New multi-phase thermo-geophysical model: Validate ERT-monitoring & assess permafrost evolution in alpine rock walls (Zugspitze, German/Austrian Alps)

2020 ◽  
Author(s):  
Tanja Schroeder ◽  
Riccardo Scandroglio ◽  
Verena Stammberger ◽  
Maximilian Wittmann ◽  
Michael Krautblatter
Keyword(s):  
Electrical Resistivity ◽  
Heat Fluxes ◽  
High Mountain ◽  
Permafrost Degradation ◽  
Mountain Areas ◽  
Rock Wall ◽  
Permafrost Rock ◽  
Geophysical Model ◽  
Multi Phase

<p><span>In the context of climate change, permafrost degradation is a key variable in understanding rock slope failures in high mountain areas. Permafrost degradation imposes a variety of environmental, economic and humanitarian impacts on infrastructure and people in high mountain areas. Therefore, new high-quality monitoring and modelling strategies are needed.</span></p><p><span>Electrical Resistivity Tomography (ERT) is the predominant permafrost monitoring technique in high mountain areas. Its high temperature sensitivity for frozen vs. unfrozen conditions, combined with the resistivity-temperature laboratory calibration on Wettersteinkalk (Zugspitze) (Krautblatter et al. 2010) gives us quantitative information on site-specific rock wall temperatures (Magnin <em>et al.</em> 2015). Long-term ERT-Measurements (2007/2014 – now) were taken at the Kammstollen along the northern Zugspitze rock face. Two high-resistivity bodies along the investigation area reach resistivity values ≥10<sup>4.5</sup></span>Ω<span>m (</span><span>∼</span><span>−0.5 </span><span>°</span><span>C), indicating frozen rock, displaying a core section with resistivities ≥10<sup>4.7</sup></span>Ω<span>m (</span><span>∼</span><span>−2 </span><span>°</span><span>C) (Krautblatter <em>et al.</em>, 2010). We can differentiate seasonal variability, seen by laterally aggrading and degrading marginal sections (Krautblatter <em>et al.</em>, 2010) and singular effects due to environmental factors and extreme weather events.</span></p><p><span>Here, we present a new local high-resolution numerical, process-orientated thermo-geophysical model (TGM) for steep permafrost rock walls. The model links apparent resistivities, the ground thermal regime and meteorological forcings as seasonality and long-term climate change to validate the ERT and project future conditions. The TGM comprises a surface energy balance model, conductive energy transport, turbulent and seasonal heat fluxes (sensible, latent, melt and rain heat fluxes) including phase-change, as well as a multi-phase rock wall composition.</span></p><p><span>Finally, we can reproduce the natural temperature field in the rock wall, assess the spatial-temporal permafrost evolution in alpine rock walls, validate the ERT measurements via the new TGM and the applicability of the laboratory derived resistivity-temperature relationship by Krautblatter et al. (2010) for natural rock-wall conditions.</span></p><p><span> </span></p><p><span>Krautblatter, M., Verleysdonk, S., Flores-Orozco, A. & Kemna, A. (2010): Temperature- calibrated imaging of seasonal changes in permafrost rock walls by quantitative electrical resistivity </span><span>tomography</span><span> (Zugspitze, German/Austrian Alps). <em>J. Geophys. Res. </em>115: F02003.</span></p><p><span>Magnin, F., Krautblatter, M., Deline, P., Ravanel, L., Malet, E., Bevington, A. (2015): Determination of warm, sensitive permafrost areas in near-vertical rockwalls and evaluation of distributed models by electrical resistivity tomography. <em>J. Geophys. Res. Earth Surf.</em>, 120, 745-762.</span></p>

A high-resolution multi-phase thermo-geophysical permafrost rock model to verify long-term ERT monitoring at the Zugspitze (German/Austrian Alps)

2021 ◽  
Author(s):  
Tanja Schroeder ◽  
Michael Krautblatter
Keyword(s):  
Electrical Resistivity ◽  
Energy Balance ◽  
Thermal Regime ◽  
Thermal Evolution ◽  
High Mountain ◽  
Permafrost Degradation ◽  
Complex Topography ◽  
Mountain Areas ◽  
Permafrost Rock

<div> <p><span>In the context of climate change, permafrost degradation is a key variable in understanding rock slope failures in high mountain areas. Permafrost degradation imposes a variety of environmental, economic and humanitarian impacts on infrastructure and people in high mountain areas. Therefore, new high-quality monitoring and modelling strategies are needed.</span></p> </div><div> <p><span>We developed a new, numerical, thermo-geophysical rock permafrost model (TGRPM) to assess spatial-temporal variations of the ground thermal regime in steep permafrost rock walls on the basis of 13-years of Electrical Resistivity Tomography (ERT) monitoring of permafrost at the Zugspitze. TGRPM is a simple to understand and workable numerical 2D MATLAB-model, which is adaptable to different topographic and sub-surface conditions, and further relies on a minimum of input-data to assess the surface energy balance and the ground thermal regime. It simulates the thermal response for permafrost rock walls, including their complex topography, to climate forcing over multiple years. It aims to assess seasonal and long-term permafrost development in steep alpine rock walls, as well as serving as a straightforward calculation routine, which is solely based on physical processes and does not require any fitting of certain parameters. </span></p> </div><div> <p><span>At first, the model was tested against direct temperature measurements from the LfU-borehole at the Zugspitze summit to prove its accuracy. Then, it is run against a 13-year ERT data-set from the Zugspitze Kammstollen to validate the ERT measurements.</span></p> </div><div> <p><span>Here, we show the first thermo-geophysical model referencing thermal evolution in a permafrost rock wall with temperature-calibrated ERT. The TGRPM successfully computes the thermal evolution within the Zugspitze mountain ridge from a 2D coupled energy balance and heat conduction scheme in complex topography. It furthermore validates the temperature-resistivity relationship by Krautblatter et al. (2010) for natural rock walls reaching a correlation of 85 to 95 % between measured, ERT-derived and modelled temperatures.</span></p> </div><div><span>Krautblatter, M., Verleysdonk, S., Flores-Orozco, A. & Kemna, A. (2010): Temperature-calibrated imaging of seasonal changes in permafrost rock walls by quantitative electrical resistivity </span><span>tomography </span>(Zugspitze, German/Austrian Alps). <em>J. Geophys. Res. </em>115: F02003.</div>

Decennial multi-approach monitoring of thermo-hydro-mechanical processes, Kammstollen outdoor laboratory, Zugspitze (Germany)

2021 ◽  
Author(s):  
Riccardo Scandroglio ◽  
Till Rehm ◽  
Jonas K. Limbrock ◽  
Andreas Kemna ◽  
Markus Heinze ◽  
...  
Keyword(s):  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Environmental Research ◽  
Permafrost Degradation ◽  
Earth Surface ◽  
Data Set ◽  
Resistivity Tomography ◽  
Near Surface ◽  
Permafrost Rock ◽  
Austrian Alps

<p>The warming of alpine bedrock permafrost in the last three decades and consequent reduction of frozen areas has been well documented. Its consequences like slope stability reduction put humans and infrastructures at high risk. 2020 in particular was the warmest year on record at 3000m a.s.l. embedded in the warmest decade.</p><p>Recently, the development of electrical resistivity tomography (ERT) as standard technique for quantitative permafrost investigation allows extended monitoring of this hazard even allowing including quantitative 4D monitoring strategies (Scandroglio et al., in review). Nevertheless thermo-hydro-mechanical dynamics of steep bedrock slopes cannot be totally explained by a single measurement technique and therefore multi-approach setups are necessary in the field to record external forcing and improve the deciphering of internal responses.</p><p>The Zugspitze Kammstollen is a 850m long tunnel located between 2660 and 2780m a.s.l., a few decameters under the mountain ridge. First ERT monitoring was conducted in 2007 (Krautblatter et al., 2010) and has been followed by more than one decade of intensive field work. This has led to the collection of a unique multi-approach data set of still unpublished data. Continuous logging of environmental parameters such as rock/air temperatures and water infiltration through joints as well as a dedicated thermal model (Schröder and Krautblatter, in review) provide important additional knowledge on bedrock internal dynamics. Summer ERT and seismic refraction tomography surveys with manual and automated joints’ displacement measurements on the ridge offer information on external controls, complemented by three weather stations and a 44m long borehole within 1km from the tunnel.</p><p>Year-round access to the area enables uninterrupted monitoring and maintenance of instruments for reliable data collection. “Precisely controlled natural conditions”, restricted access for researchers only and logistical support by Environmental Research Station Schneefernerhaus, make this tunnel particularly attractive for developing benchmark experiments. Some examples are the design of induced polarization monitoring, the analysis of tunnel spring water for isotopes investigation, and the multi-annual mass monitoring by means of relative gravimetry.</p><p>Here, we present the recently modernized layout of the outdoor laboratory with the latest monitoring results, opening a discussion on further possible approaches of this extensive multi-approach data set, aiming at understanding not only permafrost thermal evolution but also the connected thermo-hydro-mechanical processes.</p><p> </p><p> </p><p>Krautblatter, M. et al. (2010) ‘Temperature-calibrated imaging of seasonal changes in permafrost rock walls by quantitative electrical resistivity tomography (Zugspitze, German/Austrian Alps)’, Journal of Geophysical Research: Earth Surface, 115(2), pp. 1–15. doi: 10.1029/2008JF001209.</p><p>Scandroglio, R. et al. (in review) ‘4D-Quantification of alpine permafrost degradation in steep rock walls using a laboratory-calibrated ERT approach (in review)’, Near Surface Geophysics.</p><p>Schröder, T. and Krautblatter, M. (in review) ‘A high-resolution multi-phase thermo-geophysical model to verify long-term electrical resistivity tomography monitoring in alpine permafrost rock walls (Zugspitze, German/Austrian Alps) (submitted)’, Earth Surface Processes and Landforms.</p>

Using historical aerial imagery to assess multidecadal kinematics and elevation changes. Application to mountain permafrost in the French Alps.

2021 ◽  
Author(s):  
Diego Cusicanqui ◽  
Antoine Rabatel ◽  
Xavier Bodin ◽  
Christian Vincent ◽  
Emmanuel Thibert ◽  
...  
Keyword(s):  
Ice Core ◽  
Horizontal Displacement ◽  
Vertical Surface ◽  
Aerial Images ◽  
Surface Velocity ◽  
High Mountain ◽  
European Alps ◽  
Permafrost Degradation ◽  
Mountain Areas ◽  
Mountain Permafrost

<p>Glacial and periglacial environments are highly sensitive to climate change, even more in mountain areas where warming is faster and, as a consequence, perennial features of the cryosphere like glaciers and permafrost have been fast evolving in the last decades. In the European Alps, glaciers retreat and permafrost thawing have led to the destabilization of mountain slopes, threatening human infrastructures and inhabitants. The observation of such changes at decadal scales is often limited to sparse in situ observations.</p><p>Here, we present three study cases of mountain permafrost sites based on a multidisciplinary approach over almost seven decades. The goal is to investigate and quantify morphodynamic changes and understand the causes of these evolutions. We used stereo-photogrammetry techniques to generate orthophotos and (DEMs) from historical aerial images (available, in France since 1940s). From this, we produced diachronic comparison of DEMs to quantify vertical surface changes, as well as feature tracking techniques of multi-temporal digital orthophotos for estimating horizontal displacement rates. Locally, high-resolution datasets (i.e. LiDAR surveys, UAV acquisitions and Pléiades stereo imagery) were also exploited to improve the quality of photogrammetric products. In addition, we combine these results with geophysics (ERT and GPR) to estimate the ice content, geomorphological surveys to describe the complex environments and the relationship with climatic forcing.</p><p>The first study case is the Laurichard rock glacier, where we were able to quantify changes of emergence velocities, fluxes, and volume. Together with an acceleration of surface velocity, important surface lowering have been found over the period 1952-2019, with a striking spatiotemporal reversal of volume balance.</p><p>The second study site is the Tignes glacial and periglacial complex, where the changes of thermokarstic lakes surface were quantified. The results suggest that drainage probably affects the presence and the evolution of the largest thermorkarst. Here too, a significant ice loss was found on the central channel concomitant to an increase in surface velocities.</p><p>The third study site is the Chauvet glacial and periglacial complex where several historical outburst floods are recorded during the 20th century, likely related to the permafrost degradation, the presence of thermokarstic lakes, and an intra-glacial channel. The lateral convergence of ice flow, due to the terrain subsidence caused by the intense melting, may cause the closure of the channel with a subsequent refill of the thermokarstic depression and finally a new catastrophic event.</p><p>Our results highlight the important value of historical aerial photography for having a longer perspective on the evolution of the high mountain cryosphere, thanks to accurate quantification of pluri-annual changes of volume and surface velocity. For instance, we could evidence : (1) a speed-up of the horizontal displacements since the 1990s in comparison with the previous decades; (2) an important surface lowering related to various melting processes (ice-core, thermokarst) for the three study sites; (3) relationships between the observed evolution and the contemporaneous climate warming, with a long-term evolution controlled by the warming of the ground and short-term changes that may relate to snow or precipitation or to the activity of the glacial-periglacial landforms.</p>

scholarly journals Mountain permafrost degradation documented through a network of permanent electrical resistivity tomography sites

2018 ◽  
Author(s):  
Coline Mollaret ◽  
Christin Hilbich ◽  
Cécile Pellet ◽  
Adrian Flores-Orozco ◽  
Reynald Delaloye ◽  
...  
Keyword(s):  
Time Series ◽  
Electrical Resistivity ◽  
Electrical Resistivity Tomography ◽  
Permafrost Degradation ◽  
Data Set ◽  
Resistivity Tomography ◽  
Wide Range ◽  
Mountain Permafrost ◽  
Ice Water

Abstract. Mountain permafrost is sensitive to climate change and is expected to gradually degrade in response to the ongoing atmospheric warming trend. Long-term monitoring the permafrost thermal state is a key task, but it is problematic where temperatures are close to 0 °C. The energy exchange is indeed often dominantly related to latent heat effects associated with phase change (ice/water), rather than ground warming or cooling. Consequently, it is difficult to detect significant spatio-temporal variations of ground properties (e.g. ice-water ratio) that occur during the freezing/thawing process with point scale temperature monitoring alone. Hence, electrical methods have become popular in permafrost investigations as the resistivities of ice and water differ by several orders of magnitude, theoretically allowing a clear distinction between frozen and unfrozen ground. In this study we present an assessment of mountain permafrost evolution using long-term electrical resistivity tomography monitoring (ERTM) from a network of permanent sites in the Central Alps. The time series consist of more than 1000 data sets from six sites, where resistivities have been measured on a regular basis for up to twenty years. We identify systematic sources of error and apply automatic filtering procedures during data processing. In order to constrain the interpretation of the results, we analyse inversion results and long-term resistivity changes in comparison with existing borehole temperature time series. Our results show that the resistivity data set provides the most valuable insights at the melting point. A prominent permafrost degradation trend is evident for the longest time series (19 years), but also detectable for shorter time series (about a decade) at most sites. In spite of the wide range of morphological, climatological and geological differences between the sites, the observed inter-annual resistivity changes and long-term tendencies are similar for all sites of the network.

Communicating Climate Change to broad public through Educations - Project KlimaAlps

2021 ◽  
Author(s):  
Cornelia Baumann ◽  
Inga Beck
Keyword(s):  
Climate Change ◽  
Scientific Information ◽  
Environmental Research ◽  
Background Information ◽  
High Mountain ◽  
Research Station ◽  
Human Beings ◽  
Mountain Areas ◽  
The Alps

<p>Education is key in order to create a generation that thinks and acts sustainable and that considers nature as one of the most important good.Within the three years Interreg Project ‘KlimaAlps’ (www.klimaalps.eu) – making climate change visible - one major task is the establishment of a training for educators, to become a certified ‘Climate-Pedagogue’ for the alpine region. The ‘Climate-Pedagogue’-training contains background information of climate change in the Alps and a variety of innovative educational tools and methods. It covers aspects of the high mountain areas, rivers and lakes, human beings, agriculture as well as moors.  The project is managed by the ‘Energiewende Oberland’; five additional partners from Austria and Bavaria are responsible for e. g. a high quality of the taught scientific information (Environmental Research Station Schneefernerhaus), the didactical input (University of Innsbruck, Department of Geography), the outreach activities and the implementation (Naturpark Karwendel, Klimabündnis Oberösterreich, Landratsamt Garmisch-Partenkirchen). During the last one and half years, the concept for the ‘Climate-Pedagogue’- training was worked out in cooperation with other environmental facilities and in March 2021 the first lectures of a pilot run with over 30 selected participants were held. In total there will be two runs in 2021 in order to evaluate the recent version of the training as good as possible. The next and long-term steps will be the firm establishment of a chargeable ‘Climate-Pedagogue’ – Training for every interested person for at least the coming ten years, as well as the strengthening and growing of the network. The presentation will give a short overview about the entire project as well as details about the ‘Climate-Pedagogue’ – Training and some first impressions of the already hold lectures in 2021.</p>

scholarly journals Thermal characteristics of permafrost in the steep alpine rock walls of the Aiguille du Midi (Mont Blanc Massif, 3842 m a.s.l)

2015 ◽  
Vol 9 (1) ◽  
pp. 109-121 ◽  
Author(s):  
F. Magnin ◽  
P. Deline ◽  
L. Ravanel ◽  
J. Noetzli ◽  
P. Pogliotti
Keyword(s):  
Active Layer ◽  
Current Knowledge ◽  
Thermal Characteristics ◽  
Field Measurements ◽  
Heat Fluxes ◽  
Rock Surface ◽  
Mountain Areas ◽  
Rock Wall ◽  
Temperature Records ◽  
Deep Boreholes

Abstract. Permafrost and related thermo-hydro-mechanical processes are thought to influence high alpine rock wall stability, but a lack of field measurements means that the characteristics and processes of rock wall permafrost are poorly understood. To help remedy this situation, in 2005 work began to install a monitoring system at the Aiguille du Midi (3842 m a.s.l). This paper presents temperature records from nine surface sensors (eight years of records) and three 10 m deep boreholes (4 years of records), installed at locations with different surface and bedrock characteristics. In line with previous studies, our temperature data analyses showed that: micro-meteorology controls the surface temperature, active layer thicknesses are directly related to aspect and ranged from <2 m to nearly 6 m, and that thin accumulations of snow and open fractures are cooling factors. Thermal profiles empirically demonstrated the coexistence within a single rock peak of warm and cold permafrost (about −1.5 to −4.5 °C at 10 m depth) and the resulting lateral heat fluxes. Our results also extended current knowledge of the effect of snow, in that we found similar thermo-insulation effects as reported for gentle mountain areas. Thick snow warms shaded areas, and may reduce active layer refreezing in winter and delay its thawing in summer. However, thick snow thermo-insulation has little effect compared to the high albedo of snow which leads to cooler conditions at the rock surface in areas exposed to the sun. A consistent inflection in the thermal profiles reflected the cooling effect of an open fracture in the bedrock, which appeared to act as a thermal cutoff in the sub-surface thermal regime. Our field data are the first to be obtained from an Alpine permafrost site where borehole temperatures are below −4 °C, and represent a first step towards the development of strategies to investigate poorly known aspects in steep bedrock permafrost such as the effects of snow cover and fractures.

scholarly journals On the influence of topographic, geological and cryospheric factors on rock avalanches and rockfalls in high-mountain areas

2012 ◽  
Vol 12 (1) ◽  
pp. 241-254 ◽  
Author(s):  
L. Fischer ◽  
R. S. Purves ◽  
C. Huggel ◽  
J. Noetzli ◽  
W. Haeberli
Keyword(s):  
Slope Failure ◽  
Temporal Distribution ◽  
High Mountain ◽  
European Alps ◽  
Permafrost Degradation ◽  
Slope Failures ◽  
Mountain Areas ◽  
Investigation Area ◽  
Rock Avalanches ◽  
Slope Instabilities

Abstract. The ongoing debate about the effects of changes in the high-mountain cryosphere on rockfalls and rock avalanches suggests a need for more knowledge about characteristics and distribution of recent rock-slope instabilities. This paper investigates 56 sites with slope failures between 1900 and 2007 in the central European Alps with respect to their geological and topographical settings and zones of possible permafrost degradation and glacial recession. Analyses of the temporal distribution show an increase in frequency within the last decades. A large proportion of the slope failures (60%) originated from a relatively small area above 3000 m a.s.l. (i.e. 10% of the entire investigation area). This increased proportion of detachment zones above 3000 m a.s.l. is postulated to be a result of a combination of factors, namely a larger proportion of high slope angles, high periglacial weathering due to recent glacier retreat (almost half of the slope failures having occurred in areas with recent deglaciation), and widespread permafrost occurrence. The lithological setting appears to influence volume rather than frequency of a slope failure. However, our analyses show that not only the changes in cryosphere, but also other factors which remain constant over long periods play an important role in slope failures.

Phytomass and phenology of three alpine snowpatch species across a natural snowmelt gradient

2007 ◽  
Vol 55 (4) ◽  
pp. 450 ◽  
Author(s):  
Susanna E. Venn ◽  
John W. Morgan
Keyword(s):  
Plant Species ◽  
Spatial Scales ◽  
Growing Season ◽  
Plant Distribution ◽  
High Mountain ◽  
Flower Bud ◽  
Mountain Areas ◽  
Winter Snow ◽  
Landscape Scales

Alpine snowpatch vegetation in Australia is restricted to high mountain areas and occurs in locations where winter snow persists longest into the summer. The timing of annual snowmelt is considered an important determinant of vegetation patterns in alpine areas because it affects the length of the growing season for plant species at landscape scales. There are few studies in Australia that have examined the effects of the date of snowmelt on the performance of plant species at small spatial scales. The phytomass and phenology of three common snowpatch species (Celmisia pugioniformis, Luzula acutifolia, Poa fawcettiae) was examined during one growing season across a natural snowmelt gradient to examine their response to time of snow release. Peak phytomass was significantly higher in early than late-melting zones for L. acutifolia and marginally higher there for C. pugioniformis. P. fawcettiae, however, produced higher mean peak phytomass in late-melting zones where soil was initially wetter in the growing season. Flower buds of L. acutifolia were evident as the snow melted, and flowering occurred at the same time in all areas of the snowpatch. The number of days from the date of snowmelt to the date of the first observed flower bud in C. pugioniformis and P. fawcettiae was 22–25 days shorter in late-melting areas than in early melting areas. For both of these species, flowering and subsequent seed set occurred simultaneously across the snowpatch regardless of the date of the initial snowmelt, suggesting that photoperiod controls flowering in these species. Our study suggests that the predicted declines in snow cover in Australia in coming decades may affect the phytomass of species that are currently constrained by late-lying snow. This, in turn, may affect their long-term patterns of distribution. If plants respond to photoperiod for flowering, as seems to be important here for C. pugioniformis and P. fawcettiae, it is unlikely that the periods following earlier than usual snowmelt will be fully utilised by these species. Any attempts at predicting or modelling future alpine plant distribution on the basis of warming scenarios may therefore need to account for photoperiod constraints on flowering as well changes in phytomass production.

scholarly journals Recent geomorphic destabilization of mountain slopes, a possible link to climate change? Two case studies from Switzerland

2020 ◽  
Author(s):  
Hanne Hendrickx ◽  
Reynald Delaloye ◽  
Jan Nyssen ◽  
Amaury Frankl
Keyword(s):  
Climate Change ◽  
Debris Flow ◽  
Mass Movement ◽  
Swiss Alps ◽  
Aerial Photographs ◽  
High Mountain ◽  
Permafrost Degradation ◽  
Rock Wall ◽  
Rock Face ◽  
Talus Slope

&lt;p&gt;Geomorphological destabilisations in high mountain areas are often linked to permafrost degradation and changing precipitation intensities, induced by climate change. Considering the complex interaction between meteorological conditions, geology and topography, two alpine mass movements that took place in 2019 in the canton of Valais (Swiss Alps) were investigated with regard to their possible causes. During three consecutive summers (2017-2019), independent surveys were carried out on a high alpine talus slope at Col du Sanetsch (2100 &amp;#8211; 2750 m a.s.l.) and an unstable rock face at Grosse Grabe, Mattertal (2600 &amp;#8211; 2700 m a.s.l.), using unmanned aerial vehicle (UAV) and terrestrial laser scanning (TLS). The resulting high-resolution topography allows detecting and quantifying small and large geomorphic changes, such as rock tilting, rockfalls, rockslides, erosion and depositions of rock debris by snow avalanche action, debris channel cutting and fill and debris flow deposits. In both study areas, the summer of 2019 was characterized by mass movement events of greater magnitude than the geomorphic activity measured in the summers before.&lt;/p&gt;&lt;p&gt;At Grosse Grabe, the rock face was observed by webcam imagery since 2011, in the background of a rock glacier, which was initially the main object of survey. Isolated rock falls started in January 2017, launching a more accurate survey of the rock face by TLS in July 2017. In the next two summers, the entire unstable part of the rock wall, 70 m high, had been tilting at an increasing rate (1 to 3.3 cm/month). From mid-July until the end of October 2019, consecutive large rock fall events (up to &gt; 10,000 m&lt;sup&gt;3&lt;/sup&gt;) lead to the complete collapse of the monitored rock face (5000 m&lt;sup&gt;2&lt;/sup&gt;), with a total volume of more than 60,000 m&lt;sup&gt;3&lt;/sup&gt;. After the collapse of this heavily fractured, south facing rock face, the long-lasting wet rockfall scar indicated the presence of thawing permafrost ice. Beside the geological characteristics, which are favouring the rock wall instability, the consequences of the multi-decennial significant warming of the permafrost is presumably an implicated factor.&lt;/p&gt;&lt;p&gt;On the talus slope (2 km&lt;sup&gt;2&lt;/sup&gt;) that was surveyed at Col du Sanetsch, a large debris flow event (ca. 20,000 m&lt;sup&gt;3&lt;/sup&gt; spread over multiple debris flow channels) was observed in the evening of 11 August 2019. Most of the mobilized sediments originated from incision of the talus apex area, while only a small part came from intermediate debris storage within rock wall gullies. An analysis of historical aerial photographs shows that the total displaced volume during the 2019 event exceeds each historical debris flow event that occurred on the talus slope since 1946.&lt;/p&gt;&lt;p&gt;In contrast to Grosse Grabe, where weather conditions have played no role on the development of the instability, the debris flow event at Col de Sanetsch is linked to an intense prefrontal supercell, causing rainfall intensities between 10 and 25 mm/h, in some places in less than 15 minutes. As such events are presumed to become more frequent with climate change, more debris flow events of this type can be expected in the future.&lt;/p&gt;

scholarly journals Surface temperatures and their influence on the permafrost thermal regime in high-Arctic rock walls on Svalbard

2021 ◽  
Vol 15 (5) ◽  
pp. 2491-2509
Author(s):  
Juditha Undine Schmidt ◽  
Bernd Etzelmüller ◽  
Thomas Vikhamar Schuler ◽  
Florence Magnin ◽  
Julia Boike ◽  
...  
Keyword(s):  
Energy Balance ◽  
Surface Energy ◽  
Surface Temperature ◽  
Surface Energy Balance ◽  
High Arctic ◽  
Heat Fluxes ◽  
Rock Surface ◽  
Permafrost Degradation ◽  
Rock Wall ◽  
Surface Temperatures

Abstract. Permafrost degradation in steep rock walls and associated slope destabilization have been studied increasingly in recent years. While most studies focus on mountainous and sub-Arctic regions, the occurring thermo-mechanical processes also play an important role in the high Arctic. A more precise understanding is required to assess the risk of natural hazards enhanced by permafrost warming in high-Arctic rock walls. This study presents one of the first comprehensive datasets of rock surface temperature measurements of steep rock walls in the high Arctic, comparing coastal and near-coastal settings. We applied the surface energy balance model CryoGrid 3 for evaluation, including adjusted radiative forcing to account for vertical rock walls. Our measurements comprise 4 years of rock surface temperature data from summer 2016 to summer 2020. Mean annual rock surface temperatures ranged from −0.6 in a coastal rock wall in 2017/18 to −4.3 ∘C in a near-coastal rock wall in 2019/20. Our measurements and model results indicate that rock surface temperatures at coastal cliffs are up to 1.5 ∘C higher than at near-coastal rock walls when the fjord is ice-free in winter, resulting from additional energy input due to higher air temperatures at the coast and radiative warming by relatively warm seawater. An ice layer on the fjord counteracts this effect, leading to similar rock surface temperatures to those in near-coastal settings. Our results include a simulated surface energy balance with shortwave radiation as the dominant energy source during spring and summer with net average seasonal values of up to 100 W m−2 and longwave radiation being the main energy loss with net seasonal averages between 16 and 39 W m−2. While sensible heat fluxes can both warm and cool the surface, latent heat fluxes are mostly insignificant. Simulations for future climate conditions result in a warming of rock surface temperatures and a deepening of active layer thickness for both coastal and near-coastal rock walls. Our field data present a unique dataset of rock surface temperatures in steep high-Arctic rock walls, while our model can contribute towards the understanding of factors influencing coastal and near-coastal settings and the associated surface energy balance.

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