Yu Zhang, R. Touzi, W. Feng, G. Hong, T. Lantz, S. Kokelj
Soil temperature observations in permafrost regions are sparse, which limits our understanding and ability to map permafrost conditions at high spatial resolutions. In this study, we measured near‐surface soil temperatures (Tnss) at 107 sites from August 2016 to August 2017 in northern boreal and tundra areas in northwestern Canada. Active‐layer thickness (ALT), soil and vegetation conditions were also measured at these sites. Our observations show large variations in Tnss and ALT across an area with a similar climate. This high degree of spatial heterogeneity illustrates the importance of high‐resolution mapping of permafrost for infrastructure planning and understanding the impacts of permafrost thaw. Annual mean Tnss varied by 5–6°C among observation sites, which was mainly due to differences in Tnss in winter and spring, indicating the importance of snow conditions on determining landscape‐scale variation in near‐surface ground temperatures. ALT varied from about 30 cm to more than 120 cm. The variation in ALT among sites did not correlate with thawing season Tnss, but was associated with variation in soil conditions, especially the surface organic layer thickness. Freezing n‐factors varied significantly from site to site and among ecotypes, while thawing n‐factors were similar among sites, except bare soils. This study shows that ecotypes can be used to map ALT and Tnss at landscape scales in tundra areas, but the method is not as effective in the northern boreal region.
{"title":"Landscape‐scale variations in near‐surface soil temperature and active‐layer thickness: Implications for high‐resolution permafrost mapping","authors":"Yu Zhang, R. Touzi, W. Feng, G. Hong, T. Lantz, S. Kokelj","doi":"10.1002/ppp.2104","DOIUrl":"https://doi.org/10.1002/ppp.2104","url":null,"abstract":"Soil temperature observations in permafrost regions are sparse, which limits our understanding and ability to map permafrost conditions at high spatial resolutions. In this study, we measured near‐surface soil temperatures (Tnss) at 107 sites from August 2016 to August 2017 in northern boreal and tundra areas in northwestern Canada. Active‐layer thickness (ALT), soil and vegetation conditions were also measured at these sites. Our observations show large variations in Tnss and ALT across an area with a similar climate. This high degree of spatial heterogeneity illustrates the importance of high‐resolution mapping of permafrost for infrastructure planning and understanding the impacts of permafrost thaw. Annual mean Tnss varied by 5–6°C among observation sites, which was mainly due to differences in Tnss in winter and spring, indicating the importance of snow conditions on determining landscape‐scale variation in near‐surface ground temperatures. ALT varied from about 30 cm to more than 120 cm. The variation in ALT among sites did not correlate with thawing season Tnss, but was associated with variation in soil conditions, especially the surface organic layer thickness. Freezing n‐factors varied significantly from site to site and among ecotypes, while thawing n‐factors were similar among sites, except bare soils. This study shows that ecotypes can be used to map ALT and Tnss at landscape scales in tundra areas, but the method is not as effective in the northern boreal region.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":"32 1","pages":"627 - 640"},"PeriodicalIF":5.0,"publicationDate":"2021-08-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ppp.2104","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48707955","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}
V. Demidov, S. Wetterich, N. Demidov, Lutz Schirrmeister, S. Verkulich, A. Koshurnikov, V. Gagarin, A. Ekaykin, Anton Terekchov, A. Veres, A. Kozachek
Drilling of a 21.8‐m‐deep borehole on top of the 10.5‐m‐high Nori pingo that stands at 32 m asl in Grøndalen Valley (Spitsbergen) revealed a 16.1‐m‐thick massive ice enclosed by frozen sediments. The hydrochemical compositions of both the massive ice and the sediment extract show a prevalence of Na+ and Cl− ions throughout the core. The upper part of the massive ice (stage A) has low mineralization and shows an isotopically closed‐system trend in δ18O and δD isotopes decreasing down‐core. Stage B exhibits high mineralization and an isotopically semi‐open system. The crystallographic structure of Nori pingo’s massive ice provides evidence of several large groundwater intrusions that support the defined formation stages. Analysis of local aquifers leads to suggest that the pingo was hydraulically sourced through a local fault zone by low mineralized sodium–bicarbonate groundwater of a Paleogene strata aquifer. This groundwater was enriched by sodium and chloride ions while filtering through marine valley sediments with residual salinity. The comparison between the sodium–chloride‐dominated massive ice of the Nori pingo and the sodium–bicarbonate‐dominated ice of the adjacent Fili pingo that stands higher up the valley may serve as an indicator for groundwater source patterns of other Nordenskiöld Land pingos.
{"title":"Pingo drilling reveals sodium–chloride‐dominated massive ice in Grøndalen, Spitsbergen","authors":"V. Demidov, S. Wetterich, N. Demidov, Lutz Schirrmeister, S. Verkulich, A. Koshurnikov, V. Gagarin, A. Ekaykin, Anton Terekchov, A. Veres, A. Kozachek","doi":"10.1002/ppp.2124","DOIUrl":"https://doi.org/10.1002/ppp.2124","url":null,"abstract":"Drilling of a 21.8‐m‐deep borehole on top of the 10.5‐m‐high Nori pingo that stands at 32 m asl in Grøndalen Valley (Spitsbergen) revealed a 16.1‐m‐thick massive ice enclosed by frozen sediments. The hydrochemical compositions of both the massive ice and the sediment extract show a prevalence of Na+ and Cl− ions throughout the core. The upper part of the massive ice (stage A) has low mineralization and shows an isotopically closed‐system trend in δ18O and δD isotopes decreasing down‐core. Stage B exhibits high mineralization and an isotopically semi‐open system. The crystallographic structure of Nori pingo’s massive ice provides evidence of several large groundwater intrusions that support the defined formation stages. Analysis of local aquifers leads to suggest that the pingo was hydraulically sourced through a local fault zone by low mineralized sodium–bicarbonate groundwater of a Paleogene strata aquifer. This groundwater was enriched by sodium and chloride ions while filtering through marine valley sediments with residual salinity. The comparison between the sodium–chloride‐dominated massive ice of the Nori pingo and the sodium–bicarbonate‐dominated ice of the adjacent Fili pingo that stands higher up the valley may serve as an indicator for groundwater source patterns of other Nordenskiöld Land pingos.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":"32 1","pages":"572 - 586"},"PeriodicalIF":5.0,"publicationDate":"2021-07-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ppp.2124","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42063719","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 natural cyclical development of palsas makes it difficult to use visible signs of decay as reference points for environmental change. Thus, to determine the actual development stage of a palsa, investigations of the internal structure are crucial. Our study presents 2‐D and 3‐D electrical resistivity imaging (ERI) and 2‐D ground‐penetrating radar (GPR) results, measurements of surface and subsurface temperatures, and of the soil matric potential from Orravatnsrústir Palsa Site in Central Iceland. By a joint interpretation of the results, we deduce the internal structure (i.e., thickness of thaw zone and permafrost, ice/water content) of five palsas of different size and shape. The results differentiate between initial and mature development stages and show that palsas of different development stages can exist in close proximity. While internal characteristics indicate undisturbed development of four palsas, one palsa shows indications of environmental change. Our study shows the value of the multimethod geophysical approach and introduces measurements of the soil matric potential as a promising method to assess the current state of the subsurface.
{"title":"Internal structure and palsa development at Orravatnsrústir Palsa Site (Central Iceland), investigated by means of integrated resistivity and ground‐penetrating radar methods","authors":"A. Emmert, C. Kneisel","doi":"10.1002/ppp.2106","DOIUrl":"https://doi.org/10.1002/ppp.2106","url":null,"abstract":"The natural cyclical development of palsas makes it difficult to use visible signs of decay as reference points for environmental change. Thus, to determine the actual development stage of a palsa, investigations of the internal structure are crucial. Our study presents 2‐D and 3‐D electrical resistivity imaging (ERI) and 2‐D ground‐penetrating radar (GPR) results, measurements of surface and subsurface temperatures, and of the soil matric potential from Orravatnsrústir Palsa Site in Central Iceland. By a joint interpretation of the results, we deduce the internal structure (i.e., thickness of thaw zone and permafrost, ice/water content) of five palsas of different size and shape. The results differentiate between initial and mature development stages and show that palsas of different development stages can exist in close proximity. While internal characteristics indicate undisturbed development of four palsas, one palsa shows indications of environmental change. Our study shows the value of the multimethod geophysical approach and introduces measurements of the soil matric potential as a promising method to assess the current state of the subsurface.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":"32 1","pages":"503 - 519"},"PeriodicalIF":5.0,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ppp.2106","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48377609","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}
{"title":"Issue Information","authors":"","doi":"10.1002/ppp.2071","DOIUrl":"https://doi.org/10.1002/ppp.2071","url":null,"abstract":"No abstract is available for this article.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":" ","pages":""},"PeriodicalIF":5.0,"publicationDate":"2021-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ppp.2071","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47316102","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}
Y. Vasil'chuk, J. Chizhova, N. Budantseva, A. Kurchatova, V. Rogov, A. Vasil'chuk
Pingos are indicators of modern and past conditions of permafrost. In total, 1,620 pingos have been identified on the Yamal and Gydan peninsulas in western Siberia. The main purpose of this study is to consider the distribution of stable isotopes in pingo ice cores formed under conditions of open and closed systems. Two pingos from ice cores of different origin in the continuous permafrost zone of northwest Siberia have been considered: the Messoyaha‐1 pingo (10.5 m in height) and the Pestsovoe pingo (17 m in height). Drilling of the ice core was performed with continuous sampling of an undisturbed frozen core. Ice formation was estimated according to the Rayleigh fractionation in a closed‐system versus an open‐system framework. For the Pestsovoe pingo, a pronounced decrease in δ18O values with corresponding increase in dexc with depth indicates a closed system upon freezing of the lake talik from the top down. For the Messoyakha‐1 pingo, the values of δ18O and δ2Н showed a weak tendency to decrease with depth, with values of dexc varying randomly. Ice that was segregated in the overlying and underlying sediments had similar values of δ18O and δ2Н and a low slope. Isotopically nonequilibrium ice formation was established for ice which had been segregated in a closed system and for ice cores formed in an open to semiclosed system. The vacuum mechanism of water suction from the surrounding lake or lake talik may have played a significant role during the formation of the upper ice core of the Messoyakha‐1 pingo and its additional growth.
{"title":"Stable oxygen and hydrogen isotope compositions of the Messoyakha and Pestsovoe pingos in northwest Siberia as markers of ice core formation","authors":"Y. Vasil'chuk, J. Chizhova, N. Budantseva, A. Kurchatova, V. Rogov, A. Vasil'chuk","doi":"10.1002/ppp.2122","DOIUrl":"https://doi.org/10.1002/ppp.2122","url":null,"abstract":"Pingos are indicators of modern and past conditions of permafrost. In total, 1,620 pingos have been identified on the Yamal and Gydan peninsulas in western Siberia. The main purpose of this study is to consider the distribution of stable isotopes in pingo ice cores formed under conditions of open and closed systems. Two pingos from ice cores of different origin in the continuous permafrost zone of northwest Siberia have been considered: the Messoyaha‐1 pingo (10.5 m in height) and the Pestsovoe pingo (17 m in height). Drilling of the ice core was performed with continuous sampling of an undisturbed frozen core. Ice formation was estimated according to the Rayleigh fractionation in a closed‐system versus an open‐system framework. For the Pestsovoe pingo, a pronounced decrease in δ18O values with corresponding increase in dexc with depth indicates a closed system upon freezing of the lake talik from the top down. For the Messoyakha‐1 pingo, the values of δ18O and δ2Н showed a weak tendency to decrease with depth, with values of dexc varying randomly. Ice that was segregated in the overlying and underlying sediments had similar values of δ18O and δ2Н and a low slope. Isotopically nonequilibrium ice formation was established for ice which had been segregated in a closed system and for ice cores formed in an open to semiclosed system. The vacuum mechanism of water suction from the surrounding lake or lake talik may have played a significant role during the formation of the upper ice core of the Messoyakha‐1 pingo and its additional growth.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":"32 1","pages":"558 - 571"},"PeriodicalIF":5.0,"publicationDate":"2021-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ppp.2122","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46092580","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}
Icing occurs each winter along the floodplain of the Kuuguluk River in the continuous permafrost zone at Salluit in Nunavik (Quebec), Canada. The source of successive water overflows which thicken and enlarge this ice cover over time is suprapermafrost groundwater discharging from a talik below the riverbed. Electrical resistivity tomography was used to delineate the talik, while water level and temperature dataloggers were used to assess the thermo‐hydraulic conditions of the riverbed. The mean annual riverbed temperature was 1.8°C in 2016 while the mean annual air temperature was −6.0°C. Hydraulic heads below the ice cover as high as 2.8 m and events of abrupt decreases in hydraulic head due to suprapermafrost groundwater overflow through cracks in the ice cover were monitored. An analytical solution based on beam mechanics theory was used to assess the water pressure‐induced stresses which are sufficient to fracture the ice cover. A detailed conceptual model of the talik and icing dynamics is proposed to explain the cryo‐hydrogeological processes taking place in this complex groundwater–river system. The groundwater pressure buildup in the talik during the winter is due to constricted flow of suprapermafrost groundwater in the talik. These results have implications for understanding the dynamics of river taliks and their use as potential water supplies in northern communities.
{"title":"A conceptual model for talik dynamics and icing formation in a river floodplain in the continuous permafrost zone at Salluit, Nunavik (Quebec), Canada","authors":"Weibo Liu, R. Fortier, J. Molson, J. Lemieux","doi":"10.1002/ppp.2111","DOIUrl":"https://doi.org/10.1002/ppp.2111","url":null,"abstract":"Icing occurs each winter along the floodplain of the Kuuguluk River in the continuous permafrost zone at Salluit in Nunavik (Quebec), Canada. The source of successive water overflows which thicken and enlarge this ice cover over time is suprapermafrost groundwater discharging from a talik below the riverbed. Electrical resistivity tomography was used to delineate the talik, while water level and temperature dataloggers were used to assess the thermo‐hydraulic conditions of the riverbed. The mean annual riverbed temperature was 1.8°C in 2016 while the mean annual air temperature was −6.0°C. Hydraulic heads below the ice cover as high as 2.8 m and events of abrupt decreases in hydraulic head due to suprapermafrost groundwater overflow through cracks in the ice cover were monitored. An analytical solution based on beam mechanics theory was used to assess the water pressure‐induced stresses which are sufficient to fracture the ice cover. A detailed conceptual model of the talik and icing dynamics is proposed to explain the cryo‐hydrogeological processes taking place in this complex groundwater–river system. The groundwater pressure buildup in the talik during the winter is due to constricted flow of suprapermafrost groundwater in the talik. These results have implications for understanding the dynamics of river taliks and their use as potential water supplies in northern communities.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":"32 1","pages":"468 - 483"},"PeriodicalIF":5.0,"publicationDate":"2021-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ppp.2111","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45189945","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}
Periglacial rock walls are affected by an increase in rockfall activity attributed to permafrost degradation. While recent laboratory tests have asserted the role of permafrost in bedrock stability, linking experimental findings to field applications is hindered by the difficulty in assessing bedrock temperature at observed rockfall locations and time. In this study, we simulated bedrock temperature for 209 rockfalls inventoried in the Mont Blanc massif between 2007 and 2015 and 209,000 random events artificially created at observed rockfall locations. Real and random events are then compared in a statistical analysis to determine their significance. Permafrost conditions (or very close to 0°C) were consistently found for all events with failure depth > 6 m, and for some events affecting depths from 4 to 6 m. Shallower events were probably not related to permafrost processes. Surface temperatures were significantly high up to at least 2 months prior to failure, with the highest peaks in significance 1.5–2 months and 1–5 days before rockfalls. Similarly, temperatures at scar depths were significantly high, but steadily decreasing, 1 day to 3 weeks before failure. The study confirms that warm permafrost areas (> −2°C) are particularly prone to rockfalls, and that failures are a direct response to extraordinary high bedrock temperature in both frozen and unfrozen conditions. The results are promising for the development of a rockfall susceptibility index, but uncertainty analysis encourages the use of a greater rockfall sample and a different sample of random events.
{"title":"Rock temperature prior to failure: Analysis of 209 rockfall events in the Mont Blanc massif (Western European Alps)","authors":"Alexandre Legay, F. Magnin, L. Ravanel","doi":"10.1002/ppp.2110","DOIUrl":"https://doi.org/10.1002/ppp.2110","url":null,"abstract":"Periglacial rock walls are affected by an increase in rockfall activity attributed to permafrost degradation. While recent laboratory tests have asserted the role of permafrost in bedrock stability, linking experimental findings to field applications is hindered by the difficulty in assessing bedrock temperature at observed rockfall locations and time. In this study, we simulated bedrock temperature for 209 rockfalls inventoried in the Mont Blanc massif between 2007 and 2015 and 209,000 random events artificially created at observed rockfall locations. Real and random events are then compared in a statistical analysis to determine their significance. Permafrost conditions (or very close to 0°C) were consistently found for all events with failure depth > 6 m, and for some events affecting depths from 4 to 6 m. Shallower events were probably not related to permafrost processes. Surface temperatures were significantly high up to at least 2 months prior to failure, with the highest peaks in significance 1.5–2 months and 1–5 days before rockfalls. Similarly, temperatures at scar depths were significantly high, but steadily decreasing, 1 day to 3 weeks before failure. The study confirms that warm permafrost areas (> −2°C) are particularly prone to rockfalls, and that failures are a direct response to extraordinary high bedrock temperature in both frozen and unfrozen conditions. The results are promising for the development of a rockfall susceptibility index, but uncertainty analysis encourages the use of a greater rockfall sample and a different sample of random events.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":"32 1","pages":"520 - 536"},"PeriodicalIF":5.0,"publicationDate":"2021-06-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ppp.2110","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49110086","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}
Investigations of the regional distribution of ice‐wedge polygons and wedge‐ice volume allow for the assessment of the vulnerability of permafrost landscapes to thaw‐induced disturbances and related ecological feedbacks. Ice‐wedge polygons have been described in multiple studies in flat terrain and low‐gradient hillslopes, but few studies have examined ice‐wedge polygons in mountainous terrain. This study investigates the distribution, morphometry, and wedge‐ice content of ice‐wedge polygons in Tombstone Territorial Park, a mountainous permafrost region in central Yukon. Results show that ice‐wedge polygons occupy 2.6% of the park and preferentially develop in woody sedge peat, glaciofluvial, and alluvial deposits along the lower reaches of the Blackstone and East Blackstone rivers on hillslopes ≤1°. The morphometry of five of six polygonal sites studied showed statistically similar polygon sizes and trough angles, while showing different development stages based on vegetation type, surface wetness, and spatial pattern. The estimation of wedge‐ice volumes in the ice‐wedge polygons is 8–22% and is comparable to that of other Arctic regions. However, the estimated wedge‐ice volume represents a minimum value because older generations of ice wedges are truncated 3–4 m below the surface with no evidence of surface polygons, and the polygonal network can be obscured by slope processes, vegetation, and ice‐wedge inactivity. This study provides insights into the application of morphometric and soil parameters for the assessment of ice‐wedge polygon distribution and development stages.
{"title":"Distribution, morphometry, and ice content of ice‐wedge polygons in Tombstone Territorial Park, central Yukon, Canada","authors":"R. Frappier, D. Lacelle","doi":"10.1002/ppp.2123","DOIUrl":"https://doi.org/10.1002/ppp.2123","url":null,"abstract":"Investigations of the regional distribution of ice‐wedge polygons and wedge‐ice volume allow for the assessment of the vulnerability of permafrost landscapes to thaw‐induced disturbances and related ecological feedbacks. Ice‐wedge polygons have been described in multiple studies in flat terrain and low‐gradient hillslopes, but few studies have examined ice‐wedge polygons in mountainous terrain. This study investigates the distribution, morphometry, and wedge‐ice content of ice‐wedge polygons in Tombstone Territorial Park, a mountainous permafrost region in central Yukon. Results show that ice‐wedge polygons occupy 2.6% of the park and preferentially develop in woody sedge peat, glaciofluvial, and alluvial deposits along the lower reaches of the Blackstone and East Blackstone rivers on hillslopes ≤1°. The morphometry of five of six polygonal sites studied showed statistically similar polygon sizes and trough angles, while showing different development stages based on vegetation type, surface wetness, and spatial pattern. The estimation of wedge‐ice volumes in the ice‐wedge polygons is 8–22% and is comparable to that of other Arctic regions. However, the estimated wedge‐ice volume represents a minimum value because older generations of ice wedges are truncated 3–4 m below the surface with no evidence of surface polygons, and the polygonal network can be obscured by slope processes, vegetation, and ice‐wedge inactivity. This study provides insights into the application of morphometric and soil parameters for the assessment of ice‐wedge polygon distribution and development stages.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":"32 1","pages":"587 - 600"},"PeriodicalIF":5.0,"publicationDate":"2021-06-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ppp.2123","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42261125","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}
Eike Reinosch, M. Gerke, B. Riedel, A. Schwalb, Q. Ye, J. Buckel
The western Nyainqêntanglha Range on the Tibetan Plateau reaches an elevation of 7,162 m and is characterized by an extensive periglacial environment under semi‐arid climatic conditions. Rock glaciers play an important part of the water budget in high mountain areas and recent studies suggest that they may even act as climate‐resistant water storages. In this study we present the first rock glacier inventory of this region containing 1,433 rock glaciers over an area of 4,622 km. To create the most reliable inventory we combine manually created rock glacier outlines with an automated classification approach. The manual outlines were generated based on surface elevation data, optical satellite imagery and a surface velocity estimation. This estimation was generated via InSAR time series analysis with Sentinel‐1 data from 2016 to 2019. Our pixel‐based automated classification was able to correctly identify 87.8% of all rock glaciers in the study area at a true positive rate of 69.5%. In total, 65.9% of rock glaciers are classified as transitional with surface velocities of 1–10 cm/yr. In total, 18.5% are classified as active with higher velocities of up to 87 cm/yr. The southern windward side of the mountain range contains more numerous and more active rock glaciers. We attribute this to higher moisture availability supplied by the Indian Monsoon.
{"title":"Rock glacier inventory of the western Nyainqêntanglha Range, Tibetan Plateau, supported by InSAR time series and automated classification","authors":"Eike Reinosch, M. Gerke, B. Riedel, A. Schwalb, Q. Ye, J. Buckel","doi":"10.1002/ppp.2117","DOIUrl":"https://doi.org/10.1002/ppp.2117","url":null,"abstract":"The western Nyainqêntanglha Range on the Tibetan Plateau reaches an elevation of 7,162 m and is characterized by an extensive periglacial environment under semi‐arid climatic conditions. Rock glaciers play an important part of the water budget in high mountain areas and recent studies suggest that they may even act as climate‐resistant water storages. In this study we present the first rock glacier inventory of this region containing 1,433 rock glaciers over an area of 4,622 km. To create the most reliable inventory we combine manually created rock glacier outlines with an automated classification approach. The manual outlines were generated based on surface elevation data, optical satellite imagery and a surface velocity estimation. This estimation was generated via InSAR time series analysis with Sentinel‐1 data from 2016 to 2019. Our pixel‐based automated classification was able to correctly identify 87.8% of all rock glaciers in the study area at a true positive rate of 69.5%. In total, 65.9% of rock glaciers are classified as transitional with surface velocities of 1–10 cm/yr. In total, 18.5% are classified as active with higher velocities of up to 87 cm/yr. The southern windward side of the mountain range contains more numerous and more active rock glaciers. We attribute this to higher moisture availability supplied by the Indian Monsoon.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":"32 1","pages":"657 - 672"},"PeriodicalIF":5.0,"publicationDate":"2021-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ppp.2117","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48538492","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 present study presents three‐dimensional investigations of a hydrostatic pingo in the Mackenzie Delta region and a hydraulic pingo in the Ogilvie Mountains and contributes to a better understanding about the internal structures of the two pingo types. A combined approach using quasi‐three‐dimensional electrical resistivity tomography, ground‐penetrating radar and frost probing allowed a clear delineation of frozen and unfrozen areas in the subsurface. At the hydrostatic pingo a massive ice core as well as a surrounding talik could be detected, but the location of the ice core and the talik differs from previous published assumptions. In contrast to acknowledged theory, at our site the massive ice core is not located in the center of the pingo but at the western edge, whereas the eastern flank is underlain by a talik, which surrounds the massive ice core. At the hydraulic pingo, the expected internal structure could be confirmed and the pathway of upwelling water could also be detected. The combined approach of the applied methods represents the first known three‐dimensional geoelectrical investigation of pingos and provides new insights into the internal structure and architecture of the two different pingo types. The chosen approach allows further conclusions on the formation of these permafrost‐affected landforms.
{"title":"Three‐dimensional investigation of an open‐ and a closed‐system Pingo in northwestern Canada","authors":"Julius Kunz, C. Kneisel","doi":"10.1002/ppp.2115","DOIUrl":"https://doi.org/10.1002/ppp.2115","url":null,"abstract":"The present study presents three‐dimensional investigations of a hydrostatic pingo in the Mackenzie Delta region and a hydraulic pingo in the Ogilvie Mountains and contributes to a better understanding about the internal structures of the two pingo types. A combined approach using quasi‐three‐dimensional electrical resistivity tomography, ground‐penetrating radar and frost probing allowed a clear delineation of frozen and unfrozen areas in the subsurface. At the hydrostatic pingo a massive ice core as well as a surrounding talik could be detected, but the location of the ice core and the talik differs from previous published assumptions. In contrast to acknowledged theory, at our site the massive ice core is not located in the center of the pingo but at the western edge, whereas the eastern flank is underlain by a talik, which surrounds the massive ice core. At the hydraulic pingo, the expected internal structure could be confirmed and the pathway of upwelling water could also be detected. The combined approach of the applied methods represents the first known three‐dimensional geoelectrical investigation of pingos and provides new insights into the internal structure and architecture of the two different pingo types. The chosen approach allows further conclusions on the formation of these permafrost‐affected landforms.","PeriodicalId":54629,"journal":{"name":"Permafrost and Periglacial Processes","volume":"32 1","pages":"541 - 557"},"PeriodicalIF":5.0,"publicationDate":"2021-05-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/ppp.2115","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44192993","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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