Hillslope hydrology in upland permafrost regions (e.g., Alaska, High Canadian Arctic, Russia, Antarctica) is often dominated by water tracks, zones of enhanced soil moisture in unchannelized depressions that concentrate water flow downslope. Continued warming of permafrost regions may alter hydrologic cycling, leading to increased frequency of extreme hydrologic events like drought and flooding and modification to biogeochemical cycles. It is therefore imperative to parametrize the role of water tracks in the hydrology of the permafrost environments. In this study, we synthesize uniting and distinguishing hydrologic characteristics of water tracks across permafrost regions and then examine water track seasonality, occurrence, and contribution to the permafrost hydrologic cycle using field observation, remote sensing, and numerical modeling for permafrost hillslopes on the North Slope of Alaska, USA. Results suggest that water tracks occur across climate and hydrologically disparate permafrost landscapes but have ubiquitous surface wetness, vegetation, and snow duration patterns that can be identified remotely using 3-m resolution PlanetScope imagery. Detailed field investigation from 2022-2024 of three study sites with ~20 water tracks and ~15 gullies suggests that water tracks are hydrologically distinct from larger, variably channelized hillslope features and require more precipitation and time to initiate discharge following rainfall events. Across these study sites, concentration-discharge relationships reveal that water tracks can exhibit drastically different dynamics of particulate and dissolved organic carbon export based on landscape attributes. Young water fraction analysis found that in 2023, 24–78% of runoff from the study sites was young water less than 35 days old during the observed summer thaw season, and model-estimated young water fraction increased by two-fold when factoring in the fall shoulder season. Geophysical investigations indicate the presence of buried ice wedges on the margins of studied water tracks, supporting the idea that water tracks may form from the coalesced drainage of patterned ground. Over time, these drainage patterns likely evolve and widen into present-day water tracks that act as flow conduits and discharge liquid water into the fall shoulder season after the adjacent hillslope has frozen. Our ongoing analysis explores how water track flow seasonality may influence observed ground collapse and mediate or enhance the permafrost-carbon feedback.
How to cite: Evans, S., Godsey, S., Del Vecchio, J., Harris, R., Frei, R., Yokeley, B., Mohammed, A., Chew, C., Cusack, K., Ferm, E., Hatch, K., Matejowsky, G., Polk, R., and Culha, C.: The role of water tracks in permafrost hillslope hydrology, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7345, https://doi.org/10.5194/egusphere-egu25-7345, 2025.
Increasing temperatures are rapidly changing the Arctic ecosystem. Yet, we are missing a predictive understanding of the interactions within the bedrock to atmosphere column that are driving ecosystem evolution and carbon-climate feedback. A critical knowledge gap within these systems are the dynamics of surface water - groundwater interactions, and infiltration and groundwater flow processes, which drive permafrost thaw and biogeochemical processes. Geophysical techniques have been shown to be a valuable tool to assess the intermediate depths (1 - 10’s of m) that are particularly important to understanding the impact of climate change on permafrost thaw and related hydrological dynamics. In this study we highlight how automated geophysical monitoring can reveal rapid and heterogeneous changes in thermohydrological conditions that are characteristic for discontinuous permafrost systems.
Given the remote environment, we will first introduce the field setup that allowed us to acquire continuous data for over 4 years. We present the variations in ground conditions and associated changes in data quality, which highlight the expected poor data during the winter season, once the ground is frozen. Focusing on the monitoring data, we show that summer rainfall events drive distinct infiltration patterns at locations of a deep active layer. Snowmelt and rainfall events drive considerable variations in groundwater level, which are confirmed by borehole information and driven by flow below the permafrost. Data acquired in early winter shows spatially heterogeneous ground freezing, mostly controlled by the microtopography. These observations provide novel information that will help in better understanding the complex hydrological processes taking place in discontinuous permafrost environments, and will eventually lead to better parameterization of ecosystem models.
How to cite: Uhlemann, S., Wang, C., Wielandt, S., Fiolleau, S., Ulrich, C., Shirley, I., and Dafflon, B.: Geophysical monitoring of hydrological dynamics within a discontinuous permafrost environment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-12367, https://doi.org/10.5194/egusphere-egu25-12367, 2025.
Snow represents the single largest water source in most regions of the Arctic, but few investigations of snowmelt infiltration into frozen and unfrozen soils have been conducted in this region. To investigate the infiltration of snowmelt into tundra soils, we collected vertical soil cores before snowmelt (mid-April), mid-snowmelt (mid-May), and after snowmelt (early June) from Blæsedalen, Qeqertarsuaq (Disko Island), Greenland at sites varying in soil properties, snow depth, and landscape position. Soil cores were separated into sections, after which we measured bulk density, gravimetric water content (GWC), soil texture, organic content, and the water isotope composition of the soil water of each soil core section. Water isotope composition was also measured for vertically-integrated snowpack samples at each sampling location, so that we could attribute any changes in soil moisture to infiltrating snowmelt runoff. Post-snowmelt cores were separated into frozen and unfrozen sections, to compare the infiltration of snowmelt into frozen and unfrozen soil.
Initial results show that the GWC varied widely from 0.25 – 43 among soil core sections, the extremes reflecting differences between dense loamy soils with little organic material and porous, saturated peat. After snowmelt, soil water in the top 0 – 20 cm of the soil column experienced a significant shift towards the isotope composition of snow, regardless of whether the soil was frozen or not. There was little change in soil water isotope composition mid-snowmelt. Changes in GWC mirrored these results: the average GWC increased by 46% post-snowmelt in soil core sections from the top 20 cm of the soil column, with no significant change in GWC mid-snowmelt. Interestingly, frozen soils from the top 20 cm of the soil column experienced a larger increase in GWC than unfrozen soils, suggesting that frozen soils did not hinder the ability of snowmelt to infiltrate into soil. Below 20 centimetres in the soil column, no significant changes in water isotope composition or GWC were observed. We also observed no clear link between the snow water equivalent of the overlying snowpack, and the increase in GWC after snowmelt.
The landscape of Qeqertarsuaq is abundant with large snow drifts that last well into July, which could provide a significant source of water for soils downslope of drifts. We were unable to test this hypothesis because an exceptionally late snowmelt meant we collected post-snowmelt soil cores immediately after soils became snow-free, giving little time for lateral runoff from melting snow drifts to travel downslope. However, we did observe that peat soils, which develop in wet areas, were often present immediately downslope from large snow drifts, while only thin organic layers combined with other vegetation covers were present upslope of snow drifts. With this study, we have been able to provide the first insights into snowmelt infiltration on Qeqertarsuaq, and how it may be playing a role in the spatial variability of soil development.
How to cite: Wilcox, E. J., Plötz, H., Kaufmann, O., and Kutzbach, L.: Investigating snowmelt infiltration into tundra soils on Qeqertarsuaq (Disko Island), Greenland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-16642, https://doi.org/10.5194/egusphere-egu25-16642, 2025.
A fundamental research question of periglacial geomorphology is whether and how ground ice interacts with surface water flow to change grain-scale sediment transport dynamics, and how those processes translate to the landscape-scale, potentially changing the timing and intensity of erosion events. Polar deserts in the Canadian High Arctic serve as ideal field laboratories to isolate the effects of ground ice on particle transport due to a lack of vegetation and by being largely undisturbed since the last glacial maximum.
During the Summer 2024 field season at the Flying Squirrel polygon field on Devon Island, we observed a complex of pools interconnected by channelised polygon troughs and relatively steeper relict gravel deposits, as well as evidence of recent transport of gravel- and sand-sized particles. However, despite visiting during a storm event, we did not observe active transport and only limited surface water run-off. As such, the timing and magnitude(s) of the flow events that caused the gravel deposits are unclear, nor do we know the thermal state of the bed during the time of transport.
To investigate this research gap, we conducted flume experiments with an initially frozen bed under rarefied transport conditions to investigate at what thermal state sediment transport is favoured and compare the bed behaviour to unfrozen experiments. Particle flux is maximised at the start of the frozen experiments before decaying to an approximate steady-state background flux similar to the unfrozen experiments, following a power law with the relationship . At early stages of the frozen experiments, hydraulic jumps develop in concert with variations of the local thaw depth, which result in enhanced particle entrainment and relatively rapid thawing downstream, as the hydraulic jumps migrate upstream. Beneath hydraulic jumps, we observe forced injections of water into the partially-frozen bed, which can spread laterally along an evolving thaw front. Depending on the thaw front depth, the combined effects of locally-intensified melting, increased pore pressure and mechanical disruption of the bed can enhance particle entrainment locally and increase the overall erosion rate compared to unfrozen experiments. Enhanced rates of particle entrainment continue until hydraulic jump activity diminishes and the injected surface water no longer penetrates to the thaw front. Accordingly, we develop a maximum injection depth, which is strongly dependent on the local permeability, as well as the jump height.
Our experimental results show that the thermal state of the bed can have a strong influence on the local entrainment rate at the grain-scale with entrainment being promoted at a shallow thaw depth. We hypothesise that this sensitivity also translates to the landscape-scale, where all water has to travel as overland flow when the active layer is thin, whereas much of the water supply can be compensated as subsurface flow late in the summer, minimising particle entrainment. This could explain the lack of active erosion at the Flying Squirrel polygon field during the late summer when the active layer was approximately 1m deep.
How to cite: Eschenfelder, J., Chartrand, S., Jellinek, M., and Culha, C.: Where, when, and why do frozen landscapes erode faster than unfrozen ones?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7036, https://doi.org/10.5194/egusphere-egu25-7036, 2025.
The Arctic is rapidly changing due to increasing temperatures and hydrologic intensification. The Arctic is also data-limited, necessitating the development of new tools to document and quantify ecosystem responses to these changes. Some of the hardest changes to observe are in the subsurface, including thaw depth conditions in continuous permafrost regions. Thaw depth is dynamic across the thaw season as well as on a longer, interannual scale as the Arctic warms and permafrost degrades. Measuring thaw depth often requires intensive sampling or remote sensing capabilities that have spatiotemporal limitations; therefore, little is known about complex subsurface dynamics and how they will affect Arctic ecosystems in the future. Often, surface waters are our best proxy for subsurface dynamics, as streams integrate signals from the landscape as water travels through the hillslope subsurface. In permafrost systems, water and solute flowpaths are governed by thaw depth dynamics, and flowpaths through variable soil chemical conditions govern downgradient stream water chemistry. Hence, thaw depth may be reflected in stream chemistry. Prior work looking at long-term stream chemistry data suggests there are multiple soil-derived solutes that are tracers of thaw in Arctic catchments, and some increase with thaw over decadal timescales. Building on this work, we want to know if this stream chemical tracer approach works at different spatiotemporal scales, such as within a thaw season as thaw depth increases, and across catchments with varying characteristics (e.g., slope, vegetation). We hypothesize that with more frequent stream chemistry observations across a thaw season, we will also see these soil chemical tracers signal seasonal thaw, and that the signal’s strength will vary depending on catchment characteristics.
To determine whether we can use chemical tracers as proxies of thaw depth across a diverse set of catchments on Alaska’s North Slope, we sampled the stream outlets of three catchments underlain by continuous permafrost across three thaw seasons (2021-2023). We measured continuous discharge and analyzed nine different ions including Ca, Fe, Na, and S to identify seasonal patterns in stream chemistry, as these element concentrations change with soil depth in this region. As discharge could impact instream solute concentrations, we also analyzed concentration-discharge relationships to determine whether discharge was significantly influencing concentration and reducing the tracer’s utility in signalling thaw depth.
We found that the efficacy of the stream tracer approach to detect thaw on a seasonal scale is seemingly dependent on catchment characteristics, as we suspected. Our two low-gradient tundra systems did not show consistent patterns in the tracers; however, we saw patterns in multiple tracers in our high-gradient alpine catchment. In our low-gradient catchments, solute concentration was often impacted by discharge, making it difficult to assess the impact of thaw depth on chemistry. Overall, understanding thaw depth dynamics will become increasingly important with climate change, necessitating the development of tools to document and predict thaw depth at a range of scales. Here, we find that stream tracers of thaw at the catchment scale show promise, but it is much more nuanced and complex than preliminary studies indicated.
How to cite: Grose, A., Zarnetske, J., Grewal, A., Rec, A., O'Donnell, J., Shogren, A., Abbott, B., and Bowden, B.: Does stream chemistry reflect thaw depth on a seasonal scale across Alaskan Arctic permafrost catchments?, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14348, https://doi.org/10.5194/egusphere-egu25-14348, 2025.
Beavers (Castor canadensis) are rapidly colonizing the North American Arctic, transforming aquatic and riparian tundra ecosystems. Arctic tundra may respond differently than temperate regions to beaver engineering due to the presence of permafrost and the paucity of unfrozen water during winter. Here, we provide a detailed investigation of 11 beaver pond complexes across a climatic gradient in Arctic Alaska, addressing questions about the permafrost setting surrounding ponds, the influence of groundwater inputs on beaver colonization and resulting ponds, and the change in surface water and aquatic overwintering habitat. Using field measurements, in-situ dataloggers, and remote sensing, we evaluate permafrost, water quality, pond ice phenology, and physical characteristics of impoundments, and place our findings in the context of pond age, local climate, permafrost setting, and the presence of perennial groundwater inputs. We show beavers are accelerating the effects of climate change by thawing permafrost adjacent to ponds and increasing liquid water during winter. Beavers often exploited groundwater upwellings in discontinuous permafrost, and summertime water temperatures at groundwater-fed (GW) beaver ponds were roughly 5°C lower than sites lacking perennial groundwater inputs (NGW). Late winter liquid water was present at all but a recently abandoned pond complex, although liquid water below seasonal ice cover was shallow (0–82 cm at GW ponds; 0–15 cm at NGW ponds) and ice was thick (median: 83 cm at GW ponds; 120 cm at NGW ponds). Water was less acidic at GW than NGW sites and had higher specific electrical conductivity and more dissolved oxygen. We estimated 3.2 dams/km of stream at sites on the recently-colonized (last ~10 years) Baldwin Peninsula and 8.0 dams/km on the Seward Peninsula, where beavers have been present longer (~20+ years) and groundwater-surface water connectivity is more common. Our study highlights the importance of climatic and physiographic context, especially permafrost presence and groundwater inputs, in determining the characteristics of the Arctic beaver pond environment. As beavers continue their expansion into tundra regions, these characteristics will describe the future of aquatic and riparian Arctic ecosystems.
How to cite: Tape, K., Glass, T., Jones, B., Rangel, R., and Zavoico, S.: Permafrost ecohydrology of beaver ponds in Arctic Alaska, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7078, https://doi.org/10.5194/egusphere-egu25-7078, 2025.
Quantitative simulation of permafrost dynamics, both under current climatic conditions and future climate change scenarios, presents significant challenges. These include, but are not limited to, long computation times, the construction of accurate surface boundary conditions, and the estimation of transfer properties for soil, organic matter, and vegetation layers that cover (sub-)Arctic regions. The challenges of permafrost simulation are exemplified by the broad range of scenarios for near-surface permafrost evolution under climate change, as indicated by climate models. These range from minimal changes by 2100 under the SSP1-2.6 scenario to complete disappearance as early as 2080 under the SSP5-8.5 scenario (IPCC, 2022). The HiPerBorea project (hiperborea.omp.eu) has developed and applied innovative methodologies to address these challenges. This includes leveraging high-performance computing (Orgogozo et al., 2023; Xavier et al., 2024) and experimental characterizations with X-ray computed tomography (Cazaurang et al., 2023, Cazaurang, 2023). Results will be presented for case studies at two environmental monitoring sites in Siberia: a continuous permafrost area with boreal forest in Central Siberia and a discontinuous permafrost-bearing area with peatlands in Western Siberia. For instance, in the Central Siberia study site, a 40 km2 headwater catchment, projected increase of the active layer depth by 2100 under scenario SSP5-8.5 corresponds to a ∼350 km southward shift in current climatic conditions (Xavier et al., 2024). As another example of results, the hydraulic conductivity of the tens of cm thick moss cover of the Western Siberia site has been shown to be higher than previously reported in the literature (Cazaurang et al., 2023). The associated applications and perspectives for further development will also be discussed.
Intergovernmental Panel on Climate Change (IPCC), 2022. Cambridge University Press. https://doi.org/10.1017/9781009157964
Cazaurang S. et al., 2023. Hydrol. Earth Syst. Sci., 27, 431–451, 2023 https://doi.org/10.5194/hess-27-431-2023
Cazaurang S., 2023. PhD thesis of Toulouse INP.
Orgogozo L. et al., 2023. Computer Physics Communications 282 (2023) 108541 https://doi.org/10.1016/j.cpc.2022.108541
Xavier T. et al., 2024. The Cryosphere, 18, 5865–5885, https://doi.org/10.5194/tc-18-5865-2024
How to cite: Laurent, O., Thibault, X., Anatoly, P., Esteban, A.-G., Simon, G., Simon, C., Manuel, M., Michel, Q., Stéphane, A., Liudmila, S., Antonin, M., Emmanuel, M., Sergey, L., Artem, L., and Oleg, P.: Numerical and experimental studies of coupled heat and water transfers in permafrost-bearing continental surfaces: advances of the HiPerBorea project, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6315, https://doi.org/10.5194/egusphere-egu25-6315, 2025.
In the northern periphery, acceleration of hydrological cycle due to global warming include an increase in frequency and intensity of extreme events. Among the consequences of these extreme events in wintertime one can observe an increase of damage to the built environment and natural landscape in the form of fractures. These result from changes in the rain/snow relationship, snowmelt and freeze-thaw cycles. Sometimes these fractures initiate and develop in a manner accompanied by a sudden release of (seismic) energy, commonly known as frost quakes.
Our objective is to study soil freezing, cryosuction phenomena and its relation to occurrence of frost quakes in northern periphery in Finland in the city of Sodankylä. We build a 1D hydrological model that accounts for snow accumulation and melt and heat transfer into to soil and liquid/gas/ice content in subsurface. The hydrological 1D model was calibrated against the measured soil water content and temperature at five different depths in soil during the wintertime 2023/2024. The aim of this study is to understand the ice lens formation, cryosuction process, change in the air and the soil temperature and how these are connected to frost quake occurrence. During the winter 2023/2024 several frost quakes occurred in Sodankylä that are related to rapid change in air temperature, soil temperature and change in cryosuction pressure.
How to cite: Okkonen, J. and Remes, J.: Thermo-hydrological modeling of ground freezing and its relations to occurrence of frost quakes in northern Finland, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14966, https://doi.org/10.5194/egusphere-egu25-14966, 2025.
The Arctic is warming two to four times faster than the global average, leading to permafrost thaw and changes in groundwater flow due to alterations in the timing and the depth of the active layer. These changes may lead to previously immobilized contaminants being transported through the active layer; these new pathways for contaminant migration raises concerns, given that there are an estimated 13,000 to 20,000 industrially contaminated sites, many of which remain unremediated. Understanding how the mobilization of contaminants in a high-Arctic settings is crucial to understand to ensure the safety of northern community water resources. The objective of our research is to assess how changing active layer dynamics affects the transport behavior of contaminants in a continuous permafrost hillslope environment via a numerical modeling approach.
For this study, we use SUTRA-solice, a version of the US Geological Survey SUTRA model that incorporates mass transport processes with groundwater flow and energy transport with dynamic freeze-thaw processes. We simulate a 280 m long, two-dimensional transect that terminates in a lake. The site has an unconsolidated overburden of 2 m over crystalline bedrock and contains continuous permafrost. The model results focus on seasonal contaminant migration through the active layer and discharge into the lake via groundwater flux. By untangling the relationship between climate change processes (increased temperature, precipitation, etc.) alongside contaminants migration, we are able to understand how constituent migration through evolving active layers will impact down-slope water sources.
How to cite: Stribling, S., Basijokaite, R., Mohammed, A., Lamontagne-Hallé, P., and McKenzie, J.: Climate Change Impacts on Contaminant Transport and Active Layer Groundwater Dynamics in the High Arctic, Canada, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14360, https://doi.org/10.5194/egusphere-egu25-14360, 2025.
Safety assessments of high-level radioactive waste repositories require the long-term performance assessment of the repository system over a 1-million-year evaluation period. This timeframe encompasses approximately ten glacial-interglacial cycles in northern lattitudes, during which processes such as glaciation, permafrost formation, and thawing may impose significant mechanical and thermal stresses on the geological barrier. These environmental dynamics will alter the parameters of the overburden rock. Although it is not expected that this reduces the safety of the repository, it is still required to have a good understanding of the respective processes to be able to obtain an integrated safety assessment.
To investigate the effects of freeze-thaw cycles on geological and engineered barriers, in this study both consolidated materials (e.g., sandstone, granite, and claystone) and unconsolidated materials (e.g., clay and sand) will be tested. For the measurements an enhanced triaxial experimental system is used. This system allows to observe volume changes induced by freeze-thaw cycles under controlled confining pressure conditions. The experimental design captures the relationships between freeze-thaw-induced volume changes and key factors, including material properties, temperature variations, the number of cycles, and saturation.
The correlation models obtained from the experiments will be used for the validation and refinement of three-dimensional finite element models, and the experimental results will be reproduced and to extend the findings to broader spatial scales through numerical simulations.
At the hydrogeological scale, a comprehensive catchment model will be applied to evaluate the interactions between glacial cycles, regional groundwater flow mechanisms, and their cumulative impact on the safety assessment of high-level radioactive waste repositories. This study provides critical insights into the long-term stability of geological barriers under cyclical freeze-thaw conditions and offers a robust foundation for advanced repository safety assessments in glacial-interglacial scenarios.
How to cite: Sheng, H., Schedel, M., Pham, H., Schüth, C., Sass, I., and Rühaak, W.: Volume change due to thawing/freezing processes in the context of nuclear waste repository safety assessment, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-3108, https://doi.org/10.5194/egusphere-egu25-3108, 2025.
The warming climate in the Arctic terrestrial regions resulted in earlier snowmelt in spring, deeper active layer thickness, and larger rainfall in the summer season. These changes have driven the changes to higher summer evapotranspiration and increased river discharge in autumn and the cold season, evidently indicating shifts in the seasonal hydrological processes. Very few studies have provided quantitative assessments of changes in the seasonal hydrological processes, including contributions of the seasonal source waters (i.e., snow, rain, and ground ice water) to the changes. A land surface model, coupled with a tracer scheme tracking along the flow route of individual source waters in the hydrological processes, was used to assess the changes in the pan-Arctic water budget for the past four decades. The model results showed that summer-sourced rainwater contributed to the increases in summer evapotranspiration and autumnal river discharge during the study period. In addition, the autumn rainwater was connected to the peak river discharge and evapotranspiration in the spring of the following year, suggesting a soil-water memory effect that the autumnal rainfall, stored as frozen soil water during the winter season was reactivated at the spring season with soil thawing. The permafrost degradation-induced ground ice meltwater showed a weak relationship with the increasing river discharge. This model study provides a possibility to distinguish quantitatively the changes in the Arctic ecohydrological processes, resulting from the future climate warming.
How to cite: Park, H. and Suzuki, K.: Influences of seasonal source waters on changing Arctic hydrology, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-7545, https://doi.org/10.5194/egusphere-egu25-7545, 2025.
Groundwater and surface water combine to form a single water resource in Artic and Subarctic regions. Groundwater is a critical for providing water for streams, maintaining ecological systems, and as a water resource. Across Alaska, the Yukon, Northwest Territories, and Nunavut almost 50% of the population rely on groundwater for their drinking water supply, including more than 97% of Yukoners. There are many concerns about Northern groundwater vulnerability due to climate change as arctic warming is two to four times the global average rate, accompanied with increasing precipitation rates.
Detecting change in Arctic cryohydrogeologic systems is difficult due to a lack of groundwater observation data. We present results from government groundwater monitoring programs in Alaska and the Yukon, including initial results from the Yukon Observation Well Network (YOWN), a unique observatory for monitoring climate change impacts on northern groundwater. The YOWN was adapted from a small Yukon-wide observation program that started with one observation well at the outlet of the Wolf Creek Research Basin in 2001. The network is rapidly growing with now more than 75 wells between the latitudes of 60.04º and 67.57º, with continuous water level observations and periodic water quality measurements.
Observation well results show that groundwater levels follow seasonal and local climate trends, particularly for snow melt. Broadly, the wells show that groundwater recharge is dominated by snow melt, and most wells do not show a seasonal rise in water levels in the fall, as is seen at lower latitudes. The observations show that the snowpack from an antecedent winter is the primary control on a subsequent year’s groundwater levels. Many wells also show multi-year increases in both winter and summer water levels. This ‘groundwater staircase’ demonstrate that some cryohydrogeology systems are affected by multiyear climatic controls across the region. The results have important implications for managing water resource vulnerability and detecting climate change impacts on Northern groundwater systems.
How to cite: McKenzie, J., Mulligan, B., and Stribling, S.: Subsurface hydrology in Arctic and Subarctic Regions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-14997, https://doi.org/10.5194/egusphere-egu25-14997, 2025.
The Arctic and Subarctic regions are experiencing faster warming than the global average. This warming already increases the seasonal thaw depth of soils in permafrost areas, as evidenced by monitoring across the Arctic region. Accompanied by changes in the ground surface, diminishing permafrost could increase hydrological connectivity and groundwater flow, which in turn could influence the rate of thawing via impacts on soil thermal properties and advective transport of heat with groundwater. Yet, our basic understanding of the factors that drive groundwater dynamics in high-latitude landscapes remains limited. Here we report on a preliminary study in Abisko, Swedish sub-arctic that explores the meteorological factors that influence groundwater conditions. Standardized Precipitation Index (SPI), Standardized Groundwater Index (SGI), and Standardized Precipitation-Evaporation Index (SPEI) were used to calculate anomalies in precipitation and groundwater conditions from 1991-2018. These indexes indicate the dryness and wetness of a region. The SGI, SPI, and SPEI were computed using observational data from the Swedish Geological Survey, Swedish Meteorological and Hydrological Institute, and the output of LISFLOOD models. PET was calculated using the Thornthwaite method. The result shows that the observation-based SGI exhibits a strong correlation with the SPI-x, when more than six months of precipitation data are accumulated, demonstrating an R-value of 0.64 for SPI-6 and 0.58 for SPI-12. This indicates a time lag in groundwater response to precipitation, likely due to seasonal thaw cycles. Evapotranspiration also shows as an important factor although in cold regions where the correlation between SGI and SPEI-3 and SPEI-6 are 0.56 and 0.52, respectively. Evapotranspiration likely reduced the impact of precipitation based on this standardized index. Thornthwaite method might underestimate the PET value, thus, calculation with other methods might be beneficial. Although the model bias for SGI was low (0.14), the model has inadequate representation relative to observations, with a Mean Absolute Error (MAE) of 0.85 and a coefficient of determination (R²) of 0.15. The complexity of hydrology in this region results in poor model fit, which indicates that other than meteorological factors, snow depth, ground surface condition, and adjacent surface water potentially influence groundwater dynamics. Future research will examine those factors on groundwater interactions in sub-arctic climates with surrounding surface water to improve our understanding of groundwater dynamics in this region via observation and remote sensing techniques.
How to cite: Syaehuddin, W. A., Sutanto, S. J., Sponseller, R., and Sjöberg, Y.: Groundwater Dynamics in the Swedish Sub-Arctic Region: Inferring from Standardized Index Based on Model and Observation Data, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-6233, https://doi.org/10.5194/egusphere-egu25-6233, 2025.
As the acceleration of global warming and humidification continues, the thickness of the active layer in permafrost regions is increasing, and the permafrost table is significantly lowering. The melting of permafrost has triggered a series of engineering problems, such as uneven settlement and deformation of roads, tilting, cracking, and even collapse of buildings. Therefore, accurately detecting the distribution of ice content in the subsurface of permafrost regions is of great significance for the construction of new permafrost projects and the disaster prevention of existing projects. Currently, the detection of ice content in permafrost primarily relies on high-density electrical exploration, which is based on the resistivity differences between soil and ice. However, due to the small electrical differences between permafrost with varying ice content, existing methods can only roughly determine the position of the permafrost upper limit, and it is difficult to accurately determine the thickness of the active layer and the specific ice content of the permafrost. To address this issue, this paper proposes a high-density electrical inversion method based on deep neural networks. By incorporating physical laws into the inversion process, the inversion accuracy of high-density electrical exploration in permafrost areas is significantly improved. In field exploration experiments conducted in the Qinghai-Tibet Plateau, the inversion results of this method were highly consistent with the results of borehole measurements, validating its effectiveness.
Keywords: permafrost, deep learning,electrical exploration
How to cite: Cao, S. and Zhang, D.: Deep Learning-Based Electrical Exploration for High-Precision Permafrost Inversion Method , EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-17729, https://doi.org/10.5194/egusphere-egu25-17729, 2025.
The seasonal dynamic of the suprapermafrost groundwater significantly affects the runoff generation and confluence in permafrost basins and is a leading issue that must urgently be addressed in hydrological research in cold and alpine regions. In this study, the seasonal dynamic process of the suprapermafrost groundwater level (SGL), vertical gradient changes of soil temperature (ST), moisture content in the active layer (AL), and river level changes were analyzed at four permafrost watersheds in the Qinghai–Tibet Plateau using comparative analysis and the nonlinear correlation evaluation method. The impact of freeze–thaw processes on seasonal SGL and the links between SGL and surface runoff were also investigated. The SGL process in a hydrological year can be divided into four periods: (A) a rapid falling period (October–middle November), (B) a stable low-water period (late November–May), (C) a rapid rising period (approximately June), and (D) a stable high-water period (July–September), which synchronously respond to seasonal variations in soil moisture and temperature in the AL. The characteristics and causes of SGL changes significantly varied during these four periods. The freeze–thaw process of the AL regulated SGL and surface runoff in permafrost watersheds. During period A, with rapid AL freezing, the ST had a dominant impact on the SGL; in period B, the AL was entirely frozen due to the stably low ST, while the SGL dropped to the lowest level with small changes. During period C, ST in the deep soil layers of AL (below 50 cm depth) significantly impacted the SGL (nonlinear correlation coefficient R2>0.74, P <0.05), whereas the SGL change in the shallow soil layer (0–50 cm depth) showedacloserassociation with soil moisture content. Rainfall was the major cause for the stable high SGL during period D. In addition, the SGLs in periods C and D were closely linked to the retreat and flood processes of river runoff. The SGL contributed approximately 57.0–65.8% of the river runoff changes in period D. These findings will help to facilitate future hydrological research in the permafrost basins and the development and utilization of water resources in cold and alpine regions.
How to cite: Qin, J. and Ding, Y.: Links between seasonal suprapermafrost groundwater, the hydrothermal change of the active layer, and river runoff in alpine permafrost watersheds, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-1552, https://doi.org/10.5194/egusphere-egu25-1552, 2025.
The study of groundwater freezing in fractures of crystalline rock is essential for understanding subsurface flow dynamics during ice age events. Freezing significantly alters the hydraulic permeability, which is particularly relevant for the safety assessment of a nuclear waste repository in crystalline rock. German law mandates safety evaluations for at least one million years, during which multiple ice ages are likely to occur and potentially causing freezing in fractures.
Due to the challenges of directly observing fresh water freezing in real rock, an alternative measurement approach using 3D scanning of fracture surfaces and subsequently 3D printing of fracture replicas was investigated. Surface data of natural fractures in granitic rock were captured with a high-resolution 3D scanner. After post-processing the datasets, a digital model of a test cell for flow tests in the lab including the fracture surfaces was created and printed. The cell was fabricated using a high-resolution Formlabs Form 3 printer with a clear resin. This material was chosen for its transparency and durability under low temperatures.
The printed test cell was placed in a climate chamber and equilibrated to a temperature of- 5°C. Freezing processes were monitored by an industrial camera using a 0.05% methylene blue solution, which changes color from dark blue to transparent during crystallization. Initial tests did not account for the expansion of the tracer solution during freezing which proved to occur in significant proportions separating the two fracture halves. In subsequent tests, this shift was restricted using a metal frame. A series of scenarios with varying temperatures and inflow rates were tested.
It turned out that both, the freezing pattern and the point where freezing originated, varied between individual experiments. Occasionally, freezing even began in the tubing, causing blockages and leading to premature termination of the experiments.
To analyze the images, threshold segmentation was applied to the digital photographs using Matlab. This resulted in a binary array that represents the state of the methylene blue solution for each pixel. Each entry in this array corresponds to an area of approximately 150 by 150 µm. Although the image processing technique is advanced, the sensitive test setup was still affected by external disturbances. These disturbances resulted in spikes and other artifacts in the images. While some of these issues were mitigated, it was not possible to eliminate all disturbances and achieve a completely undisturbed test.
How to cite: Kröhn, M.: Observing fresh water freezing in highly detailed 3D printed fracture replicas, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-10103, https://doi.org/10.5194/egusphere-egu25-10103, 2025.
Cryo-hydrogeological behaviour of groundwater flow through a saturated variable-aperture fracture is numerically simulated in three dimensions. Simulations are carried out using the finite element Heatflow/Smoker model for groundwater flow and heat transport with freeze/thaw and latent heat. We test the effects of fracture aperture distributions and thermo-hydraulic conditions on fluid flow and heat transport through a thawing fracture within an initially frozen porous matrix, and evaluate the relationships between the pre-defined (input) local-scale freezing functions (FFs) and the derived mean (fracture-averaged) freezing functions. Simulations are carried out on a 1x1x0.4 m3 porous medium block with a single variable-aperture horizontal fracture under variable temperature conditions and hydrological forcings, and fracture statistical variables. Results show that hydraulic conditions play a more important role than fracture geometry in determining how fractures open and thaw as heat flows through the system. Derived mean freezing functions differ from the input local-scale freezing functions because of a complex interaction among several factors including heat loss to the matrix, the influence of the hydraulic gradient on fluid flow, and variations in fracture aperture. These elements combine in complex ways, affecting how temperature and unfrozen water content evolve in space and time. Nevertheless, for mean negative temperatures, the simulated mean FFs for a fracture tend to be similar to the local-scale FFs, suggesting applicability to larger fracture systems which assume metre-scale uniform apertures. Under sufficient hydraulic gradients, variable aperture fields are also crucial as they enable preferential flow which helps keep the system open, while with an equivalent mean aperture, the lack of variability results in more uniform cooling and freezing, causing the system to close more rapidly. The results also underscore the pivotal role of the frozen matrix as a thermal sink especially in scenarios characterized by extensive cooling and fracture closure, reducing advective heat transport through the fracture, and steering the system toward a conduction-dominated regime. The numerical simulations enhance our understanding of internal flow dynamics during freezing and thawing in variable-aperture fractures, providing valuable insights for experimental investigations and larger-scale numerical simulations.
How to cite: Malmir, M., Molson, J., and Therrien, R.: Cryo-Hydrogeological Dynamics of a Variable-Aperture Fracture Under Freeze-Thaw Conditions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-683, https://doi.org/10.5194/egusphere-egu25-683, 2025.
Groundwater discharge age is a useful metric for retracing flowpaths, and is essential to estimate an aquifer’s renewability and vulnerability. As permafrost thaws in cold regions, supra-permafrost aquifers will expand, which will cause new pathways to develop and potentially alter the spatiotemporal distribution, quantity, and age of groundwater discharge. While numerous modelling studies have analysed the shift in groundwater discharge magnitude and patterns in permafrost regions, the associated changes to groundwater age have been largely overlooked. Using heat-transfer and solute-transport numerical models for cold regions, we recreated various archetypical conceptual models of permafrost-groundwater distributions. The object is to use different environmental conditions to evaluate which setting could result in a pronounced shift in groundwater discharge age and to identify the most significant parameters driving alterations to groundwater discharge age. In general, the results show that groundwater discharge is expected to become gradually older with permafrost thaw. Continuous permafrost settings exhibit very small changes in groundwater age until the lowering permafrost table allows for the formation of a supra-permafrost talik. The biggest shift occurs when taliks evolve from closed to open by connecting supra- and sub-permafrost aquifers. These insights are useful to determine the potential vulnerability and renewability of newly formed aquifers in permafrost settings.
How to cite: Lamontagne-Hallé, P., McKenzie, J., and Kurylyk, B.: Modelling of groundwater age under variable permafrost and environmental conditions, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-15539, https://doi.org/10.5194/egusphere-egu25-15539, 2025.
Saline permafrost exists beneath shallow shelf seas, coastal plains shaped by past marine transgressions, and post-glacially uplifted landscapes that were once submerged. In Svalbard, the Kvadehuksletta region northwest of Ny-Ålesund features a diverse landscape comprising raised beach terraces, lagoons, paleo-lagoons (now lakes), and surface seeps. Our study aimed to decipher the evolution of uplifted permafrost over time through two extensive electrical resistivity tomography (ERT) surveys: a 2.3 km terrestrial profile and a 1.0 km amphibious profile that crossed a lagoon. Both profiles originated at the 2024 coastline, extending inland to higher elevations. The 2.3 km profile reached approximately 700 m beyond the Late Weichselian Marine Limit. Shallow sediment samples (0–200 cm deep) were collected to characterize near-surface porewater and sediment properties. Mobile LiDAR scanning was carried out to create a high-resolution topography map (3 cm/pixel, 100 m wide swath) along the 2.3 km transect for geologic context. The ERT data suggest that the state and salinity of permafrost are influenced by the surface geomorphology (e.g., frost-shattered shale/sandstone, coarse-grained beach deposits), uplift duration, storm surge flooding, and the mid-Holocene transgression. Groundwater flow, which freshens porewater, may have flushed salts from coarse-grained deposits during permafrost formation. Consequently, the behaviour of saline permafrost in the coarse-grained deposits of Svalbard may differ from that of finer-grained sediments in other Arctic regions, such as the Alaskan North Slope, where diffusive salt transport dominates in newly exposed marine sediments.
How to cite: Angelopoulos, M., Boie, K., Rau, M., Hauber, E., Zanetti, M., Sassenroth, C., Johnsson, A., Hiesinger, H., Schemdemann, N., Overduin, P. P., Boike, J., and Krautblatter, M.: Geoelectrical insights on the evolution of post-glacially uplifted permafrost on Svalbard, EGU General Assembly 2025, Vienna, Austria, 27 Apr–2 May 2025, EGU25-19953, https://doi.org/10.5194/egusphere-egu25-19953, 2025.
