Multi-decadal (1953–2017) rock glacier kinematics analysed by high-resolution topographic data in the upper Kaunertal, Austria

Fleischer, Fabian; Haas, Florian; Piermattei, Livia; Pfeiffer, Miriam; Heckmann, Tobias; Altmann, Moritz; Rom, Jakob; Stark, Manuel; Wimmer, Michael; Pfeifer, Norbert; Becht, Michael

doi:10.5194/tc-15-5345-2021

Cited by 19 publications

(44 citation statements)

References 55 publications

(109 reference statements)

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“…Typically, rock glaciers creep downslope with velocities of several decimetres up to some metres per year (e.g. Roer, 2007;Bodin et al, 2009;Fleischer et al, 2021;Kääb et al, 2021). This creep behaviour results from internal deformation of the frozen debris and shearing within narrow horizons at typical depths of around 20 m (Arenson et al, 2002;Cicoira et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, terrestrial as well as remote sensing techniques are applied to quantify the kinematics of permafrost creep, i.e. horizontal surface velocities and vertical surface changes, respectively (Lambiel and Delaloye, 2004;Kääb, 2005;Haeberli et al, 2006;Roer, 2007;Bodin et al, 2009;Strozzi et al, 2020;Cusicanqui et al, 2021;Fleischer et al, 2021;Kääb et al, 2021;Kaufmann et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

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Glacier–permafrost relations in a high-mountain environment: 5 decades of kinematic monitoring at the Gruben site, Swiss Alps

et al. 2022

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Abstract. Digitized aerial images were used to monitor the evolution of perennially frozen debris and polythermal glacier ice at the intensely investigated Gruben site in the Swiss Alps over a period of about 50 years. The photogrammetric analysis allowed for a compilation of detailed spatio-temporal information on flow velocities and thickness changes. In addition, high-resolution GNSS (global navigation satellite system) and ground surface temperature measurements were included in the analysis to provide insight into short-term changes. Over time, extremely contrasting developments and landform responses are documented. Viscous flow within the warming and already near-temperate rock glacier permafrost continued at a constant average but seasonally variable speed of typically decimetres per year, with average surface lowering limited to centimetres to a few decimetres per year. This constant flow causes the continued advance of the characteristic convex, lava-stream-like rock glacier with its oversteepened fronts. Thawing rates of ice-rich perennially frozen ground to strong climate forcing are very low (centimetres per year) and the dynamic response strongly delayed (timescale of decades to centuries). The adjacent cold debris-covered glacier tongue remained an essentially concave landform with diffuse margins, predominantly chaotic surface structure, intermediate thickness losses (decimetres per year), and clear signs of down-wasting and decreasing flow velocity. The former contact zone between the cold glacier margin and the upper part of the rock glacier with disappearing remains of buried glacier ice embedded on top of frozen debris exhibits complex phenomena of thermokarst in massive ice and backflow towards the topographic depression produced by the retreating glacier tongue. As is typical for glaciers in the Alps, the largely debris-free glacier part shows a rapid response (timescale of years) to strong climatic forcing with spectacular retreat (>10 m a−1) and mass loss (up to >1 m w.e. specific mass loss per year). The system of periglacial lakes shows a correspondingly dynamic evolution and had to be controlled by engineering work for hazard protection.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Glacier–permafrost relations in a high-mountain environment: 5 decades of kinematic monitoring at the Gruben site, Swiss Alps

et al. 2022

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“…Indeed, methods such as lidar (Micheletti et al, 2017), InSAR (e.g., Liu et al, 2013;Barboux et al, 2014;Strozzi et al, 2020), aerial photogrammetry (e.g., Kaab et al, 1997), and unpiloted aerial vehicle systems (e.g., Dall'Asta et al, 2017;Vivero and Lambiel, 2019) have made a remarkable improvement to the temporal and spatial resolution of surface velocity surveys for rock glaciers. Recent studies have shown the feasibility of using high-resolution digital elevation models (DEMs) and orthorectified images produced from historical aerial and satellite images to reconstruct the surface velocity of rock glaciers over the last 7 decades (Fleischer et al, 2021;Vivero et al, 2021;Kääb et al, 2021;Cusicanqui et al, 2021). Extrapolations from short-term surface velocities have been used to estimate the rock glacier formation time and to reconstruct their activity over longer timescales (Kaab et al, 1997;Frauenfelder and Kááb, 2000;Bodin, 2013).…”

Section: Introduction and Motivationsmentioning

confidence: 99%

Alpine rock glacier activity over Holocene to modern timescales (western French Alps)

et al. 2022

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Abstract. Active rock glaciers are some of the most frequent cryospheric landforms in midlatitude high-elevation mountain ranges. Their activity strongly influences the hydrology and geomorphology of alpine environments over short (years to decades) and long (centuries to millennia) timescales. Being conspicuous expressions of mountain permafrost and important water reserves in the form of ground ice, rock glaciers are seen as increasingly important actors in the geomorphological and hydrological evolution of mountain systems, especially in the context of current climate change. Over geological timescales, rock glaciers both reflect paleoclimate conditions and transport rock boulders produced by headwall erosion, and they therefore participate in shaping high mountain slopes. However, the dynamics of rock glaciers and their evolution over different timescales remain under-constrained. In this study, we adopt a multi-method approach, including field observations, remote sensing, and geochronology, to investigate the rock glacier system of the Vallon de la Route (Combeynot Massif, western French Alps). Remotely sensed images and correlation techniques are used to document the displacement field of the rock glacier over timescales ranging from days to decades. Additionally, to estimate displacement over periods from centuries to millennia, we employ terrestrial cosmogenic nuclide (quartz 10Be) surface-exposure dating on rock boulder surfaces located along the central flow line of the rock glacier, targeting different longitudinal positions from the headwall to the rock glacier terminus. The remote sensing analysis demonstrates that between 1960 and 2018 the two lower units of the rock glacier were motionless, the transitional unit presented an integrated surface velocity of 0.03±0.02 m a−1, and the two upper active units above 2600 m a.s.l. showed a velocity between 0.14±0.08 and 0.15±0.05 m a−1. Our results show 10Be surface-exposure ages ranging from 13.10±0.51 to 1.88±0.14 ka. The spatial distribution of dated rock glacier boulders reveals a first-order inverse correlation between 10Be surface-exposure age and elevation and a positive correlation with horizontal distance to the headwall. These observations support the hypothesis of rock boulders falling from the headwall and remaining on the glacier surface as they are transported down valley, and they may therefore be used to estimate rock glacier surface velocity over geological timescales. Our results also suggest that the rock glacier is characterized by two major phases of activity. The first phase, starting around 12 ka, displays a 10Be age gradient with a rock glacier surface velocity of about 0.45 m a−1, following a quiescent period between ca. 6.2 and 3.4 ka before the emplacement of the present-day upper two active units. Climatic conditions have favored an integrated rock glacier motion of around 0.18 m a−1 between 3.4 ka and present day. These results allow us to quantify back-wearing rates of the headwall of between 1.0 and 2.5 mm a−1, higher than catchment-integrated denudation rates estimated over millennial timescales. This suggests that the rock glacier system promotes the maintenance of high rock wall erosion by acting as debris conveyor and allowing freshly exposed bedrock surfaces to be affected by erosion processes.

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“…Rock glacier kinematics have increasingly become of interest during approximately the last two decades, as accelerating trends became apparent at many rock glaciers in the Alps (Roer, 2005;Delaloye et al, 2008Delaloye et al, , 2010Kellerer-Pirklbauer et al, 2018;Fleischer et al, 2021). These general trends are broadly attributed to rising air and ground temperatures, although interannual variations of rock glacier velocities often cannot be explained with variations in mean annual or summer air temperatures alone, indicating a multifaceted and scale-dependent relationship between climate forcing and rock glacier response (Delaloye et al, 2008(Delaloye et al, , 2010Sorg et al, 2015;Hartl et al, 2016b;Kellerer-Pirklbauer et al, 2017;Müller et al, 2016;Cicoira et al, 2019a;Fleischer et al, 2021).…”

Section: Introductionmentioning

confidence: 99%

Multisensor monitoring and data integration reveal cyclical destabilization of Äußeres Hochebenkar Rock Glacier

Hartl

Zieher

Bremer

et al. 2022

Preprint

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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, ULS). Since 2017, high-resolution 3D ALS and ULS point clouds are available at annual temporal resolution. Additional terrestrial laser scanning data collected in bi-weekly intervals during the summer of 2019 is 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 change, analysis 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 two 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 in 2020/21. 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 as well as rotational, landslide-like movement. Due to the length and granularity of the time series, the cyclic destabilization process at 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.

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Multi-decadal (1953–2017) rock glacier kinematics analysed by high-resolution topographic data in the upper Kaunertal, Austria

Cited by 19 publications

References 55 publications

Glacier–permafrost relations in a high-mountain environment: 5 decades of kinematic monitoring at the Gruben site, Swiss Alps

Glacier–permafrost relations in a high-mountain environment: 5 decades of kinematic monitoring at the Gruben site, Swiss Alps

Alpine rock glacier activity over Holocene to modern timescales (western French Alps)

Multisensor monitoring and data integration reveal cyclical destabilization of Äußeres Hochebenkar Rock Glacier

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