CR4.3 | Mountain permafrost: Advances in understanding and response to climate change
PICO
Mountain permafrost: Advances in understanding and response to climate change
Co-organized by GM10
Convener: Riccardo ScandroglioECSECS | Co-conveners: Samuel Weber, Coline MollaretECSECS, Theresa Maierhofer
PICO
| Wed, 17 Apr, 16:15–18:00 (CEST)
 
PICO spot 4
Wed, 16:15
Climate change significantly affects high mountain regions by strongly altering the cryosphere. It influences landscapes, water resources, slope stability, ecosystem balances, and human/touristic activities, all closely interconnected and interdependent.

Permafrost degradation remains often hidden but has the potential (1) to destabilize mountain slopes, leading to large-scale landslides or rock-ice avalanches, (2) to mobilize large amounts of loose materials, generating sudden and destructive debris flows, and (3) to cause ground subsidence, with adverse effects on infrastructure. These consequences and other mixed cascading effects show mountain permafrost systems' sensitivity and the importance of closely monitoring and understanding them.

This session welcomes all contributions from mountain permafrost research in all periglacial environments: from high Arctic climates through any continental regions (e.g. Alpine, Andean, Tibetan) to arid unglaciated areas of Antarctica. We welcome a broad spectrum of ice-rich and ice-poor landforms, including rock glaciers, talus slopes, plateaus, ice-cored moraines, steep rock slopes,and thermokarst.

We particularly encourage contributions that enhance understanding of thermo-hydro-mechanical-chemical processes at slope and regional scale. The combination of multiple methods and newly-developed approaches is of particular interest, as well as long-term studies or characterisation of new permafrost sites with state-of-the-art methods. Field and laboratory geophysical measurements (e.g., ERT, SRT, DAS, EM, IP, GPR, TLS), in-situ measurements (e.g., temperatures, discharge, kinematics, GPS), remote sensing surveys (e.g., optical, thermal, InSAR, UAV), modeling of past-present-future processes, early warning systems, and data analysis improvements thanks to machine learning and artificial intelligence tools can be submitted.

We aim to increase the understanding of mountain permafrost bodies’ response to climate evolutions. This session aims to create a new meeting and exchange opportunity within the mountain permafrost community and its fellows to foster common research developments and improve processes understanding.

ECS are encouraged to submit their work to this session. The presentation will be preferentially in presence (PICO).

We will meet up after the EGU for some burgers and beer. Join us at the Weinschenke (Franzensgasse 11, 1050 Wien) from 19:30!

For attending, please register here: https://forms.gle/EcyhsJLEfW191r1g9

PICO: Wed, 17 Apr | PICO spot 4

Chairpersons: Samuel Weber, Theresa Maierhofer, Riccardo Scandroglio
16:15–16:20
From gravitational mass movements ...
16:20–16:30
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PICO4.1
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EGU24-20989
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CR4.3
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solicited
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On-site presentation
Michael Krautblatter, Samuel Weber, Michael Dietze, Markus Keuschnig, Georg Stockinger, Lisa Brückner, Jan Beutel, Thomas Figl, Claudia Trepmann, Robert Hofmann, Maximilian Rau, Felix Pfluger, Laura Barbosa Mejia, and Florian Siegert

Warming in the last two decades has caused massive rockfall activity with limited mobility in the range of 101-6 m³. However, only a few highly destructive and mobile rock avalanches above 1 Mio. m³ have been documented. Rock-ice mechanical models explaining high-magnitude rock slope failure in permafrost have been postulated but not validated on real failures.

This study combines complementary expert knowledge to decipher the 1 Mio. m³ Fluchthorn rock slope failure that detached on June 12, 2023, from the before 3399 m high summit causing a rock avalanche that additionally eroded ca. 120.000 m³ of ice. InSAR data shows deformation rates in the range 4.1 – 7.1 ± 0.13 cm/a from April 2021 to March 2023, but these are surprisingly linked to a westward deformation of the entire Silvretta nappe (in the range of 3 cm/a) oversteepening the Fluchthorn. Mountain guides have observed singular failures before the event. IR drone flights immediately after the event indicate rock temperatures at the failure planes in the range of 0°C - -2°C and ice-filled fractures. Solid, scarcely fractured pseudotachilitic sequences in the summit regions may have contributed to the massive oversteepening of the Fluchthorn Westface without significant pre-failures. The grain size compositions shows massive material take up of fine-grained material and fragmentation (Pudasaini & Krautblatter 2021).

In a seismic analysis we can for the first time exactly reconstruct the temporal and spatial trajectory of a rock-ice avalanche, velocities and energy release during the 120-second rock-ice-avalanche propagation consistent with fragmentation and deposits. High-resolution photogrammetry highlights massive ice erosion and accumulation patterns during the rock avalanche propagation. In addition, we analyse all precursors in the last two years before the failure in detail (Leinauer et al. 2023): These include small prefailure volumes, seismic precursors, kinematic precursors and kinematic precursors detected in UltraCam & LiDAR surveys.

In an IRAZU model, capable of nucleation and growth of fractures based on nonlinear fracture mechanics applied stresses act to produce a progressive fracturing path that closely resembles the real failure and we can show the impact of the solid pseudotachilitic roof on the oversteepening. In a discontinuum model (UDEC), we can show the stabilizing effect of permafrost on developing fracturing patterns in a combined rock-ice mechanical approach, including temperature-dependent rock mechanical (Krautblatter et al. 2013, Draebing & Krautblatter 2019, Jia et al. 2017, 2019) and destabilization processes in ice-filled fractures and along rock-ice interfaces (Mamot et al. 2018, 2020, 2021).

In summary, we show a unique combination of datasets deciphering pre-failure tectonic and geological controls and forcing, syn-failure permafrost-related mechanics, and second-resolution data on rock avalanche evolution in a cryospheric terrain with massive ice uptake.

How to cite: Krautblatter, M., Weber, S., Dietze, M., Keuschnig, M., Stockinger, G., Brückner, L., Beutel, J., Figl, T., Trepmann, C., Hofmann, R., Rau, M., Pfluger, F., Barbosa Mejia, L., and Siegert, F.: The 2023 Fluchthorn massive permafrost rock slope failure analysed, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-20989, https://doi.org/10.5194/egusphere-egu24-20989, 2024.

16:30–16:32
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PICO4.2
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EGU24-8396
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CR4.3
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On-site presentation
Maëva Cathala, Josué Bock, Florence Magnin, Ludovic Ravanel, Matan Ben-Asher, Laurent Astrade, Xavier Bodin, Guillaume Chambon, Philip Deline, Thierry Faug, Kim Genuite, Stephane Jaillet, Jean Yves Josnin, André Revil, and Jessy Richard

Permafrost-affected rockwalls are highly sensitive to rapid climate change, sometimes leading to rock slope failures threatening human lives and activities. Many studies have demonstrated a link between permafrost degradation and rockwall instability, but there is still a need to document destabilization events to improve the understanding of triggering mechanisms to ultimately develop relevant approaches for hazard assessment.

 

Our study investigates the little rock-avalanche (c. 229,000 m3) that occurred in the Vallon d'Étache (Savoy, France) on June 18, 2020, after several days of heavy precipitation. We try to decipher the preconditioning and triggering factors of the rock avalanche by combining ground surface temperature monitoring, numerical modelling of permafrost evolution, energy balance modelling and geoelectrical survey interpreted with a petrophysical model to bring a detailed description of the hydrological and thermal mechanisms. The results show an intense permafrost warming especially since 2012 (annual trend: +0.06 °C a-1 at 30 m depth), with permafrost transitioning from cold to warm permafrost along the scar plan at a depth of c. 45 m when the event occurred. This warming may have preconditioned the rock avalanche. The geoelectrical soundings (240 to 640m long profiles) confirm that the crest around the scarp is still largely frozen with possible ice-rich layers (high resistivity values; 360 kΩ m). Furthermore, the energy balance model shows that the event occurred during the highest water input from rain and snowmelt, since at least 1985 which may have played as a triggering factor.  It also shows that the ground surface temperature experienced its highest winter and spring values before the event.

 

This multi-method approach shows that this rock avalanche occurred in still largely frozen bedrock but subject to recent and very intense warming, and that water infiltration may have played a key-role in its triggering, either due to the development of high hydrostatic pressure or to accelerated permafrost thawing along fractures.

How to cite: Cathala, M., Bock, J., Magnin, F., Ravanel, L., Ben-Asher, M., Astrade, L., Bodin, X., Chambon, G., Deline, P., Faug, T., Genuite, K., Jaillet, S., Josnin, J. Y., Revil, A., and Richard, J.: Predisposition and triggering conditions at a permafrost-affected rock avalanche site in the French Alps (Étache, June 2020), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-8396, https://doi.org/10.5194/egusphere-egu24-8396, 2024.

16:32–16:34
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PICO4.3
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EGU24-11060
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CR4.3
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ECS
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On-site presentation
Meven Philippe, Florence Magnin, Costanza Morino, Philip Deline, and Susan J. Conway

In mountainous periglacial environments, permafrost degradation can be comprised among the triggering factors of landslides. Such hazards represent a threat for human lives and infrastructures (Geertsema et al., 2009). The extent of permafrost, and hence location of areas at risk of landslides, is estimated at the global scale using models based on air temperatures (e.g. Gruber, 2012). However, at the local scale, specific geological settings can allow the persistence of permafrost beyond its climate boundaries. In talus slopes specifically, peculiar air circulation named “chimney effect” can exist and favour permafrost formation and persistence at their foot, at location where it is not always predicted by models (Wicky and Hauck, 2017).

In Iceland, talus slopes can be destabilised and generate landslides (Morino et al., 2019). However, due to the complexity of their geological setting, the thermal regime of talus slopes is difficult to model. Hence, only few numerical studies were conducted (e.g. Wicky and Hauck, 2017; Tanaka et al., 2006). This makes challenging to understand the destabilisation mechanisms of talus slopes, when determining the triggering mechanisms associated with permafrost degradation remains a crucial challenge.

 

In that scope, we installed 16 temperature sensors within the talus (and close rockwall) where the Eyjafirdi landslide originated from (October 6th 2020, Iceland). They recorded temperature hourly from August 2021 to July 2022. The primary analysis of the dataset reveals that a chimney effect indeed occurs within the talus; therefore, we suspect that an ice lens could have persisted at the bottom of the talus – outside of the predicted extent of permafrost. This hypothesis is supported by the observation of molards within the landslide deposits – i.e. cones of loose debris formed by the degradation of ice-cemented blocks of sediment, transported by the landslide (Morino et al., 2019).

In order to better characterise the thermal regime of the Eyjafirdi talus slope, we first reconstruct the temperature back to 1881 at the level of our sensors. We base that reconstruction on the correlation between our measured temperatures and air temperature datasets from meteorological stations – that go back to 1881. The reconstructed temperatures will then be used as forcing data, to constrain a thermal numerical model of the Eyjafirdi talus slope.

Model runs will be performed using the commercial software FEFLOW. It uses the finite element method (i.e. a discretisation of the studied object as a mesh) to solve equations of heat transfer, taking into account freezing and thawing processes. These numerical models will allow us to determine whether the chimney effect indeed maintained an ice lens within the Eyjafirdi talus slope. Moreover, thanks to our unique temperature dataset, our study will represent the most accurate effort to model talus slopes so far.

How to cite: Philippe, M., Magnin, F., Morino, C., Deline, P., and J. Conway, S.: Modelling the thermal regime of a recently destabilised talus: the Eyjafirdi landslide (October 6th 2020, Iceland), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-11060, https://doi.org/10.5194/egusphere-egu24-11060, 2024.

16:34–16:36
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PICO4.4
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EGU24-15928
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CR4.3
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ECS
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On-site presentation
Calvin Beck, Susan Conway, Costanza Morino, Bretwood Higman, Bill Billmeier, and Marianne Font

Permafrost is receding and warming globally due to current climate change trends. Mountain regions with areas of discontinuous to isolated permafrost are especially sensitive to these changes. In high relief mountainsides, ground ice can be essential in stabilising mountain slopes and can result in slope failures if this ice degrades. To determine the state of degrading permafrost and related slope failures, we studied the Matanuska Valley in Alaska (USA), an area characterised by a high density of landslides with permafrost molards .

Permafrost molards are cones of loose debris that can be found in landslide deposits in periglacial terrains, originating from ice-cemented blocks of debris that are transported down-slope within the landslide. These ice-cemented blocks are fragmented parts of the frozen material initially located in the landslide source area. Therefore, they can indicate the presence of degrading permafrost at the level of the detachment zone. Landslides containing permafrost molards have been detected in geographically and geologically diverse regions such as Argentina, Canada, Colorado, the European Alps, Greenland, Iceland, and Norway.

Our Alaskan field site contains 9 molard landslides within only a 15 km radius. These densely clustered landslides have a unique variety of geological, geomorphological and dynamic characteristics. This allows us to study a large parameter space of permafrost slope instabilities within a small region. Therefore, we studied the following five molard landslides in detail: Amulet, East and West Index Lake, Yellowjacket, and Matanuska River 2021 landslide.

These landslides are diverse in terms of landslide type, transported volume, run-out length, source materials, expositions, and altitudes. For instance, the Matanuska River 2021 landslide is a rotational slide of initially forested terrain with the head scarp at 780 m.a.s.l., and with a length of ~400 m plunging into the Matanuska River. In contrast, the Amulet landslide is a channelized debris slide with the head scarp at 1500 m.a.s.l., a run out length of ~2100 m, and with hundreds of molards with diameters ranging up to 44 m in the landslide deposits.

To document the variability between these landslides, we performed traditional geomorphological and geological field measurements, dug transects in the molards, took samples, and we obtained digital terrain models of the landslides by drone-based photogrammetry. We acquired drone-based photogrammetry data of Yellowjacket landslide only two weeks after the failure, before the initial ice-cemented blocks fully degraded, as well as four years after the slope failure. For the first time, this allows us to compare spatial data of permafrost molards before and after the degradation of the initial ice-cemented blocks and to perform statistical analysis on this data.

We investigated molard shape, size, and size-distribution parameters to compare these to variables such as source material and expected permafrost conditions. This allows us to confine the composition of the initially ice-cemented blocks of debris, which will help us to understand under what conditions molards can form. In the future, this will allow us to quantify the currently often uncertain state of mountain permafrost more precisely.

How to cite: Beck, C., Conway, S., Morino, C., Higman, B., Billmeier, B., and Font, M.: Field study of permafrost molards from diverse origins of landslides in Matanuska Valley, Alaska, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15928, https://doi.org/10.5194/egusphere-egu24-15928, 2024.

... over monitoring spatial and temporal changes ...
16:36–16:38
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PICO4.5
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EGU24-19057
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CR4.3
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On-site presentation
Jan Beutel, Alessandro Cicoira, Umberto Morra di Cella, Paolo Pogliotti, and Samuel Weber

High-altitude mountain areas are very susceptible to the climate evolution at all scales. However little is known about this extreme end member characterized by steep topographies and remoteness. Therefore in-situ observations are scarce and often limited in their temporal and spatial coverage as well as their fidelity. Over the past two decades teams from Italy as well as Switzerland have concentrated multiple interdisciplinary research efforts at and on the slopes of the Matterhorn. This cross-border laboratory today covers a full altitude transect from the valley floor to the summit at 4478 m asl as well as from south to north with a dense network of permanent in-situ observation locations. In addition, several research campaigns have been historically undertaken and add to this unique footprint of observation data as well as insight. Primary data observed are ground-surface temperature as well as permafrost active layer depth, meteorological parameters, surface kinematics using crackmeters as well as GNSS, resistivity, optical imaging, seismic signals as well as personal observations through a regional observer network. In this presentation, we will summarize the activities over the past two decades and discuss insights, key findings as well as data availability.

How to cite: Beutel, J., Cicoira, A., Morra di Cella, U., Pogliotti, P., and Weber, S.: Insights from steep-bedrock, high-altitude mountain permafrost laboratory at the Matterhorn, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19057, https://doi.org/10.5194/egusphere-egu24-19057, 2024.

16:38–16:40
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PICO4.6
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EGU24-18050
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CR4.3
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ECS
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Highlight
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On-site presentation
Cécile Pellet and Jeannette Noetzli and the PERMOS Scientific Committee

Permafrost is classified as an essential climatic variable (ECV) by the Global Climate Observing System (GCOS) because of its sensitivity to changes in climatic conditions. The Swiss Permafrost Monitoring Network PERMOS documents the state and changes of permafrost conditions in the Swiss Alps since 2000 based on long-term field measurements. To account for the heterogeneous distribution and characteristics of mountain permafrost, PERMOS developed and implemented a comprehensive monitoring strategy, which relies on three complementary observation elements: (1) ground temperatures near the surface and at depth, (2) permafrost electrical resistivity to determine changes in ground ice content, and (3) rock glacier velocities, which can be used as a proxy to assess the permafrost thermal regime.

In this contribution, we discuss permafrost conditions in the Swiss Alps during the hydrological year 2023 with respect to the observations of the past two decades. Combining results from the three observation elements, we analyse the short and long-term responses of permafrost to climate evolution. The hydrological years 2022 and 2023 were characterized by two consecutive winters with below average snow heights and two summers ranked second and fifth warmest on record since 1864. These weather and climate conditions lead to different permafrost evolutions at different depth levels and at different sites. While ground surface temperatures and active layer thicknesses at or close to record values were registered, a slight decrease of the permafrost temperatures was observed at 10 and 20 m depth, which is consistent with the decreasing rock glacier velocity and increasing permafrost resistivity observations. The permafrost conditions observed in 2023 constitute short term variations likely not affecting the long-term trend of warming and degrading permafrost consistently observed in the Swiss Alps for the past two decades.

How to cite: Pellet, C. and Noetzli, J. and the PERMOS Scientific Committee: State of permafrost in the Swiss Alps in 2023, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18050, https://doi.org/10.5194/egusphere-egu24-18050, 2024.

16:40–16:42
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PICO4.7
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EGU24-19517
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CR4.3
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ECS
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On-site presentation
Coline Mollaret, Christin Hilbich, Cecile Pellet, Christian Hauck, Tomasz Gluzinski, Eva De Mits, Theresa Maierhofer, Christophe Lambiel, Alex Bast, Jacopo Boaga, Adrian Flores Orozco, Hanne Hendricks, Christof Kneisel, Julius Kunz, Sarah Morard, Mirko Pavoni, Sebastian Pfaehler, Marcia Philips, Riccardo Scandroglio, and Cristian Scapozza and the Swiss Electrical Database on Permafrost Team

In permafrost research, geoelectrical surveys are increasingly used to detect the presence and extent of permafrost and to characterise the stratigraphy and material composition of permanently frozen terrain. When repeated, the resulting temporal changes in electrical resistivity can be related to changes in ground temperature and ice content, and therefore also to ground ice loss over time. However, for financial and logistical reasons, only a few continuous electrical resistivity tomography (ERT) monitoring installations on permafrost exist worldwide. An alternative approach is manual but regularly repeated ERT measurements, such as - besides other examples - in the context of the Swiss Permafrost Monitoring Network (PERMOS, 2023). In contrast, there are many permafrost sites (estimated to be over 500 in Switzerland) where single ERT measurements have been performed in the past. In the context of atmospheric warming, these historical datasets can serve as a baseline for analysing current changes in ground ice content in permafrost regions and the associated challenges to mountain slope stability.

In this contribution, we present the analysis of the Swiss datasets, which are integrated in the International Database of Geoelectrical Surveys on Permafrost (IDGSP), led by the International Permafrost Association (IPA) Action Group of the same name. Before this initiative, geoelectrical datasets (mainly ERT) were not included in a common and dedicated database. Since the launch of the IPA Action Group in 2021, a database has been designed and set up (using PostgreSQL), numerous metadata and data have been collected and homogenised, and public access via a searchable web map is available (https://resibase.unifr.ch). We present the strategy developed for consistent filtering, processing, and inversion for this extensive dataset. In this contribution, we analyse both spatial and temporal variations in surveys conducted at various Swiss mountain sites.

The overall goal is to establish a complete database of electrical measurements on permafrost in Switzerland, including all historical measurements. The data are re-processed with the newly developed filtering and inversion routines and made available to the public to facilitate the repetition of measurements in the context of permafrost degradation, geotechnical studies of permafrost stability, hydrological studies in the context of natural hazards and water availability from thawing permafrost environments, and to serve as a baseline dataset for permafrost distribution and modelling.

PERMOS 2023. Swiss Permafrost Bulletin 2022. Noetzli, J. and Pellet, C. (eds.) 22 pp, https://doi.org/doi:10.13093/permos-bull-2023

How to cite: Mollaret, C., Hilbich, C., Pellet, C., Hauck, C., Gluzinski, T., De Mits, E., Maierhofer, T., Lambiel, C., Bast, A., Boaga, J., Flores Orozco, A., Hendricks, H., Kneisel, C., Kunz, J., Morard, S., Pavoni, M., Pfaehler, S., Philips, M., Scandroglio, R., and Scapozza, C. and the Swiss Electrical Database on Permafrost Team: A database integrating the electrical resistivity data of Switzerland for mountain permafrost spatio-temporal characterisation, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-19517, https://doi.org/10.5194/egusphere-egu24-19517, 2024.

16:42–16:44
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PICO4.8
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EGU24-13408
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CR4.3
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On-site presentation
Riccardo Scandroglio, Jonas K. Limbrock, and Michael Krautblatter

Alpine permafrost degradation boosted by climate change is recorded worldwide, posing a significant threat to slope stability. A comprehensive assessment of this risk necessitates continuous monitoring of the rate of permafrost changes, for example, with electrical resistivity tomography (ERT). Although ERT has been employed in more than 1000 studies worldwide to detect permafrost, only a few sites are monitored with high temporal resolution and present more than a decade of uninterrupted observations.

Whitin the Kammstollen tunnel (2750 m asl, Mount Zugspitze, DE/AT), geoelectrical tomographies of the north face have been conducted since 2007. In the last ten years, an extensive dataset has been collected monthly employing consistent procedures and permanent electrodes. Recently, we updated the inversion methods to the most recent standards, and after reprocessing old data, we precisely quantified the evolution of permafrost in the last decade. In line with the observed increase in air temperature, the permanently frozen area shows a gradual but consistent reduction during the summer months, with the record minimum value recorded at the end of summer 2023. This study highlights the limits of laboratory calibrations, especially in the presence of different degrees of rock fragmentation (fault zone). Further, we show the influence of error models on inversion results and on the quantification of resistivity changes, confirming the need for repeated estimation of measurement errors. 

The unique geoelectrical dataset here presented, bolstered by many simultaneous supplementary information, contributes to better defining the role of geoelectrical monitoring for understanding the thermal responses of alpine permafrost environments to present and future climate-change-induced stresses.

How to cite: Scandroglio, R., Limbrock, J. K., and Krautblatter, M.: Permafrost is disappearing at the Mount Zugspitze (D/A): challenges and results after 10 years of monthly geoelectrical measurements., EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-13408, https://doi.org/10.5194/egusphere-egu24-13408, 2024.

16:44–16:46
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PICO4.9
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EGU24-12384
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CR4.3
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ECS
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On-site presentation
Clemens Moser, Barbara Funk, and Adrian Flores Orozco

In mountain permafrost areas, frozen rocks are thawing due to the rise in air temperatures and, thus, ground ice content decreases, which in turn does not only lead to changes in subsurface water storage but also affects slope stability in solid rock walls. Monitoring changes of the electrical conductivity in the subsurface has emerged as a suitable technique to differentiate between non-frozen and frozen areas because of the much lower conductivity of frozen than of unfrozen media. However, the direct estimation of ice content directly from conductivity measurements is challenging because this property is also dependent on the temperature and the geological media, i.e., porosity, saturation, and fluid conductivity of the pore-water and the surface conductivity taking place at the interface between water and grains or ice. For a proper discrimination between frozen and unfrozen areas, the induced polarization (IP) has emerged as a suitable method, as it measures not only the conductivity but also the electrical capacitive properties (polarization) in the low-frequency range (mHz - kHz). Previous studies have revealed an increase in the IP effect with decreasing temperature, arguing that such response is due to the polarization either from charges in the ice (at the kHz range) or at the interface between ice and water (around 100 Hz). In this study, we investigated the IP response from small rocks in an imaging framework under well-controlled freezing conditions in the laboratory. First, we aimed to understand the role of surface conductivity in frozen rocks by a multi-salinity analysis (in the range between 0.1 and 10 S/m), which also permits to estimate the porosity of the rocks. Second, we investigate the polarization response of rocks in presence of features with high ice content in multi-electrode imaging configurations. The rocks have been collected at different sites in the European Alps to evaluate the effect in the data due to changing lithology. IP imaging measurements were conducted over a broad range of frequencies (0.1 Hz - 30 kHz) using to-date approaches to reduce capacitive coupling arising from changes in galvanic contact of the electrodes with the rocks at frequencies above 100 Hz. The data were inverted in ResIPy, which solves for the conductivity magnitude and phase angle by using complex calculus. The salinity experiments result in porosities around 2-4% and a linear relation between the surface conductivity and the polarization (quadrature conductivity) with a slope around 0.01, which reveals the importance of surface conductivity, even at low frequencies and positive temperatures. For measurements on rocks with ice features, inversion results show that the IP imaging method is able to delineate ice-saturated holes due to a contrast in polarization. Based on our results, we evaluate existing petrophysical relationships linking the frequency-dependence of the IP results with porosity, ice content and temperature.

How to cite: Moser, C., Funk, B., and Flores Orozco, A.: Investigating IP imaging measurements in frozen rocks for a better understanding of electrical signatures in alpine permafrost investigations, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12384, https://doi.org/10.5194/egusphere-egu24-12384, 2024.

16:46–16:48
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PICO4.10
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EGU24-18614
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CR4.3
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On-site presentation
Alexander Bast, Robert Kenner, and Marcia Phillips

Rock glacier monitoring has revealed a long-term increase in rock glacier surface velocity in the European Alps, often associated with increased air and ground temperatures as well as water content. The long-term acceleration of rock glaciers is superimposed by high interannual variability of their velocity, and there is still a gap in the quantitative assessment of the role of water in rock glaciers and the factors leading to the short-term deceleration of rock glaciers.

To address this research gap, we drilled and documented the stratigraphy of three vertical boreholes in the Schafberg Ursina III rock glacier, Swiss Alps (46°29'50.391" N, 9°55'34.779" E; 2’750m asl), in August 2020. One of the boreholes was instrumented with ten Keller PAA-36XiW piezometers, which measure pore water pressure (www.keller-druck.ch) at depths ranging from 2 m to 8.5 m depth. In addition, each piezometer is equipped with a PT 1000 temperature sensor. The other two boreholes were equipped with a permanently installed cross-borehole electrical resistivity tomography (ERT) setup consisting of 24 electrodes in each borehole, spaced at 0.5 m, to a depth of 11.5 m, reaching the top of the shear horizon of the rock glacier. We used a Syscal Pro Switch 48 resistivity meter and a Syscal monitoring unit to automatically collect, record and transmit the acquired data (www.iris-intruments.com). ERT monitoring provides information on relative changes in ice water content. Rock glacier velocities were determined from terrestrial laser scans taken in July each year using a Riegel VZ6000 long-range scanner (www.riegl.com). Using data from nearby weather stations of the Intercantonal Measurement and Information System (IMIS network) and ground surface temperature sensors, we analysed the interplay between meteorological and subsurface conditions during a rock glacier deceleration period from January 2021 to June 2023, which included two snow-poor winters (2021-2022, 2022-2023) and a summer heat wave in 2022.

Our results show that a reduction of the water content of rock glaciers is crucial for intermittent, interannual rock glacier deceleration. The influence of snow cover on rock glacier kinematics is significant, both as an insulator and as a water source. Winters with little snow and relatively dry summers are ideal for cooling and drying rock glaciers, leading to deceleration. Summer heat waves have a limited effect if preceded by dry winters. The importance of rainfall and snow melt water infiltration from the entire catchment remains to be determined. High-resolution GNSS data and information on water contents in rock glacier shear horizons is needed to improve our understanding of the role of water on rock glacier kinematics.

Our contribution highlights an innovative combination of borehole data to gain insight into an alpine rock glacier's ground temperature and water content, allowing us to detect relative changes in ice/water content in ice-rich permafrost.

How to cite: Bast, A., Kenner, R., and Phillips, M.: Unveiling cooling, drying and deceleration of a rock glacier during a warm period through ground temperature, piezometer and cross-borehole ERT data, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-18614, https://doi.org/10.5194/egusphere-egu24-18614, 2024.

16:48–16:50
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PICO4.11
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EGU24-9220
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CR4.3
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ECS
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On-site presentation
Chiara Crippa, Stefan Steger, Giovanni Cuozzo, Francesca Bearzot, and Claudia Notarnicola

High-altitude regions serve as crucial indicators of climate change, with the Alps acting as a natural laboratory for studying glacial and periglacial processes. In situ and remote sensing techniques reveal permafrost degradation, coinciding with accelerated rates of rock glacier creep, potentially leading to destabilization.

Our study, focused on South Tyrol (North-East Italy), aims to screen and classify rock glaciers, thus pinpointing hotspots and unraveling the factors influencing their activity through the integration of remote sensing approaches and data-driven models. Our analyses are based on an existing inventory of periglacial landforms (1779 in total) across South Tyrol, mapped using LIDAR DTMs (2.5 m GSD) and orthophotos. The dataset already includes a descriptive attribute of activity from independent morphological observations and a DInSAR coherence-based estimation (Bertone et al., 2019). However, it lacks a comprehensive definition of activity based on climatic drivers, displacement rate, and morphometric parameters.

To quantify the velocity for each feature, we adopted a replicable workflow utilizing Sentinel 1A/B C-band images (2020-2022). This workflow involves three main steps: i) SAR pairs selection, filtering and processing using the Alaska Satellite Facility's Hybrid Pluggable Processing Pipeline (ASF HyP3); ii) atmospheric correction through a CNN (convolutional neural network) approach (Brencher et al., 2023); iii) time series inversion to produce mean LOS (Line-of-Sight) displacement rate maps through the MintPy algorithm (Yunjun et al., 2019).

We processed geomorphological (slope, aspect, insolation, curvature, etc.) and climatic maps (precipitation, temperature, snow cover duration) from both in situ (weather stations) and remote sensing products (MODIS, Landsat) to extract 19 descriptive parameters potentially influencing the development and state of activity of rock glaciers. These parameters served as predictor variables in a multiclass GAM classifier (Generalized Additive Mixing Models) to categorize all mapped landforms in active, relict, or transitional classes (RGIK, 2022).

After training the model on a subset of confidently classified features, we applied it to the entire rock glacier dataset, including features without an activity definition. Quantitative assessment of the model's performance, using the area under the ROC curve, consistently yielded results exceeding 0.86 across various k-fold cross-validation approaches.

Our analysis not only enhanced classification accuracy but also provided insights into the factors influencing activity classes. A final classification using the Bulk Creep Factor (BCF) indicator (Cicioira et al., 2021), describing the dynamic state and rheology of large-scale rock glacier datasets, facilitated the selection of key case studies for a detailed local-scale investigation.

This comprehensive approach refines the categorization of mapped features and contributes to a more detailed understanding of the factors controlling rock glacier activity in the alpine environment, particularly in South Tyrol.

How to cite: Crippa, C., Steger, S., Cuozzo, G., Bearzot, F., and Notarnicola, C.: Integration of DInSAR, climatic, and morphometric data through data-driven models for regional-scale activity classification of rock glaciers in South Tyrol (Italy), EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9220, https://doi.org/10.5194/egusphere-egu24-9220, 2024.

... to implications and significance.
16:50–16:52
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PICO4.12
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EGU24-12821
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CR4.3
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On-site presentation
Christian Hauck, Dominik Amschwand, Tomasz Gluzinski, Christin Hilbich, Martin Hoelzle, Tamara Mathys, Coline Mollaret, and Sarah Morard

Coarse-blocky landforms are assumed to be the most resilient permafrost occurrences due to low thermal conductivity and their seasonal asymmetric internal convection processes and have been addressed in many field and modelling studies. In this contribution we will put a specific focus on the most general of these landforms, the ubiquitous talus slopes, which are understudied compared to other mountain permafrost landforms such as rock glaciers. Talus slopes exist in all mountain ranges and at different elevations, including middle mountains where they give rise to specific undercooled micro-climatic conditions. In many cases, internal convection processes are the main reason that the cool micro-climatic conditions could be preserved over long time scales. The ice content can be variable, ranging from zero at low elevations to the presence of ice cores at elevations where permafrost is widespread. However, the ice content in most talus slopes is generally unknown, as boreholes are extremely scarce and standard geophysical techniques (such as Electrical Resistivity Tomography and Seismic Refraction techniques) exhibit problems in detecting medium to small ice contents in coarse blocky substrates. In this contribution we use a compilation of data from a large number of different talus slopes in Europe, the Central Andes and Central Asia to attempt to (1) quantify the influence of slope angle, substrate and thickness of the talus on the internal air circulation and its cooling effect and (2) address the application of emerging geophysical techniques to improve the quantification of ice content in these substrates.

How to cite: Hauck, C., Amschwand, D., Gluzinski, T., Hilbich, C., Hoelzle, M., Mathys, T., Mollaret, C., and Morard, S.: Permafrost in talus slopes: what are the main drivers of low temperatures and ice content ?, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-12821, https://doi.org/10.5194/egusphere-egu24-12821, 2024.

16:52–16:54
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PICO4.13
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EGU24-9757
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CR4.3
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On-site presentation
Samuel Weber and Alessandro Cicoira

Permafrost is warming and thawing globally because of climate change, which has consequences for slope stability. Despite numerous studies focusing on permafrost evolution, knowledge of the physical properties of frozen ground is based on a few in-situ measurements and laboratory experiments. There are few observations on water fluxes in permafrost, which are rapidly changing due to active layer thickening, ground ice melt, talik formation, and modified permeability. Particular attention should be given to changes in the thermal regime, an indicator of permafrost degradation and deep water infiltration, which are currently inducing deep-seated slope instabilities.

In this study, we use data from the 29 temperature boreholes of the Swiss Permafrost Monitoring Network PERMOS to quantify the thermal diffusivity in different permafrost rock slopes characterized by the three landforms: rock glacier, talus slope, or bedrock. We apply statistical and numerical modeling approaches and calculate the thermal diffusivity for each instrumented depth in a two-month window that iterates by one day. The thermal diffusivity at each instrumented depth is additionally inverted for each calendar year using analytical modeling to validate the results.

This systematic analysis of the PERMOS borehole temperature data, with three independent methods, allows us to derive a well-constrained range for the thermal properties of different substrates in mountain permafrost. Isolating spatial and temporal anomalies in thermal diffusivity, we can further investigate non-conductive processes governed by thawing and/or water advection. Given the one-dimensional heat conservation equation, the non-conductive heat flux can be quantified using the difference between the observed and modeled temperature change. Once concluded, this analysis will represent the basis for many other studies investigating the thermal and mechanical behavior of mountain permafrost rock slopes.

How to cite: Weber, S. and Cicoira, A.: Modeling thermal diffusivity in permafrost rock slopes to identify non-conductive heat fluxes, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9757, https://doi.org/10.5194/egusphere-egu24-9757, 2024.

16:54–16:56
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PICO4.14
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EGU24-17962
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CR4.3
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ECS
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On-site presentation
Simon Seelig, Magdalena Seelig, Karl Krainer, and Gerfried Winkler

Active rock glaciers represent permafrost-affected aquifers that govern the response of many alpine headwater catchments. Their heterogeneous internal structure tends to channelize groundwater flowing along the permafrost table or within the frozen rock glacier core. This study derives the hydraulic properties of such thermokarst channel systems at three active rock glaciers in the Austrian Alps. Their basic configuration is assessed through spring flow analysis and dye tracer tests. Breakthrough curves are characterized by multiple peaks and strong tailing, implying flow path separation and partial retardation of the tracer cloud travelling through the rock glaciers. Individual channels can reach diameters up to several decimeters and are characterized by a convoluted, irregular geometry. Flow along the channels is fast, highly turbulent, and characterized by high frictional resistance. Heat transfer is predominantly advective, inducing a positive feedback loop that allows larger channels to grow at the expense of smaller ones, effectively increasing the hydraulic conductivity at the rock glacier scale. The preferential flow paths provided by the thermokarst channel networks dominate flow and transport through the rock glaciers in particular during the summer months, and thus govern spring flow dynamics, solute transport, permafrost degradation, thermokarst lake outburst hazard, and rock glacier front stability.

How to cite: Seelig, S., Seelig, M., Krainer, K., and Winkler, G.: The impact of thermokarst development on flow and transport processes in alpine rock glaciers, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-17962, https://doi.org/10.5194/egusphere-egu24-17962, 2024.

16:56–16:58
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PICO4.15
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EGU24-9989
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CR4.3
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ECS
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On-site presentation
Huiru Jiang, Yonghong Yi, and Rongxing Li

Permafrost plays a crucial role in influencing regional water resources by impeding surface water infiltration and regulating surface runoff discharge. Great efforts have been made to investigate the hydrological effects of permafrost degradation, but the underlying mechanisms behind the impacts of permafrost change on runoff production remain unclear, especially in the high-altitudinal permafrost basins with high spatial heterogeneity and limited soil observations. Therefore, this study combines long-term discharge records, process-based model simulations and remote sensing measurements to investigate the characteristics of runoff recession processes, which directly reflect the variation of soil storages affected by permafrost changes. With 60-year daily discharge records from eight high-altitude permafrost basins and subbasins of the Tibetan Plateau, we first analyzed the long-term temporal evolution of runoff recession rates. Then taking the source region of the Yangtze River (SRYR) in the central Tibetan Plateau as an example, we further investigated the specific soil freeze/thaw (F/T) factors that impact the runoff recession rates, by modifying a process-based permafrost hydrology model and simulating the soil F/T dynamics and related hydrological responses.

The preliminary results show that permafrost coverage strongly impacts the storage-discharge relationships indicated by runoff recession rates. In basins with high permafrost coverage (>80%), the long-term runoff recession rates exhibit a significant decreasing trend across all recession events, and a discontinuous runoff recession process is generally observed during the autumn and early winter recession periods. With a reduction in the permafrost coverage, we did not observe a significant trend in the long-term recession rate except for the recession events during early freezing periods (around autumn). In basins with much lower permafrost coverage (<50%), no distinct long-term trend in the seasonal runoff recession rates is observed. The process-based model simulation results in the SRYR (~80% of permafrost coverage) further reveal strong regulation of permafrost on the runoff production. A slower autumn recession rate is often related to a delayed soil freeze onset, especially in the deep soils of the active layer, which facilitates a larger soil water reservoir. In addition, the observed discontinuous recession during fall and early winter runoff recession period may result from a delayed soil freeze onset and longer unfrozen state (e.g., a longer duration of zero-curtain), influencing the connectivity of groundwater flow channels. In the next phase, we plan to include more remote sensing observations, such as InSAR deformation, to further investigate how active-layer soil water dynamics and its F/T state affect regional runoff production and water balance. This study shall enhance our understanding of the fundamental influence of permafrost changes on river runoff and support predictions of permafrost hydrological responses to future climate changes.

How to cite: Jiang, H., Yi, Y., and Li, R.: Strong regulation of permafrost coverage on runoff recession in the high-altitude permafrost basin, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-9989, https://doi.org/10.5194/egusphere-egu24-9989, 2024.

16:58–17:00
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EGU24-15002
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CR4.3
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ECS
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Virtual presentation
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Dominik Büeler, Elizaveta Sharaborova, Maria Pyrina, Michael Lehning, and Daniela I. V. Domeisen

Alpine permafrost thawing due to climate warming has been rapidly intensifying in the past decades. Since permafrost stabilizes the rock, its thawing has and will become a growing risk for mountainous countries like Switzerland, with potential implications for rockfall magnitude and frequency, mountain infrastructure, mountain ecosystems, and tourism. The long-term trend in the thickening of the active layer and thus the subsidence of the permafrost table in the Swiss Alps due to climate warming is well observed and documented. However, less is known about how sub-seasonal to seasonal variability of atmospheric temperature, in particular individual multi-weekly heatwaves in summer, influence below-ground temperature from year to year. In this interdisciplinary study, we thus explore how atmospheric temperature variability on timescales of days to seasons affects the variability of below-ground temperature and the depth of the permafrost table, measured at various rock borehole stations of the Swiss Permafrost Monitoring Network PERMOS. In addition, we evaluate how well the snowpack and ground surface model SNOWPACK is able to reproduce this relationship. The insights from this analysis will pave the way to couple the SNOWPACK model to sub-seasonal to seasonal weather prediction models, which are increasingly being used to predict the probability of heatwave occurrence several weeks ahead. Such a coupling could allow for a prediction of the evolution of below-ground temperature and of significant permafrost anomalies on an operational basis, and thereby support early warning systems for alpine hazards.

How to cite: Büeler, D., Sharaborova, E., Pyrina, M., Lehning, M., and Domeisen, D. I. V.: The influence of sub-seasonal to seasonal atmospheric temperature variability on alpine permafrost, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-15002, https://doi.org/10.5194/egusphere-egu24-15002, 2024.

17:00–18:00