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Peatlands store large amounts of organic carbon, but the carbon stock is sensitive to changes in precipitation or water table manipulations. Restoration of drained peatlands by drain blocking and flooding is a common measure to conserve and augment the carbon stock of peatland soils. Here, we report to what extent flooding affected the contribution of heterotrophic and rhizosphere respiration to soil CO2 efflux in a grass-dominated mountain fen, Germany. Soil CO2 efflux was measured in three unmanipulated control plots and three flooded plots in two consecutive years. Flooding was achieved by permanent irrigation during the growing seasons. Radiocarbon signatures of CO2 from different sources including soil CO2 efflux, incubated peat cores and live grass roots were repeatedly analyzed for partitioning of soil CO2 efflux. Additionally, heterotrophic respiration and its radiocarbon signature were determined by eliminating rhizosphere respiration in trenched subplots (only control). In the control plots, rhizosphere respiration determined by 14C signatures contributed between 47 and 61% during the growing season, but was small (4 %) immediately before budding. Trenching revealed a smaller rhizosphere contribution of 33% (2009) and 22% (2010) during growing seasons. Flooding reduced annual soil CO2 efflux of the fen by 42% in 2009 and by 30% in 2010. The reduction was smaller in 2010 mainly through naturally elevated water level in the control plots. A 1-week interruption of irrigation caused a strong short-lived increase in soil CO2 efflux, demonstrating the sensitivity of the fen to water table drawdown near the peat surface. The reduction in soil CO2 efflux in the flooded plots diminished the relative proportion of rhizosphere respiration from 56 to 46 %, suggesting that rhizosphere respiration was slightly more sensitive to flooding than heterotrophic respiration. We conclude that the moderate decrease in rhizosphere respiration following flooding arises from a gradual change in vegetation in this fen ecosystem. [ABSTRACT FROM AUTHOR]

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]

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]

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]

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]

Bayesian theory of model calibration provides a coherent framework for distinguishing and encoding multiple sources of uncertainty in probabilistic predictions of flooding. This paper demonstrates the use of a Bayesian approach to computer model calibration, where the calibration data are in the form of spatial observations of flood extent. The Bayesian procedure involves generating posterior distributions of the flood model calibration parameters and observation error, as well as a Gaussian model inadequacy function, which represents the discrepancy between the best model predictions and reality. The approach is first illustrated with a simple didactic example and is then applied to a flood model of a reach of the river Thames in the UK. A predictive spatial distribution of flooding is generated for a flood of given severity. [ABSTRACT FROM AUTHOR]

Reducing the mobility of CO 2 by means of generating in situ foam is an effective method for improving the oil recovery in CO 2 flooding processes. Implementation of the CO 2 -foam technique typically involves the co-injection of CO 2 and surfactant solution into the porous medium. The surfactant molecules form bubble films that trap the flowing CO 2 molecules. The effectiveness of the CO 2 -foam process is measured in terms of foam mobility. The mobility of CO 2 -foam is affected by different operation parameters, such as pressure, temperature, foam quality, and brine concentration. However, surfactant type governs the overall efficiency of the CO 2 -foam process. This paper presents the results of a series of experiments conducted to study the effect of various parameters on the CO 2 -foam process. Bottle tests were conducted for four commercially available surfactants and among them, Chaser CD-1045 was found to be the most effective surfactant for CO 2 -foam flow under reservoir conditions. It was observed that an increase in pressure from 1, 200 psi to 1, 500 psi leads to increase of the mobility of CO 2 -foam, and an increase in temperature from 72 to 122°F reduces the mobility. Also, as the foam quality increases from 20 to 80%, the mobility decreases. It was observed that there was no significant effect on the mobility with an increase in brine concentration from 1 to 3 wt%. [ABSTRACT FROM AUTHOR]

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]

This paper examines the controlling influence of snow and rain on river ice processes in creeks and streams. Winter precipitation (in the form of rain and snow) has been observed to affect river ice processes and channel parameters of low and high gradient channels in unsuspected ways that can have significant impacts on channel hydraulics, hydrology and habitat. On a low gradient stream, a snowfall event initiated the development of an ice cover by creating unconsolidated snow slush bridges that eventually froze in place. Afterward, both snowfalls and rainfalls in alternation with cold spells dramatically increased the thickening rate of the ice cover well beyond that predicted by classic equations. In a smaller low-gradient agricultural creek, wind-blown snow impeded the formation of an ice cover by insulating the flow from cold atmospheric conditions. On steep channels (of different sizes and morphologies), anchor snow slush has been seen to accumulate on the bed substrate. As opposed to anchor ice, anchor snow slush is not believed to require supercooling water conditions to form nor to stay in place. Finally, in a steep headwater creek, a rain-on-snow event generated a snow slush flow and multiple snow slush jams. This phenomenon was seen to divert most of the water out of the channel into another watershed and concomitantly signalled a mid-winter breakup in the greater watershed downstream. These observations suggest that the role of precipitation on small channel winter ice morphology and water flows, levels and currents has been severely underestimated and that any ecological winter studies, hydraulic structure designs and river modelling efforts need to include processes that are sometimes dominated by rain, slush and snow. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

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]

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]

The Peace-Athabasca Delta (PAD) in northern Alberta is one of the world's largest inland freshwater deltas, home to large populations of waterfowl, muskrat, beaver, and free-ranging wood bison. Following construction of the Bennett Dam in the late 1960s, a paucity of ice-jam flooding in the lower Peace River has resulted in prolonged dry periods and considerable reduction in the area covered by lakes and ponds that provide habitat for aquatic life in the PAD region. Past studies have shown that both regulation and climate have contributed to the drying trend, via increased freezeup levels and reduced breakup flows, respectively. However, it has not so far been possible to assess the relative impacts of these two factors. This question is addressed herein by developing quantitative relationships based on the concept of conditional probability. The new methodology is first tested against observed frequencies of ice-jam floods both before and after regulation; it is subsequently applied to quantify the effects of climate and of regulation on the post-regulation reduction in ice-jam flood frequency. The results indicate that both factors have contributed significantly to the drying of the PAD, with regulation having had the more pronounced effect. Complications that may arise from secondary effects of regulation on breakup flows or of climate on freezeup levels are discussed and quantified. It is shown that such effects do not alter the overall conclusions of the paper. [ABSTRACT FROM AUTHOR]

The prediction of winter flooding is a complicated task since it is affected by many meteorological and hydraulic factors. Typically, information on river ice conditions is based on historical observations, which are usually incomplete. Recently, data have been supplemented by information extracted from satellite images. All the above mentioned factors provide a good background of the characteristics of ice processes, but are not sufficient for a detailed analysis of river ice, which is highly dynamic and has a local extent. The main aim of this paper is to show the possibility of the prediction of ice jams in a river using a mathematical model. The case of the Odra River was used here. Within the Lower and Middle Odra River, the most significant flood risk, in winter conditions, is posed by ice jams created when movable ice is stopped by existing obstacles such as shallow areas in the riverbed, the narrowing of the riverbed, and other obstacles caused as a result of sudden changes of the river current, backwater from sea waters, and north winds, which contribute to the creation of ice jams. This in turn causes the damming of water and flooding of adjacent areas. The DynaRICE model was implemented at two locations along the Odra River, previously selected as ice-prone areas. Also, a thermal simulation of ice cover formation on Lake Dąbie was shown with variable discharge. The results of numerical simulations showed a high risk of ice jamming on the Odra River, created within one day of ice moving downstream. The prediction of the place and timing, as well as the extent, of the ice jam is impossible without the application of a robust mathematical model. [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]

Summary: Concern has been expressed regarding the impacts of climate change on freshwater aquatic ecosystems in arctic regions. Populated with lakes controlled by flooding from spring break-up ice jams, arctic deltas such as the Mackenzie Delta in northern Canada are particularly sensitive to changing ice break-up conditions and the hydroclimatic controls on break-up and ice-jam flooding. An understanding of these controls is necessary for assessing future climate change effects. This paper presents an assessment of hydroclimatic conditions controlling break-up over the period 1974–2006, with a focus on extreme flood events. Both the upstream driving force, capturing elements of the spring discharge hydrograph, and the downstream resistance force, describing the competence of the downstream ice cover, were quantified with reference to the Mackenzie River at Arctic Red River hydrometric station such that the contribution of each to the severity and timing of break-up could be explored. Results show that the severity of peak break-up stage is most influenced by upstream discharge and the balance between upstream and downstream melt, while timing is related to delta ice conditions and the rise of the spring hydrograph. The highest peak stage events require a rapid rise in discharge and high peak discharge. Minimal downstream melting degree-days and greater ice thickness are also important, although no relationship of these appears to control the level of backwater produced from broken ice and ice jamming effects. The pattern of rapid (protracted) upstream melt and lower (higher) intensity melt in the delta characterizes the highest (lowest) break-up events. For the most severe events, upstream forces are important in controlling discharge-driven events, while an altered hydrologic response occurring for ice-driven events was noted, meriting future examination. Finally, trends toward a longer prebreak-up melt interval, lower peak discharge, rate of rise in discharge, and ice thickness, and higher freeze-up stage were observed, with greater variability of these controls and break-up severity in the most recent decade. [Copyright &y& Elsevier]

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]

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]

Abstract: While the paper by Alley et al. (Alley, R.B., Dupont, T.K., Parizek, B.R., Anandakrishnan, S., Lawson, D.E., Larson, G.J., Evenson, E.B., 2006. Outburst flooding and the initiation of ice-stream surges in response to climatic cooling: A hypothesis. Geomorphology 75, 76–89) is a welcome contribution as it presents some new arguments and expands the discussion, it unfortunately overlooked the literature on the captured ice shelf (CIS) hypothesis. Considering all recent results, the hypothesis has the potential for drastically altering our understanding of sudden climate change during the Quaternary period. Also, the interpretation of macrogeomorphology in land-ice covered continents and seas, including the Hudson Bay and the Baltic Sea, is affected. [Copyright &y& Elsevier]

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]

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]

The June 2013 flood in the Canadian Rockies featured rain-on-snow (ROS) runoff generation at alpine elevations that contributed to the high streamflows observed during the event. Such a mid-summer ROS event has not been diagnosed in detail, and a diagnosis may help to understand future high discharge-producing hydrometeorological events in mountainous cold regions. The alpine hydrology of the flood was simulated using a physically based model created with the modular cold regions hydrological modelling platform. The event was distinctive in that, although at first, relatively warm rain fell onto existing snowdrifts inducing ROS melt; the rainfall turned to snowfall as the air mass cooled and so increased snowcover and snowpacks in alpine regions, which then melted rapidly from ground heat fluxes in the latter part of the event. Melt rates of existing snowpacks were substantially lower during the ROS than during the relatively sunny periods preceding and following the event as a result of low wind speeds, cloud cover and cool temperatures. However, at the basin scale, melt volumes increased during the event as a result of increased snowcover from the fresh snowfall and consequent large ground heat contributions to melt energy, causing snowmelt to enhance rainfall-runoff by one fifth. Flow pathways also shifted during the event from relatively slow sub-surface flow prior to the flood to an even contribution from sub-surface and fast overland flow during and immediately after the event. This early summer, high precipitation ROS event was distinctive for the impact of decreased solar irradiance in suppressing melt rates, the contribution of ground heat flux to basin scale snowmelt after precipitation turned to snowfall, the transition from slow sub-surface to fast overland flow runoff as the sub-surface storage saturated and streamflow volumes that exceeded precipitation. These distinctions show that summer, mountain ROS events should be considered quite distinct from winter ROS and can be important contributors to catastrophic events. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

This study investigates icings and their role as an important element of the glacier forefields observed in the Kaffiøyra region in Svalbard. The emergence or disappearance of icings is one of the effects of changes observed in the area of a glacier and its catchment in the High Arctic. Icings were observed both in summer and spring in 1996-2015. The main objective was focused on the location and surface changes of the icings, as this is important for their responses to changes which occur across the cryosphere. In the forefields of most glaciers in the Kaffiøyra region, a generally declining trend is observed in the size of icing fields, with only occasional periods in which it increased. During the last five years, they have not been so large as they were in the preceding years. The degradation of High Arctic icings mainly occurs in summer, generally as a result of surface and mechanical ablation. The reach of icings is rather variable and their surface and thickness tend to change year by year, depending on hydrological conditions in the glacier's system. Regardless of the causes of icings' formation, their size, range and reach are related to the intensity of melting during a given season, which is conditioned by the weather, and especially by the winter outflow from a glacier. [ABSTRACT FROM AUTHOR]

Bifurcaria bifurcata is a widely extended brown macroalga, whose antimicrobial and antioxidant properties have previously been described. In this study, ethanolic extracts of B. bifurcata were included in the icing medium employed for the chilled storage of megrim ( Lepidorhombus whiffiagonis). For it, two different concentrations of this brown macroalga extract (0.67 and 2.50 g lyophilized alga L aqueous solution; B-1 and B-2 batches, respectively) were tested for a 14-day storage. The effect of the alga extract was compared with a counterpart batch stored in traditional ice prepared only from water (B-0 batch). Significant ( p < 0.05) inhibitions of microbial activity (aerobes, psychrotrophs, lipolytic bacteria, proteolytic bacteria and Enterobacteriaceae) as well as of pH and trimethylamine formation were observed as a result of the incorporation of the alga extract in the icing medium, being this effect especially relevant in the B-2 batch. Concerning lipid damage development, a significantly ( p < 0.05) lower formation of free fatty acids (lipid hydrolysis development) and of fluorescent compounds (tertiary lipid oxidation development) in samples corresponding to both alga-including batches could also be observed; this inhibitory effect was more intense in fish belonging to the B-2 batch. The icing medium proposed in this work constitutes a promising strategy in order to apply algae extracts to enhance fish quality retention during the different steps of storage and commercialization of marine species. [ABSTRACT FROM AUTHOR]

1. Early-season flooding and ice entrapment at sub-zero temperatures pose significant challenges to any polar terrestrial invertebrate. 2. The chironomid midge, Eretmoptera murphyi, is native to the sub- Antarctic island of South Georgia and has been introduced to the maritime Antarctic ( Signy Island). While the majority of its 2-year life cycle is spent as a terrestrial larva, it is found in habitats potentially exposed to prolonged flooding. 3. The current study explored the tolerance of the larvae to extended submergence, demonstrating survival for at least 28 days, underlain by their ability to respire (oxy-regulate) whilst submerged. To date, this ability is not known to be shared by any other terrestrial midge. Larvae also demonstrated notable anoxia tolerance whilst encased in ice, surviving for up to 28 days. 4. These data indicate a capacity to survive ecologically relevant periods of submergence and/or ice entrapment, such as may be experienced in their natural habitats. [ABSTRACT FROM AUTHOR]

Snowmelt flooding triggered by intense heat is a major temperature related weather hazard in northern Pakistan, and the frequency of such extreme flood events has increased during the recent years. In this study, the probabilistic temperature forecasts at seasonal and subseasonal time scales based on hindcasts simulations from three state-of-the-art models within the DEMETER project are assessed by the relative operating characteristic (ROC) verification method. Results based on direct model outputs reveal significant skill for hot summers in February 3-5 (ROC area = 0.707 with lower 95% confidence limit of 0.538) and February 4-5 (ROC area = 0.771 with lower 95% confidence limit of 0.623) forecasts when validated against observations. Results for ERA-40 reanalysis also show skill for hot summers. Skilful probabilistic ensemble forecasts of summertime temperatures may be valuable in providing the foreknowledge of snowmelt flooding and water management in Pakistan. [ABSTRACT FROM AUTHOR]

Streamflow in small forested watersheds on the Boreal Plain of western Canada can be a challenge to monitor due to high variation in flow, shifting channel morphology, aufeis obstructions, shallow channel depth, and debris in the channel. Intensive monitoring in natural channels can overcome some of these problems, but frequent assessment and recalibration of streamflow-stage relationships are necessary. Experience over 8 years indicates that in-channel structures designed to provide a stabilized stream-monitoring section (SSMS) proved beneficial to monitoring efforts during the ice-free season. The SSMS facilitated accurate gauging of the highest and lowest flows encountered during this period, provided a relatively stable foundation against streambank and channel erosion, and allowed passage of fish and the majority of debris and sediments. Functionality of the structures was markedly limited during ice-in conditions, but was improved with the addition of fitted canopies and propane heating systems. [ABSTRACT FROM AUTHOR]

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The analysis of ice jam formation processes of anthropogenic nature in the middle reach of the Lena River in 2001 and 2010 is carried out. Peculiarities of ice jam formation, springflood and inundation of villages in the Republic of Sakha (Yakut Republic) related to preventive actions are demonstrated. Intensity of variation of stages of spring ice jam flooding at the Lena River streamgage sites is considered. The degree of anthropogenic factor effect on ice jams through hydrological and hydromorphological processes is demonstrated. [ABSTRACT FROM AUTHOR]

Paleolimnological evidence from some Arctic lakes suggests that longer ice-free seasons have been experienced since the beginning of the nineteenth century. It has been inferred from some additional records that many Arctic lakes may have crossed an important ecological threshold as a result of recent warming. In the instrumental record, long-term trends exhibit increasingly later freeze-ups and earlier break-ups, closely corresponding to increasing air temperature trends, but with greater sensitivity at the more temperate latitudes. Broad spatial patterns in these trends are also related to major atmospheric circulation patterns. Future projections of lake ice indicate increasingly later freeze-ups and earlier break-ups, decreasing ice thickness, and changes in cover composition, particularly white-ice. For rivers, projected future decreases in south to north air-temperature gradients suggest that the severity of ice-jam flooding may be reduced but this could be mitigated by changes in the magnitude of spring snowmelt. [ABSTRACT FROM AUTHOR]

A hydrologically coupled flowband model of 'higher order' ice dynamics is used to explore perturbations in response to supraglacial water drainage and subglacial flooding. The subglacial drainage system includes interacting 'fast' and 'slow' drainage elements. The fast drainage system is assumed to be composed of ice-walled conduits and the slow system of a macroporous water sheet. Under high subglacial water pressures, flexure of the overlying ice is modelled using elastic beam theory. A regularized Coulomb friction law describes basal boundary conditions that enable hydrologically driven acceleration. We demonstrate the modelled interactions between hydrology and ice dynamics by means of three observationally inspired examples: (i) simulations of meltwater drainage at an Alpine-type glacier produce seasonal and diurnal variability, and exhibit drainage evolution characteristic of the so-called 'spring transition'; (ii) horizontal and vertical diurnal accelerations are modelled in response to summer meltwater input at a Greenlandtype outlet glacier; and (iii) short-lived perturbations to basal water pressure and ice-flow speed are modelled in response to the prescribed drainage of a supraglacial lake. Our model supports the suggestion that a channelized drainage system can form beneath the margins of the Greenland ice sheet, and may contribute to reducing the dynamic impact of floods derived from supraglacial lakes. [ABSTRACT FROM AUTHOR]

Catastrophic flooding in coastal areas is an ongoing problem that may be aggravated by projected sea-level rise. We present a method of flood protection called SIRGE (solid injection for raising ground elevation), where the ground surface is raised by injecting sediment-laden slurry into hydraulic fractures at shallow depths. The injection process is repeated at adjacent locations to create a network of sub-horizontal, overlapping injections of solid material (hydraulic fractures). We argue that injecting sediment over large lateral distances would cause a lasting surface uplift that scales with the thickness of injected sediment at depth. We support this concept by an analysis showing that, in contrast to hydraulic fractures in petroleum reservoirs, hydraulic fractures in soft, shallow formations would typically grow in the toughness-dominated regime. It appears that the SIRGE process could be implemented to lift ground elevations in places such as Venice or New Orleans. Experimental and geological examples indicate that hydraulic fractures of suitable orientation and size can be created in areas with appropriate in situ stresses. [ABSTRACT FROM AUTHOR]

1. Many rivers and streams experience pronounced ice dynamics caused by the formation of anchor and frazil ice, leading to flooding and disturbance of riparian and aquatic communities. However, the effects of dynamic ice conditions on riverine biota are little known. 2. We studied the formation of anchor ice in natural streams over 2 years and assessed the effects of anchor ice on riparian vegetation by comparing sites with frequent or abundant and little or no anchor ice formation. We also studied the direct impact of ice on riparian plants by experimentally creating ice in the riparian zone over three winters and by exposing plants of different life forms to −18 °C cold ice in the laboratory. 3. Riparian species richness per 1-m plot was higher at sites affected by anchor ice than at sites where anchor ice was absent or rare, whereas dominance was lower, suggesting that disturbance by ice enhances species richness. Species composition was more homogenous among plots at anchor ice sites. By experimentally creating riparian ice, we corroborated the comparative results, with species richness increasing in ice-treated plots compared to controls, irrespective of whether the sites showed natural anchor ice. 4. Because of human alterations of running waters, the natural effects of river ice on stream hydrology, geomorphology and ecology are little known. Global warming in northern streams is expected to lead to more dynamic ice conditions, offering new challenges for aquatic organisms and river management. Our results should stimulate new research, contributing to a better understanding of ecosystem function during winter. [ABSTRACT FROM AUTHOR]