Multi-sensor monitoring and data integration reveal cyclical destabilization of the Äußeres Hochebenkar rock glacier

Abstract

Abstract. This study investigates rock glacier destabilization based on the results of a unique in situ and remote-sensing-based monitoring network focused on the kinematics of the rock glacier in Äußeres Hochebenkar (Austrian Alps). We consolidate, homogenize, and extend existing time series to generate a comprehensive dataset consisting of 14 digital surface models covering a 68-year time period, as well as in situ measurements of block displacement since the early 1950s. The digital surface models are derived from historical aerial imagery and, more recently, airborne and uncrewed-aerial-vehicle-based laser scanning (ALS and ULS, respectively). High-resolution 3D ALS and ULS point clouds are available at annual temporal resolution from 2017 to 2021. Additional terrestrial laser scanning data collected in bi-weekly intervals during the summer of 2019 are available from the rock glacier front. Using image correlation techniques, we derive velocity vectors from the digital surface models, thereby adding rock-glacier-wide spatial context to the point-scale block displacement measurements. Based on velocities, surface elevation changes, analyses of morphological features, and computations of the bulk creep factor and strain rates, we assess the combined datasets in terms of rock glacier destabilization. To additionally investigate potential rotational components of the movement of the destabilized section of the rock glacier, we integrate in situ data of block displacement with ULS point clouds and compute changes in the rotation angles of single blocks during recent years. The time series shows two cycles of destabilization in the lower section of the rock glacier. The first lasted from the early 1950s until the mid-1970s. The second began around 2017 after approximately 2 decades of more gradual acceleration and is currently ongoing. Both destabilization periods are characterized by high velocities and the development of morphological destabilization features on the rock glacier surface. Acceleration in the most recent years has been very pronounced, with velocities reaching 20–30 m a−1 in 2020–2021. These values are unprecedented in the time series and suggest highly destabilized conditions in the lower section of the rock glacier, which shows signs of translational and rotational landslide-like movement. Due to the length and granularity of the time series, the cyclic destabilization process at the Äußeres Hochebenkar rock glacier is well resolved in the dataset. Our study highlights the importance of interdisciplinary, long-term, and continuous high-resolution 3D monitoring to improve process understanding and model development related to rock glacier rheology and destabilization.

Acceleration and interannual variability of creep rates in mountain permafrost landforms (rock glacier velocities) in the European Alps in 1995–2022

“…Practical examples have already confirmed that RGV derived from UAV-data, i.e. multi-temporal digital orthophotos and/or surface models, compare very well with geodetic point measurements if photos taken are of high spatial resolution [49,51].…”

“…Since 1951, creep velocity has been measured at this RG by terrestrial geodetic methods and since 2008 by Global Navigation Satellite System (GNSS) technology [69][70][71][72][73]. A06 has the worldwide longest record of RGV data [48,70] although several gaps exist [49,73]. Annual terrestrial geodetic surveys to derive RGV have been included as part of the long-term observation strategy of the Swiss Permafrost Monitoring Network PERMOS since 2008 to complement the measurements of permafrost temperature and changes in ground ice content [74].…”

“…For others, such a separation will possibly be introduced in the future, with a decorrelating movement pattern of the upper and lower parts (e.g. A06, [49]). For further RGs where such a separation has taken place already earlier, only one unit is surveyed today, partly also due to field safety reasons.…”

Climate change impacts and adaptation to permafrost change in High Mountain Asia: a comprehensive review

“…These rock glaciers are a potential outcome of permafrost in nonequilibrium conditions. Increased warming is predicted to boost the degree of activity of rock glaciers and support faster movement of rock glaciers (Hartl et al 2023), increasing the potential for such events, however investigations into this direction in HMA are lacking.…”

Go or grow? Feedbacks between moving slopes and shifting plants in high mountain environments

“…Knowledge on adaptations of high mountain species to slope movements exists already for a long time (Schröter et al, 1926), but relationships between plant traits and movement intensities have rarely been quantified. To achieve this, measurements of mountain plant traits, facilitated by well-standardized methods (Freschet et al, 2021;Pérez-Harguindeguy et al, 2013), could be carried out on slopes with known movement rates increasingly provided by new techniques such as terrestrial laser scanning, uncrewed aerial vehicle (UAV) surveys and InSAR (Hartl et al, 2023;Hendrickx et al, 2020;Rouyet et al, 2021). While extensive plant trait databases exist (Bjorkman et al, 2018a(Bjorkman et al, , 2018bKattge et al, 2011Kattge et al, , 2020Maitner et al, 2018), data availability is often limited for alpine species and many important biomechanical traits, such as root tensile strength or modulus of elasticity, are far from being included routinely in ecological databases.…”