Automated Electrical Resistivity Tomography Testing for Early Warning in Unstable Permafrost Rock Walls Around Alpine Infrastructure

Keuschnig, Markus; Krautblatter, Michael; Hartmeyer, Ingo; Fuss, C.; Schrott, Lothar

doi:10.1002/ppp.1916

Cited by 44 publications

(61 citation statements)

References 34 publications

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“…Both cirques are occupied by the Schmiedingerkees glacier, which is home to Austria's oldest glacier ski-area. Since 2010 an extensive, multi-scale monitoring of permafrostrockfall interaction ('Open-Air-Lab Kitzsteinhorn') (Keuschnig et al, 2015) includes several deep and shallow boreholes (Hartmeyer et al, 2012), two permanently installed electrical resistivity tomography profiles (Supper et al, 2014;Keuschnig et al, 2016), rock anchor load loggers (Plaesken et al, 2017), extensometers in fractures (Ewald et al, 2019) and several fully automated weather stations.…”

Section: Study Area 90mentioning

confidence: 99%

Current glacier recession causes significant rockfall increase: The immediate paraglacial response of deglaciating cirque walls

Hartmeyer¹,

Delleske²,

Keuschnig³

et al. 2020

Preprint

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In the European Alps almost half the glacier volume disappeared over the past 150 years. The loss is reflected in 10 glacier retreat and ice surface lowering even at high altitude. In steep glacial cirques surface lowering exposes rock to atmospheric conditions for the very first time in many millennia. Instability of rockwalls has long been identified as one of the direct consequences of deglaciation, but so far cirque-wide quantification of rockfall at high-resolution is missing. Based on terrestrial LiDAR a rockfall inventory for the permafrost-affected rockwalls of two rapidly deglaciating cirques in the Central Alps of Austria (Kitzsteinhorn) is established. Over six-years (2011-2017) 78 rockwall scans were acquired to generate data 15 of high spatial and temporal resolution. 632 rockfalls were registered ranging from 0.003 to 879.4 m³, mainly originating from pre-existing structural rock weaknesses. 60 % of the rockfall volume detached from less than ten vertical meters above the glacier surface, indicating enhanced rockfall activity over tens of years following deglaciation. Debuttressing seems to play a minor effect only. Rather, preconditioning is assumed to start inside the Randkluft (gap between cirque wall and glacier) where sustained freezing and ample supply of liquid water likely cause enhanced physical weathering and high plucking stresses. 20Following deglaciation, pronounced thermomechanical strain is induced and an active layer penetrates into the formerly perennially frozen bedrock. These factors likely cause the observed paraglacial rockfall increase close to the glacier surface. This paper presents the most extensive dataset of high-alpine rockfall to date and the first systematic documentation of a cirquewide erosion response of glaciated rockwalls to recent climate warming.

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Section: Study Area 90mentioning

confidence: 99%

Current glacier recession causes significant rockfall increase: The immediate paraglacial response of deglaciating cirque walls

Hartmeyer¹,

Delleske²,

Keuschnig³

et al. 2020

Preprint

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“…(ERTM) profiles have only relatively recently been introduced in this research domain (Doetsch et al, 2015;Hilbich et al, 2008aHilbich et al, , 2008bKeuschnig et al, 2017;Kneisel et al, 2008Kneisel et al, , 2014Lewkowicz et al, 2011;Supper et al, 2014;Tomaškovičová, 2018).…”

Section: Introductionmentioning

confidence: 99%

“…Since then, further ERTM case studies on permafrost were published, e.g. focusing on rock wall monitoring (Keuschnig et al, 2017), combining direct-current resistivity with induced polarization monitoring (Doetsch et al, 2015), or analysing the contact resistance effects on monitoring data in detail (Tomaškovičová et al, 2016). However, in contrast to borehole temperature monitoring networks, most of the abovecited ERTM studies focus on single field sites or on short-term monitoring (< 5 years).…”

Section: Introductionmentioning

confidence: 99%

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

Mollaret¹,

Hilbich²,

Pellet³

et al. 2018

Preprint

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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.

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“…The Kitzsteinhorn hosts an extensive research site to investigate the consequences of climate change on high-alpine infrastructure and rock stability ('Open-Air-Lab Kitzsteinhorn'). Measurements performed at the Kitzsteinhorn focus on rockfall activity (Keuschnig et al, 2015), subsurface temperature changes (Hartmeyer et al, 2012), geophysical monitoring with ERT (Supper et al, 2014;Keuschnig et al, 2016), rock mass pressure using anchor load plates (Plaesken et al, 2017) and fracture dynamics monitoring 115 with crackmeters (Ewald et al, 2019).…”

Section: Study Areamentioning

confidence: 99%

Enhanced rockwall retreat and modified rockfall magnitudes/frequencies in deglaciating cirques from a 6-year LiDAR monitoring

Hartmeyer

Keuschnig

Delleske

et al. 2020

Preprint

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Cirque erosion contributes significantly to mountain denudation and is a key element of glaciated mountain topography. Despite long-standing efforts, rates of rockwall retreat and the proportional contributions of low-, mid-and high magnitude rockfalls have remained poorly constrained. Here, a unique, terrestrial LiDAR-derived rockfall inventory (2011-2017) of two glaciated cirques in the Hohe Tauern Range, Central European Alps, Austria is analysed. The mean cirque wall retreat rate of 1.9 mm a -1 ranks in the top range of reported values and is mainly driven by enhanced rockfall from the 15 lowermost, freshly deglaciated rockwall sections. Retreat rates are significantly elevated over decades subsequent to glacier downwasting. Elongated cirque morphology and recorded cirque wall retreat rates indicate headward erosion is clearly outpacing lateral erosion, most likely due to the cataclinal backwalls, which are prone to large dip-slope failures. The rockfall magnitude-frequency distributionthe first such distribution derived for deglaciating cirquesfollows a distinct negative power law over four orders of magnitude. Magnitude-frequency distributions in glacier-proximal and glacier-distal rockwall 20 sections differ significantly due to an increased occurrence of large rockfalls in recently deglaciated areas. In this paper we show how recent climate warming shapes glacial landforms, controls spatiotemporal rockfall variation in glacial environments and indicates a transient signal with decadal scale exhaustion of rockfall activity immediately following deglaciation crucial for future hazard assessments.

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Automated Electrical Resistivity Tomography Testing for Early Warning in Unstable Permafrost Rock Walls Around Alpine Infrastructure

Cited by 44 publications

References 34 publications

Current glacier recession causes significant rockfall increase: The immediate paraglacial response of deglaciating cirque walls

Current glacier recession causes significant rockfall increase: The immediate paraglacial response of deglaciating cirque walls

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

Enhanced rockwall retreat and modified rockfall magnitudes/frequencies in deglaciating cirques from a 6-year LiDAR monitoring

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