Explore the vast range of titles available.

Exploring one of the greatest potential contributors to climate change-thawing permafrost-and the anxiety of extinction on an increasingly hostile planet Climate scientists point to permafrost as a \"ticking time bomb\" for the planet, and from the Arctic, apocalyptic narratives proliferate on the devastating effects permafrost thaw poses to human survival. In Earth, Ice, Bone, Blood , Charlotte Wrigley considers how permafrost-and its disappearance-redefines extinction to be a lack of continuity, both material and social, and something that affects not only life on earth but nonlife, too. Earth, Ice, Bone, Blood approaches the topic of thawing permafrost and the wild new economies and mitigation strategies forming in the far north through a study of the Sakha Republic, Russia's largest region, and its capital city Yakutsk, which is the coldest city in the world and built on permafrost. Wrigley examines people who are creating commerce out of thawing permafrost, including scientists wishing to recreate the prehistoric \"Mammoth steppe\" ecosystem by eventually rewilding resurrected woolly mammoths, Indigenous people who forage the tundra for exposed mammoth bodies to sell their tusks, and government officials hoping to keep their city standing as the ground collapses under it. Warming begets thawing begets economic activity- and as a result, permafrost becomes discontinuous, both as land and as a social category, in ways that have implications for the entire planet. Discontinuity, Wrigley shows, eventually evolves into extinction. Offering a new way of defining extinction through the concept of \"discontinuity,\" Earth, Ice, Bone, Blood presents a meditative and story-focused engagement with permafrost as more than just frozen ground.

Contains 10 papers resulting from a lecture series held in honour of Dr. J. Ross Mackay at the University of British Columbia during 1980-81. Papers delineate the challenge of field work in the harsh periglacial environment and the resulting difficulty in testing theory in the field with rigour. Topics covered include soil freezing, ice formation and thaw.

The influence of seasonally frozen ground (SFG) on water, energy, and solute fluxes is important in cold climate regions. The hydrological role of permafrost is now being actively researched, but the influence of SFG has received less attention. Intuitively, SFG restricts (snowmelt) infiltration, thereby enhancing surface runoff and decreasing soil water replenishment and groundwater recharge. However, the reported hydrological effects of SFG remain contradictory and appear to be highly site- and event-specific. There is a clear knowledge gap concerning under what physiographical and climate conditions SFG is more likely to influence hydrological fluxes. We addressed this knowledge gap by systematically reviewing published work examining the role of SFG in hydrological partitioning. We collected data on environmental variables influencing the SFG regime across different climates, land covers, and measurement scales, along with the main conclusion about the SFG influence on the studied hydrological flux. The compiled dataset allowed us to draw conclusions that extended beyond individual site investigations. Our key findings were: (a) an obvious hydrological influence of SFG at small-scale, but a more variable hydrological response with increasing scale of measurement, and (b) indication that cold climate with deep snow and forest land cover may be related to reduced importance of SFG in hydrological partitioning. It is thus increasingly important to understand the hydrological repercussions of SFG in a warming climate, where permafrost is transitioning to seasonally frozen conditions.

Understanding the change in soil hydraulic conductivity with temperature is key to predicting groundwater flow and solute transport in cold regions. The most commonly used models for hydraulic conductivity during freeze‒thaw cycles only consider the flow of capillary water in the soil and neglect water flowing along thin films around the particle surface. This paper proposed a new hydraulic conductivity model of frozen soil via the Clausius–Clapeyron equation based on an unsaturated soil hydraulic conductivity model over the entire moisture range using an analogy between freeze‒thaw and dry‒wet processes in soils. The new model used a single equation to describe the conductivity behaviors resulting from both capillary and adsorption forces, thus accounting for the effect of both capillary water and thin liquid film around soil. By comparison with other existing models, the results demonstrated that the new model is applicable to various types of soils and that the predicted hydraulic conductivity is in the highest agreement with the observed data, while reducing the root mean square error by 38.9% compared to the van Genuchten–Mualem model. Finally, our new model was validated with thermal–hydrological benchmark problem and laboratory experiment result. The benchmark results indicated that the advective heat transfer was more significant, and the phase change was completed earlier when considering both capillary and adsorption forces than when only considering capillary forces. Furthermore, the coupled flow–heat model with the new hydraulic conductivity expression replicated well the results from a laboratory column experiment. Key Points A new model accounting for both capillary and film water was developed to estimate soil hydraulic conductivity during freeze‒thaw process The new model based on physical mechanism has a simpler form and needs fewer parameters than existing model The new model was coupled with flow‒heat transport equations that successfully replicate the laboratory experiment data

Fresh submarine groundwater discharge (FSGD) can deliver significant fluxes of water and solutes from land to sea. In the Arctic, which accounts for ∼34% of coastlines globally, direct observations and knowledge of FSGD are scarce. Through integration of observations and process‐based models, we found that regardless of ice‐bonded permafrost depth at the shore, summer SGD flow dynamics along portions of the Beaufort Sea coast of Alaska are similar to those in lower latitudes. Calculated summer FSGD fluxes in the Arctic are generally higher relative to low latitudes. The FSGD organic carbon and nitrogen fluxes are likely larger than summer riverine input. The FSGD also has very high CO2 making it a potentially significant source of inorganic carbon. Thus, the biogeochemistry of Arctic coastal waters is potentially influenced by groundwater inputs during summer. These water and solute fluxes will likely increase as coastal permafrost across the Arctic thaws. Plain Language Summary Groundwater flows from land to sea, transporting freshwater, organic matter, nutrients, and other solutes that impact coastal ecosystems. However, along coasts of the rapidly‐warming Arctic, there is limited knowledge regarding how much fresh groundwater enters the ocean. Using field observations and numerical models, we show that groundwater flowing from tundra in northern coastal Alaska carries large amounts of freshwater, organic matter, and carbon dioxide to the Arctic lagoons during summer. These inputs are likely significant to coastal biogeochemical cycling and marine food webs. Groundwater discharge and the associated transport of dissolved materials are expected to increase due to longer periods of above‐zero temperatures that thaw frozen soils below the tundra. Key Points Summer fresh submarine groundwater discharge (FSGD) to the Alaskan Beaufort Sea is only 3%–7% of rivers but carries as much organic matter Summer FSGD delivers a median of 116 (interquartile range: 35–405) and 6 (2–21) kg/d per km dissolved organic carbon and nitrogen Fresh groundwater at the beach of Simpson Lagoon (SL) has a median PCO2 of ∼33,000 μatm implying substantial CO2 flux

Seasonally frozen ground regulates groundwater–surface water interactions in saline lake basins, altering water balance, salinity gradients, and biogeochemical processes. Using density‐dependent reactive transport simulations in the Badain Jaran Desert, China, we evaluate how freeze–thaw cycles affect groundwater flow, salt dynamics, and nutrient fluxes under varying salinity conditions. Our results show that seasonal freezing suppresses evaporation and enhances down‐gradient groundwater flow, shifting the fresh–saline interface lakeward and limiting inland saltwater intrusion. During the cold season, both fresh and recirculated groundwater to lakes increase, offsetting evaporative losses and enhancing lake water storage. Simultaneously, nutrient fluxes to lakes intensify, reflecting enhanced mobilization from groundwater reservoirs. These findings emphasize the hydrogeological and biogeochemical significance of seasonal freezing in saline basins.

Snowmelt is a major source of groundwater recharge in cold regions. Throughout many landscapes snowmelt occurs when the ground is still frozen; thus frozen soil processes play an important role in snowmelt routing, and, by extension, the timing and magnitude of recharge. This study investigated the vadose zone dynamics governing snowmelt infiltration and groundwater recharge at three grassland sites in the Canadian Prairies over the winter and spring of 2017. The region is characterized by numerous topographic depressions where the ponding of snowmelt runoff results in focused infiltration and recharge. Water balance estimates showed infiltration was the dominant sink (35 %–85 %) of snowmelt under uplands (i.e. areas outside of depressions), even when the ground was frozen, with soil moisture responses indicating flow through the frozen layer. The refreezing of infiltrated meltwater during winter melt events enhanced runoff generation in subsequent melt events. At one site, time lags of up to 3 d between snow cover depletion on uplands and ponding in depressions demonstrated the role of a shallow subsurface transmission pathway or interflow through frozen soil in routing snowmelt from uplands to depressions. At all sites, depression-focused infiltration and recharge began before complete ground thaw and a significant portion (45 %–100 %) occurred while the ground was partially frozen. Relatively rapid infiltration rates and non-sequential soil moisture and groundwater responses, observed prior to ground thaw, indicated preferential flow through frozen soils. The preferential flow dynamics are attributed to macropore networks within the grassland soils, which allow infiltrated meltwater to bypass portions of the frozen soil matrix and facilitate both the lateral transport of meltwater between topographic positions and groundwater recharge through frozen ground. Both of these flow paths may facilitate preferential mass transport to groundwater.

Mass transport in frozen ground is typically regarded slow. However, a highly permeable path can exist in frozen saline sand if the unfrozen water is interconnected at the pore scale. We therefore should consider when the unfrozen water is connected and how permeable can frozen saline sand be, yet there are few studies. This research utilizes in‐situ X‐ray CT to evaluate unfrozen water connectivity and permeability in frozen saline sand considering effects of initial salt content, temperature, freezing rate, and temperature gradient. Results show that higher initial salt content and/or temperature, both of which results in a higher unfrozen water content, easily maintains unfrozen water connectivity. Rapid freezing minimizes the brine expulsion and permits a higher unfrozen water content hence better connectivity. Permeability in frozen saline sand can be several orders higher than the typically reported value, highlighting the potential presence of rapid mass transport through the connected unfrozen water. Plain Language Summary Frozen aqueous sandy soils in nature often contain a lot of substances such as dissolved salts, gases, contaminants. Mass migration via unfrozen water is of vital importance to groundwater flow, greenhouse gas emission, even contaminated soil remediation. Permeability determination of unfrozen water is well‐studied in salt‐free soils. Our study shows there can be a highly conductive path in frozen saline sand when the unfrozen water is interconnected, even at a low unfrozen water saturation of 14%. The connectivity of unfrozen water remains at −20°C with an initial salt concentration similar to seawater. Rapid freezing causes better connectivity because less unfrozen water is squeezed out of the frozen sand during ice growth. Permeability in frozen saline sand can be several orders of magnitude higher than the typically reported value. These findings indicate that mass transport in frozen ground, via the connected unfrozen water, can be much more active than previously thought. Key Points Pore‐scale unfrozen water can be interconnected, enabling fast mass transport below 0°C when soil contains salt Rapid freezing enhances unfrozen water connectivity and permeability due to less and slower salt migration during freezing Permeability of frozen saline sand can be several orders of magnitude higher than that of salt‐free soil

Accurately characterizing groundwater level dynamics in seasonal frozen soil regions is of great significance for water resource management and ecosystem protection. To this end, this study proposes a new interpretable deep learning method to reveal the underlying causes of groundwater level dynamics on the basis of groundwater level simulation. Using the Songnen Plain in China as the study area and daily data from 138 monitoring wells, groundwater levels are simulated with an Long Short-Term Memory (LSTM) model, and the Expected Gradients (EG) method is employed to quantitatively identify the dominant factors and mechanisms of different groundwater level variation types.The results show that the LSTM model performs well on the test set, with the Nash-Sutcliffe Efficiency (NSE) exceeding 0.7 at 81.88 % of the monitoring sites, effectively capturing the temporal dynamics of groundwater levels. At the annual scale, three typical groundwater level variation types are identified: precipitation infiltration–evaporation type (29.0 %), precipitation infiltration–runoff type (18.1 %), and extraction type (52.9 %). Corresponding to the seasonal frozen-thaw period, groundwater level dynamics are classified into “V”-shaped (38.4 %), continuous decline (23.2 %), and continuous rise (38.4 %) types. Quantitative analysis using the EG method indicates that air temperature, precipitation, and snow thickness are the primary controlling factors of the “V”-shaped dynamics, reflecting the regulatory role of the frozen-thaw process on groundwater levels.When the initial groundwater level depth at the beginning of the freezing period is shallower than the sum of the frozen-thaw influence depth and the capillary rise height, a hydraulic connection is established between soil water and groundwater, resulting in typical “V”-shaped fluctuations. Conversely, when the depth exceeds this critical threshold, the frozen-thaw process cannot significantly influence the aquifer, and groundwater dynamics are mainly manifested as continuous rise or continuous decline, driven respectively by groundwater extraction and water level recovery following precipitation recharge. This study establishes an integrated framework of “simulation–classification–interpretation,” which not only improves the accuracy of groundwater level dynamic simulation and prediction but also provides new methods and perspectives for revealing the underlying mechanisms. The findings offer theoretical support and technical basis for regional groundwater resource management in cold regions.