PICO
In this session, we welcome contributions related to all methods in cryospheric measurements, including: advances in radioglaciology, active and passive seismology, geoelectrics, acoustic sounding, fibre-optic sensing, GNSS reflectometry, signal attenuation, and time delay techniques, cosmic ray neutron sensing, ROV and drone applications, and electromagnetic methods. Contributions can include field applications, new approaches in geophysical or in-situ survey techniques, or theoretical advances in data analysis processing or inversion. Case studies from all parts of the cryosphere, including snow and firn, alpine glaciers, ice sheets, glacial and periglacial environments, alpine and arctic permafrost as well as rock glaciers, or sea ice, are highly welcome.
This session will give you an opportunity to step out of your research focus of a single cryosphere type and to share experiences in the application, processing, analysis, and interpretation of different geophysical and in-situ techniques in these highly complex environments. This session has been running for over a decade and always produces lively and informative discussion. We have a successful history of PICO and other short-style presentations - submit here if you want a guaranteed short oral!
PICO: Wed, 6 May, 08:30–12:30 | PICO spot 1a
Meltwater routing through englacial and subglacial drainage systems exerts a fundamental control on glacier dynamics, water resources, and related hazards, yet detailed observations of these systems and their temporal evolution remain scarce. In this study, we present uncrewed aerial vehicle (UAV)-based four-dimensional (4D) ground-penetrating radar (GPR) measurements that resolve seasonal and interannual changes in near-terminus glacier hydrology at unprecedented spatial resolution.
We conducted repeated high-density 3D GPR surveys at the Otemma Glacier (Swiss Alps) during four field campaigns (August 2022; June, August, and October 2023). A dedicated 3D processing workflow combining reflection-based imaging of the glacier bed with coherence-based diffraction imaging of englacial scatterers enables comparison of drainage structures across surveys. The GPR results are interpreted alongside complementary observations, including dye tracing experiments, UAV photogrammetry, time-lapse imagery, and a targeted steam drill validation.
Our results reveal a drainage system composed of both persistent and dynamically reorganizing components. Subglacially, one major conduit remains stable across years and shows signs of increasing hydraulic efficiency, while a second conduit is partly rerouted. Englacially, several channels are observed in similar locations across years, indicating structural persistence, whereas other features appear transient. Seasonal drainage evolution is evident, and we observe direct coupling between englacial and subglacial drainage systems manifested by co-evolving structural changes.
These observations demonstrate the potential of UAV-based 4D GPR to capture glacier hydrological dynamics and provide critical constraints for models of meltwater routing and ice dynamics under a changing climate.
How to cite: Klahold, J., Racz, G. C., Ruols, B., and Irving, J.: Using UAV-based 4D GPR to investigate the seasonal and interannual evolution of englacial and subglacial drainage, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17913, https://doi.org/10.5194/egusphere-egu26-17913, 2026.
Located in the Monte Rosa massif in the Swiss Alps, the Grenzgletscher is one of the largest glaciers in the Alps, extending over approximately 2000 meters in height, with an accumulation zone that reaches up to 4500 meters and an ablation zone that descends to around 2500 meters. While its basal temperature reaches values of -13 °C at high elevations (Colle Gnifetti, 4450 m), it is temperate in the ablation zone, hence exhibiting at least one transition from frozen to temperate bed. As part of the ERC-funded project PHAST, a surface geophysics field campaign aimed at identifying the location of the frozen-to-temperate basal transition was conducted between 2024 and 2025. In this contribution we focus on the analysis of an active seismic survey conducted in 2024 to aid the characterization of basal conditions on a roughly 500 m x 500 m plateau at approximately 3700 m. The ELVIS-7 surface vibrator source was used to produce single-shot P-wave sweep signals along two lines of 48 geophones each, covering a total of 235 m, both parallel and perpendicular to the glacial flow. A velocity analysis was performed on the measured refracted waves, providing information on the upper part of the ice column and the depth of the firn layer. Deeper layers, the ice thickness, as well as the basal conditions, were studied via CMP/NMO processing and a phase-polarity analysis of the reflected waves. Finally, a post-stack migration was performed to obtain an accurate image of the glacier's subsurface along the receiver lines by accounting for possible steep-dipping interfaces or other structural complexities. In addition to revealing new information about the inter- and subglacial properties of the Grenzgletscher at high altitudes, the findings will be useful for identifying suitable drilling locations to study the physics of sliding onset in a natural laboratory, one of the main goals of PHAST.
How to cite: Chizzali, E., Wassermann, J., Hofstede, C., and Mantelli, E.: Characterizing inter- and subglacial properties of a 3700 m plateau on the Grenzgletscher with active seismics, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-1013, https://doi.org/10.5194/egusphere-egu26-1013, 2026.
We present an application of ground-penetrating radar-based (GPR) common midpoint method (CMP) to quantify temporal changes in firn density and compaction rates, complemented by direct observations, such as firn cores at the accumulation area of the Grosser Aletschgletscher. We identify the last summer horizon and characterise the firn stratigraphy using firn core and isotope analysis. The comparison of the acquired firn core and the CMP-derived density-depth profile from the Ewigscheefeld shows similar density-depth variations. Our three CMP gather results illustrate the spatially varied depth to the pore close-off density (830 kg/m³), which is approximately 25 and 17 m at Ewigschneefeld and Jungfraufirn, respectively, depicting the spatial variation in firn densification. Further, we identified 10-15 annual layers from the CMP-derived internal reflection horizons (IRHs) by comparing estimated snow water equivalent (SWE) with point mass-balance measurements. Temporal changes in firn density-depth profiles obtained from CMP data measured a year apart illustrate that certain identified annual layers at shallower depths are denser than deeper layers (100-150 kg/m³). Our results demonstrate that the influence of summer melts is a dominating process on Alpine firn densification, rather than the conventional densification driven by accumulated snow. We investigated the temporal changes in spatial firn stratigraphy from a 4.4 km long GPR profile by comparing it with a previously measured GPR transect from the same location. Our investigation exemplifies the possibility of quantifying firn densification and compaction rates using unique temporal GPR measurements in an Alpine glacier.
How to cite: Patil, A. and Mayer, C.: Investigating temporal changes in the Alpine firn density and compaction rate using repeat ground penetrating radar measurements at the accumulation areas of the Grosser Aletschgletscher, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12798, https://doi.org/10.5194/egusphere-egu26-12798, 2026.
Ground-penetrating radar (GPR) has long been a core tool for glacier investigations, and decades of surveys have created substantial archives of radar observations across a wide range of glaciers. Increasingly, attention is shifting from extracting ice thickness alone to exploiting a broader set of radar signatures (e.g. internal horizons, electromagnetic appearance such as transparent or scattering-dominated regions, and spatial variability) that may contain information on englacial structures. Realizing this potential requires understanding how such signatures manifest in real data, how variable their appearance can be across sites, and what this implies for interpretation confidence.
Here we investigate the variability of englacial GPR features using an archive of airborne and ground-based surveys on Swiss glaciers acquired by the Glaciology and Geophysics Groups at ETH Zurich between 2017 and 2024. The archive spans radar frequencies from 25 to 250 MHz and covers glaciers with contrasting geometries, dynamics, and site histories. To enable consistent description across heterogeneous datasets, we apply an observation-driven, appearance-based organization, informed by radar-facies concepts, classifying features by reflector geometry, continuity and coherence, as well as texture. We describe basal responses, internal layering, channelized features, transparent facies, and scattering-dominated facies, and illustrate each with representative examples from across the archive.
The examples show substantial variability and ambiguity in several features. Basal responses may be discontinuous, split into multiple reflections, obscured beneath scattering-dominated facies, or expressed as gradual facies transitions rather than discrete horizons. Similarly, internal layering varies in coherence, geometry, and continuity. Scattering-dominated facies show pronounced diversity in texture and organization. While it is often interpreted in relation to temperate ice, scattering is an electromagnetic response that is not diagnostic on its own of thermal regime, and a confident thermal interpretation requires independent constraints (e.g. borehole temperatures).
By presenting real-data examples of how radar signatures depart from commonly assumed expressions, we aim to increase awareness of the variability and interpretational ambiguity of englacial GPR features. By doing so, we highlight implications for interpretation confidence and future process-oriented studies supported by complementary observations.
How to cite: Santin, I., Ogier, C., Moser, R., Maurer, H., Horgan, H., and Farinotti, D.: How do englacial radar features appear? Variability of horizons and facies in GPR data of Swiss glaciers, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5686, https://doi.org/10.5194/egusphere-egu26-5686, 2026.
Suture zones, formed in the wake of peninsulas, are known to stall rifts on the Larsen C Ice Shelf, stabilising the shelf by delaying mass calving events. What exactly these rifts are composed of, and therefore how they are able to stall rifts, has remained elusive. Here we present direct evidence for brittle deformation within a suture zone immediately ahead of a detained rift tip, as recorded by a dense array of 29 low-noise accelerometers and three geophones. 251 icequakes were identified to originate within the network, 108 of which were successfully relocated to show a concentration of seismicity within the suture zone’s interior ice. No events were observed in the lowermost 20 m of the shelf, indicative of a porous basal marine ice layer or crevasse/cavity. The magnitude-frequency distribution yielded a catalogue b-value = 1.20 ± 0.11. For events from which source mechanisms could be derived, there is a correlation between rising/falling tides and explosive/implosive events, respectively. Collectively, these results are indicative of tidally-driven infiltration of seawater into the suture through the rift tip which will act to corrode the suture and promote brittle failure. The time-integrated effect of this process as the rift advects downstream will eventually weaken the suture zone sufficiently to allow for the rift to propagate despite lower downstream stresses, limiting the stabilising role of sutures towards the calving front.
How to cite: Dunn, A., Brisbourne, A., Thompson, S., Jones, G., Kendall, J. M., Kulessa, B., Luckman, A., Miles, K. E., and Hubbard, B.: Tidally-modulated icequakes reveal mechanisms governing rifting on Larsen C Ice Shelf, Antarctic Peninsula, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3860, https://doi.org/10.5194/egusphere-egu26-3860, 2026.
Basal friction and stick–slip processes beneath fast-flowing glaciers play a key role in modulating ice dynamics, yet the physical conditions at the ice–bed interface remain poorly constrained. Here, we use seismic observations of basal icequakes recorded within the ice stream of a fast-flowing Greenland outlet glacier to investigate frictional heterogeneity and transient slip behavior at the glacier bed. Using a three-sensor seismic array, we detect nearly 25,000 short-duration seismic events over 5-week period that occur in spatially coherent clusters, indicating repeated failure on localized basal asperities.
We analyze S-wave spectra within these clusters using the Brune source model and interpret the results within a rate-and-state friction framework to estimate relative variations in basal frictional stress through space and time. Our analysis reveals pronounced heterogeneity in basal seismic slip and stress behavior, with one persistent, spatially extensive region exhibiting systematically higher inferred frictional stresses throughout the observation period. This suggests that basal friction is not spatially uniform but instead governed by a patchwork of asperities that repeatedly load and fail, including at least one long-lived, dominant “sticky-spot”.
In addition to this localized behavior, we observe kilometre-scale downstream and upstream migration of icequake activity. These migration patterns suggest the presence of transient, propagating slip fronts, analogous to faster slip behavior previously observed beneath the Whillans Ice Stream, Antarctica, as well as in some tectonic fault systems. The inferred slip fronts propagate faster than glacier flow speeds and show a weak correlation with the tidal signal at the glacier terminus, indicating that their evolution might be controlled by small external stress changes.
Together, these observations support a view of glacier basal motion as a highly dynamic and locally controlled process rather than a spatially averaged frictional regime. The additional evidence for seismic migration highlights an interplay between localized stress accumulation at persistent asperities and more distributed, evolving slip processes, both of which may influence the dynamics and stability of fast glacier flow.
How to cite: Nap, A., Hudson, T. S., Walter, F., Wehrlé, A., Kneib-Walter, A., Rousseau, H., and Lüthi, M. P.: Seismic evidence for frictional heterogeneity and transient basal slip beneath a fast Greenland outlet glacier, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18959, https://doi.org/10.5194/egusphere-egu26-18959, 2026.
Englacial stress, the elusive variable governing glacier motion, has rarely been measured in situ. Instead, our empirical understanding of ice dynamics largely relies on laboratory flow-law experiments, but field measurements of stress-induced glacier surface velocity and englacial tilt indicate that crystal orientation, molten ice fraction and impurities may complicate the application of laboratory-derived laws in nature. Here, we present a three-year record of englacial deformation and near-vertical stress from sensors frozen 123 to 265 metres deep into the Bowdoin tidewater glacier in Northwest Greenland.
Inclinometers show that the glacier movement is largely dominated by sliding, as horizontal shear deformation of 16 to 19 metres accounts for 4 to 5 percent of independently observed surface displacement. During seasonal speed-up events, englacial tilt rates increase proportionally to surface velocities derived from geopositioning, automated cameras and satellite remote sensing. Daily and tidal components are also present in the tilt rates record but are yet to be isolated from the sampling noise before phase correlation with other signals.
Piezometers were initially intended to locate instruments in hotwater-drilled boreholes, but they continued to record pressure changes after the complete refreezing of the boreholes and the stabilisation of ice temperatures well below the melting point. All sensors recorded in-phase stress variations with 12-hour, 24-hour and 14-day periodicities, revealing a tidal signal in winter, disturbed during independently documented speed-up events in summer. The signal shows amplitudes of one to four kilopascals, only an order of magnitude weaker than the two metres tidal amplitude measured at sea. However, stress measurements are anticorrelated with the tide, and show a delay of one to two hours, so that maximum stresses occur a little after low tide. While detailed interpretations are hampered by the lack of calibration, our data indicate that direct stress measurements in glaciers are feasible.
How to cite: Seguinot, J., Podolskiy, E. A., Henning, K., Sugiyama, S., Greve, R., and Zekollari, H.: Measurements of shear and stress at Bowdoin Glacier, Northwest Greenland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19928, https://doi.org/10.5194/egusphere-egu26-19928, 2026.
The Greenland Ice Sheet is currently the largest single land-ice contributor to global sea level rise, and this contribution is expected to continue throughout the twenty-first century and beyond, although the magnitude and rate of future mass loss remain highly uncertain. A key limitation in current estimates is that most observational records span only the last few decades, providing an incomplete view of long-term glacier behavior. Improving future projections therefore requires a better understanding of how Greenland's outlet glaciers have responded to external climate forcing over centennial timescales. In this study, we combine historical aerial and ground-based photographs with modern satellite observations to reconstruct ice-sheet change from approximately 1900 to 2025 in the northwest sector of the Greenland Ice Sheet, spanning from Jakobshavn Isbræ in the south to the outlet glaciers of Melville Bugt in the north. Using these complementary datasets, including satellite altimetry, ice-flow maps, and terminus positions, we quantify ice loss, surface elevation change, frontal retreat, and ice dynamics for three major outlet glaciers. The observations provide new insight into the processes driving glacier evolution and their contribution to future sea level rise.
How to cite: Socher, T., Khan, S. A., and Bjørk, A. A.: Mass Change of the North West Sector of the Greenland Ice Sheet during 1900-2025, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19320, https://doi.org/10.5194/egusphere-egu26-19320, 2026.
In 2016, we established the first network of GNSS stations on the Northeast Greenland Ice Stream (NEGIS), enabling continuous monitoring of ice flow motion and surface elevation changes. These stations have revealed both short-term variability and longer-term accelerations that propagate far inland from the terminus (Khan 2022; Khan 2024), highlighting the dynamic coupling between the glacier front and the interior of the ice sheet. Building on this effort, in 2024 we deployed four additional GNSS stations on Jakobshavn Isbræ, one of Greenland’s fastest-flowing outlet glaciers. All stations on both Jakobshavn and NEGIS are located along the main glacier trunks, spanning distances of ~20 to ~200 km from the terminus, thereby capturing spatial gradients in flow and deformation.
The GNSS sites also enable direct validation of satellite-derived surface elevation products (ICESat-2 and CryoSat-2). Whereas satellite altimetry provides repeat measurements of ice-surface elevation once per month, GNSS observations deliver continuous, hourly records of both vertical and horizontal ice motion. This high temporal resolution allows us to resolve short-lived dynamic events, seasonal signals, and longer-term trends that are not detectable from spaceborne sensors alone. Together, these complementary datasets provide powerful constraints for improving ice-flow models and for assessing the future evolution and stability of the Greenland Ice Sheet.
In addition, we apply GNSS interferometric reflectometry (GNSS-IR) to the ice-sheet environment, using reflected GNSS signals to infer changes in ice-surface height and physical properties such as roughness and snow accumulation. This technique adds a new observational dimension to the GNSS network, further enhancing its value for characterizing glacier–atmosphere interactions and surface processes.
How to cite: Khan, S. A., Hassan, J., Colgan, W., Oniszk, K., Cheng, G., Bråtner, A., Morlighem, M., Felten, S. M., Seroussi, H., Solgaard, C., Berg, D., Barletta, V., Løkkegaard, A., Fahrner, D., Togaibekov, A., and Socher, T.: GNSS measurement of seasonal ice flow velocity of the northeast Greenland ice stream and Jakobshavn Isbræ, Greenland., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5821, https://doi.org/10.5194/egusphere-egu26-5821, 2026.
Glaciers around the world have experienced substantial mass loss due to global warming (Hugonnet et al., 2021). In Greenland, meltwater runoff is one of the major contributors to mass loss from the Greenland Ice Sheet and surrounding glaciers (Mouginot et al., 2019). This meltwater increases the discharge of proglacial rivers and poses a growing flood hazard to local communities (Kondo et al., 2021). Therefore, there is an urgent need to develop passive, robust, and low-maintenance methods for monitoring proglacial discharge under rapidly changing channel conditions.
Recent studies have shown a strong correlation between proglacial river discharge and fluvial sound (Podolskiy et al., 2023). Fluvial sound is mainly generated by air-bubble entrainment and collapse within turbulent flow features such as rapids and waterfalls, and its amplitude and spectral characteristics systematically respond to changes in discharge (Bolghasi et al., 2017). Passive acoustic monitoring therefore enables non-invasive and cost-effective discharge observation by simply recording the self-generated sound of a river, yet its applicability and limitations remain insufficiently understood.
In this study, we investigate the potential of passive acoustic monitoring to track proglacial discharge at Qaanaaq Glacier in northwestern Greenland (77°28’ N, 69°14’ W). During the summer of 2024, we deployed four passive acoustic sensors along the proglacial river and continuously recorded fluvial sound. Acoustic power in the 94–375 Hz frequency band showed a strong correlation with river discharge (R ≈ 0.90). Cross-correlation analysis between two sensors separated by 1,850 m revealed highly correlated acoustic signals (R = 0.90) with repeatable time lags of up to approximately one hour, although data gaps occurred during very low- and high-discharge conditions when the acoustic time lag became poorly resolved. This limitation suggests that larger sensor separations or array-based deployments may be required to robustly resolve time lags under variable flow conditions.
In addition to fluvial sound, the acoustic sensors recorded traffic-related noise from a bridge crossing the river. More than 200 traffic events were detected, providing supplementary information relevant to local flood risk and infrastructure usage. The usage of bridge reached maximum around 13 to 16 local time of Qaanaaq (LT), whereas discharge reached maximum around 18 to 23 LT. The peak in bridge usage occurred during the rising phase of discharge, highlighting the importance of early-stage flood awareness for local communities.
These results demonstrate that passive acoustic monitoring offers a low-cost, non-invasive tool that can complement conventional methods for monitoring proglacial river discharge, particularly in dynamically evolving glacial river systems. In addition, acoustic observations can provide complementary information on human activity near rivers, which is relevant for local flood-risk awareness and infrastructure management.
How to cite: Nakayama, T., Podolskiy, E., Imazu, T., Yazawa, K., and Sugiyama, S.: Acoustic monitoring of proglacial discharge at Qaanaaq Glacier, Northwest Greenland, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6145, https://doi.org/10.5194/egusphere-egu26-6145, 2026.
The crystal orientation fabric (COF) of glacial ice strongly influences its mechanical properties and evolves with flow. Large-scale ice flow models currently neglect COF evolution, but including it is becoming increasingly feasible. However, observations are still very sparse and often depth-averaged or point measurements. Radars, and especially polarimetric radars, are sensitive to the COF due to the birefringence of ice and provide a relatively easy way to collect observations that can be used to infer the anisotropy and orientation of the COF. In this study, we formulate the problem of inferring the COF from polarimetric radar data as an inverse problem to derive depth-resolved horizontal COF anisotropy. The method is applied to polarimetric radar data from the Northeast Greenland Ice Stream (NEGIS), where previous methods have struggled due to the high anisotropy. The method relies on an iterative linearization of the Fujita radio-wave depolarization matrix model to estimate COF orientation and scattering anisotropies. It also employs a linear maximum likelihood solution to derive eigenvalue differences from travel-time anisotropies. The inversions generally recreate the observed power anomalies and reveal a strong increase in horizontal anisotropy at shallow depths in NEGIS, followed by a rapid decrease near the ice stream base, likely due to recrystallization processes. The inversion also shows a near flow-aligned COF close to the onset of the ice stream, with increasing misalignment along a 30 km flowline downstream.
How to cite: Nymand, N. F., Lilien, D. A., and Dahl-Jensen, D.: Inferring the crystal orientation fabric of the Northeast Greenland Ice Stream using polarimetric radar data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9759, https://doi.org/10.5194/egusphere-egu26-9759, 2026.
Thick, high-resistivity ice sheets extensively cover bedrock and sedimentary layers, posing significant challenges for the identification of subglacial hydrological systems and associated geological structures. Subglacial water systems not only play a crucial role in regulating ice-sheet dynamics and material transport, but also serve as important indicators of deep geological environments, fluid activity, and potential mineralization conditions.However, high-resistivity ice sheets significantly enhance electromagnetic energy attenuation during field propagation, resulting in insufficient recoverable low-frequency signals and thereby limiting the detectability of deep low-resistivity anomalies. This challenge is widespread in polar environments and exhibits strong similarities to those encountered in other high-resistivity-covered mineral exploration settings.
In this background, this study applies the loop-source transient electromagnetic (TEM) method to to systematically analyze the spatial distribution characteristics of transient attenuation curves and electric field components by constructing various underground models (e.g., subglacial water systems and fluid-rich anomalies). Results indicate:
(1) In models containing high-conductivity anomalies (such as saturated sedimentary layer), the presence of conductive bodies significantly slows electromagnetic field diffusion. As a result, response signals maintain relatively high amplitudes during late-time sampling, resulting in attenuation curves exhibiting a characteristic S-shaped bulge. This indicates that transient electromagnetic methods possess high discrimination capability for identifying water-bearing low-resistivity anomalies.
(2) As the ice thickness increases from 50 m to 500 m, the transient electromagnetic response curve exhibits an overall rightward and downward shift. The rightward shift reflects the elongated propagation paths and delayed response times of electromagnetic fields within thick resistive cover, whereas the downward shift indicates enhanced attenuation of electromagnetic signals by the overburden, thereby reducing sensitivity to deep subsurface structures. In addition, increasing cover thickness amplifies response differences among distinct subsurface targets, leading to reduced resolution in inverted models.
(3) Under conditions of thin ice cover, differences in transient responses induced by varying transmitter loop sizes are relatively minor. However, as ice thickness increases, the required transmitter magnetic moment rises substantially. Large transmitter loops (e.g., 300 m and 500 m) generate stronger transient electromagnetic fields owing to their higher magnetic moments. Their late-time responses exhibit higher amplitudes and longer persistence, indicating enhanced sensitivity to deep low-resistivity anomalies. This improvement contributes to better imaging performance and more reliable identification of deep subsurface targets.
Overall, the loop-source transient electromagnetic method demonstrates strong applicability for detecting subglacial hydrological systems in polar regions. It exhibits significant detection potential for identifying low-resistivity anomalies associated with fluid activity and potential mineralization within thickly covered environments.These findings provide valuable technical references for subglacial hydrological investigations, deep geological structure studies, and deep mineral exploration in polar regions and other areas characterized by thick resistive cover.
How to cite: Zhang, Y., Zou, C., Boaga, J., and Peng, C.: Transient electromagnetic responses to deep low resistivity targets beneath thick resistive ice sheet, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17065, https://doi.org/10.5194/egusphere-egu26-17065, 2026.
Electromagnetic induction (EM) is one of the established techniques for in-situ sea ice thickness measurement. It is typically implemented using shipborne or airborne transmitter-receiver coil systems (e.g., EM 31, AWI, DIGHEM) operating at single or multiple frequencies. While this method can acquire reliable sea ice thickness data, limitations exist in case of thin ice and regions with severely variable ice thickness . The fixed coil spacing (e.g., 3.66 m for EM 31) constrains detection sensitivity for thin ice, particularly in shipborne or airborne measurements where altitude variations can significantly affect inversion accuracy . To enhance thin-ice detection capability and inversion stability, this study proposes a novel electromagnetic induction method utilizing dual receiver coils.
This method retains a single transmitter coil and incorporates two receiver coils with a spacing of 0.5 m. By increasing the amount of measured data, the response characteristics for thin-layer targets are optimized. Based on typical polar sea ice conductivity parameters (seawater ~2.6 S/m, sea ice ~0.06 S/m), electromagnetic numerical simulations were conducted for sea ice with thicknesses ranging from 1 to 5 m. These simulations analyzed the response relationship between the secondary field signal and ice thickness under the dual-receiver coil configuration. The results indicate that, compared to traditional single-receiver coil systems, data from the dual-receiver coils exhibit greater sensitivity to variations in thin ice thickness and help reduce inversion uncertainty caused by fluctuations in measurement altitude.
Building on the simulation data, this study further developed an inversion algorithm for dual-receiver coil data. This algorithm integrates dual-channel data continuously acquired along the same direction to achieve accurate and stable inversion of sea ice thickness. Preliminary verification shows that the inversion uncertainty of this method for thin ice in the 1~3 m range is significantly lower than that of conventional methods. This approach provides a new technical pathway for developing next-generation portable, low-platform (ground-based, shipborne, or UAV-borne) sea ice thickness detection equipment. It contributes to enhancing capabilities in climate research and safety assurance for polar navigation.
How to cite: Zou, C., Yuan, C., Peng, C., and Markov, A.: Sea Ice Thickness Measurement in Polar Environments: An Electromagnetic Detection Approach Using a Dual-Receiver Coil System, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8861, https://doi.org/10.5194/egusphere-egu26-8861, 2026.
Geophysical investigations of Alpine glaciers are essential for quantifying ice thickness and internal structures, yet traditional ground-based Ground-Penetrating Radar (GPR) remains logistically constrained in complex, high-altitude terrain. The emergence of Unoccupied Aerial Vehicle (UAV) platforms provides a transformative opportunity for radioglaciology, allowing for rapid, high-resolution data acquisition. While conventional mass balance methods focus on annual or subseasonal superficial mass changes, GPR enables the determination of the total remaining ice volume – a prerequisite for accurately forecasting future glacier evolution and glacial runoff. However, traditional ground-based GPR surveys are often logistically demanding and hazardous due to crevasses and unstable terrain, which frequently limit the spatial density and resolution of the resulting datasets. Recent advances in UAV technology have enabled the integration of lightweight geophysical sensors, offering a safer and more efficient alternative that significantly enhances spatial coverage and data resolution in glaciated environments.
This contribution presents results from ten glaciers in the Eastern Alps surveyed in 2024 and 2025 using a UAV-borne GPR system. The investigated sites range in size from 0.09 km² to 2.15 km² and encompass a diverse range of morphological types, including debris-covered, plateau, and valley glaciers. Furthermore, the study areas span contrasting geological settings and include both glaciers affected by anthropogenic activities (e.g., ski resort infrastructure) and largely undisturbed systems. Based on two years of UAV-based data acquisition, we provide a critical assessment of the associated methodological challenges, data quality limitations, and logistical constraints. We highlight key lessons learned regarding the performance of the UAV-borne GPR system in diverse cryospheric settings and outline future developments aimed at expanding this dataset to improve regional glacier volume estimates. Finally, we invite fellow researchers working with UAV-borne GPR to collaborate on establishing a new glacier thickness database.
How to cite: Siebenbrunner, A., Keuschnig, M., and Krautblatter, M.: Towards a New Regional Ice Thickness Dataset: UAV-Borne GPR for Quantifying Remaining Ice Volumes of Alpine Glaciers, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-8251, https://doi.org/10.5194/egusphere-egu26-8251, 2026.
Constraining subsurface density from seismic data is challenging, although density is fundamental to quantifying mass and structure in both the solid Earth and glaciers. Empirical scaling relationships between seismic wave speeds and density are therefore widely used. In this contribution, we show that density can instead be constrained directly from surface-wave observations when multimode dispersion and fully nonlinear inversion are combined.
We analyze distributed acoustic sensing (DAS) recordings acquired in glaciated environments, where strong serendipitous anthropogenic sources generate coherent Rayleigh-wave overtones with high signal-to-noise ratio. These dense DAS measurements allow robust extraction of surface-wave multimode dispersion. We invert the data using a probabilistic Hamiltonian Monte Carlo (HMC) framework that accounts for nonlinearity, parameter trade-offs, and uncertainty, while avoiding biases introduced by subjective regularization choices.
Our results show that Rayleigh-wave overtones carry resolvable sensitivity to density structure down to depths of order 100 m, enabling direct density estimation from seismic data with quantified uncertainties. We further evaluate commonly used velocity–density scaling relationships for firn (the transitional layer between fresh snow and glacial ice) and find that their application can lead to density errors on the order of 10%, with direct implications for inferred mass estimates.
Overall, these findings demonstrate that overtone-based probabilistic inversion enables constraints on weakly sensitive parameters and highlight the potential of DAS for quantitative near-surface parameter estimation.
How to cite: Lanteri, A., Keating, S., Gebraad, L., Klaasen, S., Pienkowska-Cote, M., Eisen, O., Zunino, A., Jonsdottir, K., Hofstede, C., Zigone, D., and Fichtner, A.: Direct Ice Density Constraints from Multimode Surface Waves Using DAS, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-21527, https://doi.org/10.5194/egusphere-egu26-21527, 2026.
Long-term ground temperature records from high-alpine environments document a persistent warming trend and a progressive thickening of the active layer of permafrost across the European Alps. This thermal evolution directly affects the internal hydrological regime of rock slopes. In frozen rock masses with ice-filled fractures, hydraulic permeability is markedly reduced relative to unfrozen conditions. Permafrost warming and thawing thus promote water infiltration, perched water, and elevated water pressures once ice melt occurs. Surface water input infiltrates through fracture systems or heterogeneous ground layers within the active layer, causing local concentrations of convective heat transport that can initiate the development of preferential thaw pathways in the underlying permafrost.
Such hydrothermal interactions are expected to exert a first-order control on the stability and kinematics of failure-prone rock slopes. However, the role of water in governing thermo-mechanical coupling and deformation in mountain permafrost remains poorly understood. Evidence for the presence, distribution, and temporal variability of water in permafrost rock slopes is scarce, with only a few studies documenting temporal changes in water content using piezometric measurements. In-situ observations and laboratory experiments remain limited, providing only partial information on the role of water in frozen ground. Consequently, non-conductive heat fluxes, phase-change processes, and their implications for rock slope deformation are still insufficiently quantified, primarily due to their strongly nonlinear nature and the challenges associated with direct measurement.
To address the role of water in permafrost rock slope dynamics, we investigate the Wisse Schijen study site (Valais, Switzerland), a deep-seated permafrost rock slope instability with an estimated volume exceeding 1 million m³, located on an approximately 40° steep, east-facing slope between 3010 and 3140 m a.s.l. We apply a multi-method analysis that integrates spatially and temporally resolved geological, thermal, kinematic, and seismic data and relates these observations to atmospheric and hydrological forcing. The combined dataset reveals a clear kinematic response of the rock slope to hydrothermal forcing, manifested by seasonally variable deformation patterns that coincide with periods of enhanced water availability and elevated subsurface temperatures. Our results indicate that water-driven thaw processes and associated hydrogeological changes likely reduce effective stresses and alter the geotechnical properties of the rock mass, thereby modulating deformation rates and kinematic behavior. These observations highlight the critical role of hydrothermal processes in controlling the mechanical response of permafrost rock slopes and emphasize the importance of explicitly accounting for hydrothermal coupling in assessments of high-alpine slope stability under ongoing climate warming.
How to cite: Weber, S., Phillips, M., Häusler, M., Kenner, R., Moser, R., Summermatter, S., Volken, M., and Bast, A.: Hydrothermally influenced rock slope kinematics: The role of water on Wisse Schijen, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-10833, https://doi.org/10.5194/egusphere-egu26-10833, 2026.
The presence of seasonal ground frost can markedly modify infiltration processes and runoff generation, yet its hydrological impacts remain inconsistently described. The literature alternately reports enhanced, uncertain, or negligible effects of frozen soils on runoff and infiltration. Few studies rely on direct field measurements of infiltration under frozen conditions, and none have directly linked infiltration rates to measured soil ice content. Expanding field observations across contrasting soil types is therefore necessary to better constrain winter hydrological behavior. Quantifying infiltration capacity under frozen conditions remains challenging, as soil freezing renders many standard measurement techniques ineffective. Yet such data are essential to understand the links between infiltration rates, soil ice content, and other frozen ground properties. We conducted field measurements using double-ring infiltrometers in a clayey agricultural field and a sandy clearing to quantify infiltration under both frozen and unfrozen conditions. A combination of in situ sensors and soil sampling was used to characterize soil ice and liquid water content, frost depth, and soil temperature. The resulting field observations reveal pronounced variability in infiltration rates under frozen conditions at both sites, with substantially greater variability in the clay-rich soil. Moreover, the relationships between infiltration rates and frozen soil properties—including frost depth, thermal state, and water and ice content—were found to depend strongly on soil composition.
How to cite: Michaud, L., Baraër, M., Kinnard, C., Poulin, A., and Wespy, T.: Influence of seasonally frozen soil properties on infiltration rates: based on field data, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3139, https://doi.org/10.5194/egusphere-egu26-3139, 2026.
Subglacial sedimentary basins in Antarctica are hypothesized to modulate ice flow and biogeochemical cycles via groundwater and geothermal feedbacks, yet their properties remain poorly constrained. As part of the International Thwaites Glacier Collaboration’s (ITGC) GHOST project, we acquired new magnetotelluric (MT) geophysical data on Thwaites Glacier (TG) and at the West Antarctic Ice Sheet (WAIS) Divide during the 2022/23 and 2023/24 austral summers.
These new data are integrated with an archive of existing MT profiles from the Whillans Ice Stream, Central West Antarctica, the South Pole, and the Ross Ice Shelf to provide a continent-scale perspective. Using a constrained 1-D transdimensional Bayesian inversion, we produce new depth-resistivity models for the uppermost crust beneath the ice at each location, and interpret these models in terms of geological, geothermal and hydrogeological conditions beneath each profile.
The new MT data reveal a shallow (< 5 km) 2-D crustal structure at TG aligned with the West Antarctic Rift System, overlying deeper 3-D architectures potentially linked to older tectonic frameworks, e.g., the Weddell Sea Rift System. Our inversion highlights that the sedimentary basin beneath TG exhibits relatively high resistivity (>10 Ωm), distinct from the low-resistivity (<10 Ωm) basins observed beneath the Whillans Ice Stream, South Pole and Ross Ice Shelf. Sensitivity analysis reveals that the TG basin is horizontally heterogeneous, with conductive signatures in thicker sections and resistive, potentially low porosity, fresh conditions at GHOST Ridge, a subglacial topographic high which has been identified as a potential future stabilizing point. Conversely, basins beneath Subglacial Lake Whillans and the South Pole exhibit vertical stratification, likely hosting fresh, cold upper layers above deep, saline, and potentially warm reservoirs.
We conclude that complex, spatially variable groundwater regimes are widespread in Antarctica. These contrasting hydrological environments imply continent-scale variability in subglacial thermodynamics and ice dynamics. Furthermore, they suggest spatially distinct biogeochemical potentials, influencing subglacial carbon sequestration and the rates of dissolved carbon discharge into the Southern Ocean.
How to cite: Killingbeck, S., Kulessa, B., Pearce, R., Brisbourne, A., Borthwick, L., Napoleoni, F., Anandakrishnan, S., Unsworth, M., and Muto, A.: Distinct Groundwater Regimes in West Antarctic Sedimentary Basins Inferred from Magnetotelluric Imaging., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-20650, https://doi.org/10.5194/egusphere-egu26-20650, 2026.
The TRIPLE project aims to develop key technologies for a future space mission dedicated to the search for extraterrestrial life on Jupiter’s moon Europa. The mission concept is based on a melting probe designed to penetrate Europa’s ice shell and deploy scientific instruments into the underlying subsurface ocean to search for life and biosignatures. To validate the feasibility of this approach, the developed technologies are tested stepwise in terrestrial analogue environments under extreme conditions.
Within the TRIPLE-FRS project, a Forefield Reconnaissance System (FRS) for these ice-penetrating melting probes is being developed that combines radar and sonar sensing to scan the probe’s forefield. To enable in-situ correction of radar and sonar wave velocities, an additional sensor is integrated into the melting probe to measure the complex permittivity of the surrounding medium.
This contribution presents the integration of the permittivity sensor into the melting probe TRIPLE-IceCraft, the achievable measurement accuracy for a wide range of dielectrics, and the results of validation experiments conducted in controlled freezer environments and on alpine glaciers. Furthermore, the role of the sensor system within an upcoming Antarctic field campaign at Neumayer Station III during the 2026/2027 season is outlined.
How to cite: Becker, F., Audehm, J., Böck, G., Do, M. G., Ellinger, E., Feldmann, M., Francke, G., Haberberger, N., Helbing, K., Rechenberg, L., Vossiek, M., and Wiebusch, C.: A permittivity sensor integrated into melting probes for in-situ cryospheric characterisation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-7859, https://doi.org/10.5194/egusphere-egu26-7859, 2026.
The Dynamic Stern Layer (DSL) model is a reliable petrophysical model to comprehend induced polarization data at various scales from the representative elementary volume of a porous rock to the interpretation of field data at the cm to 100 m scales. We first review the DSL model in presence of ice and discuss the role of ice as an interfacial protonic dirty semi-conductor in the complex conductivity spectra of rocks and sediments. The electrical current polarizes the surface of the ice crystals and generates a very high chargeability that can reach one depending on the value of the volumetric content of ice. We apply the petrophysical model to a new set of complex conductivity spectra obtained in the frequency range 10 mHz-45 kHz using a collection of 25 rock samples including metamorphic and sedimentary rocks in the temperature range +15/+20°C to -10/-15°C. We observe that the model explains very well the observed data. We also investigate the role of porosity, cation exchange capacity, and freezing curve parameters on the complex conductivity spectra of crystalline and non-crystalline rocks during freezing. Laboratory experiments demonstrate that in most field conditions including permafrost conditions, surface conductivity associated with conduction on the surface of clay minerals (and alumino-silicates in general) is expected to dominate the overall conductivity response. Therefore Archie’s law cannot be used as a conductivity equation in this context because of the contribution of surface conductivity and has been strongly abused in the context of the applications of geoelectrical methods in the realm of the cryosphere. Time-domain induced polarization data obtained in field conditions are interpreted thanks to this updated DSL model. We selected three different test sites in order to apply the DSL model to very different conditions of low and high ice contents. A first survey is performed along a cross-section of a ridge in the Kangerlussuaq mountains of Greenland. We also performed a field survey close to Col des Vés (2846 m a.s.l., Tignes, French Alps, Site II). This site corresponds to a complex ground ice body overlying a substratum made of a low-porosity marble, both having high resistivity values. The front of this body is characterized by a small amount of residual ice while the roots are ice-rich. Therefore the porosity at this site is high and the ice content highly variable. This case study showcases the role of ice in the induced polarization data in terms of high chargeability values (close to 1 as predicted by the theory) at the roots of the complex ground ice body. A third site (Site III) corresponds to a profile crossing the Aiguille du Midi (3842 m a.s.l., Chamonix), also in the French Alps in a low porosity granitic environment. We end up with an application to a rock glacier (Site IV) to show how we can image the ice content.
How to cite: Revil, A., Duvillard, P.-A., Richard, J., Abdulsamad, F., Magnin, F., Casotti, C., and Ghorbani, A.: The induced polarization geophysical method applied to permafrost at various scales and for various frozen environments, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-5188, https://doi.org/10.5194/egusphere-egu26-5188, 2026.
Understanding the evolving state of the Arctic's upper permafrost and sea ice is crucial for tracking environmental effects, yet little is known about the nanostructure and distribution of microbial life within these environments. Recent advances in X-ray computed tomography technology have made it possible to image environmental samples not only at micron-scale resolution, but also at the nanoscale. Here we present high resolution images of permafrost and sea ice samples collected from Alaska, Nunavut, and Greenland. We have developed advanced segmentation techniques to characterize the microstructure, tracking variables such as porosity with depth. We have also developed techniques to use osmium staining to image microbes in situ within these samples at the nanoscale. At this resolution, we seek to connect physical and biological attributes of terrain state to improve our understanding of microbial distributions and microbially-mediated processes in cold regions.
How to cite: Lieblappen, R., Sama, M., Goodell, E., Mazzilli, D., Tilton, C., LaPoint, A., Cuciti, G., Boggio, B., Schwenker, C., Rutkowski, O., Nichols, J., and Vermilyea, A.: Microstructural Characterization of Arctic Permafrost and Sea Ice From the Microscale to the Nanoscale Using X-Ray Microscopy, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4340, https://doi.org/10.5194/egusphere-egu26-4340, 2026.
Antarctica, a critical regulator of global climate, faces threats to its permafrost and ecosystems from recent warming. However, a quantitative understanding of subsurface responses remains limited, hindering accurate environmental modeling. This gap hinders accurate modeling of future environmental changes. This study investigates the influence of rising air temperatures on active layer and permafrost characteristics... by quantifying the links between surface environmental changes and subsurface responses. From 2018–2024, we integrated meteorological observations, drone and satellite remote sensing, and geophysical surveys—electrical resistivity tomography (ERT) and ground-penetrating radar (GPR)—to assess atmosphere, surface, and subsurface changes. Our results indicated that the average annual temperature increased by ~1°C, extending the thaw season by ~50 days. Earlier snowmelt reduced albedo, increasing soil heat absorption and meltwater infiltration. The active layer thickened from 1.1 m to 1.5 m (maximum) and from 0.65 m to 0.85 m (dry sites). ERT indicated reduced resistivity at ~1 m depth, reflecting permafrost ice melt, and localized meltwater pooling at ~3 m depth. NDVI data showed increased vegetation activity. Our study shows that even slight warming can drive linked physical and ecological shifts in Antarctica, with implications for global climate feedbacks. Quantitative evidence of active layer thickening and permafrost degradation provides critical baseline data for improving prediction models. Future research should use year-round, three-dimensional monitoring and modeling to capture spatial variability and meltwater dynamics more accurately.
How to cite: Kim, K., Lee, J., Ju, H., and Kim, W.-K.: Monitoring Climate-Change Effects on the Barton Peninsula, King George Island, Antarctica: Evidence of Accelerated Active Layer Thickening, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3238, https://doi.org/10.5194/egusphere-egu26-3238, 2026.
The Frost.ini project, Permafrost degradation and instability of high-mountain infrastructures, funded within the Interreg VI-A Italy–Austria Programme 2021–2027, aims to develop a holistic analysis of permafrost in order to monitor its degradation and integrate risk mitigation measures into territorial management policies, thereby improving the resilience of high-altitude infrastructures.
The project is structured around a series of pilot actions carried out at sites selected according to strategic and scientific criteria, including the availability of previous studies.
The Casera Razzo rock glacier is located in the northern sector of the Friulian Dolomites, in northeastern Italy, within an alpine setting of significant geomorphological and geological interest. Traditionally classified as a relict landform based solely on surface morphology, it instead shows clear evidence of frozen material within its interior. Geophysical investigations and microclimatic measurements have identified interstitial ice and small ice lenses, indicating the presence of residual permafrost even during the period of maximum seasonal thaw.
The geoelectrical method, and in particular Electrical Resistivity Tomography (ERT), is a highly effective tool for the construction of geological models and for permafrost monitoring, as it allows non-invasive subsurface investigation and the repetition of measurements over time.
An initial resistivity model based on 2D data acquired in 2015 confirmed the presence of ice. The 3D survey carried out in 2025 using the FullWaver system by IRIS Instruments, partly overlapping the previous survey area, generated a three-dimensional resistivity model that quantified the ice volumes and provided important insights into the evolution of the rock glacier.
The results demonstrate that the FullWaver system is suitable for complex electrical investigations in environmentally challenging settings. By exploiting its capabilities, it is possible to obtain key information on permafrost evolution, which is essential for the modelling of future scenarios.
How to cite: Bratus, A., Forte, E., and Giorgi, M.: The Frost.ini project: A framework enabling 4D electrical resistivity investigations on a rock glacier, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12129, https://doi.org/10.5194/egusphere-egu26-12129, 2026.
Rock glaciers are permafrost landforms typical of high-altitude mountain environments, composed of varying proportions of ice, rock debris, air, and occasionally liquid water. Their internal structure is highly heterogeneous and evolves in response to climatic, hydrological, and geological forcing. Due to global warming, the investigation of mountain permafrost has become increasingly important for evaluating its stability, ice content, and hydrology. In this context, non-invasive geophysical techniques have proven to be effective tools for imaging subsurface conditions in periglacial environments.
The Sadole Rock glacier, located in the Eastern Italian Alps, has been extensively studied in the last years through several geophysical campaigns. In this study, we present the results of a complementary gravity investigation performed along two quasi-parallel profiles, with the aim of estimating the ice fraction in the permafrost and its spatial distribution. Data were collected between October 2024 and June 2025 using a relative gravimeter Scintrex CG-5 and were processed to finally obtain the complete Bouguer anomaly (BAC) along the profiles. BAC data show negative values, that we assume being related to the presence of ice. 2D forward modelling was carried out considering different scenarios. In all the cases examined, the bedrock depth was set based on preliminary geophysical information, while permafrost densities were varied as a function of the ice content considered.
The obtained results show the potential of gravity anomaly data for the estimation of the ice fraction of mountain permafrost. However, preliminary information is needed to constrain the density model (such as a resistivity model derived from ERT measurements), due to the high degree of non-uniqueness of the solution.
How to cite: Barone, I., Ghirotto, A., Pavoni, M., Carrera, A., and Boaga, J.: Gravity surveys for mountain permafrost quantification: the Sadole Rock Glacier (Italy), EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12321, https://doi.org/10.5194/egusphere-egu26-12321, 2026.
Electrical resistivity tomography (ERT) has become a well-established geophysical method for monitoring the thermal state of permafrost sites. However, quantitative interpretation of ERT data requires corresponding temperature information, either from direct borehole temperature measurements or from laboratory-based calibrations. Borehole measurements are costly to implement and remain scarce in alpine environments. Temperature-resistivity relations derived from laboratory experiments are generally site-specific, restricted to individual lithologies, and only rarely validated against field observations.
Here, we present temperature-resistivity relations derived from laboratory experiments on 12 low-porosity rock samples representing different sedimentary, metamorphic, and igneous lithologies. The samples were collected from permafrost-affected summit areas of Zugspitze (DE/AT), Großglockner (AT), Kitzsteinhorn (AT), Gemsstock (CH), Steintälli (CH), Gámanjunni-3 (NOR), Nordnes (NOR), and the Mannen plateau (NOR). The temperature-resistivity pathways are analysed with respect to porosity and mineral composition for unfrozen, frozen, and supercooled conditions. Particular emphasis is placed on the temperature range between -5 and +5 °C, where relevant mechanical changes occur, but also the major electrical transition due to the increasing partial freezing of pore water content.
The transferability of laboratory results to field observations is evaluated using a year-round automated ERT monitoring dataset from the Kitzsteinhorn (3.029 m a.s.l.), complemented by deep borehole temperature measurements along the profile. Deviations between field resistivity values and laboratory values can be explained by temporal and spatial effects. In the field, other than in the lab, seasonal pressurised water flow occurs in fractures, evidenced by piezometric measurements reaching peak values of 1.2 bar, and rock heterogeneities lead to enhanced drying and freezing of disintegrated rock blocks.
We anticipate that our provided temperature-resistivity pathways for different lithologies under unfrozen, frozen, and supercooled conditions will improve quantitative interpretation of ERT monitoring data and the assessment of permafrost warming and associated rock slope instabilities.
How to cite: Offer, M., Leinauer, J., Weber, S., Eppinger, S., Hartmeyer, I., and Krautblatter, M.: Laboratory and field validated temperature-resistivity relations in bedrock permafrost, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13345, https://doi.org/10.5194/egusphere-egu26-13345, 2026.
When investigating Arctic permafrost sediments, Electrical Resistivity Tomography (ERT) is becoming increasingly popular due to its robust, relatively quick and non-invasive application. The interpretation of ERT data is often constrained by the knowledge of the geophysical properties of the encountered frozen materials, thereby highlighting the need for ERT calibration experiments. Lab experiments on samples can quantify the dependency of electrical resistivity on sediment temperatures. Variation in electrical resistivity also depends on sediment composition, ground ice structures and their orientation with respect to the array, and porewater chemistry, all of which need to be considered in interpreting field measurements.
This study aims to improve our interpretation of ERT field measurements by investigating controlling and limiting factors of validating measurements by laboratory tests. We performed these laboratory tests on synthetic mixtures and field samples, varying sample size, electrode array orientation, electrode spacing, electrode type and anisotropy. Samples were thawed and then refrozen during the tests to include hysteresis effects. Synthetic samples were built to provide known anisotropies. Field samples were used from sites in Canada, and on Greenland and Svalbard. Relationships between apparent electrical resistivity and temperature were compared with hydro-chemical analyses of sediment porewater, grain size and ice content.
The tests on artificial samples helped improving our experiment design and highlighted the importance of anisotropy in comparison with the effects spacing or sample sizes. The field samples showed the importance of ice content and cryostructures as well as high salt content on the temperature-resistivity curves. Our research enables a better understanding of the temperature-resistivity dependency, provides information on sample sizes and anisotropy limitations necessary for fieldwork sampling, and overall allows for a better understanding and therefore interpretation of temperature dependent ERT datasets.
How to cite: Eppinger, S., Kunz, J., Offer, M., Angelopoulos, M., Fritz, M., Overduin, P. P., and Krautblatter, M.: Resistivity vs Temperature Laboratory Experiments on Arctic Sediments: Quantifying the Effects of Texture, Salt, and Cryostructure , EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17761, https://doi.org/10.5194/egusphere-egu26-17761, 2026.
Firn aquifers retain liquid meltwater within the near-surface layers of ice sheets and ice shelves, which may influence mass balance and subglacial hydrology. Despite their importance, measuring changes in firn aquifer water storage remains a challenge using existing satellite, airborne, and ground-based active radar methods, largely due to the significant spatial and temporal variability of firn aquifers. Complementary to active radar techniques, passive radar sounding is an advancing radioglaciological method that does not transmit its own signal for echo detection, but instead receives and correlates ambient radio emissions from the Sun to detect subsurface reflections, including those from firn aquifers.
In this presentation, we investigate the geophysical constraints (e.g., firn temperature, saturation, density, and depth) that govern the sensitivity of passive radar sounding to detect firn aquifer water table fluctuations. Our analysis highlights simulation-based, site-specific case studies representative of firn aquifer environments in Greenland, Svalbard, and Antarctica. Using realistic firn properties and expected solar geometry throughout the year, we evaluate signal attenuation, depth sensitivity, and expected echo time delays to identify seasonal observation windows for passive sounding.
Our results show that passive radar sounding can achieve sufficient signal-to-noise ratio and depth sensitivity to support monitoring on daily to seasonal timescales, particularly during and after the summer melt season when the most rapid changes in firn aquifers are likely to occur. These results further highlight the conditions under which passive sounding could enable quasi-continuous monitoring of firn aquifer dynamics and address a key gap in current cryospheric observational strategies.
How to cite: Peters, S., Wang, A., Gupta, N., and Culberg, R.: Passive Radar Sounding of Firn Aquifers: Geophysical Constraints and Sensitivity, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-17188, https://doi.org/10.5194/egusphere-egu26-17188, 2026.
Seasonal snow cover plays a fundamental role in sustaining human activities in mountain communities. Runoff originating from the European Alps is a primary water source for millions of people. However, Alpine snow resources are increasingly threatened by rising temperatures and changes in precipitation patterns due to climate change. These factors underscore the need for accurate and widespread monitoring of the Alpine snow resources.
From a hydrological perspective, snow water equivalent (SWE) is crucial to assess the water amount stocked in the snowpack and, therefore, the water availability after snowmelt. The most historically widespread SWE measurement practices consist in the direct assessment of the snow bulk density through field campaigns involving vertical coring or snow pits. Although these methods are highly accurate, they provide limited temporal and spatial coverage due to the significant manpower required and the inaccessibility of many sites during the snow season.
In the last decades, the development of sensors based on cosmic ray neutron sensing (CRNS) allowed the measurement of continuous SWE data in already monitored sites, filling the gaps associated with manual measurements. However, applying CRNS to monitor snowpacks in inaccessible sites remains largely unexplored as the standard procedure to retrieve SWE from neutron counts relies on site-specific parameters derived from reference measurements.
This work presents a network of 26 CRNS sensors located across the Italian Alps. The network is among the most extensive of its kind both in terms of both the number of probes and elevation range (1422 – 2901 m a.s.l.). Its broad coverage provides unprecedented insights into the possibility of retrieving SWE data independently of most of the site-specific features usually required. Notably, the parameterisation used to convert neutron counts into SWE is common to all probes in the network.
Manual SWE data from 13 sites within the network, collected during the 2023–2024 and 2024–2025 snow seasons, were used to calibrate and validate the network-wide parameterisation. The calibration process involved 35 direct SWE measurements performed at 6 sites during the first half of the 2023 – 2024 season. A total of 111 manual SWE data were used as the validation dataset.
The analysis shows that the application of a shared set of parameters results in a good representation of the snowpack characteristics. Moreover, the data from unmonitored sites of the network show high correlations with monitored sites at similar elevations. These results suggest that deploying CRNS probes can be used to overcome common limitations of snow monitoring, such as site accessibility issues, lack of manpower to perform manual measurements, and safety hazards linked to the harsh mountain environment.
This abstract is part of the NODES project which has received funding from the MUR–M4C2 1.5 of PNRR funded by the European Union - NextGenerationEU (Grant agreement no. ECS00000036).
How to cite: Gallarate, M., Colombo, N., Gazzola, E., Valt, M., Ronchi, C., Lanteri, L., Dinale, R., Nadalet, R., Ferraris, S., Gentile, A., Gisolo, D., Freppaz, M., and Acquaotta, F.: Validation of shared parameterisation for cosmic ray neutron sensors measuring snow water equivalent in the Italian Alps, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9490, https://doi.org/10.5194/egusphere-egu26-9490, 2026.
The precise determination of liquid water content (LWC) and density in the surface layer of the snowpack is crucial for understanding hydrological, energetic, and mechanical processes in snow-covered environments. The surface quality of the snowpack controls energy exchanges with the atmosphere and influences the electromagnetic response of the medium. However, the simultaneous and non-intrusive estimation of density and LWC remains challenging due to the strong interdependence between these parameters and the limited ability of many methods to separate them.
This work presents a method for the simultaneous estimation of density and liquid water content in the surface layer of a snowpack using a Stepped Frequency Continuous Wave (SFCW) radar operating in the 0.6–6 GHz range. The methodology is based on identifying, within the Fourier transform of the received signal, the peak corresponding to the air–snow interface. From this peak, two fundamental quantities are extracted (amplitude and phase) which are used to estimate the electromagnetic and physical properties of the snowpack surface.
Phase differences of the reflection peak are used to estimate LWC, as liquid water is the only constituent of the snowpack that introduces a significant imaginary component to the refractive index within the considered frequency range. In this interval, the complex permittivity of water exhibits high values, with a dominant effective imaginary part, while air introduces no losses and ice has an imaginary component at least three orders of magnitude smaller than that of water. Consequently, the accumulated phase shift of the reflected signal is directly controlled by the presence of liquid water, allowing small variations in LWC to be detected in the phase of the reflection peak.
The amplitude of the reflection peak depends on the total material content at the surface, as all constituents contribute to the real part of the effective refractive index. The amplitude is influenced by both snow density and LWC. Since the liquid water fraction is obtained beforehand from the phase, the relative proportions of air and ice can be estimated. From this information, the dry snow density is calculated, and through a volumetric balance, the total density of the surface layer and the LWC are determined.
The method is supported by preliminary calculations of the reflection coefficient Γ, which are used to derive calibration relationships for both phase and amplitude. Validation is carried out using synthetic snow structures representative of different surface conditions, including variations in dry snow density, liquid water content and layer thickness. In addition, initial field experiments have been conducted, showing responses consistent with the synthetic analysis and demonstrating the applicability of the approach under realistic conditions.
The results indicate that the combination of phase and amplitude constitutes a robust, non-intrusive tool for in situ monitoring of the snowpack, with the potential to detect early-stage compaction, melting, refreezing and rainfall events on snow.
How to cite: Subías Martín, A., Salinas, I., Herráiz-López, V., T.Buisán, S., and Alonso, R.: Estimation of Liquid Water Content and Density in the Surface Layer of the Snowpack from the Phase and Amplitude of SFCW Radar Signals, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6792, https://doi.org/10.5194/egusphere-egu26-6792, 2026.
Abstract:
Knowledge of spatio-temporal snow storage is crucial to understand snow-hydrological dynamics in complex, high alpine environments. Due to the low cost and fast deployability, photogrammetry in combination with commercial aerial photography UAVs has become a viable method for capturing high-resolution snowpack information. We utilize this technique in a high alpine catchment at Mt. Zugspitze in Germany to capture digital snow surface models and consequently snow depth information in heterogeneous environments. The fundamental step is the acquisition of overlapping aerial images, which are used for the reconstruction of the surface in the photogrammetric processing. It is well known that the properties of the image dataset determine the quality of the resulting reconstruction. Therefore, a number of studies from different areas of research focus on this topic. For snow depth mapping, Bühler et al. 2016 recommend, for instance a single overlap value, while Lee et al. 2021 collected different overlap values. Wu et al. 2025 found that the 3D model quality in an urban environment is linked to the overlap of an oblique image dataset in a nonlinear way. Depending on the studied terrain and structures, Maes 2025 summarizes various recommendations for appropriate overlap settings. To provide an insight into how often, in what resolution, and from which angle an area is captured, the current concept of overlap is unsuited. We suggest a paradigm change towards metrics representing the image information of a surface. Our approach is to increase the image capture frequency while angling the camera in a forward direction, wherefore a high image capture frequency of current digital camera systems is fundamental. Through this combination, the near-nadir information is retained, and the changed viewing geometry provides additional information in the along path and side view directions. The potential can be used for an increase in the dataset quality or a decrease in capture time. Both are highly relevant when working in the structurally complex and remote regions of high mountain areas. Battery capacity and regulations for flight speed and height do limit other options for an increase in data capture. Our goal is to share preliminary results for increasing the information in the image dataset while staying within the capability of current hardware.
Literature:
Bühler, Y., Adams, M.S., Bösch, R., Stoffel, A., 2016. Mapping snow depth in alpine terrain with unmanned aerial systems (UASs): potential and limitations. The Cryosphere 10, 1075–1088. https://doi.org/10.5194/tc-10-1075-2016
Lee, S., Park, J., Choi, E., Kim, D., 2021. Factors Influencing the Accuracy of Shallow Snow Depth Measured Using UAV-Based Photogrammetry. Remote Sensing 13, 828. https://doi.org/10.3390/rs13040828
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How to cite: Knieß, J., Schattan, P., Koch, F., and Wetzel, K.-F.: Shifting the Metric from Overlap to Information Density – Improved UAV Photogrammetry Strategies for High-Alpine Snow Depth Mapping, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19533, https://doi.org/10.5194/egusphere-egu26-19533, 2026.
