scholarly journals Disaggregating surface change mechanisms of a rock glacier using terrestrial laser scanning point clouds acquired at different time scales

2020 ◽  
Author(s):  
Veit Ulrich ◽  
Jack G. Williams ◽  
Vivien Zahs ◽  
Katharina Anders ◽  
Stefan Hecht ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Point Clouds ◽  
Rock Glacier ◽  
Glacier Surface ◽  
Terrestrial Lidar ◽  
Surface Change ◽  
Relative Contribution ◽  
Rock Glaciers ◽  
Change Mechanisms ◽  
Glacier Flow

Abstract. Topographic change at a given location usually results from multiple processes operating over different timescales. However, interpretations of surface change are often based upon single values of movement, measured over a specified time period and in a single direction. This work presents a method to help separate surface change mechanisms related to the deformation of an active rock glacier, drawing on terrestrial lidar monitoring at sub-monthly intervals. We derive 3D topographic changes across the Äußeres Hochebenkar rock glacier in the Ötztal Alps. These are presented as the relative contribution of surface change during a three-week period of snow-free conditions (2018) to the annual surface change (2017–2018). They are also separated according to the direction perpendicular to the local rock glacier surface (using point cloud distance computation) and the direction of rock glacier flow, indicated by movement of individual boulders. In a 1500 m2 sample area in the lower tongue section of the rock glacier, the contribution of the three-week period to the annual change perpendicular to the surface is 20 %, as compared to 6 % in the direction of rock glacier flow. This shows that different directions of surface change are dominant at different times of the year. Our results demonstrate the benefit of more frequent lidar monitoring and, critically, the requirement of novel approaches to detecting change, as a step towards interpreting the mechanisms that underlie the surface change of rock glaciers.

scholarly journals Measurement of rock glacier surface change over different timescales using terrestrial laser scanning point clouds

2021 ◽  
Vol 9 (1) ◽  
pp. 19-28
Author(s):  
Veit Ulrich ◽  
Jack G. Williams ◽  
Vivien Zahs ◽  
Katharina Anders ◽  
Stefan Hecht ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Point Clouds ◽  
Rock Glacier ◽  
Glacier Surface ◽  
Terrestrial Lidar ◽  
Surface Change ◽  
Relative Contribution ◽  
Time Period ◽  
Multiple Processes ◽  
Glacier Flow

Abstract. Topographic change at a given location usually results from multiple processes operating over different timescales. However, interpretations of surface change are often based upon single values of movement, measured over a specified time period or in a single direction. This work presents a method to help separate surface change types that occur at different timescales related to the deformation of an active rock glacier, drawing on terrestrial lidar monitoring at sub-monthly intervals. To this end, we derive 3D topographic changes across the Äußeres Hochebenkar rock glacier in the Ötztal Alps. These changes are presented as the relative contribution of surface change during a 3-week period (2018) to the annual surface change (2017–2018). They are also separated according to the spatially variable direction perpendicular to the local rock glacier surface (using point cloud distance computation) and a single main direction of rock glacier flow, indicated by movement of individual boulders. In a 1500 m2 sample area in the lower tongue section of the rock glacier, the contribution of the 3-week period to the annual change perpendicular to the surface is 20 %, compared with 6 % in the direction of rock glacier flow. Viewing change in this way, our approach provides estimates of surface change in different directions that are dominant at different times of the year. Our results demonstrate the benefit of more frequent lidar monitoring and, critically, the requirement for novel approaches to quantifying and disaggregating surface change, as a step towards rock glacier observation networks focusing on the analysis of 3D surface change over time.

scholarly journals GEOMATIC METHODS APPLIED TO THE CHANGE STUDY OF THE LA PAÚL ROCK GLACIER, SPANISH PYRENEES

2019 ◽  
Vol XLII-2/W13 ◽  
pp. 1771-1775
Author(s):  
A. Martínez-Fernández ◽  
E. Serrano ◽  
J. J. Sanjosé ◽  
M. Gómez-Lende ◽  
A. Pisabarro ◽  
...  
Keyword(s):  
Laser Scanning ◽  
Satellite System ◽  
Ice Age ◽  
Rock Glacier ◽  
Glacier Surface ◽  
The North ◽  
Spanish Pyrenees ◽  
Gnss Receivers ◽  
Rock Glaciers ◽  
Global Navigation Satellite

<p><strong>Abstract.</strong> Rock glaciers are one of the most important features of the mountain permafrost in the Pyrenees. La Paúl is an active rock glacier located in the north face of the Posets massif in the La Paúl glacier cirque (Spanish Pyrenees). This study presents the preliminary results of the La Paúl rock glacier monitoring works carried out through two geomatic technologies since 2013: Global Navigation Satellite System (GNSS) receivers and Terrestrial Laser Scanning (TLS) devices. Displacements measured on the rock glacier surface have demonstrated both the activity of the rock glacier and the utility of this equipment for the rock glaciers dynamic analysis. The glacier has exhibited the fastest displacements on its west side (over 35&amp;thinsp;cm&amp;thinsp;yr<sup>&amp;minus;1</sup>), affected by the Little Ice Age, and frontal area (over 25&amp;thinsp;cm&amp;thinsp;yr<sup>&amp;minus;1</sup>). As an indicator of permafrost in marginal environments and its peculiar morphology, La Paúl rock glacier encourages a more prolonged study and to the application of more geomatic techniques for its detailed analysis.</p>

scholarly journals Late Quaternary Rock Glaciers, Mount Kenya, Kenya

1980 ◽  
Vol 25 (93) ◽  
pp. 492-497 ◽  
Author(s):  
W. C. Mahaney
Keyword(s):  
Late Quaternary ◽  
Short Interval ◽  
Morphological Characteristics ◽  
Ice Cores ◽  
Rock Glacier ◽  
Glacier Surface ◽  
Side Rock ◽  
Differential Movement ◽  
Probable Presence ◽  
Rock Glaciers

AbstractRock glaciers in Teleki Valley on Mount Kenya exist above 4 000 m below steep valley walls where they are supplied with debris from avalanche couloirs. These valley-side rock glaciers consist of three or four lobes of rubble bounded by transverse furrows resulting from differential movement. No ice cores were observed in these rubble sheets, but “drunken forest” stands of Senecio keniodendron indicate the probable presence of interstitial ice resulting either from the metamorphism of snow buried under rockfall and slide-rock debris, or from freezing of water beneath the rock mantle. A geological survey of Mount Kenya in 1976 revealed that rock glaciers are anomalous in the Mount Kenya Afroalpine zone above 3 300 m. Analysis of weathering rinds indicates that several rock-glacier lobes were built up over a short interval of time at or near the end of the last glacial maximum (Würm). Oversteepened fronts on the westernmost lobes may have resulted from re-activation coinciding with the advance of glaciers during late Holocene time (<1 000 B.P.). Soils mantle 20% of the rock-glacier surface and have morphological characteristics comparable with soils forming on moraines of late Würm age in upper Teleki, Hausberg, and Mackinder Valleys.

scholarly journals Toward a Novel Laser-Based Approach for Estimating Snow Interception

2020 ◽  
Vol 12 (7) ◽  
pp. 1146 ◽  
Author(s):  
Micah Russell ◽  
Jan U. H. Eitel ◽  
Andrew J. Maguire ◽  
Timothy E. Link
Keyword(s):  
Laser Scanning ◽  
Three Dimensional ◽  
Point Clouds ◽  
Primary Objective ◽  
Snow Accumulation ◽  
Future Research ◽  
Snow Density ◽  
Canopy Interception ◽  
Terrestrial Lidar ◽  
Large Trees

Forests reduce snow accumulation on the ground through canopy interception and subsequent evaporative losses. To understand snow interception and associated hydrological processes, studies have typically relied on resource-intensive point scale measurements derived from weighed trees or indirect measurements that compared snow accumulation between forested sites and nearby clearings. Weighed trees are limited to small or medium-sized trees, and indirect comparisons can be confounded by wind redistribution of snow, branch unloading, and clearing size. A potential alternative method could use terrestrial lidar (light detection and ranging) because three-dimensional lidar point clouds can be generated for any size tree and can be utilized to calculate volume of the intercepted snow. The primary objective of this study was to provide a feasibility assessment for estimating snow interception volume with terrestrial laser scanning (TLS), providing information on challenges and opportunities for future research. During the winters of 2017 and 2018, intercepted snow masses were continuously measured for two model trees suspended from load-cells. Simultaneously, autonomous terrestrial lidar scanning (ATLS) was used to develop volumetric estimates of intercepted snow. Multiplying ATLS volume estimates by snow density estimates (derived from empirical models based on air temperature) enabled the comparison of predicted vs. measured snow mass. Results indicate agreement between predicted and measured values (R2 ≥ 0.69, RMSE ≥ 0.91 kg, slope ≥ 0.97, intercept ≥ −1.39) when multiplying TLS snow interception volume with a constant snow density estimate. These results suggest that TLS might be a viable alternative to traditional approaches for mapping snow interception, potentially useful for estimating snow loads on large trees, collecting data in difficult to access terrain, and calibrating snow interception models to new forest types around the globe.

scholarly journals Detecting Short-Term Surface Melt on an Arctic Glacier Using UAV Surveys

2018 ◽  
Vol 10 (10) ◽  
pp. 1547 ◽  
Author(s):  
Eleanor Bash ◽  
Brian Moorman ◽  
Allison Gunther
Keyword(s):  
Mass Balance ◽  
Point Clouds ◽  
Glacier Mass Balance ◽  
Short Term ◽  
Glacier Surface ◽  
Surface Change ◽  
Glacier Ice ◽  
Arctic Glacier ◽  
Surface Changes

Current understanding of glacier mass balance changes under changing climate is limited by scarcity of in situ measurements in both time and space, as well as resolution of remote sensing products. Recent innovations in unmanned aerial vehicles (UAVs), as well as structure-from-motion photogrammetry (SfM), have led to increased use of digital imagery to derive topographic data in great detail in many fields, including glaciology. This study tested the capability of UAV surveys to detect surface changes over glacier ice during a three-day period in July 2016. Three UAV imaging missions were conducted during this time over 0.185 km 2 of the ablation area of Fountain Glacier, NU. These were processed with the SfM algorithms in Agisoft Photoscan Professional and overall accuracies of the resulting point clouds ranged from 0.030 to 0.043 m. The high accuracy of point clouds achieved here is primarily a result of a small ground sampling distance (0.018 m), and is also influenced by GPS precision. Glacier surface change was measured through differencing of point clouds and change was compared to ablation stake measurements. Surface change measured with the UAV-SfM method agreed with the coincident ablation stake measurements in most instances, with RMSE values of 0.033, 0.028, and 0.042 m for one-, two-, and three-day periods, respectively. Total specific melt over the study area measured with the UAV was 0.170 m water equivalent (w.e.), while interpolation of ablation measurements resulted in 0.144 m w.e. Using UAVs to measure small changes in glacier surfaces will allow for new investigations of distribution of mass balance measurements.

scholarly journals Late Quaternary Rock Glaciers, Mount Kenya, Kenya

1980 ◽  
Vol 25 (93) ◽  
pp. 492-497 ◽  
Author(s):  
W. C. Mahaney
Keyword(s):  
Late Quaternary ◽  
Short Interval ◽  
Morphological Characteristics ◽  
Ice Cores ◽  
Rock Glacier ◽  
Glacier Surface ◽  
Side Rock ◽  
Differential Movement ◽  
Probable Presence ◽  
Rock Glaciers

AbstractRock glaciers in Teleki Valley on Mount Kenya exist above 4 000 m below steep valley walls where they are supplied with debris from avalanche couloirs. These valley-side rock glaciers consist of three or four lobes of rubble bounded by transverse furrows resulting from differential movement. No ice cores were observed in these rubble sheets, but “drunken forest” stands ofSenecio keniodendronindicate the probable presence of interstitial ice resulting either from the metamorphism of snow buried under rockfall and slide-rock debris, or from freezing of water beneath the rock mantle. A geological survey of Mount Kenya in 1976 revealed that rock glaciers are anomalous in the Mount Kenya Afroalpine zone above 3 300 m. Analysis of weathering rinds indicates that several rock-glacier lobes were built up over a short interval of time at or near the end of the last glacial maximum (Würm). Oversteepened fronts on the westernmost lobes may have resulted from re-activation coinciding with the advance of glaciers during late Holocene time (&lt;1 000 B.P.). Soils mantle 20% of the rock-glacier surface and have morphological characteristics comparable with soils forming on moraines of late Würm age in upper Teleki, Hausberg, and Mackinder Valleys.

scholarly journals Geophysical analysis of transverse ridges and internal structure at Lone Peak Rock Glacier, Big Sky, Montana, USA

2014 ◽  
Vol 60 (221) ◽  
pp. 453-462 ◽  
Author(s):  
Caitlyn Florentine ◽  
Mark Skidmore ◽  
Marvin Speece ◽  
Curtis Link ◽  
Colin A. Shaw
Keyword(s):  
Genetic Relationships ◽  
The Body ◽  
Rock Glacier ◽  
Glacier Surface ◽  
Topographic Features ◽  
Digital Elevation ◽  
Rock Glaciers ◽  
Composition Structure ◽  
Elevation Model ◽  
Ground Penetrating

AbstractRock glaciers are periglacial alpine landforms that are found in many locations worldwide. Whereas well-developed models of deformation are established for traditional alpine glaciers, rock glacier deformation is poorly understood. Geophysical data from Lone Peak Rock Glacier (LPRG), southwest Montana, USA, are paired with lidar bare-earth 1 m digital elevation model (DEM) analysis to explore potential genetic relationships between internal composition, structure and regularly spaced arcuate transverse ridges expressed at the rock glacier surface. The internal composition of LPRG is heterogeneous, with frozen debris and clean ice overlain by an unconsolidated talus mantle. Upslope-dipping, clearly distinguished reflectors in the ground-penetrating radar (GPR) longitudinal survey at LPRG correspond to transverse ridges. The spacing and slope of individual features at the surface and in the subsurface were measured and compared and are found to be similar. The structures observed at LPRG and other rock glaciers are similar to structures detected in glaciotectonically altered sediment, ice-cored moraines and other rock glacier settings. This finding suggests that transverse ridges on rock glaciers may be used as geomorphic indicators of internal deformation. This study contributes to the body of research on the application of GPR to rock glaciers, and is the first to directly pair and analyze individual surface topographic features with internal structures.

scholarly journals Age constraints of rock glaciers in the Southern Alps/New Zealand – Exploring their palaeoclimatic potential

The Holocene ◽  
2018 ◽  
Vol 28 (5) ◽  
pp. 778-790 ◽  
Author(s):  
Stefan Winkler ◽  
Christophe Lambiel
Keyword(s):  
New Zealand ◽  
Southern Alps ◽  
Early Holocene ◽  
Age Dating ◽  
Schmidt Hammer ◽  
Rock Glacier ◽  
Glacier Surface ◽  
The Holocene ◽  
Exposure Age ◽  
Rock Glaciers

Two rock glaciers in the valley head of Irishman Stream in the central Ben Ohau Range, Southern Alps/New Zealand, have been investigated using the electronic Schmidt-hammer (SilverSchmidt). Longitudinal profiles on both features reveal a consistent trend of decreasing R(Rebound)-values and, hence, increasing weathering intensity and surface-exposure age on their numerous transverse surface ridges from rooting zone towards the front. Previously published numerical ages obtained by terrestrial cosmogenic nuclide dating (TCND) allowed the calculation of a local Schmidt-hammer exposure-age dating (SHD) age-calibration curve by serving as the required fixed points. Age estimates for the lowermost rock glacier surface ridges fall within the early Holocene between 12 and 10.5 ka and indicate a fast disappearance of the Late Glacial glacier formerly occupying the valley head, followed by the initiation of rock glacier formation around or shortly after the onset of the Holocene. Although it cannot be judged whether the rock glaciers investigated were active within the entire Holocene or only repeatedly during multiple episodes within, their location and intact morphology exclude any substantial glacial activity at Irishman Stream during the Holocene. This has considerable regional palaeoclimatic implications because it opens for the hypothesis that climatic conditions during early Holocene were possibly comparatively dry and favourable for rock glacier initiation, but less so for glaciers. It would also challenge the view that air temperature is the sole major climate driver of glacier variability in the Southern Alps. More work utilising the palaeoclimatic potential of rock glaciers in the Southern Alps is advised.

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