after 50, 100, 300, 700, and 1,000 FT cycles. The results indicate that variable frost‐induced microtextural imprints encountered on quartz grain surfaces prior to and following analysis depend largely on the mineralization (dissolved solute content) of water involved in the weathering process. The higher the water mineralization, the greater the intensity of mechanical weathering. Two predominant outcomes in the course of these micro‐scale frost weathering tests have been identified: a physical (mechanical) aspect manifested by the occurrence of conchoidal fractures and breakage block microtextures dominating up to 300 FT cycles, and a chemical aspect resulting in the occurrence of precipitation crusts and obliteration of grain microrelief. Moreover, three additional stages of microtexture development may be distinguished with the evolution of frost‐induced microrelief on the surface of quartz grains: (i) initial cracks of large‐sized conchoidal fractures, (ii) increasing frost cycles yielding additional small‐sized conchoidal fractures, and (iii) advanced breakage blocks. Frost‐induced exposure of fresh, unweathered grain surfaces leads to refreshing of the grain surface.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2022-09-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46413675","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}
Léa Bussière, M. Schmutz, R. Fortier, J. Lemieux, A. Dupuy
In this study, high resolution ground‐penetrating radar (GPR), electrical resistivity tomography (ERT), and spectral‐induced polarization tomography (SIPT) were used to (i) delineate characteristic solifluction features, (ii) map the ice distribution, and (iii) assess subsurface water content and permeability in the surrounding rampart of a thermokarst pond in the discontinuous permafrost zone. The study site is located in the Tasiapik Valley near Umiujaq in Nunavik (Québec), Canada, which benefits from decades of geological mapping, geophysical investigation, and monitoring of ground temperature and thaw subsidence, providing an extensive understanding of the cryohydrogeological context of the area. The results of geophysical investigation undertaken in this study were cross validated using core sampling, laboratory core analysis, and in situ ground temperature and water content monitoring. Based on this investigation, a conceptual model was derived and compared to the stratigraphy of cross‐section described in literature in finer‐grained context. Very good consistency was found from one in situ geophysical survey to another, as well as between the derived stratigraphic models and the ground truth. The combination of all the available data allowed the development of a detailed cryohydrogeological model across the studied thermokarst pond, which highlights the effect of lithology, topography, and land cover on the distribution and mobility of water in the ground.
{"title":"Near‐surface geophysical imaging of a thermokarst pond in the discontinuous permafrost zone in Nunavik (Québec), Canada","authors":"Léa Bussière, M. Schmutz, R. Fortier, J. Lemieux, A. Dupuy","doi":"10.1002/ppp.2166","DOIUrl":"https://doi.org/10.1002/ppp.2166","url":null,"abstract":"In this study, high resolution ground‐penetrating radar (GPR), electrical resistivity tomography (ERT), and spectral‐induced polarization tomography (SIPT) were used to (i) delineate characteristic solifluction features, (ii) map the ice distribution, and (iii) assess subsurface water content and permeability in the surrounding rampart of a thermokarst pond in the discontinuous permafrost zone. The study site is located in the Tasiapik Valley near Umiujaq in Nunavik (Québec), Canada, which benefits from decades of geological mapping, geophysical investigation, and monitoring of ground temperature and thaw subsidence, providing an extensive understanding of the cryohydrogeological context of the area. The results of geophysical investigation undertaken in this study were cross validated using core sampling, laboratory core analysis, and in situ ground temperature and water content monitoring. Based on this investigation, a conceptual model was derived and compared to the stratigraphy of cross‐section described in literature in finer‐grained context. Very good consistency was found from one in situ geophysical survey to another, as well as between the derived stratigraphic models and the ground truth. The combination of all the available data allowed the development of a detailed cryohydrogeological model across the studied thermokarst pond, which highlights the effect of lithology, topography, and land cover on the distribution and mobility of water in the ground.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2022-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49418532","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}
Qinxue Wang, T. Okadera, Masataka Watanabe, Tonghua Wu, B. Ochirbat
To detect the response of permafrost to climate change in various terrestrial ecosystems, we established a permafrost monitoring network in 2007, which includes eight boreholes to monitor ground temperatures in forest, meadow, steppe, moderately dry steppe, and wetland ecosystems and three Automatic Weather Stations (AWS) to monitor climatic factors, such as wind speed (Ws), air temperature (Ta), relative humidity (RH), precipitation (P), solar radiation (Rs), net radiation (Rn), soil heat flux (SHF), soil temperature (Ts), and soil water content (SWC), in forest, meadow, and steppe ecosystems in north‐central Mongolia. Major indicators, including mean annual ground temperature (MAGT), active layer thickness (ALT), and depth of zero annual amplitude (DZAA), were estimated to detect permafrost degradation. The results show that MAGT has increased by 0.00–0.02°C per year (almost no change) in the ice‐poor permafrost areas and by 0.03–0.06°C per year in the ice‐rich permafrost on pingos and wetlands. ALT showed an annual increase of −0.78 to 0.36 cm (almost no change) in the forest and meadow ecosystems and 2.3–7.2 cm in wetland ecosystems, whereas it increased by 23.0–28.9 cm per year in the steppe ecosystems over the last decade. This implies that the permafrost has degraded more rapidly in the steppe ecosystems than in other ecosystems. Based on correlation analysis, ALT is correlated to P in the meadow ecosystems and to SWC in the forest ecosystem, and MAGT is correlated to RH. However, both ALT and MAGT show a close correlation with major climatic factors, such as Ta, RH, SHF, and SWC in the steppe ecosystem. DZAA shows a close negative correlation with Ta in all ecosystems. These results provide evidence for permafrost degradation and its different responses to climate change in various terrestrial ecosystems.
{"title":"Ground warming and permafrost degradation in various terrestrial ecosystems in northcentral Mongolia","authors":"Qinxue Wang, T. Okadera, Masataka Watanabe, Tonghua Wu, B. Ochirbat","doi":"10.1002/ppp.2161","DOIUrl":"https://doi.org/10.1002/ppp.2161","url":null,"abstract":"To detect the response of permafrost to climate change in various terrestrial ecosystems, we established a permafrost monitoring network in 2007, which includes eight boreholes to monitor ground temperatures in forest, meadow, steppe, moderately dry steppe, and wetland ecosystems and three Automatic Weather Stations (AWS) to monitor climatic factors, such as wind speed (Ws), air temperature (Ta), relative humidity (RH), precipitation (P), solar radiation (Rs), net radiation (Rn), soil heat flux (SHF), soil temperature (Ts), and soil water content (SWC), in forest, meadow, and steppe ecosystems in north‐central Mongolia. Major indicators, including mean annual ground temperature (MAGT), active layer thickness (ALT), and depth of zero annual amplitude (DZAA), were estimated to detect permafrost degradation. The results show that MAGT has increased by 0.00–0.02°C per year (almost no change) in the ice‐poor permafrost areas and by 0.03–0.06°C per year in the ice‐rich permafrost on pingos and wetlands. ALT showed an annual increase of −0.78 to 0.36 cm (almost no change) in the forest and meadow ecosystems and 2.3–7.2 cm in wetland ecosystems, whereas it increased by 23.0–28.9 cm per year in the steppe ecosystems over the last decade. This implies that the permafrost has degraded more rapidly in the steppe ecosystems than in other ecosystems. Based on correlation analysis, ALT is correlated to P in the meadow ecosystems and to SWC in the forest ecosystem, and MAGT is correlated to RH. However, both ALT and MAGT show a close correlation with major climatic factors, such as Ta, RH, SHF, and SWC in the steppe ecosystem. DZAA shows a close negative correlation with Ta in all ecosystems. These results provide evidence for permafrost degradation and its different responses to climate change in various terrestrial ecosystems.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":null,"pages":null},"PeriodicalIF":5.0,"publicationDate":"2022-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48977830","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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