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The winter hydrological period is in transition across the Canadian subarctic, as climate warming is shifting precipitation regimes, thawing permafrost, and altering active layer dynamics, and thus increasing the overall amount, and variability, of winter streamflow. Effects of these changes are poorly understood on the Taiga Shield, which comprises ~20% of North America's permafrost‐covered area, and is characterized by a unique 'fill‐and‐spill' hydrology whereby runoff generation requires the exceedance of lake basin storage thresholds. Here, we assessed lake hydrostatic levels and used trail camera images of icings, which are sheet‐like masses of layered ice that are common manifestations of wintertime flow on the Taiga Shield, to understand landscape controls on winter water movement in this region. We further used paired geochemical measurements to explore how source water characteristics affect icing chemistry, and the degree to which icings may modify the chemical composition of active winter flow. We undertake this work over 2 years, and across watersheds of different sizes and lake basin characteristics. We show that icing growth is driven by hydroclimatic controls that include fill‐and‐spill hydrologic constraints and winter air temperatures, and that pre‐freshet pulses of water flow are common within this landscape. Across winters with variable antecedent precipitation levels, a larger catchment was able to support icing growth via continued runoff generation, while small catchments were not. Icings were often chemically dilute compared with source waters, indicating that solute exclusion may actively enrich geochemical concentrations in flowing water. Across icings, chemical variation appeared related to source water type (groundwater versus lake; lake size) and apparent redox conditions. These results highlight that streamwater hydrology and biogeochemistry can be dynamic during the understudied winter period, and illustrate that icings may alter the composition of wintertime flow as it moves through fluvial networks. [ABSTRACT FROM AUTHOR]

Water is a limited resource in Arctic watersheds with continuous permafrost because freezing conditions in winter and the impermeability of permafrost limit storage and connectivity between surface water and deep groundwater. However, groundwater can still be an important source of surface water in such settings, feeding springs and large aufeis fields that are abundant in cold regions and generating runoff when precipitation is rare. Whether groundwater is sourced from suprapermafrost taliks or deeper regional aquifers will impact water availability as the Arctic continues to warm and thaw. Previous research is ambiguous about the role of deep groundwater, leading to uncertainty regarding Arctic water availability and changing water resources. We analyzed chemistry and residence times of spring, stream, and river waters in the continuous permafrost zone of Alaska, spanning the mountains to the coastal plain. Water chemistry and age tracers show that surface waters are predominately sourced from recent precipitation and have short (<50 y) subsurface residence times. Remote sensing indicates trends in the areal extent of aufeis over the last 37 y, and correlations between aufeis extent and previous year summer temperature. Together, these data indicate that surface waters in continuous permafrost regions may be impacted by short flow paths and shallow suprapermafrost aquifers that are highly sensitive to climatic and hydrologic change over annual timescales. Despite the lack of connection to regional aquifers, continued warming and permafrost thaw may promote deepening of the shallow subsurface aquifers and creation of shallow taliks, providing some resilience to Arctic freshwater ecosystems. [ABSTRACT FROM AUTHOR]

Over the past decades, the cryosphere has changed significantly in High Mountain Asia (HMA), leading to multiple natural hazards such as rock–ice avalanches, glacier collapse, debris flows, landslides, and glacial lake outburst floods (GLOFs). Monitoring cryosphere change and evaluating its hydrological effects are essential for studying climate change, the hydrological cycle, water resource management, and natural disaster mitigation and prevention. However, knowledge gaps, data uncertainties, and other substantial challenges limit comprehensive research in climate–cryosphere–hydrology–hazard systems. To address this, we provide an up-to-date, comprehensive, multidisciplinary review of remote sensing techniques in cryosphere studies, demonstrating primary methodologies for delineating glaciers and measuring geodetic glacier mass balance change, glacier thickness, glacier motion or ice velocity, snow extent and water equivalent, frozen ground or frozen soil, lake ice, and glacier-related hazards. The principal results and data achievements are summarized, including URL links for available products and related data platforms. We then describe the main challenges for cryosphere monitoring using satellite-based datasets. Among these challenges, the most significant limitations in accurate data inversion from remotely sensed data are attributed to the high uncertainties and inconsistent estimations due to rough terrain, the various techniques employed, data variability across the same regions (e.g., glacier mass balance change, snow depth retrieval, and the active layer thickness of frozen ground), and poor-quality optical images due to cloudy weather. The paucity of ground observations and validations with few long-term, continuous datasets also limits the utilization of satellite-based cryosphere studies and large-scale hydrological models. Lastly, we address potential breakthroughs in future studies, i.e., (1) outlining debris-covered glacier margins explicitly involving glacier areas in rough mountain shadows, (2) developing highly accurate snow depth retrieval methods by establishing a microwave emission model of snowpack in mountainous regions, (3) advancing techniques for subsurface complex freeze–thaw process observations from space, (4) filling knowledge gaps on scattering mechanisms varying with surface features (e.g., lake ice thickness and varying snow features on lake ice), and (5) improving and cross-verifying the data retrieval accuracy by combining different remote sensing techniques and physical models using machine learning methods and assimilation of multiple high-temporal-resolution datasets from multiple platforms. This comprehensive, multidisciplinary review highlights cryospheric studies incorporating spaceborne observations and hydrological models from diversified techniques/methodologies (e.g., multi-spectral optical data with thermal bands, SAR, InSAR, passive microwave, and altimetry), providing a valuable reference for what scientists have achieved in cryosphere change research and its hydrological effects on the Third Pole. [ABSTRACT FROM AUTHOR]

This research presents a comprehensive environmental assessment of a small mountain permafrost catchment of the Anmangynda River in the Upper Kolyma Highland (Northeastern Asia) over the period of 2021–2023. The study reveals significant diversity in climatic, geocryological, and hydrogeological conditions within this confined area, emphasizing the need for extensive field data collection and monitoring in vast permafrost regions with limited data availability. Key findings include variations in ground temperature, maximum seasonal thaw depth, and depths of zero annual amplitudes of ground temperature at different elevations and landscape types. Groundwater and surface flow dynamics within spring aufeis basins exhibit complex geocryological regimes influenced by icing processes. The presence of aufeis and its impact on local hydrology highlight the ecological significance of this phenomenon. Future research should focus on long-term trends in permafrost dynamics and their relationship with climate change, as well as the ecological effects of aufeis formation on local ecosystems. The study underscores the importance of a multi-faceted approach to environmental assessment, incorporating various environmental parameters and processes, to gain a comprehensive understanding of the intricate interactions within the cryosphere and their responses to changing climate conditions. Such knowledge is essential for addressing broader questions related to climate change, ecosystem resilience, and sustainable resource management in Northeastern Siberia. [ABSTRACT FROM AUTHOR]

Cryosphere studies in High Mountain Asia (HMA) typically focus on glaciers, seasonal snow cover, and permafrost. As an additional and mostly overlooked cryosphere component, aufeis occurs frequently in cold-arid regions and covers extensive areas of the Trans-Himalaya and Tibetan Plateau. This largely neglected cryosphere component generally forms in winter from repeated freezing of seepage or overflow. In this article, the occurrence of aufeis fields in the endorheic Pangong Tso Basin (PTB), with a total area of 31,000 km2, is inventoried and examined. Based on a semi-automatic remote sensing approach using Sentinel-2 imagery, about 1000 aufeis fields were detected in the spring of 2019, covering a total area of approximately 86 km2 and with an average individual size of 0.08 km2, while the largest field covered an area of 14.8 km2. A striking contrast between the northern and southern portions of the PTB characterized the spatial distribution of large aufeis fields. All large (>0.5 km2) and 13 persisting aufeis fields were located along broad valleys in the northern portion. Furthermore, a multi-temporal comparison between 1994 and 2023 shows that the number of remaining aufeis fields in autumn varied between 8 and 29, with a maximum in 2019. Their total area ranged between about 0.3 km2 in 1994 and 2023 to about 1.2 km2 in 2015 and 2019. This study complements recent aufeis inventories from the Trans-Himalayan region of Ladakh and closes the gap to the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Aufeis (also known as icings) are large sheet‐like masses of layered ice that form in river channels in arctic environments in the winter as groundwater discharges to the land surface and subsequently freezes. Aufeis are important sources of water for Arctic river ecosystems, bolstering late summer river discharge and providing habitat for caribou escaping insect harassment. The aim of this research is to use numerical simulations to evaluate a conceptual model of subsurface hydrogeothermal conditions that can lead to the formation of aufeis. We used a conceptual model based on geophysical data from the Kuparuk aufeis field on the North Slope of Alaska to develop a two‐dimensional heterogeneous vertical profile model of groundwater flow, heat transport, and freeze/thaw dynamics. Modelling results showed that groundwater can flow to the land surface through subvertical high permeability pathways during winter months when the lower permeability soils near the land surface are frozen. The groundwater discharge can freeze on the surface, contributing to aufeis formation throughout the winter. We performed sensitivity analyses on subsurface properties and surface temperature and found that aufeis formation is most sensitive to the volume of unfrozen water available in the subsurface and the rate at which the subsurface water travels to the land surface. Although a trend of warming air temperatures will lead to a greater volume of unfrozen subsurface water, the aufeis volume can be reduced under warming conditions if the period of time for which air temperatures are below freezing is reduced. [ABSTRACT FROM AUTHOR]

Giant aufeis fields, common in the Northeast of Russia, are the indicators of water exchange processes in cryosphere. The development of ideas about icing processes is relevant both from the fundamental point of view of studying the permafrost evolution, and from the practical point of view – for the development of aufeis hazard measures. The aufeis in the Anmangynda River basin (aufeis glade area 7 km2) is considered representative of the region, and its studies have been carried out since 1962. In 2022, during the period of maximum thawing of the active layer Electrical Resistivity Tomography (ERT) soundings were carried out at the aufeis glade aiming to identify underchannel taliks and flooded fault zones in bedrock, including local areas of groundwater discharge. It was found that within the main river channels there are underchannel taliks up to 30 m deep. According to the results of 2D inversion, local anomalies of low electrical resistivity mark groundwater filtration channels. In 3D geoelectrical models, pipe-like anomalies of low resistivity are identified in the areas of groundwater discharge, interpreted as filtration channels in the alluvium and the zone of exogenous fracturing in bedrock formed by sandy-clay shales, as well as linear vertical anomalies of low resistivity, interpreted as faults. On vertical sections of 3D resistive models, a connection between faults and filtration channels in alluvium and a layer of exogenous fracturing is traced. In the right bank of the valley, geoelectric signs of taliks in the bedrock, presumably associated with fault tectonics, have been established. It is assumed that the identified faults are the additional transit routes for groundwater in the Anmangynda River valley, along with the alluvial aquifer and the zone of exogenous fracturing of bedrock.

The process of icing and the resulting layered ice masses, called aufeis, are caused by the freezing of overflow originating from groundwater or surface water. Aufeis can directly impact infrastructure and property, most commonly through winter ice formation and spring flooding within, against, and on the surface of hydraulic structures and transportation infrastructure. They also represent a safety concern for drivers. This geohazard often needs to be managed proactively and efficiently to mitigate associated risks. This paper provides an overview of the consequences of aufeis in northwestern Canada. A total of 50 existing and novel icing and aufeis mitigation approaches are described and classified. The context of applicability for each approach is identified, considering the source of water, the type of infrastructure, and its role in the formation of aufeis. Finally, future research avenues to support the development or improvement of aufeis risk reduction techniques are presented. [ABSTRACT FROM AUTHOR]

The process of icing involves the freezing of overflow layers, on ground or within streams, and results in ice bodies called "aufeis" that are common in most northern landscapes. Knowledge about aufeis is still limited despite the cold region engineering challenge they represent. Understanding the causes of overflow events leading to aufeis development represents a key for the prediction, mitigation, and management of this geohazard and can also support the planning and design of infrastructure in the North. This paper introduces a practical classification for the diverse range of overflow processes that generate aufeis, including under-represented processes, such as the instability of winter streamflow. Importantly, it distinguishes flow conveyance from water supply overflow processes and describes the temporal aspect of icing intensity. Finally, research topics are proposed to improve our understanding of aufeis, including their predictability, the impact of climate change on their occurrence and extent, and stream morphology–aufeis interaction. [ABSTRACT FROM AUTHOR]

This article presents materials on the long-term and seasonal variability of the morphometric characteristics of huge aufeis (taryn) in the Anmangynda River valley in the northeast of Russia. It is shown that the maximum area of the taryn has decreased by 25% and its volume by 33% over the past 60 years. The period of ablation of the ice cluster has decreased by 34 days and the aufeis has moved from the category of migrating formations to the category of seasonal formations. [ABSTRACT FROM AUTHOR]

Gigantic aufeis fields serve as indicators of water exchange processes within the permafrost zone and are important in assessing the state of the cryosphere in a changing climate. The Anmangynda aufeis, located in the upstream of the Kolyma River basin, is present in the mountainous regions of Northeast Eurasia. Recent decades have witnessed significant changes in aufeis formation patterns, necessitating a comprehensive understanding of cryospheric processes. The objective of the study, conducted in 2021–2022, was to examine the structure of the Anmangynda aufeis and its glade, aiming to understand its genesis and formation processes. The tasks included identifying above- and intra-frozen taliks, mapping groundwater (GW) discharge channels, determining permafrost base depth, and assessing ice thickness distribution. Soundings using ground-penetrating radar (GPR), capacitively coupled electrical resistivity tomography (CCERT), and the transient electromagnetic (TEM) method were employed. GW discharge channels originating from alluvial deposits and extending to the aufeis surface within river channels were identified through GPR and verified through drilling. Deep-seated sources of GW within the bedrock were inferred. CCERT data allowed us to identify large and localized frozen river taliks, from which water is forced onto the ice surface. According to the TEM data, the places of GW outlets spatially coincide with the zones interpreted as faults. [ABSTRACT FROM AUTHOR]

This article describes the compilation procedure and contents of the Atlas of giant taryn aufeis, a specific form of glaciation in the northeastern part of the Eurasian continent resulting from the freezing of groundwater that has come to the surface. The Atlas consists of two parts: analytical with illustrations and cartographic. Part I presents an overview of the extensive history of research on aufeis and the results of the digitization of small-scale maps that describe the dependence of aufeis fields on permafrost–hydrogeological, hydroclimatic, geomorphological, and geotectonic conditions. A special section of the Atlas is devoted to hazardous glacial and permafrost–geological phenomena that affect the engineering development of the territory. The results of the study indicate that about 5% of the territory of northeastern Russia can be described as an aufeis-prone zone. Part II of the Atlas contains over 100 maps of the distribution of taryn aufeis along the basins of major rivers of northeastern Russia (Yana, Indigirka, Kolyma, Anadyr, and Penzhina). The maps indicate the current positions and sizes of about 7000 aufeis fields as identified from Landsat and Sentinel-2 satellite images; they are compared with the Cadastre of Aufeis by A.S. Simakov and Z.G. Shil'nikovskaya (1958). An analysis of the data has revealed ambiguous trends of changes in aufeis fields. On the one hand, their number increased by the 21st century, but, on the other hand, the total preablation aufeis area decreased. Information on retrospective and current locations of aufeis fields is presented in the form of a digital database for large rivers of northeastern Russia. Most of the data collected in the Atlas requires detailed analysis. [ABSTRACT FROM AUTHOR]

The huge Anmangynda aufeis is located in the valley of the river of the same name in the Magadan region in North-East of Russia. This is the only in the world aufeis site with a 30-years period of ground-based observations (1962–1991). The materials of these observations were supplemented with data obtained from the analysis of Landsat and Sentinel satellite images for the period 2000–2021, as well as the results of field investigations carried out in 2020–2021. The long-term variability of the maximum area, volume and average thickness of ice, the dynamics of formation and destruction of the aufeis ice in the cold and warm periods of the year were analyzed. It was found that the maximum values of the area and volume of ice on the dates before the start of ablation decreased by 25 and 33%, respectively. In 2000–2021, the average values of the aufeis characteristics are estimated as 4.7 km2 and 7.1 million m3, while in 1962–1991 – 5.5 km2 and 8.5 million m3. The analysis of the intra-annual dynamics revealed that the Anmangynda aufeis being earlier the perennial formation has transformed to the seasonal one. Further researches of the Anmangynda aufeis will make possible to assess the influence of various factors, including climatic ones, on the processes of an aufeis formation and to forecast their changes in the future for the cryolitic zone of the North-East of our country.

Giant aufeis fields are the indicators of water exchange processes in the permafrost zone. The study of aufeis dynamics is relevant to assessing the state of the cryosphere in a changing climate. The Anmangynda aufeis which forms upstream of the Kolyma River basin, was as large as 6.8 km2 in the last century and is considered representative of the mountainous territories in the northeast Russia. In recent decades, there have been significant changes in the aufeis formation regime that require updating the understanding of the cryosphere processes. The historical observational data obtained in 1962-1990 for the Anmangynda aufeis allows using it as the present-day object of research.The main goal of geophysical research in 2021-2022 was to study the structure of the Anmangynda aufeis and aufeis glade to determine its genesis and development processes. The main tasks were to identify the boundary between frozen and unfrozen rocks, to reveal groundwater discharge channels, and to assess the aufeis thickness distribution. There were carried out georadar survey using an antenna unit with central frequency of 250 MHz and ground-based capacitively coupled electrical resistivity tomography. It was found that by April 5, 2021, the maximum ice thickness was 4.35 m with an average value of 1.35 m, and the volume of aufeis was 3.56 million m3. By means of georadar, there were performed identification and drilling verification of the groundwater discharge channels from alluvium to aufeis surface, located in the stream beds. There is geophysical evidence of deep bedrock groundwater sources. Based on the electrical resistivity tomography data, there were identified large and locally freezing river taliks, from which the water is squeezed onto the ice surface. It is recommended to conduct further interdisciplinary research to clarify the geophysical results obtained.

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The major objective of this research is to assess the effects of winter ice cover and simulate the flooding within bridge vicinity of the Grand River, Ohio, the USA for both in the historical period (1959–2014) and future period (2015–2098). The LiDAR data along with field-verified survey data were utilized for the calibration and validation of HEC-RAS. The stage increments up to 6.75 ft were detected at the upstream section of the Bridge due to historical ice jams. Moreover, the increment in the inundation area varied from 24% to 52% for various percentile winter flows. The percentage increase in the inundation area was highest for the 25-percentile flow than the higher percentile flow when the same thickness of ice cover was used in the simulation. The estimated ice thickness using Stefan's equation for various emission scenarios (RCP 2.6, RCP 4.5 and RCP 8.5) for three climate models were found to be decreasing in the future period. As per the standard practice in the United States, authors have used U.S. Customary Unit System (fps unit system) in this paper. [ABSTRACT FROM AUTHOR]

Based on the analysis of Landsat satellite images over the period of 2013–2019, the number (6683) and total area (4529 km2) of giant aufeis fields (area ≥ 0.1 km2) were estimated for the territory of North-Eastern Eurasia. The contribution of aufeis runoff to river streamflow in different seasons was calculated for 58 hydrological gauges (area 523–526,000 km2). The contribution of aufeis and glaciers to water balance is compared. The aufeis resources vary from 0.4 to 4.25 km3 (or 3.7–11 mm) for individual basins of large rivers. They are at least 10.6 km3 in total or 5 mm of water depth on average for the study area. Aufeis annual runoff varies from 0.3 to 29 mm (0.1–22%, average 3.8%), with the share in winter runoff amount about 6–712% (average 112%) and the spring freshet 0.2–43% (average 7.1%). In general, the aufeis runoff exceeds the glacial runoff. The dynamics of aufeis formation are directly related to winter runoff, whose changes are observed in different parts of the cryosphere. The presented results are relevant for studying the impact of climate change on the hydrological cycle and its components in the permafrost regions of the Northern Hemisphere. [ABSTRACT FROM AUTHOR]

Icing/Aufeis processes are a typical feature of permafrost hydrology in mountainous regions. Regional databases of Aufeis have been compiled since the 2010. In this study, we attempted to create an initial Aufeis database for the Qinghai-Tibet Plateau (QTP) to evaluate the patterns of the icing processes in the arid and high mountain regions at low latitudes. In this article, the icings/Aufeis in the Kunlun Mountains on the northern edge of the QTP were investigated. A total of 65 Landsat 8 Operational Land Imager images for 2017–2020 of the key sites were acquired. Icings occur at elevations of 2500–5400 m a. s. l. More than 1600 Aufeis were identified with a total ice-surface area of 2670 km2. About 88% of these areas are related to a gigantic Aufeis (tarin) field. Artesian aquifers related to the active faults play an important role in feeding the Aufeis in the Kunlun Mountains. About 120 Aufeis fed on glacier-melt have formed in the West Kunlun Mountains. Icing development was found to vary with the order of river channels and more than half of all of the identified Aufeis are located along first- and second-order river channels. The significance of Aufeis at the QTP related to as an indicator of climate change, and a volume of surface and ground waters conserved into Aufeis should take into consideration of river runoff estimation of the region. [ABSTRACT FROM AUTHOR]

The accurate identification of gas channeling channels during foam-assisted oxygen-reduced air flooding (FAORAF) and the analysis of the main controlling factors are essential to propose reasonable and effective countermeasures to enhance oil recovery (EOR). However, there are few comprehensive studies on identifying gas channeling channels, the influencing factors, and the corresponding plugging EOR systems in FAORAF. The channeling channels of the injection and production wells of the Changqing Oilfield, China, under varying development schemes are identified utilizing fuzzy membership function theory in this work to obtain their primary distribution. The characteristics and influence factors of gas channeling channels are analyzed by numerical simulation using CMG. The recovery performance of each foam blocking system is evaluated by twin-tube sand pack models. As well, based on the features of reservoir fractures, a new gel-enhanced foam plugging system is developed. The results show that channeling channels chiefly develop along NE 60–70° and that foam could reduce gas channeling. Natural and artificial fractures are the principal factors causing gas channeling, followed by the injection method and gas injection rate. Under the premise of the injection and migration efficiency, the optimal gel system is a 0.1% HPAM + 0.1% organic chromium crosslinking agent. The addition of gel increases the viscosity of the liquid phase and strengthens the mechanical strength of the foam liquid film. At a permeability ratio of 12, the recovery factors of the binary plugging systems composed of microspheres, PEG, and gel combined with foam are 40.89%, 45.85%, and 53.33%, respectively. The movable gel foam system has a short breaking time (only 18 days) and a recovery factor of about 40% at a permeability ratio of 20. To be suitable for oil reservoirs with microfractures, an improved ternary gel foam system—0.1% HPAM + 0.1% chromium crosslinking agent + 0.05–0.1% nano-SiO2—is developed. Compared with the binary gel foam system, the recovery rate of the new nano-SiO2 gel foam system after 15 days of ageing using the core splitting test is 25.24% during the FAORAF process, increasing by 12.38%. [ABSTRACT FROM AUTHOR]

On the basis of corrected Landsat data for 2013–2017, a modern assessment of aufeis in the Indigirka River basin and its partial catchments with an area of 1830 to 305000 km2 was conducted. The potential contribution of the aufeis flow to the formation of the water balance of rivers during various phases of hydrological regime was calculated. During the phase of the maximum development, the aufeis area of partial catchments ranges from 0.30 to 1.49%, reaching 0.54% of the total area of the Indigirka River basin. The aufeis resources (water content in aufeis) of the Indigirka River basin are 10.0 mm of the runoff level or in total 3.5 km3. For individual rivers, the aufeis flow can reach 5–28 mm per year, which makes up 2.6 to 20.8% (an average is 8.1%) of river runoff. On average, water resources stored in aufeis make up 235% of the winter river flow (135% for the Indigirka River basin). The contribution of the aufeis flow during the spring flood can reach 39% and is 13.7% in the outlet of the Indigirka River basin. The ambiguous impact of climate change on aufeis (reducing their area and increasing their number) requires further detailed studies. [ABSTRACT FROM AUTHOR]

This study discusses the environmental consequences of a major landslide that occurred on the shore of the Bureya reservoir in December 2018, for the first time in the winter period; it was the largest such phenomenon in Russia over the last decade. Toxic organic substances present in water and aufeis in the landslide impact zone and after the collapse of the dam composed of rocks were analyzed. A comparative analysis of aromatic compounds contained in water in the vicinity of the landslide body prior to and after blasting operations and in the newly-built artificial canal was performed using gas chromatography. Predominant organic components present in the water included a number of toxic substances (e.g., methanol and methylated benzene derivatives); after the drainage of the water through the landslide body, concentrations of these substances increased. Many volatile organic substances have a natural origin and could be contained in the pore space of rocks. After the blasting operations, the content of hexane and isopropyl benzene in the water of the artificial canal increased. It has been established that rock grinding caused by the landslide and by the blasting operations significantly affected the composition of volatile organic substances. Rock watering, thawing, and freezing; decomposition of plant residues; and transformations of detonation products of explosives initiate various biogeochemical processes in the pore space; aromatic compounds formed as a result of such processes pose environmental risks to the reservoir ecosystem. [ABSTRACT FROM AUTHOR]

The paper presents methods and results of creation of the digital catalogue of aufeises for the Indigirka river basin made on the basis of Landsat images and historical data. The region under study is the basin before the hydrometric section of GMS Vorontsovo, its area is about 305 000 km2. Historical data were taken from the Inventory of naleds of the North-East of the USSR territory published in 1958 and topographic maps. It includes the estimated coordinates and characteristics of 897 aufeises with total area of 2064 km2. The Landsatbased identification of aufeises for 2013–2017 allowed making description of 1213 aufeises over a total area of 1287 km2. The integrated digital catalogue of the aufeises for the Indigirka river basin based on combination of the above two sources is available at https://issues.pangaea.de/browse/PDI-17699. 10% of the largest aufeises make up about 60% of the total area of all aufeises according to both sources. The largest number of aufeises is at altitudes of 900–1300 m. The interannual variability of area of the aufeises for the period 2001-2016 was estimated by the example of the Bolshaya Momskaya naled and the group of large aufeises in the basin of the Syuryukty River which is the left tributary of the Indigirka. The conclusions cannot be considered unambiguous due to certain limitations of the imagery data but the results of the analysis is indicative of a tendency to decreasing in the area of the Bolshaya Momskaya naled in recent years, while no reduction in the aufeis area is noted in the basin of the Syuryukty River. The main results of this work are the new geodatabase of the aufeises in the Indigirka river basin, and also the comparison of the satellite observations with historical data performed for two major naleds. It is established that the satellite-estimated total area of aufeises is 1.6 times less than in the Cadastre (1958). At the same time, it was found that more than 600 aufeises recognized by the Landsat images were absent in the Cadastre of 1958. This may suggest that either the Cadastre data is incomplete or that conditions of the aufeis can be significantly changed over the past 50 years.

Coral reefs are widely recognized for providing a natural breakwater effect that modulates erosion and flooding hazards on low‐lying sedimentary reef islands. Increased water depth across reef platforms due sea‐level rise (SLR) can compromise this breakwater effect and enhance island exposure to these hazards, but reef accretion in response to SLR may positively contribute to island resilience. Morphodynamic studies suggest that reef islands can adjust to SLR by maintaining freeboard (island crest elevation above still water level) through overwash deposition and island accretion, but the impact of different future reef accretion trajectories on the morphological response of islands remains unknown. Here we show, using a process‐based morphodynamic model, that, although reef growth significantly affects wave transformation processes and island morphology, it does not lead to decreased coastal flooding and island inundation. According to the model, reef islands evolve during SLR by attuning their elevation to the maximum wave runup and islands fronted by a growing reef platform attain lower elevations than those without reef growth, but have similar overwash regimes. The mean overwash discharge Qover across the island crest plays a key role in the ability of islands to keep up with SLR and maintain freeboard, with a Qover value of O (10 l m−1 s−1) separating island construction from destruction. Islands, therefore, can grow vertically to keep up with SLR via flooding and overwash if specific forcing and sediment supply conditions are met, offering hope for uninhabited and sparely populated islands. However, this physical island response will negatively impact infrastructure and assets on developed islands. Plain Language Summary: Coral reef islands are particularly exposed to the impacts of sea‐level rise. They are usually fronted by "living" coral reef platforms that protect the island shoreline from energetic wave action. Healthy reef platforms grow vertically and can keep up with rising sea level, maintaining a constant water depth in front of the island. It is therefore suggested that future reef growth may be a critical factor in reducing the vulnerability of coral reef islands to sea‐level rise. We use a computer model to simulate the response of coral reef islands to sea‐level rise with and without future reef growth. We find that as sea level rises, the islands evolve by retreating, while at the same time building up vertically. Island build‐up is accomplished by waves overwashing the island and depositing sediment on the top of the island. According to our model results, vulnerability of the reef islands to sea‐level rise is not dependent on whether the reef platform grows or not. In both cases, islands are regularly overwashed, but this is necessary for islands to grow vertically. Island accretion by overwash offers hope for uninhabited and sparely populated islands, but will negatively impact infrastructure and assets on urbanized islands. Key Points: Reef islands evolve during SLR by attuning their elevation to the maximum wave runup; thus, gravel islands build up higher than sand islandsAs long as mean overwash discharge across the island crest is < O (10 l m−1 s−1) coral reef islands accrete vertically during sea‐level riseFuture reef growth does not increase the ability of islands to adjust to sea‐level rise on the medium‐term (<50 years) [ABSTRACT FROM AUTHOR]

Aufeis, also known as an icing or naled, is an accumulation of ice that forms primarily during winter when water is expelled onto frozen ground or ice surfaces and freezes in layers. Process‐oriented aufeis research initially expanded in the 20th century, but recent interest in changing hydrological conditions in permafrost regions has rejuvenated this field. Despite its societal relevance, the controls on aufeis distribution and dynamics are not well defined and this impedes projections of variation in aufeis size and distribution expected to accompany climate change. This paper reviews the physical controls on aufeis development, current broad‐scale aufeis distribution and anticipated change, and approaches to aufeis investigation. We propose an adjustment to terminology to better distinguish between the formation process and resulting ice bodies, a clarification of the aufeis classification approach based on source water, and a size threshold for broad‐scale aufeis inventory to facilitate collaborative research. We identify additional objectives for future research including advancing process knowledge at fine spatial scales, describing broad‐scale distribution using current remote sensing capabilities, and improving our understanding and predictive capacity over the interactions between aufeis and landscape‐scale permafrost, hydrogeological, geotectonic, and climate conditions. [ABSTRACT FROM AUTHOR]

The results of long-term studies of a group of aufeis-forming Buluus groundwater sources are given. A stow, which has been formed by the spring, contains the drainage area of the suprapermafrost–intrapermafrost aquifer, which is widespread in the sand deposits of the bestyakhskaya terrace of the Lena River in Central Yakutia. The analysis of observations of 1964–2017 showed stable water chemistry in Buluus spring at the long-term scale. Considerable seasonal variations of water chemistry are typical of low-discharge springs, which start functioning after becoming free of aufeis. The spring water also shows higher concentrations of lithium and fluorine. The possible causes of the different chemistry of spring water are discussed, with special attention paid to the local activity of rock freezing and thawing processes in the aufeis valley. It is shown that groundwater samples are to be taken from all springs in the areas of their group discharge with the aim to assess the effect of natural and technogenic factors on the permafrost–hydrogeochemical conditions. [ABSTRACT FROM AUTHOR]

Aufeis are sheets of ice unique to cold regions that originate from repeated flooding and freezing events during the winter. They have hydrological importance associated with summer flows and winter insulation, but little is known about the seasonal dynamics of the unfrozen sediment layer beneath them. This layer may support perennial groundwater flow in regions with otherwise continuous permafrost. For this study, ground penetrating radar (GPR) were collected in September 2016 (maximum thaw) and April 2017 (maximum frozen) at the Kuparuk aufeis field on the North Slope of Alaska. Supporting surface nuclear magnetic resonance data were collected during the maximum frozen campaign. These point‐in‐time geophysical data sets were augmented by continuous subsurface temperature data and periodic Structure‐from‐Motion digital elevation models collected seasonally. GPR and difference digital elevation model data showed up to 6 m of ice over the sediment surface. Below the ice, GPR and nuclear magnetic resonance identified regions of permafrost and regions of seasonally frozen sediment (i.e., the active layer) underlain by a substantial lateral talik that reached >13‐m thickness. The seasonally frozen cobble layer above the talik was typically 3‐ to 5‐m thick, with freezing apparently enabled by relatively high thermal diffusivity of the overlying ice and rock cobbles. The large talik suggests that year‐round groundwater flow and coupled heat transport occurs beneath much of the feature. Highly permeable alluvial material and discrete zones of apparent groundwater upwelling indicated by geophysical and ground temperature data allows direct connection between the aufeis and the talik below. Key Points: A multimethod approach revealed a perennial suprapermafrost groundwater flow system below an arctic aufeis field that supports a spatially extensive lateral talikGroundwater upwelling zones through several meters of frozen cobbles maintain direct connection between surface ice and the lateral talik during winterA revised conceptual hydrogeological model is developed for aufeis fields with extensive lateral groundwater flow [ABSTRACT FROM AUTHOR]

Proglacial icings (also known as naled or aufeis) are frequently observed in the forefields of polar glaciers. Their formation has been ascribed to the refreezing of upwelling groundwater that has originated from subglacial melt, and thus the presence of icings has been used as evidence of polythermal glacier regime. We provide an updated analysis of icing occurrence in Svalbard and test the utility of icings as an indicator of thermal regime by comparing icing presence with: (1) mean glacier thickness, as a proxy for present thermal regime; and (2) evidence of past surge activity, which is an indicator of past thermal regime. A total of 279 icings were identified from TopoSvalbard imagery covering the period 2008-2012, of which 143 corresponded to icings identified by a previous study of aerial photographs from 1990. Only 46% of icings observed in 2008–2012 were found to occur at glaciers with thicknesses consistent with a polythermal regime, meaning a large proportion were associated with glaciers predicted to be of a cold or transitional thermal regime. As a result, icing presence alone may be an unsuitable indicator of glacier regime. We further found that, of the 279 glaciers with icings, 63% of cold-based glaciers and 64% of transitional glaciers were associated with evidence of surge activity. We therefore suggest that proglacial icing formation in Svalbard may reflect historical (rather than present) thermal regime, and that icings possibly originate from groundwater effusion from subglacial taliks that persist for decades following glacier thinning and associated regime change. [ABSTRACT FROM AUTHOR]

For the first time, the connection between the formation of the ultra-high pressure ice dam on the Chuya-Kurai glacier-dammed lake and the development of aufeis processes on the Chuya river was substantiated. Consideration is given to the mechanisms of self-regulation in the process of glacier-dammed lake self-freezing as a consequence of a consequence of synchronous processes of Chuya river aufeis formation and the filling of the hollow with water. It is found that aufeis formation in sections of initial damming of the water flow caused an increase in the height and area of the dam and, hence, in its weight. Due to the large weight, favorable conditions were created for the development of the processes of regelation and plastic viscous flow of the monolithic ice massif, without formation of cracks and water flow channels inside the ice body. These factors were responsible for the long-term resistance of the dam to destruction processes. A possible retrospective assessment of the lake filling duration at different flow rates in the Chuya channel is made. It is established that the suggested formation mechanism for a high-pressure ice dam is consistent the well-known cryogenic-hydrophysical patterns and can, therefore, apply for realistic events. [ABSTRACT FROM AUTHOR]

Abstract Integrated sedimentological and ichnological study of the gas-bearing, upper Middle Miocene strata in the southwestern Ulleung Basin has identified five main lithofacies, arranged in order from offshore and offshore transitional environments to coastal-plain channel settings. In each of repeated successions, the basal mudstone-dominated, offshore to offshore transitional facies are sharply overlain by upper shoreface sandstones that are, in turn, erosively overlain by distributary channel sandstones. In the open-marine environment, interbedded storm and interstorm deposits are predominant with sporadic flood-event beds containing a navichnia trace-fossil suite. Bioturbation style in this facies tends to reflect depositional energy variations, alternating between dwelling structures in the storm beds and feeding and grazing trace-fossil assemblages in the interstorm beds. In the channel deposits, flood-interflood couplets are commonly expressed as cross-bedded, almost non-bioturbated sandstones that alternate with bioturbated, tidally-formed, interbedded sandstone and mudstone. From this, the co-existence of storm-wave and tide-generated structures in the studied interval suggests that the depositional environment is a wave-dominated and tide-influenced deltaic setting, with the recorded tidal influence restricted to the channels, which have a higher level of heterogeneity because of tidal sedimentation during periods of low river discharge. Stratigraphically, the 400-m thick, upper Middle Miocene section shows an overall, coarsening-upward succession, representing 3rd-order falling-stage to lowstand deposits as a result of long-term basinal uplift. This succession can, in turn, be broken into four, 4th-order stratigraphic packages, each of which comprises a transgressive (T)-regressive (R) succession that is separated by a transgressive surface. These packages can be further subdivided into small-scale, upward-coarsening successions (5th-order stratigraphic packages of parasequence scale). Each small-scale succession is sharply overlain by offshore mudstone which reflects a rapid vertical facies transition, representing a marine flooding surface. Internally, each parasequence is characterized by a progradational facies succession wherein offshore mudstones are erosively overlain by upper-shoreface sandstones, forming sharp-based shoreface deposits that are likely to be produced during a forced regression, an interpretation supported by the presence of an omission trace-fossil suite on the erosion surface. In this context, the high-frequency parasequences represent short-term relative sea-level falls superimposed on the longer-term falling sea level due to a compressional tectonic regime. Highlights • Wave-dominated tide-influenced deltaic deposits have been intensely described. • Mouth bars absent due to small river size and wave-reworking during fair-weather. • Tidal indicators are only present in low-discharge distributary channel deposits. • Fluid muds and stressed ichnofacies indicate river-proximal shoreface deposits. • Overall, progradational character is likely to represent a long-term sea-level fall. [ABSTRACT FROM AUTHOR]

• The area and volume of the giant Anmangynda aufeis has decreased since 1962. • The aufeis regime has changed from perennial to seasonal glaciation. • The changes of climate affect the regime of ground temperature. • Meteorological conditions in November-December govern the size of the aufeis. This study examines the evolving dynamics of spring aufeis fields in the mountain permafrost zone of North-Eastern Eurasia, emphasizing their significance as indicators of permafrost-hydrogeological processes. Focusing on the representative Anmangynda river basin giant aufeis field, our research spans 1962 to 2022 and unveils temporal variations in aufeis characteristics. Over the historical period (1963–1990), the aufeis maximum pre-ablation area ranged from 4.3 to 6.8 km2, with a volume of 5.3 to 11.7 million m3. In the present era (2000–2022), these figures decreased to 3.5–5.4 km2 and 5.0–8.2 million m3, respectively. The region experienced heightened air temperatures and precipitation, with the most significant shifts occurring during early winter (October–December). Increased snow cover depth and earlier formation were also observed. Ground temperatures followed suit with an upward trend. Correlation analyses reveal a noteworthy link between average air temperatures from August to November and aufeis characteristics in both historical and current contexts. Moreover, solid precipitation and air temperatures in November and December displayed a moderate yet statistically significant correlation with aufeis size parameters during 2000–2022. Notably, no significant correlation emerged between aufeis characteristics and the Anmangynda River streamflow or liquid precipitation. This research underscores the interplay between climatic variables and aufeis dynamics, offering insights into the impacts of changing climatic conditions on the permafrost-hydrogeological system. The observed reduction of aufeis area and volume, coupled with the altered freezing and melting periods, align with broader cryospheric changes. As aufeis fields continue to evolve, this study highlights the complexities in their responses and their relevance as indicators of climate-driven alterations in the cryosphere. Further research is essential to fully unravel these intricate relationships and assess their implications for regional hydrology and ecosystems. [ABSTRACT FROM AUTHOR]

Formation of aufeises (naleds) is rather widely distributed cryogenic process in the permafrost zone, therefore naleds are reasonably called the seasonal glaciation of the planet. The ever-increasing interest in aufeises significantly extends the thematic focus of studying them. Various methodological approaches (basin, geological-structural, lithologic-facies, statistical, etc.) are used to reveal regularities of the aufeis occurrence. Using several river basins in Yakutia and its territory as the examples, the perspectivity of the basin approach for investigation of the aufeis distribution is substantiated in this study. The results demonstrated the clear relationship between the quantitative indicators of areal distribution of naleds and altitudes of places of their formation for individual river basins. This relationship suggests that aufeises in river basins of the permafrost zones are important elements in the water-balance and water exchange, which is closely interrelated with not only climatic and morphometric characteristics of a basin, but it does also correlate with its hydrological, hydrogeological, geological, geocryological, landscape and other conditions.

Abstract Understanding the dynamics of a single large water droplet is needed for accurate simulations of the in-flight icing phenomenon. Obtaining information on the ratio of ejected to deposited water and the post-impact droplet distribution should improve the numerical modeling of the bulk of impinging droplets. In this study, a weakly compressible multi-phase Smoothed Particle Hydrodynamics (SPH) method with shifting algorithm and surface tension model is presented to simulate the single droplet dynamics. The validity of the approach has been proved by modeling the classical problems of Rayleigh–Taylor instability, dam break, and droplet formation by comparing against other numerical and experimental data in the literature. Finally, droplet impingement on a liquid film and dry solid surface has been simulated and compared against the experimental data. The effect of impact angle and film thickness on the crown formation is studied to demonstrate the importance of modeling SLD impingement for in-flight icing conditions. [ABSTRACT FROM AUTHOR]

Detailed spatial geodatabase of aufeis in the Indigirka River, the basin area 305 000 km², Russia was compiled from the Cadaster of aufeis of the North-East of the USSR published in 1958, topographic maps and Landsat images for 2013-2017. The aufeis area share varies from 0.26 to 1.15 % in different river sub-basins within the studied area. Digitized Cadaster (1958) contains the coordinates and characteristics of 897 aufeises with total area of 2064 km². The Landsat-based identification of aufeises for 2013-2017 allowed the description of 1213 aufeises on a total area of 128 km². The combined digital database of the aufeis is available at https://doi.pangaea.de/10.1594/PANGAEA.891036. The satellite-derived total area of aufeis is 1.6 times less than in the Cadaster (1958). At the same time, more than 600 aufeis identified by Landsat images analyses are missing in the Cadaster (1958). It implies that the aufeis formation conditions may have been changed between the mid-20th century and the present. About 60 % of total area presents 10 % of the largest aufeis. Most aufeis are located in the elevation band of 1100-1300 m. The interannual variability of the aufeis area was estimated by the example of the Bolshaya Momskaya naled (aufeis) and the group of large aufeis in the basin of the Syuryuktyakh River for the period of 2001-2016. The results of analysis indicate a tendency towards a decrease in the area of the Bolshaya Momskaya naled in recent years, at the same time the reduction in the aufeis area in the basin of the Syuryuktyakh River has not occurred. [ABSTRACT FROM AUTHOR]

Linear engineering facilities, such as gas transportation systems, extend from 30 to 500 metres in width and several hundred kilometres in length. Such routes pass through areas characterized by sufficiently diverse engineering, geological, geocryological and seismotectonic conditions. The safe and reliable functioning of gas transportation systems is ensured by their regular monitoring to prevent the development of hazardous exogenous geological processes. In particular, when monitoring ice formation, the greatest efficiency can be achieved by using unmanned aerial vehicles for low-altitude aerial surveys. In this research, remote sensing methods based on unmanned technologies were applied to assess the aufeis hazard in a section of the Power of Siberia gas pipeline in South Yakutia. The authors’ successful experience of using unmanned systems during an aeromagnetic exploration of iron ore deposits in South Yakutia was also considered. A series of studies, including georadar and electrical exploration profiling, as well as thermal imaging and high-resolution aerial photography by an aerial complex, was conducted to assess the dynamics of ice development over time in the area under study and to establish the signs of a developing hazardous process.

Aufeis problem caused by cutting construction of road is widely spread in cold regions. This paper analyzed the forming process of cut slope aufeis and its mitigation strategy. A new aufeis mitigation structure was designed according to the forming mechanism. Numerical simulation tests were used to improve the structure. Results show that there is no obvious effect on temperature of the middle of the cut slope and the bottom of the ditch whether the insulation material is placed on the top of the cut slope or not; the temperature at the foot of the cut slope increased more significantly than other sites when increasing the thickness of the insulation material. The cold source cooling the ditch mainly comes from the embankment. Both raising embankment and deepening the ditch can increase the temperature and enlarge the unfrozen area in the ditch, which is good for aufeis mitigation and raising the embankment is more effective. And the 15 cm thick XPS insulation material and at least 60 cm high embankment were suggested for the structure under the conditions of minimum boundary temperature − 35.0 °C during the winter. [ABSTRACT FROM AUTHOR]

BACKGROUND An advanced strategy for chilled fish preservation, based on the inclusion in ice of an extract of jumbo squid ( Dosidicus gigas) skin ( JSS), is proposed. Aqueous solutions including acetic acid-ethanol extracts of JSS were tested at two different concentrations as icing media, with the effects on the quality evolution of chilled hake ( Merluccius merluccius) being monitored. RESULTS A significant inhibition ( P < 0.05) of microbial activity (aerobes, psychrotrophs, Enterobacteriaceae, proteolytic bacteria; pH, trimethylamine) was obtained in hake corresponding to the icing batch including the highest JSS concentration. Additionally, fish specimens from such icing conditions showed an inhibitory effect ( P < 0.05) on lipid hydrolysis development, while no effect ( P > 0.05) was depicted for lipid oxidation. Sensory analysis (skin and mucus development; eyes; gills; texture; external odour; raw and cooked flesh odour; flesh taste) indicated a shelf life extension of chilled hake stored in ice including the highest JSS concentration. CONCLUSION A profitable use of JSS, an industrial by-product during jumbo squid commercialisation, has been developed in the present work, which leads to a remarkable microbial inhibition and a significant shelf life extension of chilled hake. In agreement with previous research, ommochrome pigments (i.e. lipophilic-type compounds) would be considered responsible for this preservative effect. © 2016 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The mid-winter break-up of a competent river ice cover can cause ice jamming and flooding, which can have profound impacts on the structure and strength of the ice cover. This research identifies 52 mid-winter break-up events in western Canada (1950-2008) and Alaska (1950-2014) and evaluates the hydro-climatic drivers including temperature and precipitation. The identified mid-winter break-up events are primarily located in the temperate zone, defined as the region between 400 and 1,000 winter (December-February) freezing degree-days. Further delineation by terrestrial biome revealed considerable variability in hydro-climatic triggers, particularly the role of freeze-thaw days (Tmax> 0 °C and Tmin<0 °C) in Tundra and Boreal Forest/Taiga biomes and short-term (3-day) warming events in Temperate Coniferous Forests and Temperate Grasslands, Savannas, and Shrublands. The classification of 5-day sequences of mid-tropospheric circulation indicates that a persistent trough of low-pressure over Alaska and the North Pacific is the dominant pattern preceding mid-winter break-ups. Furthermore, the trough is stronger for events in British Columbia and Alberta compared with Alaska and the Yukon. The results of this research improve our understanding of the hydro-climatic conditions that generate mid-winter break-up events in western Canada and Alaska and will aid in the prediction and risk management of such events. [ABSTRACT FROM AUTHOR]

The Bering Strait connects the Arctic and Pacific oceans and separates the North American and Asian landmasses. The presently shallow (~53 m) strait was exposed during the sea level lowstand of the last glacial period, which permitted human migration across a land bridge today referred to as the Bering Land Bridge. Proxy studies (stable isotope composition of foraminifera, whale migration into the Arctic Ocean, mollusc and insect fossils and paleobotanical data) have suggested a range of ages for the Bering Strait reopening, mainly falling within the Younger Dryas stadial (12.9-11.7 cal ka BP). Here we provide new information on the deglacial and post-glacial evolution of the Arctic-Pacific connection through the Bering Strait based on analyses of geological and geophysical data from Herald Canyon, located north of the Bering Strait on the Chukchi Sea shelf region in the western Arctic Ocean. Our results suggest an initial opening at about 11 cal ka BP in the earliest Holocene, which is later than in several previous studies. Our key evidence is based on a well-dated core from Herald Canyon, in which a shift from a near-shore environment to a Pacific-influenced open marine setting at around 11 cal ka BP is observed. The shift corresponds to meltwater pulse 1b (MWP1b) and is interpreted to signify relatively rapid breaching of the Bering Strait and the submergence of the large Bering Land Bridge. Although the precise rates of sea level rise cannot be quantified, our new results suggest that the late deglacial sea level rise was rapid and occurred after the end of the Younger Dryas stadial. [ABSTRACT FROM AUTHOR]

Alaska's economy is tied to oil production, with most of the petroleum coming from the Prudhoe Bay oil fields through the Trans-Alaska Pipeline System. Deadhorse, an industrial town located on the North Slope, provides support to the oil industry. The Dalton Highway is the only terrestrial connection between Deadhorse and other cities in Alaska. During winter 2015, the road was impassable twice for 12 days total due to winter overflow from the Sagavanirktok River. During spring breakup, unprecedented flooding occurred near Deadhorse, caused by ice accumulation near the road and fast snowmelt due to warm air temperatures, which resulted in the road's closure for 18 days, the first time since the highway was built in 1976. Presented in this article are antecedent hydrometeorological conditions in the Sagavanirktok and neighboring watersheds, a summary of infrastructure protection measures implemented before breakup, hydrologic data collected during breakup, and damage caused by the spring flood to the infrastructure. [ABSTRACT FROM AUTHOR]

Communities along the Slave River are concerned about changes in the river ice cover, such as the formation of air pockets and double layers of ice in the ice cover. These anomalies make it challenging to find suitable locations for river ice crossings in winter, necessary for the transportation of goods to and from remote regions and to access hunting, trapping and fishing areas. This study utilized satellite imagery and field observations to document these anomalies of the river ice during the winters from November 2013 to March 2016. Backscatter analysis of the satellite imagery identified low and high density areas of air pockets along the river. Satellite images also revealed cracks and flooding of the river ice, particularly along the downstream reach of the river. [ABSTRACT FROM AUTHOR]

Predicting the consequences of flooding is a key issue that may help the ship master of a large passenger ship to make rational decisions in emergency situations. To this end, the Delphi Emergency Decision Support System (Delphi EDSS) has been designed and is under implementation to continuously assess ship's state of survivability. Analyses are performed by means of a time-domain simulation program, where transient stages of flooding are investigated and stored off-line for all the potential damage scenarios. The Delphi EDSS evaluates the ship risk level including the most important aspects related to safety state while establishing the time-to-capsize which is of primary concern for the safe evacuation of the damaged ship. The methodology is based on a scientific approach, setting an overall platform for rational assessment of non-survivability risk. Determination of the global risk level and its components requires solution of a multicriterial problem, where the level of importance of each criterion contributing to determination of a global risk index is combined with fuzzified contributors to risk calculated at lower levels. [ABSTRACT FROM AUTHOR]

Due to local groundwater seeping and freezing in layers that accumulate over each other and create large ice clusters on the ground surface, specific conditions of energy and mass transfer are created in the atmosphere–soil–lithosphere system. In winter, the vertical temperature distribution curve is significantly deformed due to heat emission from the water layer above the ice cover during its freezing, and a thermocline is thus formed. Deformation of the temperature curve is gradually decreasing in size downward the profile and decays at the interface of frozen and thaw rocks. Values and numbers of temperature deviations from a 'normal' value depend on heat reserves of aufeis water and the number of water seeps/discharges at a given location. The production of the thermocline alters freezing conditions for underlying ground layers and changes the mechanism of ice saturation, thus leading to formation of two-layer ice-ground complexes (IGC). IGCs are drastically different from cryogenic formations in the neighbouring sections of the river valley. Based on genetic characteristics and the ratios of components in the surface and subsurface layers, seven types of aufeis IGCs are distinguished: massive-segregation, cement-basal, layered-segregation, basal-segregation, vacuum-filtration, pressure-injection, and fissure-vein. Annual processes of surface and subsurface icing and ice ablation are accompanied by highly hazardous geodynamic phenomena, such as winter flooding, layered water freezing, soil heaving/pingo, thermokarst and thermal erosion. Combined, these processes lead to rapid and often incidental reconfigurations of the surface and subsurface runoff channels, abrupt uplifting and subsiding of the ground surface, decompaction and 'shaking-up' of seasonally freezing/thawing rocks, thereby producing exceptionally unfavourable conditions for construction and operation of engineering structures.Formation and development of river networks are heavily influenced by aufeis deposits and processes taking place at the aufeis surfaces, especially in areas of discontinuous and continuous permafrost where an average thickness of the ice cover on rivers ranges from 1.0 to 2.5 m, and the major part of the ice cover is accumulated layer by layer due to freezing of discharged groundwater. In the permafrost zone, the intensity of cryogenic channelling is clearly cyclical, and the cycles depend on accumulation of aufeis ice above the river level during the autumn low-water period. Five stages of cryogenic channelling are distinguished: I – pre-glacial development, II – transgression, III – stabilization, IV – regression, and V – post-glacial development. Each stage is characterised by a specific glaciohydrological regime of runoff channels and their specific shapes, sizes and spatial patterns.The channel network is subject to the maximum transformation in aufeis development stages III and IV, when the transit flow channel is split into several shallow-water branches, producing a complicated plan pattern of the terrain. In the mature aufeis glades, there are sites undergoing various development stages, which gives evidence that aufeis channelling is variable in a wide range in both space and time. With respect to sizes of aufeis glades, river flow capacities and geological, geomorphological, cryo-hydrogeological conditions, aufeis patterns of the channel network are classified into five types as follows: fan-shaped, cone-shaped, treelike, reticular, and longitudinal-insular types. The aufeis channel network is a reliable indicator of intensity of both recent and ancient geodynamic processes in the cryolithozone.In Siberia and the Far East, the aufeis deposits are much larger, more numerous and more important in terms of morpholithology in comparison with the 'classical' (sedimentary metamorphic) icing structures. The more contrasting is the terrain, the more active are neotectonic movements, the lower is the mean annual air temperature, and the higher is the annual percentage of the territory covered by aufeis ice. The aufeis ratio of the permafrost zone is determined from parameters of over 10000 ice fields and amounts to 0.66 % (50000 km2). In mountains and tablelands, the total area of aufeis deposits amounts to 40000 km2, and the number of ice clusters (0.77 km2 in average) exceeds 60000. On the rivers up to 500 km long, the aufeis size depends on the stream rank. In all the natural zones, the majority of gigantic aufeis spots produced by groundwater are located in river valleys of ranks 3 and 4. The square area of aufeis deposits of mixed feed, i.e. produced by river water and groundwater, which occupy the entire river channel, yet do not go beyond the floodplain, amounts to 68000 km2, i.e. by a factor of 1.7 larger than the area of all the aufeis deposits (taryns). The cumulative channel-forming effect of aufeis phenomena is expressed by an increment in the channel network relative to characteristics of the river segments located upstream and downstream of the aufeis glade. This indicator is well correlated with the aufeis ratios of the river basins, morphostructural and cryo-hydrometeorological conditions of the territory under study. The incremental length of the channel network, ρn per one groundwater aufeis deposit is increased, in average, from 3.5 km in mountains in the southern regions of East Siberia to 23 km in the Verkhoyansk-Kolyma mountain system and Chukotka. The value of ρn is decreased to 2.2 km in the plains and intermountain depressions of the Baikal rift system where the average dimensions of the ice fields are smaller. An average incremental length of the channel network per one large groundwater aufeis deposit amounts to 12.2 km, and the total incremental length in continuous and discontinuous permafrost areas (F=7.6 mln km2) is estimated at 690000 km.Combined impacts of aufeis and icing processes on underlying rocks and the channel network is a specific (aufeis) form of cryogenic morpholithogenesis that is typical of regions with inclement climate and harsh environment. A more detailed research of these processes is required, including large-scale aerospace surveys, monitoring and observations on special aufeis polygons.

New challenges in flood risk management are raised by climate change and land-use development. These challenges are particularly complex in estuarine and coastal systems, where different hazard sources interact in a dynamic socio-economic context. This paper presents an innovative approach to support flood risk management in estuaries. The approach, developed at a local-scale basis, is applied in the case study of the Tagus estuary (Portugal). The methodology is supported by the regional framing of the study area and integrates hazard, exposed elements, territorial vulnerability and risk assessments considering different climate scenarios. Through the involvement of the various risk management dimensions, the results allow the definition of a new decision-making supporting framework for emergency and land-use planning. At the emergency level, the results include a WebGIS interface providing an early warning system for the locations with highest risk of flooding and the definition of emergency planning guidelines. A set of flood adaptation actions based on land-use and occupation measures are recommended to increase resilience in face of flooding and future sea level rise. The institutional capacity-building is achieved through the availability of information and tools that can effectively support decision-making. Additionally, the outcomes contribute to better understand flood risk in estuaries and to strengthen its prevention, preparedness and response, priorities defined in the Sendai Framework for Disaster Risk Reduction 2015-2030. [ABSTRACT FROM AUTHOR]