2019069069 Tang Rui (China University of Mining & Technology, Laboratory for Geomechanics and Deep Underground Engineering, Xuzhou, China); Zhou Guoqing; Jiao Wei and Ji Yukun. Theoretical model of hydraulic conductivity for frozen saline/non-saline soil based on freezing characteristic curve: Cold Regions Science and Technology, 165, Article no. 102794, illus. incl. 4 tables, September 2019. Based on Publisher-supplied data.
The hydraulic conductivity of frozen soil has significant effects on the moisture and solute migration and on the ice segregation in frost heave when the soil is being frozen. In this study, in accordance with the thermodynamic theory of unfrozen water film, the variation of chemical potential energy of water film due to salt and soil particles is considered. It is highlighted that moisture migration in the frozen soil can be considered as the Darcy flow under a new equivalent water pressure control. On that basis, the expression of pore water freezing temperature and pore radius is yielded, and then the capillary bundle theory and the soil frozen characteristic curve (SFCC) are used for the frozen soil to build a theoretical model to predict the hydraulic conductivity of frozen saline/non-saline soil. Through the comparison of four empirical equations and experimental data, the results achieved using our theoretical model can help to predict the hydraulic conductivity of the frozen soil. Furthermore, frozen non-saline soil achieves 12.47% the contribution of unfrozen water film to hydraulic conductivity, and frozen saline soil achieves 11.25% according to warm frozen soil from 0 to -2°C. Thus, this important channel cannot be ignored for water migration. Actually, this theoretical model gives an important parameter to the numerical simulation of frost heave in cold regions engineering, which can be referenced for the study on hydraulic conductivity of frozen saline/non-saline soil.
2019069073 Liang, Renxing (Princeton University, Princeton, NJ); Lau, Maggie; Vishnivetskaya, Tatiana; Lloyd, Karen G.; Wang, Wei; Wiggins, Jessica; Miller, Jennifer; Pfiffner, Susan; Rivkina, Elizaveta M. and Onstott, Tullis C. Predominance of anaerobic, spore-forming bacteria in metabolically active microbial communities from ancient Siberian permafrost: Applied and Environmental Microbiology, 85(15), Article No. e00560-19, August 1, 2019.
2019069058 Kadivar, Mehdi (University of Delaware, Department of Civil and Environmental Engineering, Newark, DE) and Manahiloh, Kalehiwot Nega. Revisiting parameters that dictate the mechanical behavior of frozen soils: Cold Regions Science and Technology, 163, p. 34-43, illus., July 2019. Based on Publisher-supplied data.
Construction of infrastructure in seasonally freezing and permafrost areas and the need for temporary improvement of slopes and weak sites with artificial freezing have been the impetuses for the observed growth in frozen ground engineering. A proper understanding of the mechanical behavior of frozen soils is necessary for the development of prediction models and the successful implementation of frozen ground engineering. The major parameters that affect the mechanical behavior of frozen soils were identified as the ice content, temperature, confining pressure, and strain rate. Focusing on the contribution of each phase, the effect of these parameters, on the mechanical behavior of frozen soil, is investigated. Bishop's effective stress for unsaturated soils is extended, to account for the aforementioned parameters, and introduced for frozen soils. The new effective stress is defined to have two components so that it accommodates the intergranular stresses carried by the soil grains and the ice crystals.
2019069061 Liu Weibo (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Yu Wenbing; Hu, Da; Lu Yan; Chen Lin; Yi, Xin and Han Fenglei. Crack damage investigation of paved highway embankment in the Tibetan Plateau permafrost environments: Cold Regions Science and Technology, 163, p. 78-86, illus. incl. 5 tables, July 2019. Based on Publisher-supplied data.
Field surveys focusing on the crack damages in paved embankment of the Qinghai-Tibet Highway were carried out at 17 sections. Some severe cracks were found in the road embankment constructed on the permafrost ground affecting the smooth operation of the highway. Road orientation, thaw settlement, crack width and length were measured at the typical crack sections. Besides, embankment slope surface temperatures were monitored at two road sections, and the temperature difference as high as 10°C was observed in the cold winter time. Three scenarios were employed in the numerical modeling to assess the impact of climate warming, embankment slope surface temperature, and embankment itself on the underlying permafrost evolution process. Thereafter, a method was introduced to obtain the thaw settlement of the road embankment according to the simulated thawing front depth. The results indicate that the thaw settlement difference across the road embankment width is the main cause results in the crack damages. This uneven thaw settlement can be amplified due to the presence of the original ground slope. Additionally, climate warming intensified the underlying permafrost degradation and accelerated the thawing front penetrating into the subgrade permafrost. In summary, road orientation, original ground slope, climate warming, and underlying permafrost type are major but not the sole causes for the crack damages of the paved embankment in the Tibetan permafrost environments. It is recommended that steep slope and ice-rich permafrost ground should be avoided in the early design of the highway embankment.
2019069097 Vigneron, Adrien (Laval University, Quebec City, QC, Canada); Lovejoy, Connie; Cruaud, Perrine; Kalenitchenko, Dmitri; Culley, Alexander and Vincent, Warwick F. Contrasting winter versus summer microbial communities and metabolic functions in a permafrost thaw lake: Frontiers in Microbiology, 10, Article 1656, Article no. 1656, illus., 70 ref., July 16, 2019.
2019069059 Yu Qihao (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Mu Yanhu; Yuan Chang; Ma Wei and Pan Xicai. The cold accumulative effect of expressway embankment with a combined cooling measure in permafrost zones: Cold Regions Science and Technology, 163, p. 59-67, illus. incl. 3 tables, July 2019. Based on Publisher-supplied data.
The thermal performance of an experimentally built expressway embankment with a combined cooling measure at Beiluhe Basin in the Qinghai-Tibet Plateau was investigated based on long-term field monitoring. Six-year records of soil temperatures showed that the embankment cooled by a measure combining hollow concrete bricks and ventilation ducts had a significant cooling effect on the subgrade soil. Over the investigated time period, the permafrost table beneath the embankment moved upward to the natural ground surface, and the subgrade soil layers down to a depth of -15 m underwent a considerable cooling. Then, the long-term thermal performance of this kind of cooled embankment with different surface widths (13 and 26 m) is comparatively studied using numerical simulations. The simulated results show that both embankments perform well in cooling the subgrade soil. However, the annual heat loss of the subgrade soil beneath the wider cooled embankment is greater than that of the narrow ones. Via the wider cooled embankment, more cold accumulates in the subgrade soil after the embankment's construction, which we term as the "cold accumulative" effect. This cold accumulative effect can ensure the underlying permafrost thermal stability better in the context of climate warming and strength the long-term embankment stability.
2019069095 Box, Jason E. (Geological Survey of Denmark and Greenland, Copenhagen, Denmark); Colgan, William T.; Christensen, Torben Rojle; Schmidt, Niels Martin; Lund, Magnus; Parmentier, Frans-Jan W.; Brown, Ross; Bhatt, Uma S.; Euskirchen, Eugénie S.; Romanovsky, Vladimir E.; Walsh, John E.; Overland, James E.; Wang, Muyin; Corell, Robert W.; Meier, Walter N.; Wouters, Bert; Mernild, Sebastian; Mard, Johanna; Pawlak, Janet and Olsen, Morten Skovgard. Key indicators of Arctic climate change; 1971-2017: Environmental Research Letters, 14(4), Article no. 045010, illus. incl. 2 tables, 60 ref., April 2019.
Key observational indicators of climate change in the Arctic, most spanning a 47 year period (1971-2017) demonstrate fundamental changes among nine key elements of the Arctic system. We find that, coherent with increasing air temperature, there is an intensification of the hydrological cycle, evident from increases in humidity, precipitation, river discharge, glacier equilibrium line altitude and land ice wastage. Downward trends continue in sea ice thickness (and extent) and spring snow cover extent and duration, while near-surface permafrost continues to warm. Several of the climate indicators exhibit a significant statistical correlation with air temperature or precipitation, reinforcing the notion that increasing air temperatures and precipitation are drivers of major changes in various components of the Arctic system. To progress beyond a presentation of the Arctic physical climate changes, we find a correspondence between air temperature and biophysical indicators such as tundra biomass and identify numerous biophysical disruptions with cascading effects throughout the trophic levels. These include: increased delivery of organic matter and nutrients to Arctic near-coastal zones; condensed flowering and pollination plant species periods; timing mismatch between plant flowering and pollinators; increased plant vulnerability to insect disturbance; increased shrub biomass; increased ignition of wildfires; increased growing season CO2 uptake, with counterbalancing increases in shoulder season and winter CO2 emissions; increased carbon cycling, regulated by local hydrology and permafrost thaw; conversion between terrestrial and aquatic ecosystems; and shifting animal distribution and demographics. The Arctic biophysical system is now clearly trending away from its 20th Century state and into an unprecedented state, with implications not only within but beyond the Arctic. The indicator time series of this study are freely downloadable at AMAP.no. Copyright (Copyright) 2019 (Copyright) 2018 The Author(s). Published by IOP Publishing Ltd
2019069072 Burkert, Alexander (California State University, Northridge, Department of Biology, Northridge, CA); Douglas, Thomas A.; Waldrop, Mark P. and Mackelprang, Rachel. Changes in the active, dead, and dormant microbial community structure across a Pleistocene permafrost chronosequence: Applied and Environmental Microbiology, 85(7), Article No. e02646-18, illus. incl. 3 tables, 80 ref., April 1, 2019.
2019069053 Kim, Sang Yeob (Korea University, School of Civil, Environmental and Architectural Engineering, Seoul, South Korea); Hong, Won-Taek and Lee, Jong-Sub. Role of the coefficient of uniformity on the California bearing ratio, penetration resistance, and small strain stiffness of coarse Arctic soils: Cold Regions Science and Technology, 160, p. 230-241, illus. incl. 4 tables, April 2019. Based on Publisher-supplied data.
For seasonally frozen-thawed Arctic soils, soil properties are significantly affected by the particle size distribution. The objective of this study is to study the role of the coefficient of uniformity (Cu) on the California bearing ratio (CBR), strength, and stiffness. Six poorly-graded sand (SP) samples with various Cu are collected from a depth from 20 cm to 120 cm in the active layer. The amounts of the organic matter range from 0.22% to 2.11%. Specimens are prepared with each natural water content into a CBR mold, and the CBR, mini-cone tip resistance (qc), and shear wave velocity (Vs) are measured. Field tests using an instrumented dynamic cone penetrometer (IDCP), which can gather force and acceleration signals at the cone tip, are performed. The IDCP index (IDCPI), energy-corrected DCPI (EDCPI), and dynamic cone resistance (qd) are estimated during penetration. Test results show that the CBR, qc, qd, Vs, and maximum shear modulus (Gmax) decrease with increasing Cu value. The IDCPI and EDCPI increase according to the Cu value. Thus, CBR is inversely proportional to the DCPI, and linearly proportional to the qd and Gmax. This study demonstrates that the CBR, strength, and stiffness of Arctic soils are affected by the particle size distribution because the main skeleton comprised of large particles can be disrupted by small particles.
2019069049 Ling Feng (Zhaoqing University, School of Mathematics and Statistics, Zhaoqing, China) and Zhang, Tingjun. Simulating heat source effect of a thermokarst lake in the first 540 years on the Alaskan Arctic using a simple lake expanding model: Cold Regions Science and Technology, 160, p. 176-183, illus. incl. 3 tables, April 2019. Based on Publisher-supplied data.
Thermokarst lakes are an important heat source to ground surrounding the lake, a strong greenhouse gas methane source if taliks develop under the lakes, and a sensitive indicator of climatic and environmental changes. This study proposes a simple lake radius expanding model (EM) by imposing a step increase process of thermokarst lake radius to the lake radius unchanged model (UM) as an external condition, and simulates the temporal and spatial variation of ground temperature and talik thickness beneath an expanding thermokarst lake on the Alaskan Arctic during the period that the lake radius expands from the initial length of 15 m to a length of 150 m. The differences of the simulated ground thermal regime and talik development process between using the EM and the UM under the identical computation conditions are compared. The sensitivity of talik thickness to lake expansion time interval is also analyzed. The simulated results by using the EM show that the maximum permafrost temperature increase and talik thickness increase below the expanding thermokarst lake is 6.4°C and 17.5 m respectively during the simulation period of 540 years, the corresponding ground temperature increase of >1.0°C beneath the original lake bottom occurs at a depth of 175.3 m. The maximum talik thickness simulated by using the UM is observably greater than that calculated by using the EM. The mean talik increase rates by using the EM and the UM are 2. 4 cm yr-1 and 3.1 cm yr-1 in the first 420 years, and 1.6 cm yr-1 and 1.3 cm yr-1 in the last 120 years from year 420 to year 540. The UM may overestimate the heat source effect of the thermokarst lake when lake radius in the EM is less than the radius in the UM, and underestimate the heat source effect when the radius in the EM is greater than the radius in the UM, and the magnitudes of the overestimate and underestimate depend on the difference of the radius in the two models. The EM can be applied to simulate permafrost thermal regime and talik development beneath an expanding thermokarst lake easily as the method is simple and the needed data to drive the model are easy to obtain. The selection of a field measurements based lake expansion time interval or lakeshore collapse width is essential for numerical simulation since decreases in lake expansion time interval have limited increases in talik thickness.
2019069042 Wang Jiahui (Harbin Institute of Technology, School of Civil Engineering, Harbin, China); Zhang Feng and Yang, Zhaohui. Anisotropy in small-strain shear modulus of permafrost at rising temperatures: Cold Regions Science and Technology, 160, p. 1-12, illus. incl. 3 tables, sketch map, April 2019. Based on Publisher-supplied data.
Perennially frozen soils, or permafrost, exist extensively on the Arctic Coastal Plain of Alaska and can reach up to 600 m deep. This paper describes the cryostructure of permafrost cores obtained from a deep borehole in this area, presents the shear wave velocities measured in different directions by the bender element method, exhibits the small-strain shear moduli of clay, silt and sand permafrost specimens from -10°C to 20°C, and discusses the anisotropy in the small-strain shear modulus of permafrost in both frozen and thawed states. It was found that the specimen site is covered by a few meters of syngenetic permafrost with massive wedge ice, below which is a deep epigenetic permafrost with numerous visible ice lenses primarily located in the top 120 m, oriented in horizontal or subhorizontal directions. The shear modulus ratio found for thawed clay permafrost falls in the higher end of those reported for natural or reconstituted clays, while the ratio for thawed sand permafrost is clearly higher than those previously reported. The anisotropy in the small-strain shear modulus was found to be strongly temperature dependent. The temperature dependency of anisotropy can be attributed to volumetric expansion, occurring during the freezing of pore water followed by the thawing of pore ice that, respectively, disrupts then allows the recovery of the preferential alignment of soil particles, or fabric, formed during geological sedimentation processes. In addition, deep permafrost cores with shear stiffness comparable to hard rock exhibit a very low stiffness ratio Ghh/Gvh, likely due to the in situ geostatic stress-induced anisotropy in pore ice crystals.
2019069048 Zhang Jiaming (China University of Geosciences, Faculty of Engineering, Wuhan, China); Mei Guoxiong; Bao, Ting and Yan Li-E. An experimental study on thermal analyses of crushed-rock layers with single-size aggregates: Cold Regions Science and Technology, 160, p. 110-118, illus. incl. 1 table, April 2019. Based on Publisher-supplied data.
Crushed-rock layers have been widely used in roadway embankments in warm permafrost regions to preserve the permafrost ground via the convective cooling through the cavity of the rock layer. Under the scenario of global warming, reducing the solar absorption of the rock layer for further preserving the permafrost in the roadbed has gained momentum recently. Except the convective cooling, the albedo, temperature, and heat flux of a rock layer are also fundamentally correlated to the thermal performance of the layer but have not been fully understood. Here we prepared three crushed limestone layers with mean particle sizes of 15.0, 24.4, and 36.5 mm, respectively. We sequentially coated rock surface with different colors. After a rock layer was coated to be unicolor by a matte paint, we measured the layer's albedo and logged the heat flux and temperature at the bottom of the layer simultaneously. The measurement lasted for two days; then the layer was coated by another paint to have a different color and the next measurement cycle started. We found that a smaller-particle crushed-rock layer absorbs less sunlight, stays cooler, transmits less heat downward, and has smaller thermal inertia. It is also found that a smaller-particle rock layer has a lower probability to trap the reflected radiation on the rock surface. Special efforts should be made to lowering this probability for curtailing the absorption of solar radiation by crushed-rock layers to embankments.
2019069043 Zhao Hongting (Chinese Academy of Sciences, Laboratory of Frozen Soil Engineering, Lanzhou, China); Wu Qingbai and Zhang Zhongqiong. Long-term cooling effect of the crushed rock structure embankments of the Qinghai-Tibet Railway: Cold Regions Science and Technology, 160, p. 21-30, illus. incl. 8 tables, April 2019. Based on Publisher-supplied data.
Crushed rock embankments are widely applied in the Qinghai-Tibet Railway. Most of previous studies have focused on the short-term cooling performance of crushed rock embankments, but few studies have concerned about the long-term cooling effect to ensure its service performance though monitored data. The long-term cooling effects of the U-shaped crushed rock embankment (UCRE), closed-system crushed rock-based embankment (CCRBE) and open-system crushed rock-based embankment (OCRBE) were evaluated based on 13-year monitored data at the Beiluhe experimental section. Compared with the conventional roadbed, the average ground temperature in 2017 at depths of 2, 5, and 10 m with the UCRE was decreased by 2.20°C, 1.60°C, and 0.94°C, respectively. In the OCRBE, the mean annual temperature at the same depths dropped by 1.67°C, 1.26°C, and 0.80°C, respectively. The mean annual temperature with the CCRBE dropped by 1.20°C, 0.79°C, and 0.45°C, respectively. Therefore, the UCRE has the best long-term effect to decrease the temperature of underlying permafrost. Otherwise, crushed rock embankments existed as a staged cooling process. Engineering activities decreased temperature of underlying permafrost in short-term, but climate warming had a negative impact on the long-term cooling effect
2019069038 Liu Weibo (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Laboratory of Frozen Soil Engineering, Lanzhou, China); Yu Wenbing; Fortier, Richard; Chen, Lin; Lu Yan; Zhang Mingyi and Hu, Da. Thermal effect of rainwater infiltration into a replicated road embankment in a cold environmental chamber: Cold Regions Science and Technology, 159, p. 47-57, illus., 44 ref., March 2019. Based on Publisher-supplied data.
A laboratory experiment was performed to investigate the thermal effect of rainwater infiltration into a one-half scale replicated road embankment built on artificial permafrost subjected to four 15-day freeze-thaw cycles and several rainfall events during thaw periods in a cold environmental chamber. The ground temperature, water content, and heat flux were monitored at different depths at three key locations in the road subbase. Based on the experimental results, the rainwater infiltration has a significant heating effect on the shallow subbase layers down to a depth no more than 30 cm. The heat transfer in the road embankment is directly correlated to the amount of rainfall. Moreover, rainwater infiltration has different heating effects according to the locations in the road subbase. The most important heating effect is underneath the embankment slope, the second one in the embankment shoulder, and the third one underneath the concrete pavement. The changes in temperature, moisture, and heat flux in the road subbase due to the rainwater infiltration are delayed and attenuated with the increase in depth. Even if the road subbase was frozen at these depths, moisture changes in the road subbase as deep as 60 cm were observed. The volumetric unfrozen water content in the road subbase and subgrade depends on the ground temperature and exhibits hysteretic behavior during cooling and warming cycles. The observed variations in heat flux are related to the changes in temperature and moisture in the road subbase. For road embankments located in permafrost environments, the thermal effect of rainwater infiltration into the road subbase may lead to permafrost degradation at depth.
2019066623 Moon, Twila A. (University of Colorado Boulder, National Snow and Ice Data Center, Boulder, CO); Overeem, Irina; Druckenmiller, Matt; Holland, Marika; Huntington, Henry; Kling, George; Lovecraft, Amy Lauren; Miller, Gifford; Scambos, Ted; Schädel, Christina; Schuur, Edward A. G.; Trochim, Erin; Wiese, Francis; Williams, Dee and Wong, Gifford. The expanding footprint of rapid Arctic change: Earth's Future, 7(3), p. 212-218, illus., 60 ref., March 2019.
Arctic land ice is melting, sea ice is decreasing, and permafrost is thawing. Changes in these Arctic elements are interconnected, and most interactions accelerate the rate of change. The changes affect infrastructure, economics, and cultures of people inside and outside of the Arctic, including in temperate and tropical regions, through sea level rise, worsening storm and hurricane impacts, and enhanced warming. Coastal communities worldwide are already experiencing more regular flooding, drinking water contamination, and coastal erosion. We describe and summarize the nature of change for Arctic permafrost, land ice, and sea ice, and its influences on lower latitudes, particularly the United States. We emphasize that impacts will worsen in the future unless individuals, businesses, communities, and policy makers proactively engage in mitigation and adaptation activities to reduce the effects of Arctic changes and safeguard people and society. Abstract Copyright (2019), The Authors.
2019064962 Yang, Jinhai (Heriot-Watt University, Institute of Petroleum Engineering, School of Energy, Geoscience, Infrastructure and Society, Edinburgh, Edinburgh, United Kingdom); Hassanpouryouzband, Aliakbar; Tohidi, B.; Chuvilin, E.; Bukhanov, Boris; Istomin, V. and Cheremisin, Alexey. Gas hydrates in permafrost; distinctive effect of gas hydrates and ice on the geomechanical properties of simulated hydrate-bearing permafrost sediments: Journal of Geophysical Research: Solid Earth, 124(3), p. 2551-2563, illus. incl. 4 tables, 66 ref., March 2019.
The geomechanical stability of the permafrost formations containing gas hydrates in the Arctic is extremely vulnerable to global warming and the drilling of wells for oil and gas exploration purposes. In this work the effect of gas hydrate and ice on the geomechanical properties of sediments was compared by triaxial compression tests for typical sediment conditions: unfrozen hydrate-free sediments at 0.3°C, hydrate-free sediments frozen at -10°C, unfrozen sediments containing about 22 vol% methane hydrate at 0.3°C, and hydrate-bearing sediments frozen at -10°C. The effect of hydrate saturation on the geomechanical properties of simulated permafrost sediments was also investigated at predefined temperatures and confining pressures. Results show that ice and gas hydrates distinctively influence the shearing characteristics and deformation behavior. The presence of around 22 vol% methane hydrate in the unfrozen sediments led to a shear strength as strong as those of the frozen hydrate-free specimens with 85 vol% of ice in the pores. The frozen hydrate-free sediments experienced brittle-like failure, while the hydrate-bearing sediments showed large dilatation without rapid failure. Hydrate formation in the sediments resulted in a measurable reduction in the internal friction, while freezing did not. In contrast to ice, gas hydrate plays a dominant role in reinforcement of the simulated permafrost sediments. Finally, a new physical model was developed, based on formation of hydrate networks or frame structures to interpret the observed strengthening in the shear strength and the ductile deformation. Abstract Copyright (2019). American Geophysical Union. All Rights Reserved.
2019069091 Yonemura, Seiichiro (Institute for Agro-Environmental Sciences, Tsukuba, Japan); Uchida, Masao; Iwahana, Go; Kim, Yongwon and Yoshikawa, Kenji. Technical advances in measuring greenhouse gas emissions from thawing permafrost soils in the laboratory: Polar Science, 19, p. 137-145, illus. incl. 2 tables, sketch map, 41 ref., March 2019.
2019069034 Zhang Mingyi (Chinese Academy of Sciences, Northwest Institute of Eco-Environment and Resources, Lanzhou, China); Wu Zhiqiang; Wang Jiwei; Lai Yuanming and You Zhilang. Experimental and theoretical studies on the solar reflectance of crushed-rock layers: Cold Regions Science and Technology, 159, p. 13-19, illus. incl. 1 table, 37 ref., March 2019. Based on Publisher-supplied data.
Crushed-rock layers have been widely used to cool subgrades in permafrost regions. The convective cooling effect of crushed-rock layers depends not only on the cavities of the layers but also the outmost skin temperature, which is mainly regulated by the solar absorption. Here we experimentally studied the solar reflectance of crushed-rock layers with mean particle sizes of 0.9 cm, 1.5 cm, 2.2 cm, 3.5 cm, 5.4 cm, 8.4 cm, 11.8 cm, 17.3 cm and 26.4 cm, respectively. The experimental results indicate that the solar reflectance of the crushed-rock layers firstly decreases, and then increases with the mean particle size. It is found that the crushed-rock layer with a mean particle size of 5.4 cm reflects the least sunlight. The theoretical analysis indicates that a crushed rock layer absorbs more sunlight as the cavity ratio increases and as the mean intersection angle of crushed-rock surfaces decreases. Our findings imply that the solar reflectance of a crushed-rock layer can be raised by reducing the surface cavity ratio of the crushed-rock layer and/or flattening the crushed-rock layer surface; however, the surface cavity ratio of the crushed-rock layers and the mean intersection angle of the crushed-rock surfaces are uncertain because the crushed-rocks with different shapes were randomly poured into the wood trays; therefore, it is expected that the trend, the macro-reflectance of the crushed-rock layers changes with mean particle sizes, is validated by further refined experiments.
2019069033 Bertran, Pascal (Institut National de Recherches Archeologiques Preventives (INRAP), Begles, France); Andrieux, Eric; Bateman, Mark; Font, Marianne; Manchuel, Kevin and Sicilia, Deborah. Features caused by ground ice growth and decay in late Pleistocene fluvial deposits, Paris Basin, France; discussion: Geomorphology, 327, p. 629-633, illus., 31 ref., February 15, 2019. For reference to discussion see Van Vliet-Lanoe, B., et al., Geomorphology, Vol. 327, p. 613-628, DOI: 10.1016/j.geomorph.2018.08.036, 2019; for reference to original see Bertran, P., et al., Geomorphology, Vol. 310, p. 81-101, DOI: 10.1016/j.geomorph.2018.03.011, 2018.
The response by Van Vliet-Lanoe et al. to our paper on potential thermokarst features in Pleistocene alluvial deposits from the Paris Basin (France) presents inconsistencies that we consider here successively. These are (1) the map of the maximum extent of Pleistocene permafrost in France, (2) the genesis of liquefaction and fluidization structures in periglacial environments, (3) the origin of thermokarst lakes and recumbent folds, (4) the depositional context of sandy units, and (5) the age of the studied deposits. All structures result from the interplay between (1) the growth and degradation of ice wedges, which are responsible for the development of a mound-like topography (badland thermokarst reliefs) on the edge of the alluvial terrace and from the initiation of ponding elsewhere on the terrace, (2) the degradation of lithalsa that developed later in the lacustrine deposits. The sequence was dated confidently to the Late Weichselian.
2019069032 Van Vliet-Lanoë, Brigitte (Université de Bretagne Occidentale, Domaines Océaniques, Plouzane, France); Pissart, Albert; Baize, Stéphane; Brulhet, Jacques and Ego, Fréderic. Evidence of multiple thermokarst events in northeastern France and southern Belgium during the two last glaciations; discussion: Geomorphology, 327, p. 613-628, illus. incl. geol. sketch maps, 82 ref., February 15, 2019. For reference to original see Bertran, P., et al., Features caused by ground ice growth and decay in late Pleistocene fluvial deposits, Paris Basin, France, Geomorphology, Vol. 310, p. 84-101, DOI: 10.1016/j.geomorph.2018.03.011, 2018.
The past thermokarst activities in valleys of northern France and Belgium covered the Upper Weichselian and the Upper Saalian periods. To develop in western Europe, thermokarst first requires an accumulation of ground ice close to the surface progressively stored along the glacial-time permafrost aggradation: it is regionally uncommon during the early glacials, especially on the plateau, but frequent during the Upper Pleniglacials in valleys. These features mostly relate to various frost mounds created by injection and segregated ices. The role of ice wedges is really very limited in this zone of southern extent of the European palaeo-permafrost on plateau and terraces. Thermokarst events are mostly susceptible to occur during the coldest part of the glacial. With a more progressive warming or a retrogressive thermokarst triggered by erosion, as in Arctic today, deformations are more gradual, in direct relation with the rheological properties of the sediments and usually local drainage. They are in concurrence with the vegetation dynamic that will limit its expression. Thermokarst events are in first order orbitally forced under control of a maximum insolation and a minimum in precession, as well as during the Weichselian and the Saalian. They are moreover, associated with abrupt warming transmitted by Dansgaerd Oeschger events. Snowiness and mild winter temperatures are probably the main triggers for thermokarst activity as of today. Other events can be triggered by solar activity as at 20 ka or perhaps enhanced by major ash splay as during the MIS 6b Zeiffen interstadial. Thermokarst events are usually followed on the continent by a reorganization of the rivers from braided to meandering systems.
2019068860 Gasser, T. (International Institute for Applied Systems Analysis, Laxenburg, Austria); Kechiar, M.; Ciais, P.; Burke, E. J.; Kleinen, T.; Zhu, D.; Huang, Y.; Ekici, A. and Obersteiner, M. Path-dependent reductions in CO2 emission budgets caused by permafrost carbon release: Nature Geoscience, 11(11), p. 830-835, illus. incl. 1 table, 65 ref., November 2018.
2019068859 Serikova, Svetlana (Umea University, Department of Ecology and Environmental Science, Umea, Sweden); Pokrovsky, Oleg S.; Ala-Aho, Pertti; Kazantsev, V.; Kirpotin, Sergey N.; Kopysov, Sergey G.; Krickov, Ivan V.; Laudon, Hjalmar; Manasypov, Rinat M.; Shirokova, Liudmila S.; Soulsby, C.; Tetzlaff, Doerthe and Karlsson, Jan. High riverine CO2 emissions at the permafrost boundary of western Siberia: Nature Geoscience, 11(11), p. 825-829, illus. incl. sketch map, 49 ref., November 2018.
2019065656 Comyn-Platt, Edward (Centre for Ecology and Hydrology, Wallingford, United Kingdom); Hayman, Garry; Huntingford, Chris; Chadburn, Sarah E.; Burke, Eleanor J.; Harper, Anna B.; Collins, William J.; Webber, Christopher P.; Powell, Tom; Cox, Peter M.; Gedney, Nicola and Sitch, Stephen. Carbon budgets for 1.5 and 2°C targets lowered by natural wetland and permafrost feedbacks: Nature Geoscience, 11(8), p. 568-573, illus. incl. 1 table, 45 ref., August 2018.
2019069080 Fedorov-Davydov, D. G. (Rossiyskaya Akademiya Nauk, Institut Fiziko-Khimicheskih i Biologicheskiih Problem Pochvovedeniya, Pushchino, Russian Federation); Davydov, S. P.; Davydova, A. I.; Ostroumov, V. E.; Kholodov, A. L.; Sorokovnikov, V. A. and Shmelev, D. G. Temperaturnyy rezhim pochv Severnoy Yakutii [Temperature regime of soils in northern Yakutia]: Kriosfera Zemli = Earth Cryosphere, 22(4), p. 15-24 (English sum.), illus. incl. 2 tables, 18 ref., August 2018.
Soils in northern Yakutia differ in average duration of the season of positive temperatures, the difference being 2.3 times between soil types and 1.8 between zonal loam soils, at a depth of 20 cm. The seasons of >0 and >5°C soil temperatures vary from 1-2 months for tundra cryozems and gleyzem (turbic glacic cryosols) to 2.3-3.5 months for taiga cryometamorphic soils (cambic turbic cryosols), peat-cryozem (folic cryosol), and tundra podburs (spodic turbic cryosols). The active layer freezes mostly from above (top to base), except some years of cool summers mainly in the tundra zone when it freezes partly from below. The tundra and taiga soils show a warming trend of the soil climate since the late 1990s according to dynamics of annual freezing degree-day sums. The soils of northern Yakutia vary in total heat spent on the active layer warming, the difference reaching 10 times.
2019069084 Kaverin, D. A. (Rossiyskaya Akademiya Nauk, Ural'skoye Otdeleniye, Komi Nauchnyy Tsentr, Institut Biologii, Syktyvkar, Russian Federation); Khil'ko, A. V. and Patukhov, A. V. Vysokochastotnoye georadiolokatsionnoye zondirovaniye pochvogruntov mnogoletnemerzlykh bugristykh bolot (Yevropeyskiy Severo-Vostok Rossii) [Application of high-frequency ground-penetrating radar to investigations of permafrost-affected soils of peat plateaus; northeastern Russia]: Kriosfera Zemli = Earth Cryosphere, 22(4), p. 86-95 (English sum.), illus. incl. table, sect., sketch map, 16 ref., August 2018.
Application of high-frequency GPR to investigating permafrost-affected soils of peat plateaus has been analyzed. To assess the technical capabilities of high-frequency antennas, the depth of both permafrost table and lithological contacts at virgin (peat mounds and fens) and anthropogenically transformed (zone of defrosting influence of the cement-concrete road) sites of peat plateaus have been determined. Both surface shielded antennas (300 and 900 MHz) have been used simultaneously in the conditions of considerable variations of the depth of permafrost table and mineral horizon's bedding in the upper 10-meter soil strata. Application of aerial shielded antennas (1000 and 2000 MHz) to determine the depth of permafrost table has been additionally assessed.
2019069079 Slagoda, E. A. (Rossiyskaya Akademiya Nauk, Sibirskoye Otdeleniye, Institut Kriosfery Zemli, Tyumen, Russian Federation); Simonova, G. V.; Tikhonravova, Ya. V.; Kuznetsova, A. O.; Popov, K. A. and Orekhov, P. T. Radiouglerodnoye datirovaniye mnogoletnemerzlyih otlozhemiy ostrova Belyy, Karskoye more [Radiocarbon dating of permafrost in Bely Island, Kara Sea]: Kriosfera Zemli = Earth Cryosphere, 22(4), p. 3-14 (English sum.), 2 tables, sects., sketch map, 37 ref., August 2018.
Twenty radiocarbon ages have been obtained for permafrost sections on Bely Island (Kara Sea) sampled in 2015-2016. The results make the basis for sketch maps of the late Pleistocene (Karginian and Sartanian) and Holocene deposits of marine terraces I and II, the laida, and the floodplain of the Rogozin tidal channel. The Karginian Shelf sediments make up terrace II and the uneven base of terrace I, and lie below sea level under the laida; the Sartan Shelf and subaerial deposits are widespread on terrace I. The new radiocarbon ages place for the first time constraints on the Sartan sediments and record the northward sea retreat within the island at the Karga/Sartan boundary. The laida and the Rogozin channel floodplain formed during the Atlantic, Subboreal, and Little Ice Age deposition in the Holocene simultaneously with peat deposition in drained lakes (hasyreys) on terraces.
2019069074 Buddovich, S. N. (Moskovskiy Gosudarstvennyy Universitet, Moscow, Russian Federation); Ospennikov, E. N. and Khilimonyuk, V. Z. Fenomen geokriologicheskikh usloviy vostochnoy chasti Olekmo-Charskogo nagor'ya [Phenomenon of geocryological conditions in the eastern part of the Olekma and Chara highlands]: Kriosfera Zemli = Earth Cryosphere, 22(3), p. 3-17 (English sum.), illus. incl. sketch map, 12 ref., June 2018.
This paper discusses results of the study on geocryological (permafrost) conditions in the eastern part of the Olekma-Chara upland at the watershed of the Tokko River and its tributary, the Choruoda River. The study was carried out within the framework of field research at the sites of mineral showings, whose permafrost conditions are extremely contrasting. The combined impact of hydrogeological factors acting in the middle altitude environment is found to be largely responsible for the unique permafrost conditions in the study area.
2019069077 Fedorov-Davydov, D. G. (Rossiyskaya Akademiya Nauk, Institut Fiziko-Khimicheskikh i Biologicheskih Problem Pochvovedeniya, Pushchino, Russian Federation); Davydov, S. P.; Davydova, A. I.; Shmelev, D. G.; Ostroumov, V. E.; Kholodov, A. L. and Sorokovnikov, V. A. Termicheskoye sostoyaniye pochv Severnoy Yakutii [Thermal state of soils in northern Yakutia]: Kriosfera Zemli = Earth Cryosphere, 22(3), p. 52-66 (English sum.), illus. incl. 6 tables, sketch map, 39 ref., June 2018.
The soil profile temperature in northern Yakutia depends on its location in tundra or taiga zones and subzones, water content (drainage conditions), ice content in the underlying permafrost vegetation cover, as well as soil particle size (texture) and thickness of organic horizons. The studied soils differ mainly in winter temperatures. The mean coldest month temperatures of loam soils measured at 20 cm below the surface are 10°C higher in the northern taiga than in the southern tundra. However the mean annual temperatures at this depth vary from -4.3 to -9.7°C in tundra and from -1.2 to -4.9°C in taiga. This discrepancy is primarily due to the effect of the snow cover which is thicker, less dense, and more stable in the forest landscapes. Sandy podburs have larger thawing degree-day sums and deeper 0, 5, and 10 C isotherms than the loamy soils of tundra or taiga zones. Xeromorphic soils of steppe ecosystems in the northern taiga subzone have the warmest summer temperatures and are most responsive to temperature change.
2019069076 Khimenkov, A. N. (Rossiyskaya Akademiya Nauk, Institut Geoekologii, Moscow, Russian Federation); Gagarin, V. E.; Koshurnikov, A. V.; Sheshin, Yu. B. and Skosar', V. V. Laboratornoye modelirovaniye protsessov formirovaniya kriogennogo stroyeniya morskih otlozheniy [Laboratory modeling of formation of the cryogenic structure of marine sediments]: Kriosfera Zemli = Earth Cryosphere, 22(3), p. 40-51 (English sum.), illus. incl. table, 34 ref., June 2018.
This article is devoted to peculiarities of formation of the cryogenic structure of modern coastal sediments using laboratory simulation. The authors have conducted comparative analysis of the results of laboratory and field studies and have shown how the cryogenic structure of coastal sediments depends on the composition, salinity and moisture. They have also analyzed redistribution of soil moisture in different types of soils and the features of ice formation in the zone of contact between fast ice and sea bottom.
2019069075 Makarov, V. N. (Rossiyskaya Akademiya Nauk, Sibirskoye Otdeleniye, Institut Merzlotovedeniya, Yakutsk, Russian Federation) and Torgovskiy, N. V. Geokhimicheskiye osobennosti tekhnogennykh otlozheniy v gorode Yakutsk [Geochemistry of anthropogenic deposits in Yakutsk]: Kriosfera Zemli = Earth Cryosphere, 22(3), p. 27-39 (English sum.), illus. incl. 12 tables, 16 ref., June 2018.
The geochemical nature of the anthropogenic deposits (the cultural layer) in the urban area of Yakutsk is described. The presence of permafrost has determined the geodynamic and geochemical stability of the anthropogenic deposits, which vary in their chemical and mineral composition, structure, and physical and mechanical properties, as well as in the mode of chemical migration and concentration. It has been shown that the occurrence of anomalous concentrations of microelements in the urban soils is due to anthropogenic processes and the chemistry of Quaternary alluvial deposits. Human-induced salinization and contrasting anomalies of toxic elements in the older parts of the city occur throughout the cultural layer and extend to the upper layers of the alluvium. The thickness of the human-induced geochemical haloes in the cultural layer depends on the age of urban development, reaching 8 to 10 m.
2019068983 Semeriya, A. A. (Rossiyskaya Akademiya Nauk, Sibirskoye Otdeleniye, Institut Merzlotovedeniya, Yakutsk, Russian Federation); Gagarin, L. A. and Bazhin, K. I. Merzlotno-gidrogeologicheskiye osobennosti uchastka rasprostraneniya mezhmerzlotnogo vodonosnogo kompleksa v rayone istochnika Eryyu (Tsentral'naya Yakutiya) [Cryohydrogeological features of the site of intrapermafrost aquifer distribution at the Eruu spring area, Central Yakutia]: Kriosfera Zemli = Earth Cryosphere, 22(2), p. 29-38 (English sum.), illus. incl. table, sect., sketch map, 23 ref., June 2018.
The paper presents the results of long-term permafrost and hydrogeological research conducted by Melnikov Permafrost Institute in the area of one of the perennial intrapermafrost springs residing in the territory of Central Yakutia. Spatial boundaries of the intrapermafrost aquifer recharging the Eruu spring are determined from the drilling and geophysical survey data. Results of the groundwater level monitoring data allowed us to define conditions of groundwater accumulation and discharge, as well as to determine the major role of icings in the hydrodynamic regime of intrapermafrost waters. The revealed specific geothermal characteristics of the upper rock layers may serve as indicators of groundwater presence on the fourth (Bestyakhskaya) terrace of the Lena River, which is evidenced by the maximum thaw depth coinciding with the depth of zero annual amplitude.
2019068987 Ala-aho, P. (University of Aberdeen, School of Geosciences, Northern Rivers Institute, Aberdeen, United Kingdom); Soulsby, C.; Pokrovsky, O. S.; Kirpotin, S. N.; Karlsson, J.; Serikova, S.; Manasypov, R.; Lim, A.; Krickov, I.; Kolesnichenko, L. G.; Laudon, H. and Tetzlaff, D. Permafrost and lakes control river isotope composition across a boreal Arctic transect in the Western Siberian lowlands: Environmental Research Letters, 13(3), Paper no. 034028, illus. incl. 1 table, sketch map, 86 ref., March 2018.
The Western Siberian Lowlands (WSL) store large quantities of organic carbon that will be exposed and mobilized by the thawing of permafrost. The fate of mobilized carbon, however, is not well understood, partly because of inadequate knowledge of hydrological controls in the region which has a vast low-relief surface area, extensive lake and wetland coverage and gradually increasing permafrost influence. We used stable water isotopes to improve our understanding of dominant landscape controls on the hydrology of the WSL. We sampled rivers along a 1700 km South-North transect from permafrost-free to continuous permafrost repeatedly over three years, and derived isotope proxies for catchment hydrological responsiveness and connectivity. We found correlations between the isotope proxies and catchment characteristics, suggesting that lakes and wetlands are intimately connected to rivers, and that permafrost increases the responsiveness of the catchment to rainfall and snowmelt events, reducing catchment mean transit times. Our work provides rare isotope-based field evidence that permafrost and lakes/wetlands influence hydrological pathways across a wide range of spatial scales (10-105 km2) and permafrost coverage (0%-70%). This has important implications, because both permafrost extent and lake/wetland coverage are affected by permafrost thaw in the changing climate. Changes in these hydrological landscape controls are likely to alter carbon export and emission via inland waters, which may be of global significance. Copyright (Copyright) 2018 The Author(s). Published by IOP Publishing Ltd.
2019068986 Dean, J. F. (University of Stirling, Biological and Environment Sciences, Stirling, United Kingdom); van der Velde, Y.; Garnett, M. H.; Dinsmore, K. J.; Baxter, R.; Lessels, J. S.; Smith, P.; Street, L. E.; Subke, J. A.; Tetzlaff, D.; Washbourne, I.; Wookey, P. A. and Billett, M. F. Abundant pre-industrial carbon detected in Canadian Arctic headwaters; implications for the permafrost carbon feedback: Environmental Research Letters, 13(3), Paper no. 034024, illus. incl. 1 table, sketch map, 47 ref., March 2018.
Mobilization of soil/sediment organic carbon into inland waters constitutes a substantial, but poorly-constrained, component of the global carbon cycle. Radiocarbon (14C) analysis has proven a valuable tool in tracing the sources and fate of mobilized carbon, but aquatic 14C studies in permafrost regions rarely detect "old" carbon (assimilated from the atmosphere into plants and soil prior to AD1950). The emission of greenhouse gases derived from old carbon by aquatic systems may indicate that carbon sequestered prior to AD1950 is being destabilized, thus contributing to the "permafrost carbon feedback" (PCF). Here, we measure directly the 14C content of aquatic CO2, alongside dissolved organic carbon, in headwater systems of the western Canadian Arctic - the first such concurrent measurements in the Arctic. Age distribution analysis indicates that the age of mobilized aquatic carbon increased significantly during the 2014 snow-free season as the active layer deepened. This increase in age was more pronounced in DOC, rising from 101-228 years before sampling date (a 120%-125% increase) compared to CO2, which rose from 92-151 years before sampling date (a 59%-63% increase). "Pre-industrial" aged carbon (assimilated prior to ~AD1750) comprised 15%-40% of the total aquatic carbon fluxes, demonstrating the prevalence of old carbon to Arctic headwaters. Although the presence of this old carbon is not necessarily indicative of a net positive PCF, we provide an approach and baseline data which can be used for future assessment of the PCF. Copyright (Copyright) 2018 The Author(s). Published by IOP Publishing Ltd.
2019066020 Fernandes, Marcelo (Universidade de Lisboa, Centre for Geographical Studies - IGOT, Portugal); Palma, P.; Lopes, L.; Ruiz-Fernández, Jesús; Pereira, P. and Oliva, Marc. Spatial distribution and morphometry of permafrost-related landforms in the central Pyrenees and associated paleoclimatic implications: in Past environments in mid-latitude mountain regions (Oliva, Marc, editor; et al.), Quaternary International, 470(Part A), p. 96-108, illus. incl. geol. sketch map, 5 tables, sects., 82 ref., March 15, 2018.
Present and past permafrost distribution in the Pyrenees is still under discussion. As in other mid-latitude mountain regions, rock glaciers and protalus lobes are the main indicators of permafrost conditions. In this paper we examine the distribution of these landforms in Aran and Boi valleys, formerly glaciated U-shaped valleys ranging from 600 to 3000 m in the southern and northern sides of the Central Pyrenees, respectively. The spatial distribution of these landforms and their chronostratigraphic position within the valley allow a better understanding of the climatic and environmental conditions necessary for their development. Up to 151 permafrost-related landforms were identified in the Boi valley, including 56 rock glaciers and 95 protalus lobes. In the case of the northern Aran valley, 76 rock glaciers and 89 protalus lobes were cataloged corresponding to 165 landforms. Most of the landforms (93% for rock glaciers and 95% for protalus lobes) are located inside the glacial cirques, with a few distributed in the slopes of the formerly glaciated valleys. The lowest elevation of rock glaciers is situated at 1744 m (Aran) and 2007 m (Boi), whereas the lowest protalus lobes are located at 1740 m and 2033 m, respectively. Therefore, this altitude may be indicative of the lowest level recording permafrost conditions during the period in which these landforms formed, with paleotemperatures ca. 7-8°C lower than present-day. Between 60 and 70% of the protalus lobes and rock glaciers are located between 2300 and 2600 m in Boi valley and 2100 and 2400 m in Aran valley. The aspect shows a prevailing orientation of NW, N and NE for both cases of rock glaciers and protalus lobes, being almost absent in the S, SE and SW aspects. The average slope of both landforms lies between 11 and 27°, with a maximum of 35° for rock glaciers and 29° for protalus lobes. The amplitude/length ratio reveals that rock glaciers placed at lower altitudes are more elongated. The chronostratigraphic position of these landforms within the valley and with respect to the moraine complexes suggests the existence of three generations of permafrost-related landforms which are associated to the massive deglaciation process between the maximum glacial advance of the Last Glaciation and the Holocene.
2019066255 Bushueva, I. S. (Russian Academy of Sciences, Institute of Geography, Moscow, Russian Federation); Glazovskiy, A. F. and Nosenko, G. A. Razvitiye podvizhki v zapadnoy chasti lednikovogo kupola Vavilova na Severnoy Zemle v 1963-2017 gg [Evolution of displacements in the western Vavilov ice dome, Severnaya Zemlya, 1963-2017]: Led i Sneg = Ice and Snow, 58(3), p. 293-306 (English sum.), illus. incl. 2 tables, sketch map, 16 ref., 2018.
The glaciers and ice caps in the Arctic are experiencing noticeable changes which are manifested, in particular, in the intensification of their dynamic instability. In this paper we present data on a large scale surge in the Western basin of the Vavilov ice dome on the archipelago Severnaya Zemlya, derived from satellite images and supplemented by airborne RES-2014 and available publications. Analysis of 28 space images of 1963-2017 demonstrated that the surge developed over the whole period. In the first decade (1963-1973), the advance was very slow--from 2-5 to 12 m/year. Since the 1980s, the ice movement began to accelerate from tens to a hundred of meters per a year in the 2000s. The sudden change happened in the year 2012 when the surge front began to move already at speeds of about 0.5 km/year. In 2015, the volume of advanced part reached almost 4 km3. Maximal speed 9.2 km/year was recorded in 2016. From 1963 to 2017, the edge of the glacier advanced by 11.7 km, and its area increased by 134.1 km2 (by 47% relative to the basin area of 1963), that caused spreading of crevasse zone up the glacier. Surface speeds reached a maximum of 25.4 m/day in 2016 and decreased to 7.6 m/day in 2017. The authors suggest that the initial activation of the southern and western edges of the ice dome could be a reaction to the climate signal, possibly occurred several centuries ago. The ice crevassing and cryo-hydrological warming of ice, enhanced by positive feedback, resulted in instability of the glacier and the displacement of the edge of the ice belt containing moraine and frozen to the bed, which transformed into a catastrophic movement. The surge was facilitated by change of bedrock conditions as the ice lobe progressed offshore from permafrost coastal zone to the area of loose marine bottom sediments with low shear strength. The surge seems to be also stimulated by anomalously warm summer of 2012.
2019069093 Vasilevich, Roman (Russian Academy of Sciences, Ural Branch, Institute of Biology, Komi, Russian Federation); Lodygin, Evgeny and Abakumov, Evgeny. Molecular composition of humic substances isolated from permafrost peat soils of the eastern European Arctic: Polish Polar Research, 39(4), p. 481-503, illus. incl. 4 tables, sketch map, 39 ref., 2018.
Humification plays an important role in stabilization of organic matter in soils of the cryolithic zone. In this context, the degree of organic matter stabilization has been assessed, using instrumental methods, for permafrost peat soils of the eastern European Arctic, based on selected plots from within the Komi Republic (Russian Federation). Humic substances (HSs) isolated from the mire permafrost peats of the forest-tundra subzone of the European Arctic have been characterized in terms of molecular composition. This was accomplished using elemental and amino acid fragments (AAFs) composition. Solid-state 13C nuclear magnetic resonance (13C NMR) spectroscopy was utilized to identify the structure of HSs. Changes in the molar x(H) : x(C) ratio, ratio of aromatic to paraffin fragments and ratio of hydroxy AAFs to heterocyclic AAFs along the peat profiles have been revealed. They are due to the activation of cryogenic processes in the upper part of the seasonally thawing layer, the natural selection of condensed humic molecules, the botanical composition and degree of degradation of peat, which reflect the climatic features of the area in the Holocene. Humic acids and fulvic acids of the peat soils showed the prevalence of compounds with a low degree of condensation and a low portion of aromatic fragments. The aromaticity degree showed the trend to increase within the depth. Changes of quantitative and qualitative parameters of specific organic compounds occur at the permafrost boundary of peatlands, which can serve as an indicator of recent climate changes in environments from the high latitudes. The presented data can be useful in the evaluation of soil organic matter stabilization degree in the active layer and below the permafrost table.
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