20 years of mountain permafrost monitoring in the Swiss Alps: key results and major challenges

2020 ◽  
Author(s):  
Jeannette Noetzli ◽  
Cécile Pellet
Keyword(s):  
Monitoring Network ◽  
Warming Trend ◽  
Phase Changes ◽  
Swiss Alps ◽  
High Mountain ◽  
The Past ◽  
Heat Effects ◽  
Mountain Permafrost ◽  
Ice Content

<p>Permafrost is a widespread thermal subsurface phenomenon in polar and high mountain regions and was defined as an essential climatic variable (ECV) by the Global Climate Observing System (GCOS). The Swiss Permafrost Monitoring Network was started in the year 2000 as an unconsolidated network of sites from research projectsand as the first national long-term observation network for permafrost it is an early component of the Global Terrestrial Network for Permafrost (GTN-P). After 20 years of operation, development and evaluation, PERMOS holds the largest and most diverse collection of mountain permafrost data worldwide and has a role model regarding its structure and organization. PERMOS aims at the systematic long-term documentation of the state and changes of mountain permafrost in the Swiss Alps. The scientific monitoring strategy is now based on three observation elements: ground-surface and subsurface temperatures, changes in subsurface ice content, and permafrost creep velocities. These three elements complement each other in a landform-based approach to capture the influence of the topography as well as the surface and subsurface conditions of different landforms on the ground thermal regime. These influences are considered to be more relevant than regional climatic conditions in the small country.</p><p>Over the past 20 years, all observation elements indicate a clear warming trend of mountain permafrost in the Swiss Alps. Borehole temperatures generally increase at 10 and 20 m depth. This warming trend was intensified after 2009 and temporarily interrupted following winters with a thin and late snow cover, particularly winter 2016. Further, the trend is more pronounced at cold permafrost sites like rock glacier Murtèl-Corvatsch, where an increase of +0.5°C has been observed at 20 m over the past 30 years. For permafrost temperatures close to 0 °C, climate warming does not result in significant temperature increase but is masked by phase changes and latent heat effects. These result in significant changes in ice content, which can be registered by electrical resistivity tomography (ERT). Further, the warming trend of mountain permafrost in the Swiss Alps is corroborated by increasing creep rates of rock glaciers, which follow an exponential relationship with ground temperatures. In this contribution, we present and discuss the key results from two decades of mountain permafrost monitoring within the PERMOS network. In addition to the measurement data, we identified considerable challenges for long-term monitoring network of mountain permafrost based on experience collected over two decades. The acquisition of reliable data at a limited number of stations in extreme environments with difficult access requires robust strategies, standards and traceability for the entire data acquisition chain: installation > measurement > raw data > processing > archiving and, finally, reporting.</p>

scholarly journals Time-lapse refraction seismic tomography for the detection of ground ice degradation

2010 ◽  
Vol 4 (3) ◽  
pp. 243-259 ◽  
Author(s):  
C. Hilbich
Keyword(s):  
Seismic Tomography ◽  
Time Lapse ◽  
Phase Changes ◽  
Swiss Alps ◽  
P Wave ◽  
Permafrost Degradation ◽  
Travel Times ◽  
Refraction Seismic ◽  
Velocity Changes ◽  
Ice Content

Abstract. The ice content of the subsurface is a major factor controlling the natural hazard potential of permafrost degradation in alpine terrain. Monitoring of changes in ice content is therefore similarly important as temperature monitoring in mountain permafrost. Although electrical resistivity tomography monitoring (ERTM) proved to be a valuable tool for the observation of ice degradation, results are often ambiguous or contaminated by inversion artefacts. In theory, the sensitivity of P-wave velocity of seismic waves to phase changes between unfrozen water and ice is similar to the sensitivity of electric resistivity. Provided that the general conditions (lithology, stratigraphy, state of weathering, pore space) remain unchanged over the observation period, temporal changes in the observed travel times of repeated seismic measurements should indicate changes in the ice and water content within the pores and fractures of the subsurface material. In this paper, a time-lapse refraction seismic tomography (TLST) approach is applied as an independent method to ERTM at two test sites in the Swiss Alps. The approach was tested and validated based on a) the comparison of time-lapse seismograms and analysis of reproducibility of the seismic signal, b) the analysis of time-lapse travel time curves with respect to shifts in travel times and changes in P-wave velocities, and c) the comparison of inverted tomograms including the quantification of velocity changes. Results show a high potential of the TLST approach concerning the detection of altered subsurface conditions caused by freezing and thawing processes. For velocity changes on the order of 3000 m/s even an unambiguous identification of significant ice loss is possible.

scholarly journals Semi-automated calibration method for modelling of mountain permafrost evolution in Switzerland

2015 ◽  
Vol 9 (5) ◽  
pp. 4787-4843 ◽  
Author(s):  
A. Marmy ◽  
J. Rajczak ◽  
R. Delaloye ◽  
C. Hilbich ◽  
M. Hoelzle ◽  
...  
Keyword(s):  
Climate Change ◽  
Calibration Method ◽  
Swiss Alps ◽  
European Alps ◽  
Permafrost Degradation ◽  
Future Evolution ◽  
Automated Calibration ◽  
Mountain Permafrost ◽  
The Future

Abstract. Permafrost is a widespread phenomenon in the European Alps. Many important topics such as the future evolution of permafrost related to climate change and the detection of permafrost related to potential natural hazards sites are of major concern to our society. Numerical permafrost models are the only tools which facilitate the projection of the future evolution of permafrost. Due to the complexity of the processes involved and the heterogeneity of Alpine terrain, models must be carefully calibrated and results should be compared with observations at the site (borehole) scale. However, a large number of local point data are necessary to obtain a broad overview of the thermal evolution of mountain permafrost over a larger area, such as the Swiss Alps, and the site-specific model calibration of each point would be time-consuming. To face this issue, this paper presents a semi-automated calibration method using the Generalized Likelihood Uncertainty Estimation (GLUE) as implemented in a 1-D soil model (CoupModel) and applies it to six permafrost sites in the Swiss Alps prior to long-term permafrost evolution simulations. We show that this automated calibration method is able to accurately reproduce the main thermal condition characteristics with some limitations at sites with unique conditions such as 3-D air or water circulation, which have to be calibrated manually. The calibration obtained was used for RCM-based long-term simulations under the A1B climate scenario specifically downscaled at each borehole site. The projection shows general permafrost degradation with thawing at 10 m, even partially reaching 20 m depths until the end of the century, but with different timing among the sites. The degradation is more rapid at bedrock sites whereas ice-rich sites with a blocky surface cover showed a reduced sensitivity to climate change. The snow cover duration is expected to be reduced drastically (between −20 to −37 %) impacting the ground thermal regime. However, the uncertainty range of permafrost projections is large, resulting mainly from the broad range of input climate data from the different GCM-RCM chains of the ENSEMBLES data set.

scholarly journals Changes in Ground Temperature and Dynamics in Mountain Permafrost in the Swiss Alps

2021 ◽  
Vol 9 ◽  
Author(s):  
Anna Haberkorn ◽  
Robert Kenner ◽  
Jeannette Noetzli ◽  
Marcia Phillips
Keyword(s):  
Ground Temperature ◽  
Swiss Alps ◽  
Permafrost Degradation ◽  
Rock Glacier ◽  
Borehole Data ◽  
Ground Temperatures ◽  
Air Temperatures ◽  
Mountain Permafrost ◽  
Permafrost Warming

Rising air temperatures and increasingly intense precipitation are being observed in the Swiss Alps. These changes strongly affect the evolution of the temperature regime and the dynamics of mountain permafrost. Changes occur at different rates depending on ground ice content. Long-term monitoring reveals progressive warming and degradation of permafrost and accelerating rock glacier velocities. This study analyses changes occurring in ice-rich (excess-ice) and ice-poor mountain permafrost in Switzerland between 1997 and 2019 on the basis of ground temperature and rock glacier dynamics measurements carried out by the WSL Institute for Snow and Avalanche Research SLF at seven sites. Long-term borehole data indicate an increase of ground temperatures at all depths, in particular at ice-poor and nearly snow-free sites. Active layers are thickening at most sites and prolonged periods of active layer thaw are observed. Long autumn zero curtains are observed in ice-rich permafrost, possibly leading to an overall acceleration of rock glaciers. All these changes point towards ongoing permafrost warming and permafrost degradation in future.

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

2019 ◽  
Vol 13 (10) ◽  
pp. 2557-2578 ◽  
Author(s):  
Coline Mollaret ◽  
Christin Hilbich ◽  
Cécile Pellet ◽  
Adrian Flores-Orozco ◽  
Reynald Delaloye ◽  
...  
Keyword(s):  
Time Series ◽  
Electrical Resistivity ◽  
Latent Heat ◽  
Electrical Resistivity Tomography ◽  
Permafrost Degradation ◽  
Resistivity Tomography ◽  
Heat Effects ◽  
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 of the permafrost thermal state is a key task, but problematic where temperatures are close to 0 ∘C because the energy exchange is then 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 in 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 datasets from six sites, where resistivities have been measured on a regular basis for up to 20 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 dataset provides valuable insights at the melting point, where temperature changes stagnate due to latent heat effects. The longest time series (19 years) demonstrates a prominent permafrost degradation trend, but degradation is also detectable in 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.

Long-term energy balance measurements at three different mountain permafrost sites in the Swiss Alps

2020 ◽  
Author(s):  
Martin Hoelzle ◽  
Christian Hauck ◽  
Jeannette Noetzli ◽  
Cécile Pellet ◽  
Martin Scherler
Keyword(s):  
Energy Balance ◽  
Air Temperature ◽  
Bowen Ratio ◽  
Heat Fluxes ◽  
Swiss Alps ◽  
Ratio Method ◽  
Fine Grained ◽  
Mountain Permafrost ◽  
Ice Content

<p>The surface energy balance is one of the most important influencing factors for the ground thermal regime. It is therefore crucial to understand the interactions of the individual heat fluxes at the surface and within the subsurface layers as well as their relative impacts. A unique set of high-altitude meteorological measurements has been analysed to determine the energy balance at three mountain permafrost sites in the Swiss Alps, where data is being collected since the late 1990s in collaboration with the Swiss Permafrost Monitoring (PERMOS). The three stations have a standardized equipment with sensors for four-component radiation, air temperature, humidity, wind speed and direction as well as ground temperatures and snow height. The three sites differ considerably by their surface and ground material composition ranging from a coarse blocky active layer above ice supersaturated permafrost at rock glacier Murtèl-Corvatsch to deeply weathered micaceous shales, which are covered by fine grained debris of sandy and silty material with a low ice content at the Northern slope of Schilthorn summit. The third site at the Stockhorn plateau shows intermediate ice contents and heterogeneous surface conditions with medium-size debris, fine grained material and outcropping bedrock. Ice content estimation and general ground characterisation are based on geophysical surveying and borehole drilling.</p><p> </p><p>The energy fluxes are calculated based on around two decades of field measurements. While the determination of the radiation budget and the ground heat flux is comparatively straightforward (by the four-component radiation sensor and thermistor measurements within the boreholes, respectively), larger uncertainties exist for the determination of sensible and latent turbulent heat fluxes. They are therefore determined on the one hand by the bulk aerodynamic method using the bulk Richardson number to describe the stability of the surface layer relating the relative effects of buoyancy to mechanical forces and on the other hand by the bowen ratio method.</p><p> </p><p>Results show that mean air temperature at Murtèl-Corvatsch (1997–2018, elevation 2600 m asl.) is –1.66°C and has increased by about 0.7°C during the observation period. The Schilthorn (1999–2018, elevation 2900 m asl.) site shows a mean air temperature of –2.48°C with a mean increase of 1.0°C and the Stockhorn (2003–2018, elevation 3400 m asl.) site shows lower air temperatures with a mean of –5.99°C with an increase of 0.6°C. Measured net radiation, as the most important energy input at the surface, shows substantial differences with mean values of 33.41 Wm<sup>-2</sup> for Murtèl-Corvatsch, 40.65 Wm<sup>-2</sup> for Schilthorn and 24.88 Wm<sup>-2</sup> for Stockhorn. The calculated turbulent fluxes show values of around 7 to 12 Wm<sup>-2</sup> using the bowen ratio method and 8 to 18 Wm<sup>-2</sup> using the bulk method at all sites. Large differences are observed regarding the energy used for melting of the snow cover: at Schilthorn a value of 12.41 Wm<sup>-2</sup>, at Murtèl-Corvatsch of 7.31 Wm<sup>-2</sup> and at Stockhorn of 3.46 Wm<sup>-2</sup> is calculated reflecting the differences in snow height at the three sites.</p>

scholarly journals Pollen analysis and 14C age of moss remains in a permafrost core recovered from the active rock glacier Murtèl-Corvatsch, Swiss Alps: geomorphological and glaciological implications

1999 ◽  
Vol 45 (149) ◽  
pp. 1-8 ◽  
Author(s):  
Wilfried Haeberli ◽  
Andreas Kääb ◽  
Stephan Wagner ◽  
Daniel Vonder Mühll ◽  
Patricia Geissler ◽  
...  
Keyword(s):  
Small Sample ◽  
Swiss Alps ◽  
Rock Glacier ◽  
Moss Species ◽  
14C Age ◽  
Accretion Rates ◽  
Pollen And Spores ◽  
Ice Content ◽  
Debris Cone

AbstractWithin the framework of core-drilling through the permafrost of the active rock glacier Murtèl–Corvatsch in the Swiss Alps, subfossil stem remains of seven different bryophyte species were found at a depth of 6 m below surface and about 3 m below the permafrost table in samples from massive ice. The composition of the moss species points to the former growth of the recovered mosses in the nearest surroundings of the drill site. A total of 127 pollen and spores captured by the mosses and representing 23 taxa were determined. The local vegetation during deposition time must be characterized as a moss-rich alpine grassland meadow rich in Cyperaceae, Poaceae, Chenopodiaceae and Asteraceae, comparable to today’s flora present around the study site. For l4C analysis, accelerator mass spectrometry had to be used due to the small sample mass (about 0.5 mg Carbon content). The mean conventional 14C age of 2250 ± 100 years (1σ variability) corresponds to ranges in the calibrated calendar age of 470–170 BC and 800 BC to AD 0 at statistical probabilities of 68% and 95%, respectively. This result is compared with the present-day flow field as determined by high-precision photogrammetry and with information about the thickness, vertical structure and flow of the permafrost from borehole measurements. Total age of the rock glacier as a landform is on the order of 104 years; the development of the rock glacier most probably started around the onset of the Holocene, when the area it now occupies became definitely deglaciated. The bulk of the ice/rock mixture within the creeping permafrost must be several thousand years old. Characteristic average values are estimated for (1) surface velocities through time (cm a-1), (2) long-term ice and sediment accretion rates (mm a-1) on the debris cone from which the rock glacier develops, (3) retreat rates (1–2 mm a-1) of the cliff which supplies the debris to the debris cone and rock glacier, and (4) ice content of the creeping ice/rock mixture (50–90% by volume). The pronounced supersaturation of the permafrost explains the steady-state creep mode of the rock glacier.

scholarly journals Decadal O3 variability at the Mt. Cimone WMO/GAW global station (2,165 m a.s.l., Italy) and comparison with two high-mountain “reference” sites in Europe

Elem Sci Anth ◽  
2020 ◽  
Vol 8 (1) ◽  
Author(s):  
P. Cristofanelli ◽  
F. Fierli ◽  
F. Graziosi ◽  
M. Steinbacher ◽  
C. Couret ◽  
...  
Keyword(s):  
Atmospheric Transport ◽  
Dispersion Model ◽  
Particle Dispersion ◽  
Air Pollutant ◽  
Swiss Alps ◽  
High Mountain ◽  
Near Surface ◽  
Specific Source ◽  
Surface O3

Tropospheric ozone (O3) is a greenhouse gas as well as a harmful air pollutant with adverse effects on human health and vegetation: The observation and attribution of its long-term variability are key activities to monitor the effectiveness of pollution reduction protocols. In this work, we present the analysis of multi-annual near-surface O3 (1996–2016) at the Mt. Cimone (CMN, Italian northern Apennines) WMO/GAW global station and the comparison with two “reference” high-mountain sites in Europe: Jungfraujoch (JFJ, Swiss Alps) and Mt. Zugspitze (ZUG/ZSF, German Alps). Negative O3 trends were observed at CMN over the period 1996–2016 (from –0.19 to –0.22 ppb yr–1), with the strongest tendencies as being observed for the warm months (May–September: –0.32 ppb yr–1 during daytime). The magnitude of the calculated O3 trends at CMN are 2 times higher than those calculated for ZUG/ZSF and 3–4 times higher than for JFJ. With respect to JFJ and ZUG/ZSF, higher O3 values were observed at CMN during 2004–2008, while good agreement is found for the remaining periods. We used Lagrangian simulations by the FLEXPART particle dispersion model and near-surface O3 data over different European regions, for investigating the possibility that the appearance of the O3 anomalies at CMN could be related to variability in the atmospheric transport or in near-surface O3 over specific source regions. Even if it was not possible to achieve a general robust explanation for the occurrence of the high O3 values at CMN during 2004–2008, the variability of (1) regional and long-range atmospheric transport at CMN and (2) European near-surface O3 could motivate the observed anomalies in specific seasons and years. Interestingly, we found a long-term variability in air mass transport at JFJ with enhanced (decreased) contributions from Western European (intercontinental regions).

scholarly journals Pollen analysis and 14C age of moss remains in a permafrost core recovered from the active rock glacier Murtèl-Corvatsch, Swiss Alps: geomorphological and glaciological implications

1999 ◽  
Vol 45 (149) ◽  
pp. 1-8 ◽  
Author(s):  
Wilfried Haeberli ◽  
Andreas Kääb ◽  
Stephan Wagner ◽  
Daniel Vonder Mühll ◽  
Patricia Geissler ◽  
...  
Keyword(s):  
Small Sample ◽  
Swiss Alps ◽  
Rock Glacier ◽  
Moss Species ◽  
14C Age ◽  
Accretion Rates ◽  
Pollen And Spores ◽  
Ice Content ◽  
Debris Cone

Abstract Within the framework of core-drilling through the permafrost of the active rock glacier Murtèl–Corvatsch in the Swiss Alps, subfossil stem remains of seven different bryophyte species were found at a depth of 6 m below surface and about 3 m below the permafrost table in samples from massive ice. The composition of the moss species points to the former growth of the recovered mosses in the nearest surroundings of the drill site. A total of 127 pollen and spores captured by the mosses and representing 23 taxa were determined. The local vegetation during deposition time must be characterized as a moss-rich alpine grassland meadow rich in Cyperaceae, Poaceae, Chenopodiaceae and Asteraceae, comparable to today’s flora present around the study site. For l4C analysis, accelerator mass spectrometry had to be used due to the small sample mass (about 0.5 mg Carbon content). The mean conventional 14C age of 2250 ± 100 years (1σ variability) corresponds to ranges in the calibrated calendar age of 470–170 BC and 800 BC to AD 0 at statistical probabilities of 68% and 95%, respectively. This result is compared with the present-day flow field as determined by high-precision photogrammetry and with information about the thickness, vertical structure and flow of the permafrost from borehole measurements. Total age of the rock glacier as a landform is on the order of 104 years; the development of the rock glacier most probably started around the onset of the Holocene, when the area it now occupies became definitely deglaciated. The bulk of the ice/rock mixture within the creeping permafrost must be several thousand years old. Characteristic average values are estimated for (1) surface velocities through time (cm a-1), (2) long-term ice and sediment accretion rates (mm a-1) on the debris cone from which the rock glacier develops, (3) retreat rates (1–2 mm a-1) of the cliff which supplies the debris to the debris cone and rock glacier, and (4) ice content of the creeping ice/rock mixture (50–90% by volume). The pronounced supersaturation of the permafrost explains the steady-state creep mode of the rock glacier.

Prospecting alpine permafrost with Spectral Induced Polarization in different geomorphological landforms

2020 ◽  
Author(s):  
Theresa Maierhofer ◽  
Timea Katona ◽  
Christin Hilbich ◽  
Christian Hauck ◽  
Adrian Flores-Orozco
Keyword(s):  
Electrical Resistivity ◽  
Thermal State ◽  
Geophysical Methods ◽  
Induced Polarization ◽  
Swiss Alps ◽  
High Mountain ◽  
Monitoring Site ◽  
European Alps ◽  
Mountain Permafrost

<p>Permafrost regions are highly sensitive to climate changes, which has significant implications for the hydrological regimes and the mechanical state of the subsurface leading to natural hazards such as rock slope failures. Therefore, a better understanding of the future evolution and dynamics of mountain permafrost is highly relevant and monitoring of the thermal state of permafrost has become an essential task in the European Alps. Geophysical methods have emerged as well-suited to support borehole data and investigate the spatial distribution and temporal changes of temperature and the degradation of permafrost. In particular, electrical resistivity tomography (ERT) has developed into a routine imaging tool for the quantification of ice-rich permafrost, commonly associated with a significant increase in the electrical resistivity. However, in many cases, the interpretation of the subsurface electrical resistivity is ambiguous and additional information would improve the quantification of the ice content within the subsurface. Theoretical and laboratory studies have suggested that ice exhibits a characteristic induced electrical polarization response. Our results from an extensive field programme including many morphologically different mountain permafrost sites now indicate that this IP response may indeed be detected in the field suggesting the potential of the Induced Polarization (IP) method to overcome such ambiguities. We present here Spectral IP (SIP) mapping results conducted over a broad range of frequencies (0.1-225 Hz) at four representative permafrost sites of the Swiss-, Italian- and Austrian Alps. The mapping results have been used to install long-term permafrost monitoring arrays for a better understanding of subsurface variations associated to climate change. All SIP study sites are located at elevations around 2600 - 3000 m and include comprehensive geophysical and temperature data for validation. We focus on the spatial characterization of each site to address different research questions: to (i) reproduce and improve the mapping of the spatial permafrost extent inferred from previous investigations in the Lapires talus slope,Western Swiss Alps, to (ii) improve the geophysical characterization of the Sonnblick monitoring site located in the Austrian Central Alps, to (iii) determine the transition between permafrost and non-permafrost at the Schilthorn site, Bernese Alps, Switzerland, and to (iv) find the best-suited location for a SIP monitoring profile and conduct year-round measurements at the Cime Bianche site, Western Italian Alps. Our various field applications demonstrate the potential of the IP method for characterizing and monitoring permafrost systems in high-mountain environments.</p>

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