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Climatic and environmental change is leading to increased frequency and intensity of permafrost degradation processes; however, our knowledge of their mechanisms and rate is still limited. We examined structure of deposits, surface topography, and weather conditions during the initiation of a thermo‐erosion gully in eastern Siberia and monitored its changes between 2020 and 2022. The initiation of the gully was caused by a combination of processes: (1) the catchment area of the gully was artificially increased several decades ago as a result of the interception of runoff by the winter road; (2) ice‐wedge degradation led to surface runoff concentration above the gully head, while a large volume of ground ice remained in other parts of the slope, and frost cracking continued; (3) the entry of water into frost cracks formed underground tunnels; and (4) high air temperatures and heavy rainfall immediately before the gully appearance resulted in the expansion of the tunnels and collapse of their roof. In 2 years, the volume of the gully reached 1000 m3; at least 40% of that volume consists of ground ice. The gully development did not significantly change the water chemistry due to significant water freshening caused by melting of ground ice. [ABSTRACT FROM AUTHOR]

Abstract: Whether permafrost systematically alters the rate of riverbank erosion is a fundamental geomorphic question with significant importance to infrastructure, water quality, and biogeochemistry of high‐latitude watersheds. For over four decades, this question has remained unanswered due to a lack of data. Using remotely sensed imagery, we addressed this knowledge gap by quantifying riverbank erosion rates across the Arctic and subarctic. To compare these rates to non‐permafrost rivers, we assembled a global data set of published riverbank erosion rates. We found that erosion rates in rivers influenced by permafrost are on average nine times lower than non‐permafrost systems; erosion rate differences increase up to 40 times for the largest rivers. To test alternative hypotheses for the observed erosion rate difference, we examined differences in total water yield and erosional efficiency between these rivers and non‐permafrost rivers. Neither of these factors nor differences in river sediment loads provided compelling alternative explanations, leading us to conclude that permafrost limits riverbank erosion rates. This conclusion was supported by field investigations of rates and patterns of erosion along three rivers flowing through discontinuous permafrost in Alaska. Our results show that permafrost limits maximum bank erosion rates on rivers with stream powers greater than 900 Wm−1. On smaller rivers, however, hydrology rather than thaw rate may be the dominant control on bank erosion. Our findings suggest that Arctic warming and hydrological changes should increase bank erosion rates on large rivers but may reduce rates on rivers with drainage areas less than a few thousand km2.

River bed deformations in the permafrost zone are studied. Modem studies of the deformation processes due to thermal erosion are reviewed. New results of numerical and laboratory modeling based on filling thermally eroded zones with sand are presented. Particular attention is paid to the erosion of curved sections. For quantitative estimation of the dependence of erosion on the type of channel curvature, a shape factor is introduced and substantiated. The dependence of the intensity of channel deformations and melting of bank ice inclusions on the channel shape is established. [ABSTRACT FROM AUTHOR]

Evidence for a population of craters buried beneath the nearside lunar maria has been found in the gravity data returned from the Gravity Recovery and Interior Laboratory mission. Although the total population of buried and visible craters within maria is comparable to the crater population in non‐mare regions at large diameters, a deficit was observed for craters less than ∼90 km in diameter. This deficit is surprising because the data can resolve craters down to 10 km in diameter. Similarly, the Imbrium basin only has a partially exposed ring system, with individual ring widths of up to ∼100 km, but where those rings should be buried beneath the mare surface, we find the gravitational signature mostly non‐existent. In this study, we test a series of mechanisms and scenarios that may explain the observed deficits in the buried crater populations by comparing localized Bouguer gravity power spectra and recovered crater size‐frequency distributions from models of a simulated volcanically flooded cratered surface to the observed data. Our results indicate that the observed crater deficit and missing rings of Imbrium are best explained by a smoothing of the pre‐mare surface. We represent this smoothing as a diffusional process, as might occur with thermomechanical erosion during the earliest stages of the mare eruptions. The removal of the missing craters and Imbrium rings was a massive and unprecedented event that sheds light on the early evolution of the mare region, possibly supporting high temperature voluminous floods of lava early during mare formation. Plain Language Summary: A visual comparison of the nearside mare and the highlands shows a clear deficit in crater density in the nearside mare regions, as expected due to the mare covering up the past craters. However, gravity data should reveal the buried craters. While gravity data show signatures of the larger buried craters, we do not see much signal from buried craters that are less than ∼90 km in diameter, even though the resolution of the gravity data should allow buried craters of 10 km in diameter to be detected. In addition, very large impacts produce ring structures of 100 km in width around the basin center, as seen in the Orientale basin on the farside. In contrast, only a fraction of the Imbrium ring system is exposed above the mare surface, but the gravitational signatures of ring structures buried beneath the maria are largely absent in both topography and gravity data. In this work, we test different hypotheses of mechanisms that could have resulted in the missing buried craters and the missing Imbrium rings. We find that smoothing or erosional processes, such as the sustained thermomechanical erosion due to the hot mare floodings, best explain the observed data. The removal of so many buried craters as well as a structure as large as the Imbrium rings may imply past mare floodings of unprecedented scale, intensity, and duration. Key Points: A deficit in the nearside mare buried crater population and a lack of buried ring structures around the Imbrium impact basin are observedWe use gravity data to test different hypotheses that may explain the missing buried craters and the missing rings of ImbriumA smoothing or erosional process, possibly the sustained thermomechanical erosion due to the mare floodings, is our preferred hypothesis [ABSTRACT FROM AUTHOR]

Current research in real-time water simulation can also calculate hydraulic erosion to a landscape; however, vegetation, which carries one of the biggest impacts on hydraulic erosion, is often not considered. We proposed an improvement upon the virtual pipes model for real-time hydraulic and thermal erosion simulation by incorporating considerations for vegetation cover. This method advances previous work by considering the limiting of soil erosion in vegetated areas due to soil binding, leaf cover, and transpiration from the plants. It also considers the impacts of vegetation death and the erosion and transportation of dead vegetation matter. Our algorithm creates a more realistic real-time erosion simulation, as seen by comparing erosion results with and without considering vegetation. Our results run in real time and clearly show the erosion effects expected by combining these methods. [ABSTRACT FROM AUTHOR]

The Batagay megaslump, in the Yana Uplands of northern Yakutia, Russia, is the largest known retrogressive thaw slump in the world. The slump exposes a remarkable sequence of Ice Age permafrost deposits that record the interaction of colluvial, eolian and periglacial processes on a hillslope episodically forested during the last 650 ka or more in response to climate variability on glacial–interglacial timescales. Numerous bones, teeth, and occasional carcasses of Pleistocene and Holocene mammals have been recovered from the permafrost. The megaslump developed over the course of several decades in three stages: (1) gullying, (2) thaw slumping, and (3) megaslumping. After disturbance to the taiga vegetation cover in the 1940s–1960s, a hillslope gully formed by the early 1960s. The gully initiated thaw slumping along its central part during the 1980s, with the slump enlarging to megaslump (>20 ha) proportions during the 1990s. By 2019, the area of the slump had reached about 80 ha and its headwall above the slump floor was up to about 55 m high. The main geomorphic processes of slump growth are headwall ablation and thermal erosion, producing a distinctive terrain of icy badlands on the slump floor. Though much of the megaslump is rapidly growing at present, it will probably stabilize eventually as an irregular terrain characterized by sandy ridges and sand‐filled elongate depressions formed by degradation of the badlands. Comparison of the Batagay megaslump with megaslumps from northwest Canada reveals several similarities and differences in terms of their geomorphology, permafrost deposits, and Quaternary history. [ABSTRACT FROM AUTHOR]

The results of laboratory and mathematical modeling of pollutant propagation from thawed sources on bank slopes in curvilinear reaches of rivers in permafrost zone are presented. Particular attention is paid to studying the effect of channel deformations caused by thermal erosion on the speed and character of pollutant spot propagation. The laboratory experiments in the hydraulic flume were primarily focused on determining the difference in the deformation dynamics and solute propagation from thawing sources at different shapes of channel curvature for the farther use of these data as input parameters of mathematical model for its verification. The analysis of a series of numerical calculations at a scale of laboratory experiment and an actual natural object suggested the conclusion regarding the effect of channel morphometric characteristics, the hydrological and thermal parameters of water flow, the characteristics of permafrost channel-forming ground on the dynamics of pollutant propagation in curvilinear reaches of the permafrost zone. [ABSTRACT FROM AUTHOR]

Abrupt thaw of ice‐rich permafrost in the Arctic Foothills yielded to the formation of hillslope erosional features. In the infrastructure corridor, we observed thermal erosion and thaw slumping that self‐healed near an embankment. To advance our understanding of processes between infrastructure and hillslope erosional features (INF‐HEF), we combined climate and remote sensing analyses to field investigations to assess an INF‐HEF system and validate our findings in a broader area along the infrastructure corridor. We identified that thaw consolidation along an embankment formed a thermokarst ditch that was ubiquitous in the broader study area, and which was extensively affected by shrubification and supported other positive feedback (e.g., snow accumulation, water impoundment, and weakened vegetation mat). The thermokarst ditch facilitated channelization of cross‐drainage water, thus increasing the terrain vulnerability to thermal erosion that evolved into thaw slumping after heavy rainfalls. The terrain resilience to thaw slumping benefited from the type of ground ice and topography prevailing at our site. The lateral discontinuity of massive ice in an ice‐wedge polygonal system (i.e., interchange soil and massive ice) compounded to a low‐slope gradient with topographic obstacles (e.g., baydzherakhs) decreased slumping activity and supported self‐stabilization. [ABSTRACT FROM AUTHOR]

The results of a study of the processes involved in the production of indium oxide In2O3 powder, which is widely used to create transparent and electrically conducting ceramics, are described. The powder was produced in a flow of rare gas (argon or helium) at atmospheric pressure under conditions for the formation of metal-containing plasma in a non-arc discharge mode. The discharge operated in pulsed mode with a pulse repetition rate of 70 kHz and pulse duration of 12 μs. The discharge current was 670 mA and discharge voltages were 180 V and 250 V when the working gases were argon and helium, respectively. These parameters ensure a mode in which the indium cap of a molybdenum cathode suffers thermal erosion. The morphology and elemental and phase composition of the erosion products were studied using transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analysis. It was shown that the structure of the synthesized powder particles corresponded to a phase of indium oxide (III) with a body-centered cubic (bcc) lattice with lattice parameter a = 1.013 nm. The powder particles, regardless of the working gas (Ar or He), consisted of non-stoichiometric indium oxide In2O3 with a nanocrystalline structure. The average particle diameter was = 13–16 nm. [ABSTRACT FROM AUTHOR]

New results from studying the possible mechanisms of formation and degradation of the Chuya–Kurai ultra-high-pressure ice-dammed lake are presented. The conclusions are based on an analysis of the climatic hydrothermal regime, which governs the development of the processes of self-freezing of the ice dam and its subsequent degradation. According to updated data, at the maximum filling to the absolute level of 2133 m, the depth of the paleolake is 657 m, the volume of water is 753 km3, the water area is 3054 km2, and the maximum hydrostatic pressure is 65 kg/cm2 (6.37MPa/cm2). The drainage of the lake basin is accompanied by the formation of 200 abrasive-accumulative terraces on the slopes of the basins in a height range of 1530‒2133 m. A quantitative assessment of the formation time of one abrasive terrace in periglacial conditions is made, as is an estimation of the duration of the action of wind–wave processes for the development of abrasion: it did not exceed 90 days of a warm season. The water layers drained during the year through the thermal erosion channels of the ice dam are determined by the difference in the heights of the abrasive terraces. The duration of the existence of an ice-dammed lake has been clarified. The study used current quantitative data on measuring the average annual flow rate of the Chuya River at the nearest Chagan-Uzun hydrological post. Calculations have shown that the filling of the lake basin to the maximum volume of water of 753 km3 (taking into account the water accumulating in the ice dam, 68 km3 (total V = 821 km3)) is carried out for 5324 years. The duration of water discharge, determined by the number of abrasion terraces, is no more than 200 years. The frequency of retrogression of the lake level, equal to 20 years, has been revealed. Apparently, it is caused by climatic fluctuations: changes in cooling and warming. [ABSTRACT FROM AUTHOR]

The Cr-plated coating inside a gun barrel can effectively improve the barrel’s erosion resistance and thus increase the service life. However, due to the cyclic thermal load caused by high-temperature gunpowder, micro-element damage tends to occur within the Cr coating/steel substrate interface, leading to a gradual deterioration in macro-mechanical properties for the material in the related region. In order to mimic this cyclic thermal load and, thereby, study the thermal erosion behavior of the Cr coating on the barrel’s inner wall, a laser emitter is utilized in the current study. With the help of in-situ tensile test and finite element simulation results, a shear stress distribution law of the Cr coating/steel substrate and a change law of the interface ultimate shear strength are identified. Studies have shown that the Cr coating/steel substrate interface’s ultimate shear strength has a significant weakening effect due to increasing temperature. In this study, the interfacial ultimate shear strength decreases from 2.57 GPa (no erosion) to 1.02 GPa (laser power is 160 W). The data from this experiment is employed to establish a Cr coating/steel substrate interface shear damage model. And this model is used to predict the flaking process of Cr coating by finite element method. The simulation results show that the increase of coating crack spacing and coating thickness will increase the service life of gun barrel.

• Hyperthermal erosion of knitted graphene nanoribbon sheet (KGS) is investigated. • KGS holds better anti-hyperthermal erosion performance than monolayer graphene. • Porosity significantly affects erosion and mechanical properties of 2D / 2.5D KGS. With outstanding thermal, mechanical, and chemical properties, graphene has been proposed as a promising heat shield material for hypersonic applications. Knitted graphene composites have shown further improved properties, whose behavior under highly non-equilibrium hyperthermal conditions, however, is still unknown. This work investigates the hyperthermal erosion and mechanical behaviors of 2D and 2.5D knitted graphene-nanoribbon sheet (KGS) under hyperthermal atomic oxygen impact conditions using the Reactive Molecular Dynamics (RMD) method. The simultaneous analysis of the morphology evolution and gaseous products demonstrate that knitted structures possess improved anti-erosion and mechanical properties than those of the plain graphene, and the 2.5D knitted graphene structure shows better performance than those of 2D knitted ones. 2D structure porosity, ribbon aspect ratio, and 2.5D knitting volumetric porosity show significant influence on the hyperthermal erosion of materials under atomic oxygen bombardment, which suggests strategies for future optimization of knitted graphene properties. [ABSTRACT FROM AUTHOR]

Recent excavation in the new CRREL Permafrost Tunnel in Fox, Alaska provides a unique opportunity to study properties of Yedoma — late Pleistocene ice- and organic-rich syngenetic permafrost. Yedoma has been described at numerous sites across Interior Alaska, mainly within the Yukon-Tanana upland. The most comprehensive data on the structure and properties of Yedoma in this area have been obtained in the CRREL Permafrost Tunnel near Fairbanks — one of the most accessible large-scale exposures of Yedoma permafrost on Earth, which became available to researchers in the mid-1960s. Expansion of the new ∼4-m-high and ∼4-m-wide linear excavations, started in 2011 and ongoing, exposes an additional 300 m of well-preserved Yedoma and provides access to sediments deposited over the past 40,000 years, which will allow us to quantify rates and patterns of formation of syngenetic permafrost, depositional history and biogeochemical characteristics of Yedoma, and its response to a warmer climate. In this paper, we present results of detailed cryostratigraphic studies in the Tunnel and adjacent area. Data from our study include ground-ice content, the stable water isotope composition of the variety of ground-ice bodies, and radiocarbon age dates. Based on cryostratigraphic mapping of the Tunnel and results of drilling above and inside the Tunnel, six main cryostratigraphic units have been distinguished: 1) active layer; 2) modern intermediate layer (ice-rich silt); 3) relatively ice-poor Yedoma silt reworked by thermal erosion and thermokarst during the Holocene; 4) ice-rich late Pleistocene Yedoma silt with large ice wedges; 5) relatively ice-poor fluvial gravel; and 6) ice-poor bedrock. Our studies reveal significant differences in cryostratigraphy of the new and old CRREL Permafrost Tunnel facilities. Original syngenetic permafrost in the new Tunnel has been better preserved and less affected by erosional events during the period of Yedoma formation, although numerous features (e.g., bodies of thermokarst-cave ice, thaw unconformities, buried gullies) indicate the original Yedoma silt in the recently excavated sections was also reworked to some extent by thermokarst and thermal erosion during the late Pleistocene and Holocene.

This study evaluates long-term and seasonal changes of sediment budget in Lena delta based on remote sensing dataset. Since 2000 Landsat images have been applying during ice-free period, from June to September. The sediment concentration at the delta topset was compared with sediment concentrations data at the outlets of: the Main, the Olenekskaya, the Tumatskyaya, the Trofimovskaya and the Bykovskaya channels to calculate suspended sediment budget in delta. The sediment concentration was calculated based on the archive Landsat images (more than 30 images). We have estimated influence of air temperature on thermal coastal erosion and the accumulation of sediments in the river Lena's delta. The increase of the daily average air temperature from 5°С to 14°С plays critical role in the degradation of permafrost and the activation of the processes of thermal erosion and thermal denudation of the right channels coasts and this fact means that these results can help to estimate special aspects of biochemical budget of the delta. [ABSTRACT FROM AUTHOR]

Riverbank erosion in yedoma regions strongly affects landscape evolution, biogeochemical cycling, sediment transport, and organic and nutrient fluxes to the Arctic Ocean. Since 2006, we have studied the 35‐m‐high Itkillik River yedoma bluff in northern Alaska, whose retreat rate during 1995–2010 was up to 19 m/yr, which is among the highest rates worldwide. This study extends our previous observations of bluff evolution and shows that average bluff‐top retreat rates decreased from 8.7–10.0 m/yr during 2011–2014 to 4.5–5.8 m/yr during 2015–2019, and bluff‐base retreat rates for the same time period decreased from 4.7–7.5 m/yr to 1.3–1.7 m/yr, correspondingly. Bluff evolution initially involves rapid fluvio‐thermal erosion at the base and block collapse, following by slowdown in river erosion and continuing thermal denudation of the retreating headwall with formation of baydzherakhs. Eventually, input of sediment and water from the headwall diminishes, vegetation develops, and slope gradually stabilizes. The step change in the fluvial–geomorphic system has resulted in a 60% decline in the volumetric mobilization of sediment and organic carbon between 2011 and 2019. Our findings stress the importance of sustained observations at key permafrost region study sites to elucidate critical information related to past and potential landscape evolution in the Arctic. [ABSTRACT FROM AUTHOR]

Thermal erosion is a major mechanism of permafrost degradation, resulting in characteristic landforms. We inventory thermo‐erosional valleys in ice‐rich coastal lowlands adjacent to the Siberian Laptev Sea based on remote sensing, Geographic Information System (GIS), and field investigations for a first regional assessment of their spatial distribution and characteristics. Three study areas with similar geological (Yedoma Ice Complex) but diverse geomorphological conditions vary in valley areal extent, incision depth, and branching geometry. The most extensive valley networks are incised deeply (up to 35 m) into the broad inclined lowland around Mamontov Klyk. The flat, low‐lying plain forming the Buor Khaya Peninsula is more degraded by thermokarst and characterized by long valleys of lower depth with short tributaries. Small, isolated Yedoma Ice Complex remnants in the Lena River Delta predominantly exhibit shorter but deep valleys. Based on these hydrographical network and topography assessments, we discuss geomorphological and hydrological connections to erosion processes. Relative catchment size along with regional slope interact with other Holocene relief‐forming processes such as thermokarst and neotectonics. Our findings suggest that thermo‐erosional valleys are prominent, hitherto overlooked permafrost degradation landforms that add to impacts on biogeochemical cycling, sediment transport, and hydrology in the degrading Siberian Yedoma Ice Complex. [ABSTRACT FROM AUTHOR]

Studies of erosion processes in river channels of the permafrost zone are reviewed. Mathematical models of thermal erosion and the deformations it induces are discussed in different formulations; the results of numerical calculations by two models are compared with one another and with laboratory measurement data. The major factors that have an effect on channel transformations in permafrost-zone rivers are identified. [ABSTRACT FROM AUTHOR]

Methods to control two-phase reactive flow induced by the combustion of propellant particles are important for improving the service life of mechanical systems. A novel groove structure was proposed to control the two-phase reactive flow. A two-phase flow model was utilized to predict propellant combustion in fluid fields and coupled with the transient heat transfer process. The numerical model was validated by comparing numerical and experimental results. Numerical results indicate that the groove structure effectively decreases the scouring velocity of two phases and the accumulation of particles near the barrel surface. The groove also reduces the peak temperature of the barrel surface, which contributes to less thermal erosion. Furthermore, shooting tests prove that the groove structure greatly extends the service life of the barrel. The findings of the study will be applied to improve the service life of propulsion systems. [Display omitted] • Two-phase reactive flow in combustion chambers is controlled by a novel groove structure. • The groove reduces the thermal effect suffered by the gun barrel. • Groove size affects the peak temperature of barrel, but the larger one has a better result. • Shooting tests demonstrate the groove improves the service life of gun barrel by 50%. [ABSTRACT FROM AUTHOR]

A common problem for the Arctic region is pollution by persistent organic compounds and other substances that have accumulated over the years in these areas. With temperature increasing, these substances can get out of the snow, ice, permafrost in the human environment. With climate warming and permafrost degradation the risk of toxic substances from the burial sites of chemical and radioactive waste increases. The work is devoted to research the pollution propagation in the rivers flowing in the permafrost taking into account the possible deformations of the channels caused by the melting of the permafrost with increasing temperature of the river flow water. We also consider the distribution of pollutants released during erosion of the coastal slopes, caused thermal erosion. Numerical experiments confirmed the quantitative assessment obtained from the field observations of the erosion rate increases with increasing temperature. Study the impact of thermal and mechanical erosion of the distribution of impurities led to the conclusion that as a result of the formation of taliks uniform flow conditions are violated, resulting in a non-stationary distribution of impurities. The increase in the volume of the test section of the river due to the appearance of cavities in the coastal slope leads to an increase in impurity concentration. Analysis of the results of modeling the spread of contamination during thawing sources in the frozen shores, demonstrated the relationship in the process of distribution of impurities from the position of the source and allowed to give a preliminary quantitative assessment.

Thermokarst is a geomorphologic/genetic designation for areas where thawing of permafrost leads to local or widespread collapse, subsidence, erosion, and instability of the ground surface. Although thermokarst processes are recently peculiar to regions underlain by permafrost, i.e. in particular to lowlands of high latitudes Arctic areas (Alaska, Canada, northern and eastern Siberia), geomorphology and sediments reflecting former thermokarst presence can also be found in middle latitudes, far from the recent permafrost areas. The so-called "fossil thermokarst" features, including thermokarst gullies, lakes and other kind of depressions, have been documented from many areas of northern and northwestern Europe as well as from Northern America. In contrast to those areas, the knowledge on the thermokarst processes and landscapes along the southern margin of the Last Glacial permafrost zone (i.e. ~ 44-47°N) is still relatively fragmental. The presented paper deals with the Late Pleistocene geomorphological and sedimentological evolution of the Třeboň region in South Bohemia (49.1°N, 14.7°E; 400-430 m asl) located during the Last Glacial Maximum ~ 110 km north of the Alpine piedmont glaciers and ~ 420 km from the southern edge of the North European Ice Sheet. The geological basement of the flat landscape of the Třeboň region consists of Cretaceous sandstones and Miocene sandy/ clayey fluvio-lacustrine sediments. Periglacial features like fossil polygons, nets or ice-wedge pseudomorphs documented in the study area prove the presence of permafrost in the region during the Late Pleistocene. We have also observed involution features (ball-and-pillow structures, injection tongues, and festoons) formed in unpaved sandy sediment, which testify permafrost degradation processes, probably during the Late Weichselian. Moreover, besides these periglacial features, we have discovered a total of 27 depressions filled with lacustrine sediments and peat (Figs 1 and 2). Most of them are covered by artificial fishponds of Medieval and Modern origin and thus hardly recognized in the landscape. These basins vary in size (tens up to hundreds of meters in diameter) in the depth of their infilling (1-12 m). Nevertheless, they share several common features such as their location on Miocene sedimentary bedrock, elongated shape, and the presence of tectonic faults that often run along their major axis. According to radiocarbon and relative palynological dating, the largest basins (Figs 2 and 3) were formed along the Pleniglacial/Late Glacial transition (~ 16-15 ka), whereas the smaller depressions originated during the Late/ Glacial/Early Holocene. Based on detail geomorphological investigations (approx. 300 hand drilling) and comparison of the geological and hydrogeological setting of the study area with the classicthermokarst landscape of Central Yakutia (Fig. 5), we assume that these basins are the result of the complex of thermokarst processes, including formation and collapse of alases and consequent surface degradation of the permafrost, which occurred here during periglacial conditions of the Late Weichselian (Fig. 6). [ABSTRACT FROM AUTHOR]

Abstract: Frozen islands in the Lena River, Siberia, experience rates of fluvial thermal erosion exceeding 10m/year. The islands erode differentially, with rates of frontal retreat exceeding those on island sides. We define the erosion ratio (ER) between the front and sides to estimate this differential erosion. A GIS‐based study of 19 islands from 1967 to 2010 indicated average erosion rates of 19.7 and 3.7 m/year for the island heads and sides, respectively. The average ER over the period was 4.7. An analytical model of local thermal erosion for a frozen cylinder of sand in a turbulent water flow is proposed, assuming an ablation process. Thermal erosion of 19 frozen cylinders was measured for water flows of different temperature and velocity in a cold chamber. As observed in the field, frontal erosion always exceeded lateral erosion, with an average ER of 1.6. The ER decreased with increasing temperature from 5 to 15°C. The higher value of ER in the field may be due to interactions with neighboring islands and banks. An empirical law including phase change and the process of erosion is proposed, and validates our model compared with previous laws that do not account for erosion. The erosion process enhances heat transfer. [ABSTRACT FROM AUTHOR]

Arctic warming is leading to substantial changes to permafrost including rapid degradation of ice and ice-rich coasts and riverbanks. In this study, we present and evaluate a high spatiotemporal resolution three-year time series of X-Band microwave satellite data from the TerraSAR-X (TSX) satellite to quantify cliff-top erosion (CTE) of an ice-rich permafrost riverbank in the central Lena Delta. We apply a threshold on TSX backscatter images and automatically extract cliff-top lines to derive intra- and inter-annual CTE. In order to examine the drivers of erosion we statistically compare CTE with climatic baseline data using linear mixed models and analysis of variance (ANOVA). Our evaluation of TSX-derived CTE against annual optical-derived CTE and seasonal in situ measurements showed good agreement between all three datasets. We observed continuous erosion from June to September in 2014 and 2015 with no significant seasonality across the thawing season. We found the highest net annual cliff-top erosion of 6.9 m in 2014, in accordance with above-average mean temperatures and thawing degree days as well as low precipitation. We found high net annual erosion and erosion variability in 2015 associated with moderate mean temperatures but above average precipitation. According to linear mixed models, climate parameters alone could not explain intra-seasonal erosional patterns and additional factors such as ground ice content likely drive the observed erosion. Finally, mean backscatter intensity on the cliff surface decreased from 􀀀5.29 to 􀀀6.69 dB from 2013 to 2015, respectively, likely resulting from changes in surface geometry and properties that could be connected to partial slope stabilization. Overall, we conclude that X-Band backscatter time series can successfully be used to complement optical remote sensing and in situ monitoring of rapid tundra permafrost erosion at riverbanks and coasts by reliably providing information about intra-seasonal dynamics. [ABSTRACT FROM AUTHOR]

Cryogenic processes are quite numerous, but among them the most significant, from the viewpoint of influence on human activities, we mention frost swelling, thermokarst processes, thermal abrasion, thermal erosion, cryogenic cracking, and solifluction. Frost heaving represents a danger for motor roads, railroads and airfields, communication and transmission lines, bridges, and other structures. Thermokarst endangers the safety, stability, and normal operation of structures. Thermoabrasion affects industrial and civil site development, water transport, pipeline transport, mineral resource industry, hydropower engineering, and agriculture. Frost cracking constitutes a certain danger for the following engineering structures: motor roads (roadways may go over the discontinuity); residential and industrial buildings (breakage of continuous footings, cracks in the walls); airfields (damage to airfield pavements); pipelines (deformations and even breaks of underground steel pipelines); underground communication cables. The influences of fast and slow solifluction are the most urgent for the following kinds of human activity: mineral resource industry; transport (motor, rail, pipeline); and industrial and civil engineering. Thus, the present paper aims at rendering the global dimension of these processes stressing their consequences worldwide.

Cryolithic zone occupies almost quarter of our planet area or 66% of the territory of Russian Federation. For our country longstanding permafrost is an essential factor of nature, economy and social sphere. Construction, deposit of commercial minerals within area of longstanding permafrost is very sophisticated activity for the following factors: availability of hazardous geological (geocryological) processes and occurrences - thermokarst, soilfluction, crack formation of soils and ettls, freeze over, knobs, stratificated missives, ice of repeated ice veins, thermal erosion, bogging of territories, cryopeg development and permafrost mound. Nowadays Extreme North is the biggest raw hydrocarbon deposit together with other treasures of the soil. Negligence of design specialties and construction within area of longstanding permafrost, lack of information regarding natural conditions of severe environment are the reason of man-made accidents with crucial effects to nature. Being conducted climatic change of our planet has negative influence on interaction of men with environment. Permafrost may form continuous, broken and island type features. Concerning temperature it may be classified as low temperature and high temperature permafrost soils. Very often permafrost has various grade of salinity with presence of salt brine which makes serious influence on soil features and interaction with buildings and other facilities under construction stage. To preserve permafrost basic characteristics systems of soil thermo stabilization are being applied (STS). The experience of Bovanenkovsky oil and gas condensate field showed that foundations are 42-60% of cost estimate and the share of STS considered from 5.8 up to 16.4% from construction expenses. During design stage of underground mine openings within permafrost conditions it is very important to be familiar with nature specialties for the reason to avoid man-made disasters as we had on minery Ihal. [ABSTRACT FROM AUTHOR]

The objectives were (i) to evaluate the relationship between recent climate change and extreme hydrological events and (ii) to characterize the behavior of hydrological events along the Alazeya River. The warming rate of air temperature observed at the meteorological station in Chersky was 0.0472 °C.year-1, and an extraordinary increase in air temperatures was observed in 2007. However, data from meteorological stations are somewhat limited in sparsely populated regions. Therefore, this study employed historical remote sensing data for supplementary information. The time-series analysis of the area-averaged Global Precipitation Climatology Project (GPCP) precipitation showed a positive trend because warming leads to an increase in the water vapor content in the atmosphere. In particular, heavy precipitation of 459 ± 113 mm was observed in 2006. On the other hand, the second-highest summer National Oceanic and Atmospheric Administration (NOAA) Advanced Very High Resolution radiometer (AVHRR) brightness temperature (BT) was observed in 2007 when the highest air temperature was observed in Chersky, and the anomaly from normal revealed that the summer AVHRR BTs showed mostly positive values. Conversely, riverbank, lakeshore and seashore areas were much cooler due to the formation, expansion and drainage of lakes and/or the increase in water level by heavy precipitation and melting of frozen ground. The large lake drainage resulted in a flood. Although the flooding was triggered by the thermal erosion along the riverbanks and lakeshores--itself induced by the heat wave in 2007--the increase in soil water content due to the heavy precipitation in 2006 appeared to contribute the magnitude of flood. The flood was characterized by the low streamflow velocity because the Kolyma Lowlands had a very gentle gradient. Therefore, the flood continued for a long time over large areas. Information based on remote sensing data gave basic insights for understanding the mechanism and behavior of climate-induced extreme hydrologic events. [ABSTRACT FROM AUTHOR]

Yedoma, a suite of syngenetically frozen silty ice- and organic-rich deposits with large ice wedges that accumulated during the late Pleistocene, is vulnerable to thermal degradation and erosion because of the extremely high ice contents. This degradation can result in significant surface subsidence and retreat of coastal bluffs and riverbanks with large consequences to landscape evolution, infrastructure damage, and water quality. We used remote sensing and field observations to assess patterns and rates of riverbank erosion at a 35-m-high active yedoma bluff along the Itkillik River in northern Alaska. The total volumetric ground-ice content—including wedge, segregated, and pore ice—was estimated to be ~ 86%. The process of riverbank erosion and stabilization include three main stages typical of the areas with ice-rich permafrost: (1) thermal erosion combined with thermal denudation, (2) thermal denudation, and (3) slope stabilization. Active riverbank erosion at the main study site started in July 1995, when the Itkillik River changed its channel. The total retreat of the riverbank during 1995–2010 within different segments of the bluff varied from 180 to 280 m; the average retreat rate for the most actively eroded part of the riverbank was almost 19 m/y. From August 2007 to August 2011, the total retreat varied from 10 to almost 100 m. The average retreat rate for the whole 680-m-long bluff was 11 m/y. For the most actively eroded central part of the bluff (150 m long) it was 20 m/y, ranging from 16 to 24 m/y. More than 180,000 m 3 of ground ice and organic-rich frozen soil, or almost 70,000 metric tons (t) of soil solids including 880 t of organic carbon, were transported to the river from the retreating bank annually. This study reports the highest long-term rates of riverbank erosion ever observed in permafrost regions of Eurasia and North America. [ABSTRACT FROM AUTHOR]

Arctic warming is leading to substantial changes to permafrost including rapid degradation of ice and ice-rich coasts and riverbanks. In this study, we present and evaluate a high spatiotemporal resolution three-year time series of X-Band microwave satellite data from the TerraSAR-X (TSX) satellite to quantify cliff-top erosion (CTE) of an ice-rich permafrost riverbank in the central Lena Delta. We apply a threshold on TSX backscatter images and automatically extract cliff-top lines to derive intra- and inter-annual CTE. In order to examine the drivers of erosion we statistically compare CTE with climatic baseline data using linear mixed models and analysis of variance (ANOVA). Our evaluation of TSX-derived CTE against annual optical-derived CTE and seasonal in situ measurements showed good agreement between all three datasets. We observed continuous erosion from June to September in 2014 and 2015 with no significant seasonality across the thawing season. We found the highest net annual cliff-top erosion of 6.9 m in 2014, in accordance with above-average mean temperatures and thawing degree days as well as low precipitation. We found high net annual erosion and erosion variability in 2015 associated with moderate mean temperatures but above average precipitation. According to linear mixed models, climate parameters alone could not explain intra-seasonal erosional patterns and additional factors such as ground ice content likely drive the observed erosion. Finally, mean backscatter intensity on the cliff surface decreased from −5.29 to −6.69 dB from 2013 to 2015, respectively, likely resulting from changes in surface geometry and properties that could be connected to partial slope stabilization. Overall, we conclude that X-Band backscatter time series can successfully be used to complement optical remote sensing and in situ monitoring of rapid tundra permafrost erosion at riverbanks and coasts by reliably providing information about intra-seasonal dynamics.

The temporal–spatial evolution of low-SiO 2 lavas from the Pleistocene West Eifel volcanic field (Central European Volcanic Province) and linked petrogenetic variations are evaluated using 40 Ar/ 39 Ar age and geochemical data. Geochronological and petrological evidence is related to the physical structure of the previously established seismologically anomalous asthenosphere interpreted as thermally upwelling mantle (Eifel Plume). Lava flows >480 ka (Middle Pleistocene) occur exclusively in the NW of the volcanic field. After a time span of ca. 400 ka lacking significant activity, volcanism has migrated to the SE generating flows <80 ka (Late Pleistocene). Middle Pleistocene occurrences form a bilaterally structured, SE-striking zone comprising an internal domain of intense activity between ca. 560 and 480 ka and an external domain of less intense preceding activity initiated at ca. 720 ka. The tectonic pattern corresponds to recent stress field conditions probably analogous to the Pleistocene setting, which may have reactivated major transverse structures of Hercynian origin providing preferred pathways for melt transfer through the brittle crust. At melting depth >70 km of parental asthenospheric melts in garnet–spinel peridotite the surface-projected contour of the low-velocity P -wave anomaly coincides with the geographical boundary separating >480 ka volcanism in the NW from <80 ka volcanism in the SE. Thus, the melting zones of <80 ka and >480 ka volcanism reside within and beyond the P -wave velocity anomaly, respectively. The coupling between time-space pattern of volcanism and seismological contrast in the mantle sources indicates that volcanic activity is linked to a highly dynamic low-velocity anomaly with lateral and vertical motion rates of 4–5 cm/year and up to 6 cm/year, respectively. The change in seismological contrast is accompanied by a transition in the petrogenetic style resulting from differently intense thermal erosion of multiply metasomatized lithosphere by upwelling asthenosphere. Asthenosphere-lithosphere interaction is widespread in the NW and subordinate in the SE of the volcanic field, where melts ascended through a more refractory lithosphere which has been affected by preferential melting of hydrous portions by pre-80 ka thermal exposure. [ABSTRACT FROM AUTHOR]

ABSTRACT Breccias were investigated on the terrace of the Toruń-Eberswalde ice-marginal valley at Rozwarzyn (NW Poland). Breccia layers include soft-sediment clasts with diameters between 2 and 256 mm and soft-sediment megaclasts with diameters from 256 mm to 7 m. The shape of the soft-sediment clasts and megaclasts (derived from frozen sediments) in the breccia is diverse: from angular and irregular in the case of debris-flow breccias to slightly rounded and tabular in fluvial breccias. These two types of breccias were developed during the Late Weichselian when the periglacial climate favored extensive lateral erosion by currents of frozen braided channels in the ice-marginal valley. The dual presence of breccias of fluvial and debris-flow origin in channel deposits is unique for Quaternary sediments. Zones of breccias existed in the channels where scours and obstacle marks related to megaclasts developed. The study of breccias shed new light on the fluvial processes in ice-marginal valleys during the Pleistocene and can be considered as diagnostic for fluvio-periglacial conditions. [ABSTRACT FROM AUTHOR]

Laser gas-assisted drilling of holes into alumina coated carbon steel is considered and heat transfer characteristics and the skin friction at the wall surface are investigated for various gases. The hole wall is considered to be at the melting temperature of the coating material and carbon steel to resemble the drilling process in the simulations. Laser drilling experiments are carried out to demonstrate the thermal erosion in the close region of the coating and the base material interface. It is found that the presence of coating at the hole inlet increases the assisting gas temperature significantly in the vicinity of the coating. This, in turn, results in heat transfer from assisting gas to the hole wall while causing thermal erosion at the interface region between the alumina coating and the carbon steel. The skin friction changes for different assisting gases and helium results in the highest skin friction at the hole wall surface. [ABSTRACT FROM AUTHOR]

We present a quantitative account of the thermodynamical and fluid-mechanical aspects of granitic host rock erosion related to dyke emplacement by considering the latent heat released from the dyke, subsequent thermal damage, and erosion processes. When these processes are coupled with the fluid-dynamic shear forces induced by magma turbulence, they provide the main driving force for mechanical fragmentation and xenolith entrainment. To make these inferences, we have estimated the Reynolds Number related to magma flow in a series of well-exposed dykes in Eastern India. We define the thresholds of turbulent to laminar flow based on Reynolds Numbers, where values over 2000 indicate that the magma had flowed turbulently. In these cases, both thermal erosion and fluid-dynamic shear stresses would have combined to fragment the adjacent host rock. Equations for the conservation of mass are derived and presented in order to quantify the complex interactions between magma and cold host rock. We further propose a novel linear integro-differential equation to determine xenolith size resulting from internal collisions and secondary fragmentation. Our model and results will be helpful in interpreting magma flow characteristics, magmatic evolution, and host rock entrainment processes in exposed outcrops of magmatic intrusions. • Thicker dykes (>10 m) are thermally and mechanically eroded. • Magma flow as turbulently in thicker dykes. • Thermally and mechanically eroded dykes are attributed to inelastic growth of dykes. • Understanding the thermal and mechanical aspects of dykes is critical for volcano behaviors. [ABSTRACT FROM AUTHOR]

Abstract: The structure and rheology of the lithosphere can provide constraints on our understanding of the geodynamic processes in the Earth''s interior. The lateral heterogeneity of the strength and rheological structure of the lithosphere are closely correlated with the lateral variation in the thickness of the seismogenic layer. It is still unclear how geodynamic process(es) are linked with this lateral variation in the geophysical properties of the lithosphere. In order to understand the possible links between geodynamical process and lateral variation of lithosphere strength, we compiled crustal velocity and density structure, the elastic thickness of the lithosphere, and the temperature field, and then construct a northeast–southwest transect of the lithosphere across the eastern part of the North China Craton (NCC) with an overall length of 1660km. Along the lithosphere-scale transect, we observe that (a) a thinner (80–120km) Archean lithosphere at the North China Plain (NCP), (b) a lateral variation of the seismogenic brittle layer, which is about 15km thick beneath the Qinling-Dabie orogenic belt (QDOB) and the Yanshan orogenic belt (YSOB), and about 25km thick under the NCP. Together, these characteristics represent an excellent illustration of the scale of geodynamic processes necessary to accommodate lateral variations in lithospheric strength and the contribution of these to the mechanism of disruption of the Archean NCC. The thick seismogenic layer beneath the NCP can be formed due to: (1) deeper fault penetration beneath the NCP than beneath the QDOB and the YSOB; (2) the thick brittle layer is preserved after delamination of the lower part of the thickened crust; (3) thickening by changes to brittleness of the brittle/ductile transition layer (BDTL). With constraints of above mentioned geophysical properties of the lithosphere, we propose that (1) only the first and third processes can successfully explain the lateral variation of the thickness of the seismogenic layer across the eastern part of the NCC, and (2) the extensional tectonics and thermal erosion (notwithstanding the delamination of the lithosphere) play their significant roles in the disruption of the NCC. [Copyright &y& Elsevier]

Virtually all of the economic Ni-Cu-(platinum group element (PGE)) mineralization in the central part of the Cape Smith Belt of New Québec is hosted by thick olivine cumulate units in the Katinniq Member of the Raglan Formation at the base of the 1.9 Ga Chukotat Group. These units transgress underlying gabbros and pelitic metasediments, forming 50-200-m deep and 300-1,000-m wide V-shaped embayments and have been interpreted on the basis of surface geology, deep diamond core drilling, and magnetic inversion models to represent the remnants of one or more large, long (at least 20 km, possibly ≥50 km), sinuous, komatiitic basalt lava channels that formed by thermomechanical erosion of their substrates. We have used a mathematical model to test these hypotheses regarding komatiitic lava emplacement and erosion by lava. Our modeling predicts that an initially 10-m thick komatiitic basalt flow should have flowed turbulently near the vent and should have thermomechanically eroded unconsolidated pelitic sediment during emplacement to reach the observed degree of contamination of ≤10% at distances of ~30-60 km downstream from the source. Furthermore, our models predict that, at these distances downstream, a fully inflated 100-m thick komatiitic basalt flow would have had thermal erosion rates over consolidated gabbroic substrate of ~0.7-1.5 m/day, requiring ~70-140 days to incise a 100-m deep channel, depending on the initial temperature of the lava, the paleoslope, and the initial temperature and solidus temperature of the gabbro. These erosion rates would have been associated with volumetric flow rates of >10-10 m/s and eruption volumes of >10-10 km. Although these flow rates are orders of magnitude larger than those of most modern terrestrial basaltic flows, they are of the same order as those estimated for the largest terrestrial flood basalt flows and with those inferred for some of the largest extraterrestrial flows. Our predicted flow volumes are also of the same order as those of the largest terrestrial flood basalt units, consistent with the great thickness and widespread distribution of the Chukotat Group. Our modeling of thermomechanical erosion of gabbro by komatiitic basalt results in negligible contamination (<1%), and geochemical studies show that the spatially and petrogenetically related Chukotat basalts are uncontaminated, suggesting that the observed enrichments in U-Th-Light Rare Earth Elements (REE) > Middle REE-Heavy REE > Nb-Ta-Ti represent contamination by underlying Povungnituk semipelites. This result is consistent with present models for the genesis of the Ni-Cu-(PGE) mineralization in the Raglan Formation that involve thermomechanical erosion of unconsolidated, sulfidic semipelitic sediments, and decoupling of the miscible silicate and immiscible sulfide components. [ABSTRACT FROM AUTHOR]

Cryogenic processes are quite numerous, but among them the most significant, from the viewpoint of influence on human activities, we mention frost swelling, thermokarst processes, thermal abrasion, thermal erosion, cryogenic cracking, and solifluction. Frost heaving represents a danger for motor roads, railroads and airfields, communication and transmission lines, bridges, and other structures. Thermokarst endangers the safety, stability, and normal operation of structures. Thermoabrasion affects industrial and civil site development, water transport, pipeline transport, mineral resource industry, hydropower engineering, and agriculture. Frost cracking constitutes a certain danger for the following engineering structures: motor roads (roadways may go over the discontinuity); residential and industrial buildings (breakage of continuous footings, cracks in the walls); airfields (damage to airfield pavements); pipelines (deformations and even breaks of underground steel pipelines); underground communication cables. The influences of fast and slow solifluction are the most urgent for the following kinds of human activity: mineral resource industry; transport (motor, rail, pipeline); and industrial and civil engineering. Thus, the present paper aims at rendering the global dimension of these processes stressing their consequences worldwide. [ABSTRACT FROM AUTHOR]