scholarly journals Rock glaciers on the run – understanding rock glacier landform evolution and recent changes from numerical flow modeling

2016 ◽  
Vol 10 (6) ◽  
pp. 2865-2886 ◽  
Author(s):  
Johann Müller ◽  
Andreas Vieli ◽  
Isabelle Gärtner-Roer
Keyword(s):  
Morphological Changes ◽  
Holistic Approach ◽  
Swiss Alps ◽  
Dynamical Response ◽  
Dynamics Modeling ◽  
Rock Glacier ◽  
Modeling Framework ◽  
Rock Glaciers ◽  
Numerical Flow Modeling ◽  
The Impact

Abstract. Rock glaciers are landforms that form as a result of creeping mountain permafrost which have received considerable attention concerning their dynamical and thermal changes. Observed changes in rock glacier motion on seasonal to decadal timescales have been linked to ground temperature variations and related changes in landform geometries interpreted as signs of degradation due to climate warming. Despite the extensive kinematic and thermal monitoring of these creeping permafrost landforms, our understanding of the controlling factors remains limited and lacks robust quantitative models of rock glacier evolution in relation to their environmental setting. Here, we use a holistic approach to analyze the current and long-term dynamical development of two rock glaciers in the Swiss Alps. Site-specific sedimentation and ice generation rates are linked with an adapted numerical flow model for rock glaciers that couples the process chain from material deposition to rock glacier flow in order to reproduce observed rock glacier geometries and their general dynamics. Modeling experiments exploring the impact of variations in rock glacier temperature and sediment–ice supply show that these forcing processes are not sufficient to explain the currently observed short-term geometrical changes derived from multitemporal digital terrain models at the two different rock glaciers. The modeling also shows that rock glacier thickness is dominantly controlled by slope and rheology while the advance rates are mostly constrained by rates of sediment–ice supply. Furthermore, timescales of dynamical adjustment are found to be strongly linked to creep velocity. Overall, we provide a useful modeling framework for a better understanding of the dynamical response and morphological changes of rock glaciers to changes in external forcing.

scholarly journals Rockglaciers on the run – Understanding rockglacier landform evolution and recent changes from numerical flow modeling

2016 ◽  
Author(s):  
Johann Müller ◽  
Andreas Vieli ◽  
Isabelle Gärtner-Roer
Keyword(s):  
Morphological Changes ◽  
Holistic Approach ◽  
Swiss Alps ◽  
Dynamical Response ◽  
Modelling Framework ◽  
Digital Terrain ◽  
Material Deposition ◽  
General Dynamics ◽  
Numerical Flow Modeling ◽  
The Impact

Abstract. Rockglaciers are landforms indicative of permafrost creep and received considerable attention concerning their dynamical and thermal changes. Observed changes in rockglacier motion on seasonal to decadal timescales have been linked to ground temperature variations and related changes in landform geometries interpreted as signs of degradation due to climate warming. Despite the extensive kinematic and thermal monitoring of these creeping permafrost landforms, our understanding of the controlling factors remains limited and lacks robust quantitative models for rockglacier evolution in relation to their environmental setting. Here, we use a holistic approach to analyze the current and long-term dynamical development of two rockglaciers in the Swiss Alps. Site-specific sedimentation and ice generation rates are linked with an adapted numerical flow model for rockglaciers that couples the process chain from material deposition to rockglacier flow in order to reproduce observed rockglacier geometries and their general dynamics. Modelling experiments exploring the impact of variations in rockglacier temperature and sediment/ice supply show that these forcing processes are not sufficient for explaining the currently observed short-term geometrical changes derived from multitemporal digital terrain models at the two different rockglacier. The modelling also shows that rockglacier thickness is dominantly controlled by slope and rheology while the advance rates are mostly constrained by rates of sediment/ice supply. Furthermore, timescales of dynamical adjustment are found to be strongly linked to creep velocity. Overall, we provide a useful modelling framework for a better understanding of the dynamical response and morphological changes of rockglaciers to changes in external forcing.

scholarly journals Towards a palaeoclimatic model of rock-glacier formation in the Swiss Alps

2000 ◽  
Vol 31 ◽  
pp. 281-286 ◽  
Author(s):  
Regula Frauenfelder ◽  
Andreas Kääb
Keyword(s):  
Regional Scale ◽  
Thermal Conditions ◽  
Late Glacial ◽  
Climatic Conditions ◽  
Swiss Alps ◽  
Inventory Analysis ◽  
Rock Glacier ◽  
Altitudinal Distribution ◽  
Polymorphic Type ◽  
Rock Glaciers

AbstractClimate and its long-term variability govern ground thermal conditions, and for this reason represent one of the most important impacts on creeping mountain permafrost. The decoding and better understanding of the present-day morphology and distribution of rock glaciers opens up a variety of insights into past and present environmental, especially climatic, conditions on a local to regional scale. The present study was carried out in the Swiss Alps using two different approaches: (1) kinematic analysis of specific active rock glaciers, and (2) description of the altitudinal distribution of relict rock glaciers. Two theoretical shape concepts of active rock-glacier morphology were derived’ a"monomorphic" type, representing presumably undisturbed, continuous development over several millennia and a ˚polymorphic" type, reflecting a system of (possibly climatically affected) individual creep streams several centuries old. The topoclimatic-based inventory analysis indicated an average temperature increase at relict rock-glacier fronts of approximately +2°C since the time of their decay, which is a sign of rock-glacier ages reaching back to the Alpine Late Glacial. The temperature difference of some tenths of a degree Celsius found for active/inactive rock glaciers is typical for the bandwidth of Holocene climate variations. These results confirm the importance of Alpine rock glaciers as highly sensitive indicators of past temperature evolution.

scholarly journals A new model for quantifying subsurface ice content based on geophysical data sets

2010 ◽  
Vol 4 (2) ◽  
pp. 787-821 ◽  
Author(s):  
C. Hauck ◽  
M. Böttcher ◽  
H. Maurer
Keyword(s):  
Seismic Velocity ◽  
Geophysical Methods ◽  
Geophysical Data ◽  
Swiss Alps ◽  
Unfrozen Water ◽  
Detailed Knowledge ◽  
Data Sets ◽  
Rock Glacier ◽  
Heterogeneous Distribution ◽  
Rock Glaciers

Abstract. Detailed knowledge of the material properties and internal structures of frozen ground is one of the prerequisites in many permafrost studies. In the absence of direct evidence, such as in-situ borehole measurements, geophysical methods are an increasingly interesting option for obtaining subsurface information on various spatial and temporal scales. The indirect nature of geophysical soundings requires a relation between the measured variables (e.g. electrical resistivity, seismic velocity) and the actual subsurface constituents (rock, water, air, ice). In this work we present a model, which provides estimates of the volumetric fractions of these four phases from tomographic electrical and seismic images. The model is tested using geophysical data sets from two rock glaciers in the Swiss Alps, where ground truth information in form of borehole data is available. First results confirm the applicability of the so-called 4-phase model, which allows to quantify the contributions of ice-, water- and air within permafrost areas as well as detecting the firm bedrock. Apart from a similarly thick active layer with enhanced air content for both rock glaciers, the two case studies revealed a heterogeneous distribution of ice and unfrozen water within rock glacier Muragl, where bedrock was detected at depths of 20–25 m, but a comparatively homogeneous ice body with only minor heterogeneities within rock glacier Murtèl.

scholarly journals A two-sided approach to estimate heat transfer processes within the active layer of the Murtèl–Corvatsch rock glacier

2014 ◽  
Vol 2 (1) ◽  
pp. 141-154 ◽  
Author(s):  
M. Scherler ◽  
S. Schneider ◽  
M. Hoelzle ◽  
C. Hauck
Keyword(s):  
Heat Transfer ◽  
Surface Layer ◽  
Energy Balance ◽  
Active Layer ◽  
Heat Sink ◽  
Air Flow ◽  
Swiss Alps ◽  
Rock Glacier ◽  
Transfer Processes ◽  
Rock Glaciers

Abstract. The thermal regime of permafrost on scree slopes and rock glaciers is characterized by the importance of air flow driven convective and advective heat transfer processes. These processes are supposed to be part of the energy balance in the active layer of rock glaciers leading to lower subsurface temperatures than would be expected at the lower limit of discontinuous high mountain permafrost. In this study, new parametrizations were introduced in a numerical soil model (the Coup Model) to simulate permafrost temperatures observed in a borehole at the Murtèl rock glacier in the Swiss Alps in the period from 1997 to 2008. A soil heat sink and source layer was implemented within the active layer, which was parametrized experimentally to account for and quantify the contribution of air flow driven heat transfer on the measured permafrost temperatures. The experimental model calibration process yielded a value of about 28.9 Wm−2 for the heat sink during the period from mid September to mid January and one of 26 Wm−2 for the heat source in the period from June to mid September. Energy balance measurements, integrated over a 3.5 m-thick blocky surface layer, showed seasonal deviations between a zero energy balance and the calculated sum of the energy balance components of around 5.5 Wm−2 in fall/winter, −0.9 Wm−2 in winter/spring and around −9.4 Wm−2 in summer. The calculations integrate heat exchange processes including thermal radiation between adjacent blocks, turbulent heat flux and energy storage change in the blocky surface layer. Finally, it is hypothesized that these deviations approximately equal unmeasured freezing and thawing processes within the blocky surface layer.

scholarly journals A two-sided approach to estimate heat transfer processes within the active layer of rock glacier Murtèl-Corvatsch

2013 ◽  
Vol 1 (1) ◽  
pp. 141-175 ◽  
Author(s):  
M. Scherler ◽  
S. Schneider ◽  
M. Hoelzle ◽  
C. Hauck
Keyword(s):  
Heat Transfer ◽  
Surface Layer ◽  
Energy Balance ◽  
Active Layer ◽  
Heat Sink ◽  
Air Flow ◽  
Swiss Alps ◽  
Rock Glacier ◽  
Transfer Processes ◽  
Rock Glaciers

Abstract. The thermal regime of permafrost in scree slopes and rock glaciers is characterized by the importance of air flow driven convective and advective heat transfer processes. These processes are supposed to be part of the energy balance in the active layer of rock glaciers leading to lower subsurface temperatures than would be expected at the lower limit of discontinues high mountain permafrost. In this study, new parameterizations were introduced in a numerical soil model to simulate permafrost temperatures observed in a borehole at rock glacier Murtèl in the Swiss Alps in the period from 1997 to 2008. A soil heat sink and source layer was implemented within the active layer which was parameterized experimentally to account for and quantify the contribution of air flow driven heat transfer on the measured permafrost temperatures. The experimental model calibration process yielded a value of about 28.9 Wm−2 for the heat sink during the period from mid September to mid January and one of 26 Wm−2 for the heat source in the period from June to mid September. Energy balance measurements, integrated over a 3.5 m thick blocky surface layer, showed seasonal deviations between a zero energy balance and the calculated sum of the energy balance components of around 6.8 Wm−2 in fall/winter, −2.2 Wm−2 in winter/spring and around −5.6 Wm−2 in summer. The calculations integrate heat exchange processes including thermal radiation between adjacent blocks, turbulent heat flux and energy storage change in the blocky surface layer. Finally, it is hypothesized that these deviations approximately equal unmeasured freezing and thawing processes within the blocky surface layer.

scholarly journals A new model for estimating subsurface ice content based on combined electrical and seismic data sets

2011 ◽  
Vol 5 (2) ◽  
pp. 453-468 ◽  
Author(s):  
C. Hauck ◽  
M. Böttcher ◽  
H. Maurer
Keyword(s):  
Seismic Velocity ◽  
Geophysical Methods ◽  
Swiss Alps ◽  
Unfrozen Water ◽  
Detailed Knowledge ◽  
Data Sets ◽  
Rock Glacier ◽  
Borehole Data ◽  
Heterogeneous Distribution ◽  
Rock Glaciers

Abstract. Detailed knowledge of the material properties and internal structures of frozen ground is one of the prerequisites in many permafrost studies. In the absence of direct evidence, such as in-situ borehole measurements, geophysical methods are an increasingly interesting option for obtaining subsurface information on various spatial and temporal scales. The indirect nature of geophysical soundings requires a relation between the measured variables (e.g. electrical resistivity, seismic velocity) and the actual subsurface constituents (rock, water, air, ice). In this work, we present a model which provides estimates of the volumetric fractions of these four constituents from tomographic electrical and seismic images. The model is tested using geophysical data sets from two rock glaciers in the Swiss Alps, where ground truth information in form of borehole data is available. First results confirm the applicability of the so-called 4-phase model, which allows to quantify the contributions of ice-, water- and air within permafrost areas as well as detecting solid bedrock. Apart from a similarly thick active layer with enhanced air content for both rock glaciers, the two case studies revealed a heterogeneous distribution of ice and unfrozen water within Muragl rock glacier, where bedrock was detected at depths of 20–25 m, but a comparatively homogeneous ice body with only minor heterogeneities within Murtèl rock glacier.

scholarly journals Monitoring Rock Glacier Kinematics with Satellite Synthetic Aperture Radar

2020 ◽  
Vol 12 (3) ◽  
pp. 559 ◽  
Author(s):  
Tazio Strozzi ◽  
Rafael Caduff ◽  
Nina Jones ◽  
Chloé Barboux ◽  
Reynald Delaloye ◽  
...  
Keyword(s):  
Swiss Alps ◽  
European Alps ◽  
Remotely Sensed Data ◽  
Rock Glacier ◽  
Sar Images ◽  
Mountain Permafrost ◽  
Rock Glaciers ◽  
Satellite Radar ◽  
Offset Tracking

Active rock glaciers represent the best visual expression of mountain permafrost that can be mapped and monitored directly using remotely sensed data. Active rock glaciers are bodies that consist of a perennially frozen ice/rock mixture and express a distinct flow-like morphology indicating downslope permafrost creep movement. Annual rates of motion have ranged from a few millimeters to several meters per year, varying within the annual cycle, from year to year, as well as at the decennial time scale. During the last decade, in situ observations in the European Alps have shown that active rock glaciers are responding almost synchronously to inter-annual and decennial changes in ground temperature, suggesting that the relative changes of their kinematics are a general indicator of the evolution of mountain permafrost conditions. Here, we used satellite radar interferometry (InSAR) to monitor the rate of motion of various active rock glaciers in the Swiss Alps, Qeqertarsuaq (Western Greenland), and the semiarid Andes of South America. Velocity time series computed with Sentinel-1 SAR images, regularly acquired since 2014, every six days over Europe and Greenland and every 12 days over the Andes, show annual fluctuations, with higher velocities at the end of the summer. A JERS-1 image pair of 1996 and stacks of very high-resolution SAR images from TerraSAR-X and Cosmo-SkyMed from 2008 to 2017 were analyzed using InSAR and offset tracking over the Western Swiss Alps in order to extend the main observation period of our study. A quantitative assessment of the accuracy of InSAR and offset tracking was performed by comparison with in situ methods. Our results for the three different study regions demonstrate that Sentinel-1 InSAR can complement worldwide in situ measurements of active rock glacier kinematics.

scholarly journals Internal structure of two alpine rock glaciers investigated by quasi-3-D electrical resistivity imaging

2017 ◽  
Vol 11 (2) ◽  
pp. 841-855 ◽  
Author(s):  
Adrian Emmert ◽  
Christof Kneisel
Keyword(s):  
Electrical Resistivity ◽  
Internal Structure ◽  
Swiss Alps ◽  
Electrical Resistivity Imaging ◽  
Rock Glacier ◽  
Ground Ice ◽  
Resistivity Imaging ◽  
Wide Range ◽  
Rock Glaciers ◽  
Ice Content

Abstract. Interactions between different formative processes are reflected in the internal structure of rock glaciers. Therefore, the detection of subsurface conditions can help to enhance our understanding of landform development. For an assessment of subsurface conditions, we present an analysis of the spatial variability of active layer thickness, ground ice content and frost table topography for two different rock glaciers in the Eastern Swiss Alps by means of quasi-3-D electrical resistivity imaging (ERI). This approach enables an extensive mapping of subsurface structures and a spatial overlay between site-specific surface and subsurface characteristics. At Nair rock glacier, we discovered a gradual descent of the frost table in a downslope direction and a constant decrease of ice content which follows the observed surface topography. This is attributed to ice formation by refreezing meltwater from an embedded snow bank or from a subsurface ice patch which reshapes the permafrost layer. The heterogeneous ground ice distribution at Uertsch rock glacier indicates that multiple processes on different time domains were involved in the development. Resistivity values which represent frozen conditions vary within a wide range and indicate a successive formation which includes several advances, past glacial overrides and creep processes on the rock glacier surface. In combination with the observed topography, quasi-3-D ERI enables us to delimit areas of extensive and compressive flow in close proximity. Excellent data quality was provided by a good coupling of electrodes to the ground in the pebbly material of the investigated rock glaciers. Results show the value of the quasi-3-D ERI approach but advise the application of complementary geophysical methods for interpreting the results.

scholarly journals Investigation on protalus ramparts in the Swiss Alps

2015 ◽  
Vol 70 (2) ◽  
pp. 135-139 ◽  
Author(s):  
C. Scapozza
Keyword(s):  
Diagnostic Criteria ◽  
Scientific Literature ◽  
Swiss Alps ◽  
Rock Glacier ◽  
Rock Glaciers ◽  
Talus Slopes ◽  
Definition Of ◽  
Alpine Environments ◽  
Large Diffusion

Abstract. The origin and classification of landforms denominated as "protalus ramparts" in the scientific literature is a problem that is far from being resolved. The main objective of this contribution is to support a permafrost-related definition of protalus ramparts. If we consider the Alpine framework, protalus ramparts are generally very rare landforms; by contrast, the Alpine periglacial belt is characterised by a large diffusion of talus slopes and talus rock glaciers. The investigations carried out in six sites of the Valais Alps (Switzerland) allow eight major "diagnostic criteria" to be presented that help to define protalus ramparts in Alpine environments and that support the permafrost-related genesis of most of them. The major source of controversy is related to the use of the term protalus rampart to designate both a nivo-gravitational landform (also called "pronival ramparts") and a permafrost-related landform. All the considerations presented here allow an active protalus rampart to be defined simply as a (small) active talus rock glacier.

A complementary kinematic approach to inventory rock glaciers applied to case studies of the Swiss and Italian Alps

2021 ◽  
Author(s):  
Aldo Bertone ◽  
Chloé Barboux ◽  
Francesco Brardinoni ◽  
Reynald Delaloye ◽  
Volkmar Mair ◽  
...  
Keyword(s):  
Swiss Alps ◽  
Research Network ◽  
Italian Alps ◽  
The South ◽  
Rock Glacier ◽  
Climatic Forcing ◽  
Mountain Permafrost ◽  
Rock Glaciers ◽  
Kinematic Information ◽  
Velocity Class

<p>Rock glaciers are the best visual expression of creeping mountain permafrost. Their dynamics, which largely depend on climatic forcing, provide information about the mountain permafrost and may locally pose risk to infrastructures.</p><p>The International Permafrost Association (IPA) Action Group on Rock glacier inventories and kinematics, launched in 2018, fosters the activities of a research network focused on the definition of standardized guidelines for inventorying rock glaciers, including information on rock-glacier displacement rate. The ESA Permafrost_CCI project further sustains this initiative, and proposes a standardized method to implement kinematics-based rock glacier inventories.</p><p>The proposed method exploits interferometric data from spaceborne Synthetic Aperture Radar (InSAR) to derive the kinematic information of existing or newly-compiled rock glacier inventories. In particular, areas identified as slope movements within rock glacier polygons are delineated on interferograms as “moving areas”, and are assigned a velocity class. Subsequently, a specific kinematic class is assigned to each rock glacier unit according to the velocity class and extension of the relevant moving areas.</p><p>This method is applied on two regions: the Western part of the Swiss Alps and the South-Western part of the South Tyrol (Italian Alps). Both are located at the same latitude, with rock glaciers in the Swiss part lying at slightly higher altitudes, and experiencing higher mean annual precipitation. Rock glacier polygons were drawn from existing inventories, the kinematic information was extracted exploiting InSAR data acquired between 2018 and 2019 from the Sentinel-1 constellation.</p><p>In the Swiss and Italian parts, we inventoried 660 and 783 moving areas (1443 in total). Collectively, it was possible to assign a kinematic attribute to 913 rock glaciers, providing a more objective and quantitative activity classification (compared to the qualitative active, inactive, and relict categories). In the Swiss part, 14% of the rock glaciers are moving in the magnitude order of a meter/year or faster, 43% in the magnitude order of one to several dm/yr, 36% from one to several cm/yr, the others are with unreliable movements (7%). In the Italian part, these percentages are 1% (meter/year or faster), 42% (one to several dm/yr), 39% (one to several cm/yr) and 18% (no reliable), respectively. Preliminary analyses on the Italian part are conducted on 467 additional rock glaciers recognized as geomorphologically relict: 68% are not moving or not moving fast enough to be detected, 9% have sectors moving up to several cm/yr, and the remaining 23% of relict rock glaciers have no reliable information on movement.</p><p>Preliminary results show how this approach allows to provide complementary kinematic information to the geomorphological approach, improving the knowledge on the activity status in a given time and in a given region. Since several studies have reported trends towards displacement acceleration, applying this approach over long periods will allow assessing the response of a wide selection of landforms to (warmer) climatic forcing. Furthermore, this approach is a very useful tool to help select representative rock glaciers of a region, on which to apply more accurate monitoring approaches.</p>

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