Chapter

Chapter 15. Ice Loss and Slope Stability in High-Mountain Regions

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Abstract

The present time is one significant stage in the adjustment of mountain slopes to climate change, and specifically atmospheric warming. This review examines the state of understanding of the responses of mid-latitude alpine landscapes to recent cryospheric change, and summarizes the variety and complexity of documented landscape responses involving glaciers, moraines, rock and debris slopes, and rock glaciers. These indicate how a common general forcing translates into varied site-specific slope responses according to material structures and properties, thermal and hydrological environments, process rates, and prior slope histories. Warming of permafrost in rock and debris slopes has demonstrably increased instability, manifest as rock glacier acceleration, rock falls, debris flows, and related phenomena. Changes in glacier geometry influence stress fields in rock and debris slopes, and some failures appear to be accelerating toward catastrophic failure. Several sites now require expensive monitoring and modeling to design effective risk-reduction strategies, especially where new lakes as multipliers of hazard potential form, and new activities and infrastructure are developed.

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... This latter process can be typical during the warmest periods of the year (Deline et al., 2012). Warming trends also intensify moraine erosion, resulting in an increase in rockfall and landslide events (Deline et al., 2015;Ravanel et al., 2018). Degradation/warming is another critical concern for permafrost (e.g. ...
... For the SAFRAN data estimated (2400 m a.s.l.) from 1952, we extrapolated the data for all elevation bands. We used a standard gradient of −0.53 • C (100 m) −1 increase in elevation based on the observations of Magnin et al. (2015) for the MBM. ...
... Heating from rock surfaces is predominantly the cause of permafrost degradation, which further affects mountain slope stability, leading to an increased rock mass wasting (Magnin et al., 2017). Cold surfaces demonstrate more ice cohesion with the underlying surfaces, while a rise in surface temperatures decreases basal cohesion, increasing the sliding process and leading to more ice flow (Deline et al., 2015). Thus, it is likely that underlying permafrost conditions aid the sustainability of IAs in the long term, and an increase in rock surface temperatures around IAs could result in IAs losing mass more rapidly. ...
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Ice aprons (IAs) are part of the critical components of the Alpine cryosphere. As a result of the changing climate over the past few decades, deglaciation has resulted in a surface decrease of IAs, which has not yet been documented, except for a few specific examples. In this study, we quantify the effects of climate change on IAs since the mid-20th century in the Mont Blanc massif (western European Alps). We then evaluate the role of meteorological parameters and the local topography in the behaviour of IAs. We precisely mapped the surface areas of 200 IAs using high-resolution aerial and satellite photographs from 1952, 2001, 2012 and 2019. From the latter inventory, the surface area of the present individual IAs ranges from 0.001 to 0.04 km2. IAs have lost their surface area over the past 70 years, with an alarming increase since the early 2000s. The total area, from 7.93 km2 in 1952, was reduced to 5.91 km2 in 2001 (−25.5 %) before collapsing to 4.21 km2 in 2019 (−47 % since 1952). We performed a regression analysis using temperature and precipitation proxies to better understand the effects of meteorological parameters on IA surface area variations. We found a strong correlation between both proxies and the relative area loss of IAs, indicating the significant influence of the changing climate on the evolution of IAs. We also evaluated the role of the local topographic factors in the IA area loss. At a regional scale, factors like direct solar radiation and elevation influence the behaviour of IAs, while others like curvature, slope and size of the IAs seem to be rather important on a local scale.
... As a consequence, predicting the future variations in sediment transport associated with climate change in glacierised basins is very challenging. Nonetheless, this knowledge would be highly beneficial for land use planning and civil protection purposes, i.e. to mitigate the effects on population and tourism of potentially increasing sediment-related hazards Deline et al., 2015;Beniston et al., 2018;Hock et al., 2019). Additionally, hydroelectric power plants (Schaefli et al., 2007;Huss et al., 2017) and river management strategies (Huss et al., 2017;Milner et al., 2017) will need to adapt to changes in sediment loads expected for the future decades. ...
... By analysing the sediment transport networks and their attributes, we aim to identify how functional connectivity in glacierised basins may be affected by: i) runoff origin (snow-vs glacier melt), ii) occurrence of high-intensity meteorological events (e.g., heatwaves and rainfall events), and iii) basin characteristics, such as lithology and morphology. Finally, we discuss the most likely consequences in terms of sediment transfer associated to the expected future glacier retreat (Huss et al., 2008;Micheletti and Lane, 2016), permafrost degradation (Gobiet et al., 2014;Stoffel et al., 2014;Deline et al., 2015) and higher frequency of extreme meteorological events (rainstorms and heatwaves, Pachauri et al., 2014;Pfleiderer et al., 2019). ...
... In comparison, the steep, nearly vertical cliffs of the Trafoi subcatchment do not allow the formation of these morphological units. Such landforms feature very large sediment availability, and they might become more instable and thus release sediment during glacier retreat and permafrost degradation (Deline et al., 2015;Porter et al., 2019). Several instability events associated to glacial and periglacial processes occurred in the last few years in the study area, with the most prominent being the rock glacier front collapse described in Kofler et al. (2021) and an ice-debris flow in 2012 in the Trafoi subcatchment, which determined a temporary blocking of the main river (Mair et al., 2015). ...
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In the past decade, sediment connectivity has become a widely recognized characteristic of a geomorphic system. However, the quantification of functional connectivity (i.e. connectivity which arises due to the actual occurrence of sediment transport processes) and its variation over space and time is still a challenge. In this context, this study assesses the effects of expected future phenomena in the context of climate change (i.e. glacier retreat, permafrost degradation or meteorological extreme events) on sediment transport dynamics in a glacierised Alpine basin. The study area is the Sulden river basin (drainage area 130 km²) in the Italian Alps, which is composed of two geomorphologically diverse sub-basins. Based on graph theory, we evaluated the spatio-temporal variations in functional connectivity in these two sub-basins. The graph-object, obtained by manually mapping sediment transport processes between landforms, was adapted to 6 different hydro-meteorological scenarios, which derive from combining base, heatwave and rainstorm conditions with snowmelt and glacier-melt periods. For each scenario and each sub-basin, the sediment transport network and related catchment characteristics were analysed. To compare the effects of the scenarios on functional connectivity, we introduced a connectivity degree, calculated based on the area of the landforms involved in sediment cascades. Results indicate that the area of the basin connected to its outlet in terms of sediment transport might feature a six-fold increase in case of rainstorm conditions compared to “average” meteorological conditions assumed for the base scenario. Furthermore, markedly different effects of climate change on sediment connectivity are expected between the two sub-catchments due to their contrasting morphological and lithological characteristics, in terms of relative importance of rainfall-triggered colluvial processes vs temperature-driven proglacial fluvial dynamics.
... Glacial environments and corresponding proglacial areas are among the most rapidly changing areas on earth, as they are strongly affected by climate change. After ice release, the exposed areas, especially the steep and, to a high degree, unvegetated lateral moraines, are reworked by different geomorphological processes, such as fluvial and nival erosion, debris flows, slope failures and landslides, which can be associated with high erosion rates [3][4][5][6]. Generally, this phase is described as the paraglacial slope adjustment process, which can last several decades to centuries [7][8][9]. ...
... Photos were used to process the entire catchment of the upper Kaunertal, 2 Data set were processed into one orthophoto,3 the Province of Tyrol (Office of the Provincial Government of Tyrol/Department of Geoinformation) provided the orthophoto as download (https://www.tirol.gv.at/sicherheit/geoinformation/geodaten/orthophotos/, accessed on 2 May 2022). ...
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Aerial photographs of the European Alps usually only reach back to the middle of the 20th century, which limits the time span of corresponding studies that quantitatively analyse long-term surface changes of proglacial areas using georeferenced orthophotos. To the end of the Little Ice Age, this leads to a gap of about 100 years. Using digital monoplotting and several historical terrestrial photographs, we show the quantification of surface changes of a Little Ice Age lateral moraine section until the late second half of the 19th century, reaching a total study period of 130 years (1890–2020). The (initial) gully system expands (almost) continuously over the entire study period from 1890 to 2020. Until 1953, the vegetation-covered areas also expanded (mainly scree communities, alpine grasslands and dwarf shrub communities), before decreasing again, especially between 1990 and 2003, due to large-scale erosion within the gully system. Furthermore, our results show that the land-cover development was impacted by temperature and precipitation changes. With the 130-year study period, we contribute to a substantial improvement in the understanding of the processes in the proglacial by analysing the early phase and thus the immediate response of the lateral moraine to the ice exposure.
... Thus the monitoring of this phenomenon should be established as a precautionary measure in places where human populations and infrastructure are located downstream from potentially dangerous sites. In steep terrains, thawing of mountain permafrost can also influence the frequency and magnitude of gravitational natural hazards with consequences for local communities and infrastructure (Arenson and Jakob, 2015;Deline et al., 2015). To date, only few studies have focused on the issue of volcanic activity and ice-volcano interactions Rivera and Bown, 2013). ...
... As discussed above, the recent publication of up-to-date inventories of glaciers and rock glaciers has improved substantially the knowledge about their current state and distribution in the Andes. An increasing number of studies has focused on quantifying the amount of ice present in rock glaciers (Monnier and Kinnard, 2013;Janke et al., 2017;Jones et al., 2018), and on the possible impacts of climate change on rock glacier dynamics (Deline et al., 2015;Iribarren et al., 2015). Increasingly, both regionally (Rangecroft et al., 2015;Schaffer et al., 2019), and globally (Jones et al., 2018(Jones et al., , 2019, the importance of rock glaciers as water reserves is being recognized in semi-arid areas (Rangecroft et al., 2013;Jones et al., 2019). ...
Chapter
This chapter addresses the distribution and characteristics of the Patagonian glaciers together with their recent changes and hydrological implications. Recently published national glacier inventories for the Andes between ca. 37 °S and 55 °S indicate that this region contains 24,000 ice masses covering ca. 26,100 km2. This includes the Southern Patagonia Icefield (SPI), the largest ice mass of the Southern Hemisphere outside Antarctica. The region also includes several thousand smaller ice masses, such as mountain glaciers, valley glaciers, rock glaciers, and perennial snowfields, which collectively are crucial water resources to sustain nature contributions to people, socioeconomic activities, and hydropower generation. Recent findings in mass balance and ice dynamics along the Patagonian Andes highlight the processes behind the mass change and differential response of glaciers to climate change. Although most glaciers have experienced considerable thinning and recession in recent decades, they have not responded in the same manner to climate change. Ice-dynamic processes, such as calving, drive mass change of larger Patagonian glaciers. However, ice melt increases, and snowfall depletion have been attributed as the main cause for the shrinkage of the smaller ice masses. It is expected that glacier retreat will continue impacting runoff and glacier-related hazards. Modeling studies suggest strongest impacts due to this recent ice mass loss can be expected, particularly during the dry season. In concordance with the increase in the number and size of proglacial lakes, there has been an increase in the magnitude and frequency of glacial lake outburst floods in the Patagonian Andes.
... Where should landslide researchers look for changes in slope stability induced by a warming climate? The most straightforward answer, which has been recognized since at least 1990 (e.g., Slaymaker 1990;Haeberli and Beniston 1998;Geertsema et al. 2006;Gruber and Haeberli 2007;Coe and Godt 2012;Huggel et al. 2012;Deline et al. 2015a;Gariano and Guzzetti 2016), is steep-cryospheric terrain in mountainous regions of the world because ice (either in permafrost or glaciers) in these areas is being degraded and reduced by warming temperatures (e.g., Paul et al. 2004;Harris et al. 2009;Huss and Hock 2015;Pastick et al. 2015;Kos et al. 2016;Zemp et al. 2019;Hock et al. 2020). An added benefit to these areas is that landslides are unlikely to be influenced by land use changes brought on by climate change. ...
... About 10% of the worldwide populace lives in mountainous regions that are susceptible to hazards resulting from a degrading cryosphere (Hock et al. 2020). The loss of ice in these regions impacts rock slopes in a variety of ways (e.g., Evans and Clague 1994;McColl 2012) including causing a reduction in cohesion and an increase in pore-water pressure in fractures in rocks (e.g., Gruber and Haeberli 2007) and debutressing (e.g., Deline et al. 2015a) and/or thermomechanically damaging (Grämiger et al. 2018) rock slopes when it occurs in the form of receding glaciers. Rock-slope failures in mountainous regions can trigger cascading hazard events, particularly when they enter lakes or fiords, where outburst floods, debris flows, and tsunamis can be generated (e.g., Evans and Delaney 2015;Haeberli et al. 2017;Higmann et al. 2018). ...
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Permafrost and glaciers are being degraded by the warming effects of climate change. The impact that this degradation has on slope stability in mountainous terrain is the subject of ongoing research efforts. The relatively new availability of high-resolution (≤ 10 m) imagery with worldwide coverage and short (≤ 30 days) repeat acquisition times, as well as the emerging field of environmental seismology, presents opportunities for making remote, systematic observations of landslides in cryospheric mountainous terrain. I reviewed the literature and evaluated landslide activity in existing imagery to select five ~ 5000-km2 sites where long-term, systematic observations could take place. The five proposed sites are the northern and eastern flanks of the Northern Patagonia Ice Field, the Western European Alps, the eastern Karakoram Range in the Himalayan Mountains, the Southern Alps of New Zealand, and the Fairweather Range in Southeast Alaska. Systematic observations of landslide occurrence, triggers, size, and travel distance at these sites, especially if coupled with observations from in situ instrumental monitoring, could lead to a better understanding of changes in slope stability induced by climate change. The suggested sites are not meant to be absolute and unalterable. Rather, they are intended as a starting point and discussion starter for new work in this expanding landslide research frontier.
... Because rock avalanches are common in cryosphericmountainous terrain (e.g., Deline et al., 2015a) that is susceptible to degradation by warming from climate change (e.g., Beniston, 2003;Paul et al., 2004;Gruber and Haeberli, 2007;Fischer et al., 2012;Huss and Hock, 2015;Hock et al., 2019;Patton et al., 2019), studies of ice-degradation processes and their impact on slope stability (e.g., Fischer et al., 2006;Gruber and Haeberli, 2007;Krautblatter et al., 2013), as well as climateinduced changes in rock avalanche recurrence intervals and sizes, are active landslide research frontiers. For mountainous terrain, process research is generally of two types: studies on the degradation of mountain permafrost and the resulting impact on cohesion and pore pressure in rock slopes (e.g., Gruber and Haeberli, 2007), and studies investigating how the reduction and complete removal of glacial ice will impact steep rock slopes that were previously supported by ice (e.g., Grämiger et al., 2018). ...
... The opposite effect would also be true, that is, future earthquakes could be more impactful because intense shaking could have a greater effect on slopes that are increasingly susceptible to failure as a result of glacial retreat or permafrost degradation; a phenomenon that has been demonstrated for the combination of earthquake shaking and increased precipitation in soil landslides (Bontemps et al., 2020). Overall, the relative number of rock avalanches is likely to increase in the future as a result of warming temperatures in mountain cryosphere environments (e.g., Huggel et al., 2010;McColl, 2012;Deline et al., 2015a;Coe et al., 2018). The distinct, overlapping temporal clusters of rock avalanche activity in the St. Elias (2013 and GBNPP (2012-2016) study areas encompassed a 3-year period (2014-2016) of record-breaking warmth in Alaska (e.g., NOAA, 2017;Walsh et al., 2017), and demonstrate that this phenomenon has already begun to occur. ...
Article
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Glacial retreat and mountain-permafrost degradation resulting from rising global temperatures have the potential to impact the frequency and magnitude of landslides in glaciated environments. Several recent events, including the 2015 Taan Fiord rock avalanche, which triggered a tsunami with one of the highest wave runups ever recorded, have called attention to the hazards posed by landslides in regions like southern Alaska. In the Saint Elias Mountains, the presence of weak sedimentary and metamorphic rocks and active uplift resulting from the collision of the Yakutat and North American tectonic plates create landslide-prone conditions. To differentiate between the typical frequency of landsliding resulting from the geologic and tectonic setting of this region, and landslide processes that may be accelerated due to changes in climate, we used Landsat imagery to create an inventory of rock avalanches in a 3700 km2 area of the Saint Elias Mountains. During the period from 1984 to 2019, we identified 220 rock avalanches with a mean recurrence interval of 60 days. We compared our landslide inventory with a catalog of M ≥ 4 earthquakes to identify potential coseismic events, but only found three possible earthquake-triggered rock avalanches. We observed a distinct temporal cluster of 41 rock avalanches from 2013 through 2016 that correlated with above average air temperatures (including the three warmest years on record in Alaska, 2014–2016); this cluster was similar to a temporal cluster of recent rock avalanches in nearby Glacier Bay National Park and Preserve. The majority of rock avalanches initiated from bedrock ridges in probable permafrost zones, suggesting that ice loss due to permafrost degradation, as opposed to glacial thinning, could be a dominant factor contributing to rock-slope failures in the high elevation areas of the Saint Elias Mountains. Although earthquake-triggered landslides have episodically occurred in southern Alaska, evidence from our study suggests that area-normalized rates of non-coseismic rock avalanches were greater during the period from 1964 to 2019, and that the frequency of these events will continue to increase as the climate continues to warm. These findings highlight the need for hazard assessments in Alaska that address changes in landslide patterns related to climate change.
... Thus the monitoring of this phenomenon should be established as a precautionary measure in places where human populations and infrastructure are located downstream from potentially dangerous sites. In steep terrains, thawing of mountain permafrost can also influence the frequency and magnitude of gravitational natural hazards with consequences for local communities and infrastructure (Arenson and Jakob, 2015;Deline et al., 2015). To date, only few studies have focused on the issue of volcanic activity and ice-volcano interactions Rivera and Bown, 2013). ...
... As discussed above, the recent publication of up-to-date inventories of glaciers and rock glaciers has improved substantially the knowledge about their current state and distribution in the Andes. An increasing number of studies has focused on quantifying the amount of ice present in rock glaciers (Monnier and Kinnard, 2013;Janke et al., 2017;Jones et al., 2018), and on the possible impacts of climate change on rock glacier dynamics (Deline et al., 2015;Iribarren et al., 2015). Increasingly, both regionally (Rangecroft et al., 2015;Schaffer et al., 2019), and globally (Jones et al., 2018(Jones et al., , 2019, the importance of rock glaciers as water reserves is being recognized in semi-arid areas (Rangecroft et al., 2013;Jones et al., 2019). ...
Article
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The Andes Cordillera contains the most diverse cryosphere on Earth, including extensive areas covered by seasonal snow, numerous tropical and extratropical glaciers, and many mountain permafrost landforms. Here, we review some recent advances in the study of the main components of the cryosphere in the Andes, and discuss the changes observed in the seasonal snow and permanent ice masses of this region over the past decades. The open access and increasing availability of remote sensing products has produced a substantial improvement in our understanding of the current state and recent changes of the Andean cryosphere, allowing an unprecedented detail in their identification and monitoring at local and regional scales. Analyses of snow cover maps has allowed the identification of seasonal patterns and long term trends in snow accumulation for most of the Andes, with some sectors in central Chile and central-western Argentina showing a clear decline in snowfall and snow persistence since 2010. This recent shortage of mountain snow has caused an extended, severe drought that is unprecedented in the hydrological and climatological records from this region. Together with data from global glacier inventories, detailed inventories at local/regional scales are now also freely available, providing important new information for glaciological, hydrological, and climatological assessments in different sectors of the Andes. Numerous studies largely based on field measurements and/or remote sensing techniques have documented the recent glacier shrinkage throughout the Andes. This observed ice mass loss has put Andean glaciers among the highest contributors to sea level rise per unit area. Other recent studies have focused on rock glaciers, showing that in extensive semi-arid sectors of the Andes these mountain permafrost features contain large reserves of freshwater and may play a crucial role as future climate becomes warmer and drier in this region. Many relevant issues remain to be investigated, however, including an improved estimation of ice volumes at local scales, and detailed assessments of the hydrological significance of the different components of the cryosphere in Andean river basins. The impacts of future climate changes on the Andean cryosphere also need to be studied in more detail, considering the contrasting climatic scenarios projected for each region. The sustained work of various monitoring programs in the different Andean countries is promising and will provide much needed field observations to validate and improve the analyses made from remote sensors and modeling techniques. In this sense, the development of a well-coordinated network of high-elevation hydro-meteorological stations appears as a much needed priority to complement and improve the many glaciological and hydro-climatological assessments that are being conducted across the Andes.
... The rapid retreat of glaciers provides water and space for the expansion of glacial lakes. It exposes lateral moraines and mountain slopes initially covered by glaciers, which may reduce their stability [55,56]. Since these lateral moraine slopes are located above the glacial lake, a GLOF hazard may be induced in the event of instability. ...
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On 25 June 2020, a glacial lake outburst flood (GLOF) occurred in Jinwuco, Nidou Zangbo, and southeast Tibet, causing catastrophic damage to multiple infrastructures such as roads, bridges, and farmlands in the surrounding and downstream areas. Due to the lack of long-term monitoring of glacial lake and glacier changes in the region and the surrounding surface, the spatial and temporal evolutionary characteristics and triggering factors of the disaster still need to be determined. Here, we combine multi-temporal optical remote sensing image interpretation, surface deformation monitoring with synthetic aperture radar (SAR)/InSAR, meteorological observation data, and corresponding soil moisture change information to systematically analyze the spatial and temporal evolution characteristics and triggering factors of this GLOF disaster. Optical images taken between 1987 and 2020 indicate that the glacial lake’s initial area of 0.39 km2 quickly grew to 0.56 km2, then plummeted to 0.26 km2 after the catastrophe. Meanwhile, we found obvious signs of slippage beside the lateral moraine at the junction of the glacier’s terminus and the glacial lake. The pixel offset tracking (POT) results based on SAR images acquired before and after the disaster reveal that the western lateral moraine underwent a 40 m line of sight (LOS) deformation. The small baseline subset InSAR (SBAS-InSAR) results from 2017 to 2021 show that the cumulative deformation of the slope around the lateral moraine increased in the rainy season before the disaster, with a maximum cumulative deformation of −52 mm in 120 days and gradually stabilized after the disaster. However, there are three long-term deformation areas on the slope above it, showing an increasing trend after the disaster, with cumulative deformation exceeding −30 mm during the monitoring period. The lateral moraine collapse occurred in a warm climate with continuous and intense precipitation, and the low backscatter intensity prior to the slide suggests that the soil was very moist. Intense rainfall is thought to be the catalyst for lateral moraine collapse, whereas the lateral moraine falling into the glacier lake is the direct cause of the GLOF. This study shows that the joint active–passive remote sensing technique can accurately obtain the spatial and temporal evolution characteristics and triggering factors of GLOF. It is helpful to understand the GLOF event caused by the slide of lateral moraine more comprehensively, which is essential for further work related to glacial lake hazard assessment.
... As these landscapes are in an unstable condition, they exhibit high geomorphic activity due to paraglacial processes (e.g., [6][7][8][9]). Concurrently, warming permafrost (e.g., [10,11]) can contribute to the destabilization of rock faces [12][13][14][15]. This may affect landscape development by increasing the input of debris to the glacier from remobilized lateral moraine deposits (e.g., [16]) or gravitational processes originating from the steep walls of the glacier catchment, such as snow avalanches (e.g., [17]), rockfalls, or rock avalanches (e.g., [18][19][20]). ...
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Deglaciation in high mountain areas signifies the transition from glacial to periglacial conditioned landscapes. Due to the reduced melt rate of debris-covered glacier ice, these areas of the glacier may persist long after the surrounding glacier has melted, resulting in the formation of distinct post-glacial landforms. In this study, we examine the geomorphological evolution and potential future development of a 19,267 m3 ± 204 m3 rockfall from the permafrost-affected headwall on the low elevated Zwieselbachferner in the Horlachtal, Stubai Alps, Austria. The analysis uses multi-epochal remote sensing data, including photogrammetrically and airborne laser scanning-derived digital elevation models, orthophotos, and satellite data, covering a period from the initial rockfall in 2003/2004 to 2022. The data reveals that the rockfall event resulted in the formation of a supraglacial debris layer of varying thickness, spanning an area of 15,920 m2. Subsequently, 13 further rockfalls ranging from 67 m3 ± 6 m3 to 4250 m3 ± 121 m3 were detected. The mean ice thickness of the debris-covered area only slightly decreased between 2006 and 2022, in contrast to the surrounding glacier, whose thickness and length have strongly decreased. This results in the formation of a steep front and flanks that become increasingly covered by debris redistribution. The study suggests that the glacier ice covered by rockfall-derived debris will remain as a periglacial landform of glacial origin after the complete melting of the surrounding glacier.
... Perennial subsurface ice content acts as a significant fresh-water resource although the time-scales of melting and corresponding runoff contributions are still unclear (Hilbich et al., 2022;Jones et al., 2018;Villarroel et al., 2021). Rock and debris-slope instability results in increased rock-fall and debris-flow frequency and intensity, as well as landslide activity (Chiarle et al., 2021;Deline et al., 2015;Frauenfelder et al., 2018;Haeberli et al., 2017;Patton et al., 2019). These permafrost-related natural hazards threaten infrastructure, habitants, tourists, and alpine sport activities in high 40 alpine regions (Duvillard et al., 2019;Keuschnig et al., 2017;Mourey et al., 2021). ...
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Ongoing global warming intensifies the degradation of mountainous permafrost. Permafrost thawing impacts landform evolution, reduces fresh water resources, enhances the potential of natural hazards, and thus has significant socio-economic impact. Electrical resistivity tomography (ERT) has been widely used to map the ice-containing permafrost by its resistivity contrast compared to the surrounding non-frozen medium. This study aims to reveal the effects of ongoing climate warming on alpine permafrost by repeating historical ERT and analysing the temporal changes in the resistivity distribution. In order to facilitate the measurements, we introduce and discuss the employment of textile electrodes. These newly developed electrodes significantly reduce working effort, are easy to deploy on blocky surfaces, and yield sufficiently low contact resistances. We analyse permafrost evolution on three periglacial landforms (two rock glaciers and one talus slope) in the Swiss and Austrian Alps by repeating historical surveys after periods of 10, 12, and 16 years, respectively. The resistivity values have been significantly reduced in ice-poor permafrost landforms at all study sites. Interestingly, resistivity values related to ice-rich permafrost in the studied active rock glacier partly increased during the studied time period. To explain this apparently counterintuitive (in view of increased resistivity) observation, geomorphological circumstances such as the relief and increased creeping velocity of the active rock glacier, are discussed by using additional remote sensing data. The present study highlights ice-poor permafrost degradation in the Alps resulting from ever-accelerating global warming.
... Rapid acceleration and longitudinal extension develop surface disturbances (e.g., cracks, crevasses and scarps) as signs of the so-called landform destabilization (Delaloye et al., 2013;Marcer et al., 2019;Vivero and Lambiel, 2019;Marcer et al., 2020;RGIK, 2022). In this context, the main factors of rock glacier acceleration and destabilization have been attributed to permafrost degradation due to increased atmospheric warming (Roer et al., 2005;Roer et al., 2008;Deline et al., 2015;Bodin et al., 2017), and by related feedback mechanisms such as increasing water content Wirz et al., 2016;Buchli et al., 2018;Cicoira et al., 2019). Likewise, mechanical overload caused by rockfall deposits (Delaloye et al., 2013;Scotti et al., 2017) or artificial overload by mining waste deposits (Valenzuela, 2004) have also been identified as triggers of rock glacier destabilization. ...
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Accurately assessing landform evolution and quantifying rapid environmental changes are gaining importance in the context of monitoring techniques in alpine environments. In the European Alps, glaciers and rock glaciers are among the most characteristic cryospheric components bearing long and systematic monitoring periods. The acceleration in rock glacier velocities and the onset of destabilization processes, mainly since 1990, have raised several concerns due to the potential effects on the high alpine natural and anthropic environments. This study presents a combination of uncrewed aerial vehicle (UAV) and terrestrial laser scanning (TLS) surveys for monitoring the current changes on the quickly accelerating, destabilised Tsarmine rock glacier in the Arolla Valley, Western Swiss Alps, delivering a considerable volume of debris to a steep torrential gully. High-resolution digital elevation models (DEMs) and orthomosaics are derived from UAV image series combined with structure from motion (SfM) photogrammetry techniques. Multitemporal orthomosaics are employed for measuring spatially continuous rock glacier kinematics using image matching algorithms. Superficial displacements are evaluated with simultaneous in-situ differential global navigation satellite system (GNSS) measurements. Elevation and volume changes are computed from TLS and UAV-derived DEMs at similar periods. Between June 2017 and September 2019, both datasets showed a similar elevation change pattern and surface thinning rates of 0.15 ± 0.04 and 0.16 ± 0.03 m yr −1 , respectively. Downward of a rupture zone developing about 150 m above the front, the rock glacier doubled its overall velocity during the study period, from around 5 m yr −1 between October 2016 and June 2017 to more than 10 m yr −1 between June and September 2019. The kinematic information reveals striking differences in the velocity between the lower and upper rock glacier sections. The monitoring approach based on close-sensing techniques provides accurate surface velocity and volume change information, allowing an enhanced description of the current rock glacier dynamics and its surface expression.
... ;Deline et al., 2015;Huss and Hock, 2015;Pastick et al., 2015;Kos et al., 2016;Saemundsson et al., 2021Saemundsson et al., , 2018Zemp et al., 2019;Magnin et al., 2019;Morino et al., 2019Morino et al., , 2021 These changes, if maintained or worsen, can have significant implications for the prevention, mitigation and adaptation strategies, sustainable development and geoheritage conservation. ...
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Landslides are important components of global geoheritage, but awareness of their significance and value in such terms seems scanty in the scientific community. Landslides are normally identified among various features of geological and geomorphological interest, and often considered a source of hazard. However, they are seldom identified as geosites and as part of geoheritage. This paper aims at filling these gaps by highlighting the importance of landslides in the global geoheritage. After a short introduction on the values and criteria to define landforms as geosites, based on literature review, we show to what extent landslides have been defined as geomorphosites and as part of geoheritage around the world. We then outline three aspects that should be specifically considered in the identification of landslides as geomorphosites, namely 1) past and present climate changes, 2) anthropic signature, and 3) risk perception. Finally, we describe four cases of spectacular landslides that serve as significant examples worldwide.
... Historic and current social, economic, and environmental changes have influenced local and regional interpretations of risk and hazards and shaped responses in complex ways. For example, loss of landscape identity leads to the loss of the sense of place, local customs, identity, and religion (Deline et al., 2014;Drenkhan et al., 2019;Huggel et al., 2015;Jurt, Brugger, et al., 2015). ...
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Alpine glaciers worldwide will lose most of their volume by the end of the 21st century, placing alpine ecosystems and human populations at risk. The new lands that emerge from retreating glaciers provide a host of challenges for ecological and human adaptation to climate change. In these novel proglacial landscapes, ecological succession and natural hazards interplay with local agriculture, hydroelectric production, mining activities, and tourism. Research has emphasized the importance of understanding adaptation around socio‐environmental systems, but regional and global management efforts that support local initiatives and connect novel proglacial landscapes to ecological, social, and cultural conservation opportunities are rare and nascent. The characteristics of these emerging lands reflect the nexus of alpine ecosystems with socio‐political histories. Often overlooked in glacial‐influenced systems are the interdependencies, feedbacks, and tradeoffs between these biophysical systems and local populations. There is no coordinated strategy to manage and anticipate these shifting dynamics, while affirming local practices and contexts. There is an opportunity to initiate a new conversation and co‐create a governance structure around these novel landscapes and develop a new framework suitable to the Anthropocene era. This article first synthesizes the rapid socio‐environmental changes that are occurring in proglacial landscapes. Second, we consider the need for integrating “bottom‐up” with “top‐down” approaches for the sustainable management of proglacial landscapes. Finally, we propose establishing a transdisciplinary initiative with policy‐related goals to further dialogues around the governance and sustainable management of proglacial landscapes. We call for increased cooperation between actors, sectors, and regions, favoring multiscale and integrated approaches. This article is categorized under: Climate, Ecology, and Conservation > Conservation Strategies
... This is due to the fact that permafrost-related landforms with high ice content are often very sensitive to variations of climatic conditions. During recent years a significant acceleration of creep processes has been detected for some sites in the European Alps characterized by alpine permafrost (Delaloye et al., 2008;Deline et al., 2015;Bodin et al., 2018;Vivero and Lambiel, 2019). Apart from rock glaciers, thrust moraine complexes resulting from glacier-permafrost interactions and ice-cored moraines often contain high amounts of (buried) ice enabling significant morphological activity. ...
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This study presents results on the internal structure and recent dynamics of a thrust moraine complex in the Zay Valley (Italian Alps) by means of geophysical surveying and remote sensing time series. Results from electrical resistivity tomography, refraction seismic tomography, ground-penetrating radar as well as a four-phase modeling approach provided detailed information on the internal moraine structure and confirmed the presence of partly ice-rich permafrost within the moraine complex as well as buried massive ice of sedimentary origin within the proximal moraine flank. The use of Synthetic Aperture Radar interferometry (InSAR) enabled the derivation of detailed surface displacement patterns showing subsidence rates of up to 5 cm within a 30-day period (August/September 2020) over the central part of the moraine complex. Further, preliminary InSAR results indicated an eastward displacement back towards the glacier forefield. The comparison of the results from geophysical measurements and InSAR time series suggested a strong relationship between the subsurface conditions and the surface displacement, as highest displacement rates were found over locations with highest ice content. The consistency of the results enables an area wide estimation of subsurface conditions and highlights the benefits from combining geophysical and remote sensing methods.
... High mountain permafrost plays an important role in triggering rockfalls and other mass movements and has become an emerging field of research over the past decades. [1][2][3] Rock wall permafrost distribution is mainly determined by elevation (air temperature [AT]) and incoming short-wave solar radiation. These permafrost areas are exceptionally sensitive to climate change because of the direct contact with the atmosphere, relatively low ice content, and multisided heat propagation into sharp and complex topographies. ...
Article
Permafrost is a relevant component of the Pyrenean high mountains, triggering a wide range of geomorphological cryogenic processes. Although in the past decades there has been an increase in frozen ground studies in the Pyrenees, there are no specific studies about rock wall permafrost, its presence, distribution, thermal regime, or historical evolution. This work combines measured rock surface temperatures (RSTs, from August 2013 to April 2016) along an elevation profile (four sites) on the north facing the rock wall of the Vignemale peak (3,298 m a.s.l., 42°46′16″N/0°08′33″W) and temperature modeling (CryoGRID2) to determine the presence of permafrost and to analyze its evolution since the mid-20th century. Simulations are run with various RST forcings and bedrock properties to account for forcing data uncertainty and varying degrees of rock fracturing. Results reveal that warm permafrost may have existed down to 2,600 m a.s.l. until the early 1980s and that warm permafrost is currently found at ~2,800 m a.s.l. and up to 3,000 m a.s.l. Cold (<−2°C) permafrost may exist above 3,100–3,200 m a.s.l. Systematic investigations on rock wall permafrost must be conducted to refine those results in the Pyrenees. The elevation shift in warm permafrost suggests an imminent disappearance of permafrost in the Vignemale peak.
... They are often dammed by unstable or unconsolidated material and can therefore pose a hazard to downstream human activities, infrastructure and lives (Clague & Evans, 2000;Costa & Schuster, 1988;Richardson & Reynolds, 2000;Walder & Costa, 1996). Glacial lake hazards are likely to increase in most glaciated regions worldwide due to the growing number of such lakes, the progression of glacier retreat towards steeper terrain, and due to (increasing) destabilization of rock walls, rock glaciers, and glaciers (Deline et al., 2015;Haeberli et al., 2017). ...
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Retreating glaciers give way to new landscapes with lakes as an important element. In this study, we combined available data on lake outlines with historical orthoimagery and glacier outlines for six time periods since the end of the Little Ice Age (LIA; ~1850). We generated a glacial lake inventory for modern times (2016) and traced the evolution of glacial lakes that formed in the deglaciated area since the LIA. In this deglaciated area, a total of 1192 lakes formed over the period of almost 170 years, 987 of them still in existence in 2016. Their total water surface in 2016 was 6.22 ±0.25 km2. The largest lakes are >0.4 km2 (40 ha) in size, while the majority (>90%) are smaller than 0.01 km2. Annual increase rates in area and number peaked in 1946‐1973, decreased towards the end of the 20th century, and reached a new high in the latest period 2006‐2016. For a period of 43 years (1973‐2016), we compared modelled overdeepenings from previous studies to actual lake genesis. For a better prioritisation of formation probability, we included glacier‐morphological criteria such as glacier width and visible crevassing. About 40% of the modelled overdeepened area actually got covered by lakes. The inclusion of morphological aspects clearly aided in defining a lake formation probability to be linked to each modelled overdeepening. Additional morphological variables, namely dam material and type, surface runoff, and freeboard, were compiled for a subset of larger and ice‐contact lakes in 2016, constituting a basis for future hazard assessment.
... Hubbard et al., 2005)and their relation to deglaciation history are still missing for the Cordillera Blanca. This is despite the fact that observations from other glaciated mountains suggest that their activity or frequencies of occurrence will most likely increase in the near future (Deline et al., 2015;Kos et al., 2016). This article takes advantages of rarely available but abundant historical data providing pre-and postfailure information about the 2002 Safuna Lake rock avalanche (Hubbard et al., 2005), including slope topography and geology, glacier tongue retreat and downwasting history as well as the 70 years history of slope failures and recent (2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017) surface movement records. ...
Article
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Landslides or landslide-induced impact waves in high mountain lakes represent a highhazard for society, calling for realistic assessments of rock slope stability responsible forthe process chain initiation. This task is often hampered by complex interplays of triggers, which effects on slope stability may be delayed by decades or even millennia, while historical records describing slope topography or landslide occurrences are usually shorter and incomplete. This article builds on rarely available detailed historical data describing the site of the 2002 rock avalanche in the Cordillera Blanca, Peru. It caused a dangerous impact wave in the Safuna Alta Lake resulting in a minor flood, but ongoing downstream development significantly increased the risk of a comparable event. Pre-2002 and post-2002 failure slope topography, 70 years long history of glaciation and landslide occurrences were combined with non-invasive field geological surveys and laboratory geotechnical analyses to characterize the distinct morphological parts of the failed slope with reliable engineering geological slope models. Slope stability was calculated for a series of environmental scenarios providing insights into the 2002 rock avalanche failure mechanism and dynamics as well as the role of glacier slope support for its stability. Results show that the rock slope stability is governed by discontinuous slip planes where rock bridges represent the most likely additional resisting forces. The effect of glacier support on the slope stability is limited under full-water saturation of the rocks and due to specific morpho-structural conditions. Importance of the long-term, progressive deterioration of the rock slope strength under paraglacial environment and repeated seismic shaking is illustrated by the fact that even the Little Ice Age maximum glacier extend only had minor positive effect on the pre-2002 rock avalanche slope stability. Despite of that, the slope remained without a major failure for decades or possibly even centuries. Its collapse in 2002 caused retrogressive movements of the adjacent slope, which remains highly unstable until now. Therefore the future safety of the lake would largely benefit from the implementation of a reliable slope movement monitoring system.
... Hubbard et al., 2005) and their relation to deglaciation history are still missing for the Cordillera Blanca. This is despite the fact that observations from other glaciated mountains suggest that their activity or frequencies of occurrence will most likely increase in the near future (Deline et al., 2015;Kos et al., 2016). This article takes advantages of rarely available but abundant historical data providing pre-and postfailure information about the 2002 Safuna Lake rock avalanche (Hubbard et al., 2005), including slope topography and geology, glacier tongue retreat and downwasting history as well as the 70 years history of slope failures and recent (2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017) surface movement records. ...
Article
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Landslides or landslide-induced impact waves in high mountain lakes represent a high hazard for society, calling for realistic assessments of rock slope stability responsible for the process chain initiation. This task is often hampered by complex interplays of triggers, which effects on slope stability may be delayed by decades or even millennia, while historical records describing slope topography or landslide occurrences are usually shorter and incomplete. This article builds on rarely available detailed historical data describing the site of the 2002 rock avalanche in the Cordillera Blanca, Peru. It caused a dangerous impact wave in the Safuna Alta Lake resulting in a minor flood, but ongoing downstream development significantly increased the risk of a comparable event. Pre-2002 and post-2002 failure slope topography, 70 years long history of glaciation and landslide occurrences were combined with non-invasive field geological surveys and laboratory geotechnical analyses to characterize the distinct morphological parts of the failed slope with reliable engineering geological slope models. Slope stability was calculated for a series of environmental scenarios providing insights into the 2002 rock avalanche failure mechanism and dynamics as well as the role of glacier slope support for its stability. Results show that the rock slope stability is governed by discontinuous slip planes where rock bridges represent the most likely additional resisting forces. The effect of glacier support on the slope stability is limited under full-water saturation of the rocks and due to specific morpho-structural conditions. Importance of the long-term, progressive deterioration of the rock slope strength under paraglacial environment and repeated seismic shaking is illustrated by the fact that even the Little Ice Age maximum glacier extend only had minor positive effect on the pre-2002 rock avalanche slope stability. Despite of that, the slope remained without a major failure for decades or possibly even centuries. Its collapse in 2002 caused retrogressive movements of the adjacent slope, which remains highly unstable until now. Therefore the future safety of the lake would largely benefit from the implementation of a reliable slope movement monitoring system.
... For the ice in the ocean and land, the melting of ice can produce liquid water and remove the support system for the upper ice or soil layer (Joughin et al., 2014;Kääb et al., 2018;Kokelj and Jorgenson, 2013;Qin et al., 2018). These processes can lead to the destabilization of cryospheric environments, including ice shelf (Feldmann and Levermann, 2015;Hogg and Gudmundsson, 2017;Ingels et al., 2021;Martin et al., 2019;Robel and Banwell, 2019) and glacier collapse (Deline et al., 2015;Falaschi et al., 2019;Paul, 2019;Tian et al., 2017), rock and ice avalanche (Chiarle et al., 2007;Dufresne et al., 2019;Dunning et al., 2015;Schaub et al., 2016), glacier and snow melting flood (Brown et al., 2014;Duan et al., 2020;Janský et al., 2010;Sikorska et al., 2015), glacial lake outburst (Bajracharya and Mool, 2009;Ding and Liu, 1992;Harrison et al., 2018;Schwanghart et al., 2016;Shangguan et al., 2017;Veh et al., 2019), and thermokarst development (Farquharson et al., 2019;Mu et al., 2020b;Nelson et al., 2002;Saito et al., 2018;Turetsky et al., 2020). These phenomena are closely associated with the processes of the cryosphere, and thus are called cryospheric hazards. ...
Article
The cryosphere is an important component of the global climate system. Cryospheric components are sensitive to climate warming, and changes in the cryosphere can lead to serious hazards to human society, while the comprehensive understanding of cryospheric hazards largely remains unknown. Here we summarized the hazards related to atmospheric, oceanic and land cryosphere. The different types of cryospheric hazards, including their phenomena, mechanisms and impacts were reviewed. Our results suggested that: 1) The recorded hazards from atmospheric cryosphere including frost, hail, freezing rain decreased or showed great spatial heterogeneities, while their future changes are difficult to predict, and the extreme cold events in winter may increase in the future; 2) Sea ice extent declines rapidly, and iceberg numbers will increase. The permafrost-dominated coastline erosion will be exacerbated by climate warming. Meanwhile, the sea level rise is expected to continue in the next decades; 3) The glacier collapse, glacial lake outbursts and paraglacial readjustments will increase in the future. Although the total area of snow cover will decrease, the heavy snow events, snow avalanches, and snowmelt floods will not decrease simultaneously. The permafrost-related rock and debris flow and thaw slump will also increase with permafrost degradation. Taken together, we concluded the cryosphere is shrinking, while cryospheric hazards will likely in a warming climate.
... Implications of this are widespread glacier recession and subsequent hydrological and morphological changes that also affect sediment fluxes (Huss et al., 2008;Micheletti & Lane, 2016). Additionally, sediment fluxes change in response to permafrost degradation (Deline et al., 2015;Gobiet et al., 2014;Stoffel et al., 2014), or a higher frequency of intense rainfall events and heat periods (Micheletti & Lane, 2016;Pachauri et al., 2014;Pfleiderer et al., 2019). The identification of sediment source, transport and depositional areas (and of the relative sediment pathways) is highly beneficial for the authorities responsible for water and sediment management in mountain areas (Skolaut et al., 2015). ...
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An area-wide digital geomorphological map consisting of 12,180 non-overlapping polygons was created for the Sulden river basin (South Tyrol, Italian Alps) with the purpose to carry out a GIS-based sediment connectivity analysis. Thirty-one landform types were defined with respect to their role within sediment cascades. As such, the classification and the related symbology partly differ from a traditional geomorphological map where several areal objects are frequently represented by scaled and rotated point symbols. The catchment (∼130 km²), exhibits a high geomorphological variability as well as relatively large glacierized areas. We used the geomorphological map for a first qualitative estimate of the main differences between the two major sub-basins concerning the components of the sediment cascades: while the Trafoi sub-catchment exhibits a high number of small landslides and debris flow channels (i.e. source and transport landforms), the Sulden sub-catchment is rather characterized by large proglacial and talus landforms (i.e. temporary storage landforms).
... In high mountains, rockfalls are an important consequence of paraglacial rock slope adjustment (Ballantyne 2002). A progressive rock strength degradation can result from: i) stress change in slopes and rock weathering following glacier recession (McColl and Davies 2012;Deline et al. 2015;Purdie et al. 2015;Vehling et al. 2016); ii) rock damage due to glacier fluctuations (Grämiger et al. 2018); iii) frost weathering (Thapa et al. 2017) and thermo-mechanical stresses due to temperature fluctuations, inducing crack opening or widening (Draebing and Krautblatter 2019); iv) permafrost degradation (Fischer et al. 2012;Krautblatter et al. 2013); v) diurnal and seasonal freeze/thaw cycles (Matsuoka et al. 1998;Regmi and Watanabe 2009;Nagai et al. 2013;Jia et al. 2015) and, more in general, cycles of thermal expansion/contraction (Collins and Stock 2016). Several studies have pointed out the crucial role of snow cover in controlling ground temperature and, consequently, thermal processes taking place in rock slopes (Haberkorn et al. 2015;Magnin et al. 2015;Draebing et al. 2017). ...
Article
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Rockfalls are one of the most common instability processes in high mountains. They represent a relevant issue, both for the risks they represent for (infra) structures and frequentation, and for their potential role as terrestrial indicators of climate change. This study aims to contribute to the growing topic of the relationship between climate change and slope instability at the basin scale. The selected study area is the Bessanese glacial basin (Western Italian Alps) which, since 2016, has been specifically equipped, monitored and investigated for this purpose. In order to provide a broader context for the interpretation of the recent rockfall events and associated climate conditions, a cross-temporal and integrated approach has been adopted. For this purpose, geomorphological investigations (last 100 years), local climate (last 30 years) and near-surface rock/air temperatures analyses, have been carried out. First research outcomes show that rockfalls occurred in two different geomorphological positions: on rock slopes in permafrost condition, facing from NW to NE and/or along the glacier margins, on rock slopes uncovered by the ice in the last decades. Seasonal thaw of the active layer and/or glacier debutressing can be deemed responsible for slope failure preparation. With regard to timing, almost all dated rock falls occurred in summer. For the July events, initiation may have been caused by a combination of rapid snow melt and enhanced seasonal thaw of the active layer due to anomalous high temperatures, and rainfall. August events are, instead, associated with a significant positive temperature anomaly on the quarterly scale, and they can be ascribed to the rapid and/or in depth thaw of the permafrost active layer. According to our findings, we can expect that in the Bessanese glacierized basin, as in similar high mountain areas, climate change will cause an increase of slope instability in the future. To fasten knowledge deepening, we highlight the need for a growth of a network of high elevation experimental sites at the basin scale, and the definition of shared methodological and measurement standards, that would allow a more rapid and effective comparison of data.
... As such, they form an important key to understanding sediment dynamics and sediment transfers in larger alpine catchments (Sass, 2006). Recent research has demonstrated that climate-change-induced changes in the cryosphere will cause more rock and slope instabilities and alter sediment transfers in high alpine environments (Gruber, 2004;Keiler et al., 2010;Deline et al., 2014;Dietrich and Krautblatter, 2017;Beniston et al., 2018;IPCC, 2019;Schlögel et al., 2020). The activity (velocity, frequency or magnitude) of processes such as rock glacier creep, rockfall and debris flows may be altered due to permafrost degradation, leading to local hazards in downslope areas. ...
Article
Talus slopes are common places for debris storage in high‐mountain environments and form an important step in the alpine sediment cascade. To understand slope instabilities and sediment transfers, detailed investigations of talus slope geomorphology are needed. Therefore, this study presents a detailed analysis of a talus slope on Col du Sanetsch (Swiss Alps), which is investigated at multiple time scales using high‐resolution topographic surveys (HRT) and historical aerial photographs. HRT surveys were collected during three consecutive summers (2017‐2019), using Uncrewed Aerial Vehicle (UAV) and terrestrial laser scanning (TLS) measurements. To date, very few studies exist that use HRT methods on talus slopes, especially to the extent of our study area (2 km²). Data acquisition of ground control and in‐situ field observations are challenging on a talus slope due to the steep terrain (30°‐37°) and high surface roughness. This results in poor spatial distribution of ground control points (GCPs), causing unwanted deformation of up to 2 m in the gathered UAV‐derived HRT. The co‐alignment of UAV imagery from different survey dates improved this deformation significantly, as validated by the TLS data. Sediment transfer is dominated by small‐scale but widespread snow push processes. Pre‐existing debris flow channels are prone to erosion and redeposition of material within the channel. A debris flow event of high‐magnitude occurred in the summer of 2019, as a result of several convective thunderstorms. While low‐magnitude debris flow events (< 5000 m³) are frequent throughout the historical record with a return period of 10‐20 years, this 2019 event exceeded all historical debris flow events both in extent and volume since 1946. Future climate predictions show an increase of such intense precipitation events in the region, potentially altering the frequency of debris flows in the study area and changing the dominant geomorphic process which are active on such talus slopes.
... Thinning of glaciers and a warming atmosphere can lead to permafrost melting and slope instability at higher altitudes (Deline et al., 2015). Glacier changes in the Karakoram Mountains have been attributed to the dynamics of the Indian monsoon and the westerlies (Qureshi et al., 2017). ...
Article
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Supra-glacial debris cover is key to glacier ablation through increasing (thin debris layer) or decreasing (thick debris layer) melt rates, thereby regulating the mass balance of a glacier and its meltwater runoff. The thickening or lateral expansion of supra-glacial debris cover correlates with a reduction of glacier ablation and, consequently, runoff generation, which is also considered to be an influential factor on the rheology and dynamics of a glacierized system. Studies on supra-glacial debris cover have recently attracted wide attention especially for glaciers in the Himalayas and Karakoram, where the glaciers have heterogeneously responded to climate change. In this study, we used 32 images from the Landsat Thematic Mapper, Enhanced Thematic Mapper Plus, and Operational Land Imager archive, going back to 1990, which are available on the Google Earth Engine cloud-computing platform, to map the supra-glacial debris cover in the Hunza Valley, Karakoram, Pakistan, based on a band ratio segmentation method (normalized difference snow index [NDSI] < 0.4), Otsu thresholding, and machine learning algorithms. Compared with manual digitization, the random forest (RF) model was found to have the greatest accuracy in identifying supra-glacial debris, with a Kappa coefficient of 0.94 ± 0.01 and an overall accuracy of 95.5 ± 0.9%. Overall, the supra-glacial debris cover in the study area showed an increasing trend, and the total area expanded by 8.1–21.3% for various glaciers from 1990 to 2019. The other two methods (Otsu thresholding and NDSI < 0.4) generally overestimated the supra-glacial debris covered area, by 36.3 and 18.8%, respectively, compared to that of the RF model. The supra-glacial debris cover has migrated upward on the glaciers, with intensive variation near the equilibrium-line altitude zone (4,500–5,500 m a.s.l.). The increase in ice or snow avalanche activity at high altitudes may be responsible for this upward expansion of supra-glacial debris cover in the Hunza Valley, which is attributed to the combined effect of temperature decrease and precipitation increase in the study area.
... ice break-offs, glacier outbursts, snow/ice avalanches) can threaten population, urban areas and infrastructures [3]. In densely populated areas, such as the European Alps, the interaction between glaciers and anthropic activities is very frequent and it is of crucial importance to study the glaciers to understand their evolution and response to climate change, which is expected to reduce their area coverage and increase their instability [4]. ...
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Glacial processes can have a strong impact on human activities in terms of hazards and freshwater supply. Therefore, scientific observation is fundamental to understand their current state and possible evolution. To achieve this aim, various monitoring systems have been developed in the last decades to monitor different geophysical and geochemical properties. In this manuscript, we describe examples of close-range monitoring sensors to measure the glacier dynamics: (i) terrestrial interferometric radar, (ii) monoscopic time-lapse camera, (iii) total station, (iv) laser scanner, (v) ground-penetrating radar and (vi) structure form motion. We present the monitoring applications in the Planpincieux and Grandes Jorasses glaciers, which are located in the touristic area of the Italian side of the Mont Blanc massif. In recent years, the Planpincieux-Grandes Jorasses complex has become an open-air research laboratory of glacial monitoring techniques. Many close-range surveys have been conducted in this environment and a permanent network of monitoring systems that measures glacier surface deformation is presently active.
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Mount Garibaldi Volcanic System (MGVS) is the southernmost member of Garibaldi Volcanic Belt (GVB), the northern (Canadian) segment of the Cascade Volcanic Arc. Temporally episodic explosive to effusive eruptions may be associated with peak ice unloading after glacial maxima. Rapid and widespread deglaciation of the overlying ice sheet, and glacial rebound, have altered the physical characteristics of the landscape whilst the system is thought to have been in long repose for over 10,000 years. Over the last 60 years, the region has become heavily populated due to increased tourism and all-season recreation opportunities. MGVS poses the greatest volcanic threat to the human population and built infrastructure between Vancouver and the resort municipality of Whistler. We believe that this system is a priority for further scientific research, given that its already “very high” overall threat score would likely increase if there was a better understanding of its eruptive history and hazards. Using published and field evidence, we show that potential hazards, related to the volcanic environment of this system, to the settlement of Squamish include voluminous lava flows, pyroclastic density currents triggered by lava dome collapse, tephra fallout, debris flows, and lahars. As relatively few exposures in the system have been dated using modern geochronological techniques, we take this opportunity to (re)calibrate published radiocarbon ages of relatively recent eruptions in GVB.
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We show a long-term erosion monitoring of several geomorphologically active gully systems on Little Ice Age lateral moraines in the central Eastern Alps covering a total time period from 1953 to 2019 including several survey periods in order to identify corresponding morphodynamic trends. For the implementation, DEM of Differences were calculated based on multitemporal high-resolution digital elevation models from historical aerial images (generated by structure-from-motion photogrammetry with multi-view-stereo) and light detection and ranging from airborne platforms. Two approaches were implemented to achieve the corresponding objectives. First, by calculating linear regression models using the accumulated sediment yield and the corresponding catchment area (on a log-log scale), the range of the variability of the spatial distribution of erosion values within the areas of interest is shown. Secondly, we use volume calculations to determine the total/mean sediment output (and erosion rates) of the entire areas of interest. Subsequently, a comparison is made between the areas of interest and the epochs of both approaches. Based on the slopes of the calculated regression lines, it could be shown that the highest range of the variability of sediment yield within all areas of interest is in the first epoch (mainly 1950s to 1970s), as in some areas of interest sediment yield per square metre increases clearly more (regression lines with slopes up to 1.5), which in the later epochs (1970s to mid-2000s and mid-2000s to 2017/2019) generally decreases in 10 out of 12 cases (regression lines with slopes around 1). However, even in the areas of interest with an increase in the variability of sediment yield over time, the earlier high variabilities are no longer reached. This means that the spatial pattern of erosion in the gully heads changes over time as it becomes more uniform. Furthermore, using sediment volume calculations and corresponding erosion rates, we show a generally decreasing trend in geomorphic activity (amount of sediment yield) between the different epochs in 10 out of 12 areas of interest, while 2 areas of interest show an opposite trend where morphodynamics increase and remain at the same level. Finally, we summarise the results of long-term changes in the morphodynamics of geomorphologically active areas on lateral moraines by presenting the "sediment activity concept", which, in contrast to theoretical models, is based on actually calculated erosion. The level of geomorphic activity depends strongly on the characteristics of the areas of interest, such as size, slope length and slope gradient, some of which are associated with deeply incised gullies. It is noticeable that especially areas with decades of dead ice influence in the lower slope area show high geomorphic activity. Furthermore, we show that system-internal factors as well as the general paraglacial adjustment process have a greater influence on long-term morphodynamics than changing external weather and climate conditions, which, however, had a slight impact mainly in the last, i.e. most recent epoch (mid-2000s to 2017/2019) and may have led to an increase in erosion at the areas of interest.
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Proglacial areas represent the counterpart of glacial retreat, where a new environmental equilibrium will be reached. During this long and complex stage, which represents the response to ongoing climate change, several abiotic and biotic processes occur in these freshly exposed fragile environments. Proglacial areas, considered as open-air laboratories, have been attracting the attention of scientists recent last decades, and the diversity of their features allows us to classify them based on different aspects (i.e., lithological and structural geodiversity, geomorphodiversity, hydrogeodiversity, pedodiversity) of geodiversity. In this paper, we review the diversity of features of proglacial areas using several examples mainly from the European Alps. The geosystem services (i.e., regulating, supporting, provisioning and cultural) provided by these areas to society are also discussed, revealing the value of these regions as part of geoheritage. As these fragile and vulnerable areas are highly relevant to society, it is important to monitor them, and to set up adequate management strategies, including geoconservation, but also sustainable promotion.
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The evaluation and analysis of the slopes stability that are in danger of collapse is one of the things that require studies based on scientific grounds to determine the type of collapse and how it occurs and the factors affecting it, The rock masses that make up the slopes often contain cracks or joints or rock cutouts, Thus different types of collapses are formed, plane and Wedge Failure or rotational Failure, The Importance of studying rock falls increases if their occurrence leads to human or material damages, plane Failure is one of those collapses that occur on slopes parallel to mountain roads, In this study, weak spots were observed on a sandstone slope parallel to the Abu Rashada mountain road in Gharyan Area, It also observed the occurrence of rock fall of the slope, some of which reached the road, In the initial study of the slope, it was found that there is a collapsing mass separated from the mass of the original slope. The main objective was to evaluate and study the stability of the parallel slope of the road and analyze its stability using the field and laboratory study and the use of the (RocPlane) program, The most important
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Climate change leads to deep modifications of high Alpine environments. Those modifications have significant consequences on mountaineering itineraries and make them technically more difficult and more dangerous. Although a growing number of studies have recently documented this issue, they only list the processes affecting the itineraries and do not document their characteristics. Therefore, the acquired data lack relevance to be spread and for prevention making among climbers. In the present study, on the basis of the processes identified in previous studies in the Mont Blanc massif, we developed a legend in order to map the processes related to climate change that affect the itineraries and modify their climbing parameters. Following the UNIL geomorphological legend and using the same color code, 21 symbols were defined to map 23 processes. In order to evaluate the applicability and interest of the legend proposed, we present a first application in the Valais Alps (Switzerland), based on 21 semi-structured interviews with local Alpine guides and hut keepers. The map then allowed to list the processes affecting each of the 36 itineraries studied. On average, an itinerary is affected by 9 different processes and 25% of the itineraries have greatly evolved, which means their ascent in summer cannot be recommended anymore because of climate change. More generally, this legend would provide a common methodological basis, destined to be completed within future studies and to be relevant beyond the European Alps. This basis would also ease the comparability and compilation of results from different future studies. © 2022 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.
Article
Huge voluminous debris supplies that are transported because of the extreme rainfall events and glacial lake outburst floods has resulted in the accumulation of excessive sediments, thereby depleting the capacities of desilting chambers in the downstream hydropower projects. Therefore, the present article is focused on understanding the textural facies, bulk mineralogical composition, and environmental magnetic properties of suspended sediments to highlight the transport characteristics within the Chorabari glacierized catchment. Sediment representatives were analyzed by the X-Ray diffraction (XRD) and routine mineral magnetic parameters for the ablation seasons (June–September) of 2009, 2011, and 2012. Results reveal that monthly and seasonal fluctuations in the runoff magnitude exhibit significant influence on the linked-conduit system resulting in the enlargement of transport pathways. Flemming’s (sand/silt/clay) trigon reflects the dominance of silty sand facies with little clay content implying that the influence of hydrometeorological conditions transport the glacial debris to the downstream areas. Proglacial meltwater stream transported more than 60% of the total weight percentages of hard mineral aggregates such as quartz and feldspar fractions indicating high intensity of physical disaggregation that occurs at the high-altitude environment. Environmental magnetic properties reflect unimodal source showing combined signatures of weak ferrimagnetic and high nonmagnetic minerals. Analysis of Pearson correlation coefficient (PCC) revealed heterogeneity in the production and transportation of silt- and sand-sized sediments for each ablation season. These findings conclude that considerable percentages of fine glacial debris gets entrained into the linked-conduits from where they get exported as suspended sediments along with glacier meltwater through the subglacial opening.
Article
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Over the last 2 decades, permafrost degradation has been observed to be a major driver of enhanced rock slope instability and associated hazards in high mountains. While the thermal regime of permafrost degradation in high mountains has been addressed in several modelling approaches, no mechanical models that thoroughly explain rock slope destabilisation controls in degrading permafrost have been developed. Meanwhile, recent laboratory studies have shown that degrading permafrost affects both, rock and ice mechanical strength parameters as well as the strength of rock–ice interfaces. This study presents a first general approach for a temperature-dependent numerical stability model that simulates the mechanical response of a warming and thawing permafrost rock slope. The proposed procedure is exemplified using a rockslide at the permafrost-affected Zugspitze summit crest. Laboratory tests on frozen and unfrozen rock joint and intact rock properties provide material parameters for discontinuum models developed with the Universal Distinct Element Code (UDEC). Geophysical and geotechnical field surveys reveal information on permafrost distribution and the fracture network. This model can demonstrate how warming decreases rock slope stability to a critical level and why thawing initiates failure. A generalised sensitivity analysis of the model with a simplified geometry and warming trajectory below 0 ∘C shows that progressive warming close to the melting point initiates instability above a critical slope angle of 50–62∘, depending on the orientation of the fracture network. The increase in displacements intensifies for warming steps closer to 0 ∘C. The simplified and generalised model can be applied to permafrost rock slopes (i) which warm above −4 ∘C, (ii) with ice-filled joints, (iii) with fractured limestone or probably most of the rock types relevant for permafrost rock slope failure, and (iv) with a wide range of slope angles (30–70∘) and orientations of the fracture network (consisting of three joint sets). Here, we present a benchmark model capable of assessing the future destabilisation of degrading permafrost rock slopes.
Book
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Geomorphometry is the science of quantitative land surface analysis also known under names Digital Terrain Modelling, Digital Terrain Analysis and/or relief analysis. It has deep roots in geomorphology and finally oriented towards supervised and unsupervised landform classification. This volume is a contribution to the 4th bi-annual global meeting of the International Society for Geomorphometry (ISG). Every two years worldwide top specialists on geocomputation of digital elevation data meet to discuss existing and emerging trends of DEM acquisition, processing and application. Themes in this volume revolve around three main threads. Data acquisition concentrates on different methods of high resolution of new elevation data acquisition: from local through regional to world-wide scale. Geoprocessing thread focuses on novel method of computation of big elevation data as well as improvement of existing ones. Finally application path presents among others how different data and methods gives a new prompt to the various aspects of monitoring natural processes and natural hazards geomodelling. However the interdisciplinary nature of geomorphometry makes it a key science for natural hazards: from land observations which can serve as ground truth to mathematical models. Therefore the key theme of the Conference and workshops Geomorphometry 2015 is Geomorphometry for natural hazards geomodelling. Changes in appearance of land surface are either incremental or more abrupt if caused by catastrophic processes such as floods, earthquakes, landslides, tornadoes, storms, etc. The possibility of prediction of resultant hazards is one of the most important challenges for many disciplines of environmental sciences, geomorphological modelling had focused on incremental processes with catastrophic processes or natural hazards receiving less attention. Development of new technologies of data acquisition and new software as well as monitoring of Earth surface both on global and local scales provides a growing amount of worldwide-extend high resolution DEMs which require a new kind of geomorphometric tools capable of handling, analyzing, and visualizing large quantities of data in real time.
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Rock glaciers are creeping bodies of ice and rock that account for an important part of the mountain cryosphere. In this study, we investigated long‐term changes of the Laurichard rock glacier (French Alps), to understand how this rock glacier is responding to climate change. Using feature‐tracking and photogrammetric measurements between 1952 and 2019, we quantified changes in thickness, flow velocities and from which we derived the ice/rock flux of the rock glacier at a decadal time scale. This is the first time that emergence velocity and surface mass balance changes have been reconstructed for a rock glacier. Our results reveal a very small surface mass balance ranging from −0.1 m a⁻¹ to +0.05 m a⁻¹, reflecting the role of debris in damping the melt rate of the underlying ice. Surprisingly, we found a more negative surface mass balance in the upper part than in the lower part of the rock glacier during the 1952–1971 cold period, likely due to a reduction in rock and snow mass accumulation. Our study shows that thickness changes are mainly driven by changes in surface mass balance except during the most recent period in the lower part of the rock glacier, which was also influenced by a compressive flow related to a protrusion that prevented the rock glacier from advancing. We conclude that the period 1994–2019 witnessed a marked acceleration in rock glacier flow, in agreement with the observations of other rock glaciers in the European Alps. This strong increase in surface speed is likely a consequence of changes in the basal conditions.
Article
Synthetic aperture radar interferometry (InSAR) measurements demonstrate that lobate, blocky depositional landforms, located in southern Norway at an altitude of ~530 m above sea level, with an estimated mean annual air temperature of ~1.6°C, currently exhibit deformation attributed to viscous creep. Five years of InSAR measurements for six lobes demonstrate average surface velocities of 1.2–22.0 mm/year with maximum rates of 17.5–55.6 mm/year. New Schmidt-hammer exposure-age dating (SHD) of two proximal lobes reveals mid-Holocene ages (7.6 ± 1.3 ka and 6.0 ± 1.2 ka), which contrast with the early-Holocene SHD and ¹⁰ Be ages obtained previously from distal lobes, and late-Holocene SHD ages presented here from two adjacent talus slopes (2.3 ± 1.0 ka and 2.4 ± 1.0 ka). Although passive transport of boulders on the surfaces of these small, slow-moving rock glaciers affected by compressive flow means that the exposure ages are close to minimum estimates of the time elapsed since lobe inception, disturbance of boulders on rock glaciers is a source of potentially serious underestimates of rock-glacier age. Rock-glacier development at Øyberget began shortly after local deglaciation around 10 ka before present and continued throughout the Holocene in response to microclimatic undercooling within the coarse blocky surface layer of the talus and rock-glacier lobes. We suggest this enhanced cooling lowers mean annual surface-layer temperature by at least ~3.6°C, which is needed at such a low altitude to sustain sporadic permafrost and avoid fast thawing as atmospheric temperatures rise. Our results point to circumstances where inferences about rock glaciers as indicators of regional climate should be interpreted with caution, and where they may be less useful in palaeoclimatic reconstruction than previously thought.
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Glacier-permafrost interactions are investigated to understand glacial-hydrological influence along a partly glacierised valley on the NE flank of the Snøhetta massif, Dovrefjell, southern Norway. Of particular interest is how processes are controlled by a hydrological connection between landforms. Field mapping identified an ice-marginal landsystem comprising a polythermal glacier, a proglacial lake, an ice-cored moraine complex and a river-lake with perennial frost mounds. A clear interaction between glacial and periglacial processes was observed in transitional landforms, most prominently in the ice-cored moraine which constitutes a permafrost environment that is directly reworked by glaciofluvial processes. The role of this interaction in controlling seasonal, partial drainage of the proglacial lake was assessed using remote sensing-based observations of lake surface size evolution and seasonal surface subsidence. Results suggest a two-fold threshold for lake drainage: Depending on the dynamics of glacial discharge and active layer depth, the ice-cored moraine may either act as a barrier or a pathway to meltwater exiting the glacier. This demonstrates the importance of meltwater dynamics in controlling landform evolution in a glacial-periglacial landscape. To further assess the importance of surface and subsurface hydrology in linking glacial and periglacial domains, water stable oxygen isotope ratios across the study area were studied to map the flow of meltwater from glacier to permafrost. Results include a model of the surface and subsurface hydrology in the catchment and promote a conceptual understanding of water as a thermal, hydraulic and mechanical agent of transient glacier-permafrost interaction operating at heterogeneous timescales.
Article
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Bedrock overdeepenings exposed by continued glacial retreat can store precipitation and melt-water, potentially leading to the formation of new proglacial lakes. These lakes may pose threats of glacial lake outburst floods (GLOFs) in high mountain areas, particularly if new lakes form in geomorphological setups prone to triggering events such as landslides or moraine collapses. We present the first complete inventory for future glacial lakes in High Mountain Asia by computing the subglacial bedrock for ∼100 000 glaciers and estimating overdeepening area, volume and impact hazard for the larger potential lakes. We detect 25 285 overdeepenings larger than 10^4 m^2 with a volume of 99.1 ± 28.6 km^3 covering an area of 2683 ± 773.8 km^2. For the 2700 overdeepenings larger than 10^5 m^2, we assess the lake predisposition for mass-movement impacts that could trigger a GLOF by estimating the hazard of material detaching from surrounding slopes. Our findings indicate a shift in lake area, volume and GLOF hazard from the southwestern Himalayan region toward the Karakoram. The results of this study can be used for anticipating emerging threats and potentials connected to glacial lakes and as a basis for further studies at suspected GLOF hazard hotspots.
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Glaciers and Polar regions provide important clues to understanding the past and present status of the Earth system, as well as to predict future forms of our planet. In particular, Antarctica, composed of an ice-covered continent in its center and the surrounding Sothern Ocean, has been gradually investigated during the last half century by all kinds of scientific branches; bioscience, physical sciences, geoscience, oceanography, environmental studies, together with technological components. This book covers topics on the recent development of all kinds of scientific research on glaciers and Antarctica, in the context of currently on-going processes in the extreme environment in polar regions. https://www.intechopen.com/books/glaciers-and-the-polar-environment
Article
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In recent decades, slope instability in high‐mountain regions has often been linked to increase in temperature and the associated permafrost degradation and/or the increase in frequency/intensity of rainstorm events. In this context we analyzed the spatiotemporal evolution and potential controlling mechanisms of small to medium‐sized mass movements in a high‐elevation catchment of the Italian Alps (Sulden/Solda basin). We found that slope‐failure events (mostly in the form of rockfalls) have increased since the 2000s, whereas the occurrence of debris flows has increased only since 2010. The current climate‐warming trend registered in the study area apparently increases the elevation of rockfall‐detachment areas by approximately 300 m, mostly controlled by the combined effects of frost‐cracking and permafrost thawing. In contrast, the occurrence of debris flows does not exhibit such an altitudinal shift, as it is primarily driven by extreme precipitation events exceeding the 75th percentile of the intensity‐duration rainfall distribution. Potential debris‐flow events in this environment may additionally be influenced by the accumulation of unconsolidated debris over time, which is then released during extreme rainfall events. Overall, there is evidence that the upper Sulden/Solda Basin (above ca. 2500 m asl), and especially the areas in the proximity of glaciers, have experienced a significant decrease in slope stability since the 2000s, and that an increase in rockfalls and debris flows during spring and summer can be inferred. Our study thus confirms that “forward‐looking” hazard mapping should be undertaken in these increasingly frequented, high‐elevation areas of the Alps, as environmental change has elevated the overall hazard level in these regions.
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Rockfalls are a major aspect concerning morphodynamics in high mountain areas and represent a serious hazard for people and infrastructure. Recently, an increase of rockfall activity has been observed which is probably related to the destabilization of rock slopes through climate-related changes of the mountain cryosphere. This study investigates the rockfall distribution during a 4-year monitoring period by systematic observation with bi-temporal Airborne Laser Scanning DTMs in an area of 610.7 km² in the Ötztal Alps/Tyrol, Austria. The analyses of the 93 detected rockfall events indicate that rockfall activity is highest in proglacial areas. Further 83.9% of all rockfall source areas were mapped in bedrock where the modelled mean annual ground temperature (MAGT) indicates perennial frozen conditions. The results demonstrate the importance of thermal effects on the destabilization of rock faces and show that the triggering of rockfalls is closely related to changes in the glacier and permafrost regime. 18 low-magnitude rockfalls with volumes between 69 ± 3 m³ and 8420 ± 89 m³ are examined in detail. On the base of the analysis of these events energy line angles of 28.7° for the Fahrböschung and 19.9° for the minimum shadow angle can be derived and significantly longer runout distances on glaciated rockfall paths are observed.
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Permafrost as a climate-sensitive parameter and its occurrence and distribution play an important role in the observation of global warming. However, field-based per-mafrost distribution data and information on the subsur-face ice content in the large area of the southern mountainous Tibetan Plateau (TP) are very sparse. Existing models based on boreholes and remote sensing approaches suggest permafrost probabilities for most of the Tibetan mountain ranges. Field data to validate permafrost models are generally lacking because access to the mountain regions in extreme altitudes is limited. The study provides geomorphological and geophysical field data from a north-orientated high-altitude catchment in the western Nyainqêntanglha Range. A multi-method approach combines (A) geomorphological mapping, (B) electrical resistivity tomography (ERT) to identify sub-surface ice occurrence and (C) interferometric synthetic aperture radar (InSAR) analysis to derive multi-annual creeping rates. The combination of the resulting data allows an assessment of the lower occurrence of permafrost in a range of 5350 and 5500 m above sea level (a.s.l.) in the Qugaqie basin. Periglacial landforms such as rock glaciers and pro-talus ramparts are located in the periglacial zone from 5300-5600 m a.s.l. The altitudinal periglacial landform distribution is supported by ERT data detecting ice-rich permafrost in a rock glacier at 5500 m a.s.l. and ice lenses around the rock glacier (5450 m a.s.l.). The highest multiannual creeping rates up to 150 mm yr −1 are typically observed on these rock glaciers. This study closes the gap of unknown state of periglacial features and potential permafrost occurrence in a high-elevated basin in the western Nyainqêntanglha Range (Tibetan Plateau).
Article
This paper investigates the elevation‐warming relationships across the Carpathian Mountains, using the 0.1° × 0.1° gridded daily air temperature dataset developed within the CARPATCLIM project, in order to understand the spatial patterns of annual and seasonal temperature trends and test the hypothesis of enhanced warming with elevation. Temperature trend and elevation‐warming analyses were conducted over the 50 years of the dataset (1961–2010). The vertical variations of five key isotherms relevant for the development of cold‐climate weathering, presence of permafrost (−2°C, 0°C, +2°C, +3°C) and spread of forest vegetation (July +10°C) were also examined. The Carpathian Mountains are under visible annual and seasonal warming (stronger in the summer and winter), both daytime and nighttime. The warming process shows a great spatial inhomogeneity, but is more pronounced in the lowlands of the region, generally below 1,000–1,200 m. The correlations between elevation and warming rates across the Carpathians have been found both to be positive and negative, while mostly significant at the 5% level. Evidence of enhanced warming with elevation was found to be related to the minimum temperature increase mostly across the NW and SW Carpathians, at both annual and seasonal scales (winter, summer and spring). Less prominent EDW signals have been identified in the NE, E and S Carpathians (summer), as well as in the NE Carpathians (spring). Parts of the detected temperature trends and EDW signals have been considered to be an effect of the changing atmospheric circulation (i.e. westerly intensification especially in the winter), although other mechanisms and processes could be involved (e.g. snow‐albedo feedbacks in the spring). These results could serve as a reference for further investigations of climate warming effects across the Carpathian Mountains region (e.g. ecological and geomorphic), especially in relation to the augmented summer heat stress (e.g. more frequent heatwaves) and milder winters (e.g. less freezing days). This study represents the first assessment of the elevation dependency of climate warming for the entire Carpathian Mountains region, using a fine‐resolution climatic dataset covering the period 1961–2010. Observed vertical patterns of temperature change in relation to the shifts of five key isotherms, relevant for the development of cold‐climate weathering process, presence of permafrost and spread of vegetation is discussed. Parts of the detected temperature trends and EDW signals have been considered an effect of the changing atmospheric circulation. Changes in seasonal mean of air temperature in the Carpathian Mountains over 1961–2010 (in °C⋅decade–1). Black dots denote statistical significant trends at 10% level (two‐tail); the grey lines show the boundaries of the Carpathian Mountains, while the black line is the 800 m.a.s.l. isoline.
Chapter
Volcanic landslides are controlled by a combination of magmatic, tectonic and surficial processes, the last of which is predominantly influenced by climate. In this chapter, we consider the influences of present and geologically recent climates on the occurrence of volcanic landslides. We begin by summarizing Quaternary climatic variability to illustrate the wide range of conditions and rates of change experienced by modern edifices. A focus on geologically recent volcanoes is prudent because both their morphologies and evidence of the climatic conditions affecting them are typically better preserved; pre-Quaternary climates similarly affected edifices that are now largely lost from the geomorphic record. We then review the climatic factors that condition and possibly trigger volcanic landslides, the challenges in dating landslides and climatic changes, and the difficulties in determining triggers of volcanic landslides. Finally, case studies of present and past climate influences on volcanic landslides collected from scientific literature–covering both subaerial and coastal settings–illustrate several key points: edifice collapses were numerous at the end of the last glaciation; current glacial retreat is conditioning volcanic slope failure in some specific settings; shallow landslides in volcanic environments appear to be increasing due to changes in weather extremes; and sea level fluctuation plays a role in volcanic island collapses. As knowledge on climate variability, volcanic, and surficial processes progresses, the understanding of how climate and its changes affect volcanic landslides will further improve.
Article
Fox Glacier/Te Moeka o Tuawe is a fast-responding maritime glacier that has undergone multiple advance and retreat phases during recent decades. Here we use a combination of repeat photography, Structure from Motion (SfM), and ice discharge measurement, to identify key morphological differences associated with these repeated phase changes, and assess how much of the current terminus is still dynamically active. Increasing surface-debris cover at the margins and topographic shading result in the asymmetry of the retreating terminus, with central portions receding faster than the margins. In 2019, the glacier is shorter than at any time in recorded history, and ice flux is insufficient to sustain the current glacier length, with a further ∼300 m of the glacier terminus region potentially vulnerable to retreat. However, due to the high climate sensitivity of this maritime glacier, even a slight shift towards increasing mass flux could see this trend reverse.
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Plain Language Summary Climate warming and the resulting retreat of glaciers may destabilize mountain slopes, triggering landslides. For those landslides that enter fjords, the induced tsunamis are a significant hazard to coastal communities. Despite this risk, most periglacial landslides have been detected only after the event. Using satellite data, we detect a large, slow‐moving landslide in Barry Arm, Alaska, and assess its hazard potential. The volume of the landslide is estimated to be 8 times larger than the 17 June 2017 Karrat Fjord landslide in Greenland, which generated a tsunami and killed four people. We found that the Barry Arm landslide moved rapidly between 2010 and 2017, while Barry Glacier quickly thinned and retreated from the landslide area. If the entire unstable slope would collapse, it could generate a tsunami with a runup up to 300 m in the vicinity of the landslide with hazardous waves reaching local communities in Prince William Sound, which is frequently visited by fishermen, tourists, and cruise ships. Our study highlights the need to systematically assess the emerging hazards of landslides and tsunamis influenced by climate change.
Article
Debris flows originating in the mountain cryosphere (DFMC) are one of the most globally important, widely distributed mass flows (and natural geohazards) in mountain areas with a high altitude and/or high latitude. This is particularly the case in high mountain areas that have been undergoing rapid glacier retreat, permafrost degradation, and other melt/thaw related processes. As a consequence, the actual hazards and potential risks of DFMC have drawn increasing attention in the context of global climate change (i.e. a rising temperature and higher occurrence of strong precipitation events). Unlike debris flows at low elevations, where their occurrence is closely related to precipitation (intensity and duration), the breach of a DFMC event depends on precipitation and/or air temperature, which in turn influence melt/thaw processes, rending the formation mechanism much more complicated. Although research has been widely carried out on DFMC in past decades, there is still a long way to go before we have reached a complete understanding of the formation mechanism and triggering conditions. This review summarizes recent progress in the study of DFMC, including typical DFMC events and their causes, the failure mechanisms of rock (or ice-rock joints), the characteristics of moraine deposits, initiation through hydraulic erosion (entrainment), the relationship between DFMC initiation and meteorological conditions, and the slope stability of the mountain cryosphere under a changing climate. Several issues that should be addressed in future research are also discussed.
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Large rock avalanches on glaciers are an annual occurrence in the mountains of western North America. Following an event, landslide investigators may strive to quickly arrive on site to assess the deposit. Satellite remote sensing imagery demonstrates that caution is warranted for on- site field assessments. We combine Landsat, Sentinel-1(radar), Sentinel-2 and Planet imagery to reconstruct the events of four recent double overlapping rock avalanche deposits in British Columbia. In our examples substantial precursory rock avalanches are closely followed (days - months) and buried by much larger landslides. We suggest that landslide investigators exercise caution when assessing fresh rock avalanches avalanche deposits in the field.
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In the Mont Blanc massif (European Western Alps), rockfalls are one of the main natural hazards for alpinists and infrastructure. Rockfall activity after the Little Ice Age is well documented. An increase in frequency during the last three decades was related to permafrost degradation caused by rising air temperatures. In order to understand whether climate exerts a long‐term control on rockfall occurrence, a selection of paleo‐rockfall scars was dated in the Glacier du Géant basin (> 3200 m a.s.l.) using terrestrial cosmogenic nuclides. Rockfall occurrence was compared to different climatic and glacial proxies. This study presents 55 new samples (including replicates) and 25 previously‐published ages from nine sampling sites. In total, 62 dated rockfall events display ages ranging from 0.03 ± 0.02 ka to 88.40 ± 7.60 ka. Holocene ages and their uncertainties were used to perform a Kernel density function into a continuous dataset displaying rockfall probability per 100 years. Results highlight four Holocene periods of enhanced rockfall occurrence: (i) c . 7‐5.7 ka, related to the Holocene Warm Periods; (ii) c . 4.5‐4 ka, related to the Sub‐boreal Warm Period; (iii) c . 2.3‐1.6 ka, related to the Roman Warm Period; and (iv) c . 0.9‐0.3 ka, related to the Medieval Warm Period and beginning of the Little Ice Age. Laser and photogrammetric 3D models of the rock walls were produced to reconstruct the detached volumes from the best‐preserved rockfall scars (≤ 0.91 ± 0.12 ka). A structural study was carried out at the scale of the Glacier du Géant basin using aerial photographs, and at the scale of four selected rock walls using the 3D models. Two main vertical and one horizontal fracture sets were identified. They correspond respectively to alpine shear zones and veins opened‐up during long‐term exhumation of the Mont‐Blanc massif. Our study confirms that climate primarily controls rockfall occurrence, and that structural settings, coincident at both the massif and the rock wall scales, control the rock‐wall shapes as well as the geometry and volume of the rockfall events.
Article
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Deglaciation of high mountain rockwalls alters slope stability as rockwalls become more sensitive to modifications in environmental factors (e.g. seasonal temperature variations). In the past decades, increasing efforts focused on studying deglaciated Alpine rockwalls. Yet, currently deglaciating rockfaces remain unstudied. Here, we quantify surface area variations of massive ice bodies lying on high mountain rockwalls (ice aprons) in the French sector of the Mont Blanc massif between the end of the Little Ice Age (LIA) and 2018. Surface area estimates are computed from terrestrial and aerial oblique photographs via photogrammetry. This technique allows using photographs taken without scientific intent, and to tap into diverse historical or recent photographic catalogs. We derive an ice apron surface area model from precipitation records and the positive degree-days. The studied ice aprons shrank from 1854 to the 1950s, before expanding until the end of the 1990s. The beginning of the 21st century shows a decrease in surface area, leading to the complete melt of one of the studied ice aprons in 2017. Observed variations correlate with modeled surface area, suggesting strong sensitivity of ice aprons to changes in climatic variables. By studying site-specific correlations, we explore the importance of local drivers over the balance of ice aprons.
Thesis
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The objective of the thesis is the development of methodologies for coupling data collected by different ground-based remote sensing sensors in order to obtain 3D representations of the actual surface deformation vectors. The developed methodologies can be applied to study natural phenomena to define an interpretative model of the investigated processes. The monitoring techniques studied in the PhD have been adopted in two main case studies to detect the displacement of two mountain glaciers: the Planpincieux Glacier (Italian Alps), Monte Perdido Glacier (Spanish Pyrenees). However, such techniques might be used in general to monitor gravitational slope phenomena. The sensors studied during the PhD are digital single-lens reflex (DSLR) camera and ground-based synthetic aperture radar (GB-SAR). The photographs acquired by the DSLR camera have been processed with image analysis techniques. In particular, the image cross-correlation (ICC) has been used to measure the surface deformations of Planpincieux Glacier. The ICC provides the two displacement components orthogonal to the line of sight (LOS). Furthermore, it has been developed an innovative technique to automatically apply ICC in monitoring surveys. The key of the method consists in the automatic selection of images acquired in conditions of diffuse illumination to minimise shadow-related errors. The adoption of the terrestrial radar interferometry (TRI) to GB-SAR data provides the surface displacement parallel to the LOS. Therefore, it is possible to detect the complementary component of the ICC measurements, hence obtaining the three displacement components by coupling the two instruments. The techniques developed in the methodological part of the PhD study have been applied in operative case studies.
Article
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Measured englacial temperatures at the Colle Gnifetti core-drilling site are presented and compared with model calculations concerning possible effects of 20th century warming. The firn/ice saddle at the 124 m deep saddle borehole is cold throughout with a mean annual surface temperature near –14°C and a basal temperature slightly below –12°C. Influence of refreezing meltwater is weak and limited to near-surface formation of ice layers (recrystallization-infiltration). Temperature gradients in the saddle borehole are positive and increase from 0.015° to 0.019°C m−1 between 30 m depth and bedrock, corresponding to a mean vertical heat flow of around 50mWm−2. The observed temperature profile is close to steady-state conditions. It can well be reproduced with time-dependent model calculations using mean annual air temperatures from the nearby weather station of Grand St. Bernard within the main chain of the Swiss Alps, but it significantly deviates from similar calculations based on Säntis data, reflecting developments of air temperatures on the northern slope of the Alps. 20th century warming of cold Alpine firn seems to be much less pronounced than in polar areas, where strong heat-flow anomalies are commonly observed.
Article
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Direct shear box tests have revealed that the stiffness and strength of an ice-filled joint are a function of both normal stress and temperature. Comparison of these data with the results of similar experiments conducted on unfrozen joints indicates that at low temperatures and normal stresses the strength of an ice-filled joint can be significantly higher than that of an unfrozen joint. However, in the absence of sufficient closure pressure, the strength of an ice-filled joint can be significantly less than that of an unfrozen joint. This implies that if the stability of a slope is maintained by ice-filled joints, its factor of safety will reduce with temperature rise. This hypothesis suggests that a jointed rock slope that is stable when there is no ice in the joints and is also stable when ice in the joints is at low temperatures will become unstable as the ice warms. Results from the model tests have confirmed this hypothesis. Copyright (C) 2001 John Wiley St Sons, Ltd.
Article
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Debris flows in the Swiss Alps constitute a widespread phenomenon with distinct geomorphological features. Starting zones can be found on steep slopes with poorly consolidated debris or within creeks and gullies. All altitudinal belts are involved but activity is especially significant within periglacial areas. Due to the prominent influence of glacier and ground ice, the formation of debris flows within the periglacial belt, and especially at its lower boundary, is highly susceptible to climate changes. Glacier shrinkage, disappearance of glacierets and perennial snow patches and probably also degradation of low-lying permafrost has occurred since the Little Ice Age. Uncovered and thawed debris masses on steep slopes have become exposed to erosive processes. Continued or even accelerated warming could further enlarge this zone and may amplify the activity of periglacial debris flows in the next decades or centuries. -from Authors
Article
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Flood and debris-flow hazards at Grubengletscher near Saas Balen in the Saas Valley, Valais, Swiss Alps, result from the formation and growth of several lakes at the glacier margin and within the surrounding permafrost. In order to prevent damage related to such hazards, systematic investigations were carried out and practical measures taken. The evolution of the polythermal glacier, the creeping permafrost within the large adjacent rock glacier and the development of the various periglacial lakes were monitored and documented for the last 25 years by photogrammetric analysis of annually flown high-resolution aerial photographs. Seismic refraction, d.c. resistivity and gravimetry soundings were performed together with hydrological tracer experiments to determine the structure and stability of a moraine dam at a proglacial lake. The results indicate a maximum moraine thickness of > 100 m; extremely high porosity and even ground caverns near the surface may have resulted from degradation of sub- and periglacial permafrost following 19th/20thcentury retreat of the partially cold glacier tongue. The safety and retention capacity of the proglacial lake were enhanced by deepening and reinforcing the outlet structure on top of the moraine complex. The water level of an ice-dammed lake was lowered and a thermokarst lake artficially drained.
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Glacier shrinkage in the Alps has been clearly manifest since the middle of the 19th century and could continue beyond the limits of holocene variability in the near future. Changes in Alpine permafrost are less well documented but are likely to take place at various time and depth scales. This development leads to a variety of slope stability problems in bedrock and non-consolidated sediments (moraines and scree slope). A brief overview, with references to recent literature, is given with regard to characteristic situations and interactions as illustrated by recent events observed in the Alps. The achievement of progress in recognizing and mitigating risks from such slope stability problems in high mountain areas requires improved process understanding from field observations and computer modelling, systematic investigation of natural archives reflecting former slope instability processes and adequate monitoring of potentially critical situations.
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Acqua e ghiaccio: una convivenza difficile. Con l'aumento delle temperature sulle Alpi, si moltiplica la formazione di nuovi specchi lacustri in ambiente glaciale. Il Lago Effimero sul Ghiacciaio del Belvedere (versante italiano del Monte Rosa) è un caso emblematico a livello europeo. In queste pagine tutti i dati sulla sua breve ma minacciosa esistenza. La parete nord-orientale del Monte Rosa è uno dei più grandiosi spettacoli dell'arco alpino, ma anche uno straordinario laboratorio geodinamico in cui è maturata l'emergenza del Lago Effimero nelle estati 2002 e 2003. Questo volume, voluto dall'Amministrazione Regionale del Piemonte, richiama le azioni messe in campo per mitigare il rischio di una rotta glaciale e prospetta scenari futuri alla luce del riscaldamento globale nelle Alpi.
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The acceleration of rock glacier surface velocities over the two last decades and the destabilization of several landforms show that permafrost creep conditions are changing in the Alps. This article summarizes and presents current understanding of creep behaviour of rock glaciers in the Swiss Alps and emphasises changes that have occurred over the last years and decades. The almost homogeneous interannual behaviour of rock glaciers despite different geometry and activity rates indicates a common dependence on external climatic factors (summer air temperature, seasonal snowcover development) which govern changes observed in rock glacier creep rate. The article highlights ongoing efforts to document interannual variations of rock glacier kinematics for the whole area of the Swiss Alps.
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Tasman Glacier is the largest glacier in the New Zealand Southern Alps. Despite a century of warming and down-wastage, the glacier remained at its Little Ice Age terminus until the late 20th century. Since then, a proglacial lake formed, and comparatively rapid calving retreat has been initiated. In this paper we use sequential satellite imagery to document terminus retreat, growth of supraglacial ponds, and expansion of the proglacial Tasman Lake. Between 2000 and 2008, the glacier terminus receded a maximum of c. 3.7 km on the western margin, and the ice-contact Tasman Lake expanded concomitantly. This northward expansion of Tasman Lake up-valley proceeded at a mean annual rate of 0.34 x 10(6) m(2) a(-1) 2000-2008, attaining a surface area of 5.96 x 10(6) m(2) in May 2008, with a maximum depth of c. 240 m. Terminus retreat rates (U(r)) vary in both space and time, with two distinct periods of calving retreat identified during the study period: 2000-2006 (mean U(r) = 54 m a(-1)) and 2007-2008 (mean U(r) = 144 m a-1). Terminus retreat can also be categorized into two distinct zones of activity: (1) the main ice cliff (MIC), and (2) the eastern embayment ice cliff (EEIC). During the period 2000-2006, and between 2006 and 2008 for the EEIC, the controlling process of ice loss at the terminus was iceberg calving resulting from thermal undercutting. In contrast, the retreat of the MIC between 2006 and 2008 was controlled by buoyancy-driven iceberg calving caused by decreasing overburden pressure as a result of supraglacial pond growth, increased water depth, and rainfall. The presence of a >130-m-long subaqueous ice ramp projecting from the terminal ice cliff into the lake suggests complex interactions between the glacier and ice-contact lake during the 8-10 km of possible future calving retreat.
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Climate effects relating to air temperature, radiation, snow cover, and rainfall combine with thaw and infiltration processes to cause changes in the thermal response and associated creep deformations in rock glaciers, which are the geomorphological expression of Alpine permafrost. The annual surface creep of some rock glaciers has accelerated recently by an order of magnitude. A multidisciplinary field study links characterization, monitoring, and modeling for such a rock glacier in the Turtmann valley in Switzerland. The first phase consisted of characterization using seismic refraction and ground-penetrating radar (GPR), as well as borehole information and monitoring of meteorological, hydrothermal, and geotechnical variables over 2 yr. The ground model confirmed the heterogeneity of the internal structure, with rock glacier topography affecting the thermal distribution in boreholes and seepage flows from tracer tests at between 10 and 40 m h(-1). Temperatures were generally warmer than -0.25 degrees C in the permafrost zone, with some variability in terms of thermal degradation of some layers to 0 degrees C and an active layer of about 3 to 5 m depth. Unique internal shear movements were measured by an automatic inclinometer, which indicated downslope creep rates in the shear zone and at the surface of about 2.4 and 3.2 m yr(-1) respectively, which could not be directly linked to temperature at the same depth. These rock glaciers have potential for future instability, which could damage infrastructure in the valley below. It is essential to understand why they have accelerated over the past decade through the complex interactions that have controlled the thermo-hydromechanical response.
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The travel angles of landslides continue to be an important parameter in risk analyses. We report on travel angles of 112 long runout landslides in the Canadian Cordillera, expanding on our 2008 study of 61 landslides. The lowest travel angles we report belong to the following groups (in ascending order) sensitive glaciomarine sediments, early deglacial earth flows in lake sediments, diamicts derived from clay shales (they may involve permafrost), glaciolacustrine sediments, earth flows generated by rock slides, confined and unconfined debris flows generated by rock slides, rock avalanches on glaciers, dry planar rock avalanches, and undifferentiated rock avalanches.
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The Bulkley and Babine Ranges of the Hazelton-Skeena Mountains, west-central British Columbia, have experienced three recent large catastrophic rock avalanches: Howson, 19 September 1999; Zymoetz, 8 June 2002; Harold Price, 22 or 23 June 2002. These landslides are large relative to contemporary landslides, although many large prehistoric landslides are evident within the Hazelton-Skeena Mountains. The recent landslides may be a result of climate change. Climate warming has resulted in: a pronounced thinning and recession of mountain glaciers causing debutressing of unstable rock slopes; possible degradation of mountain permafrost; and, an apparent increase in precipitation (rain and snow) over the past few years. Large rock avalanches place utilities and transportation routes in the mountain valleys at a significant risk. In addition, risks are increased to forest workers and recreation users in the valleys. The tremendous down valley travel distance of these landslides suggest some communities may also be at risk.
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In Lambiel C., Reynard E. et Scapozza C. (Eds) (2011). La géomorphologie alpine: entre patri-moine et contrainte. Actes du colloque de la Société Suisse de Géomorphologie, 3-5 sep-tembre 2009, Olivone (Géovisions n° 36).
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The potential of space-borne synthetic aperture radar interferometry (InSAR) to estimate both magnitude and spatial pattern of slope motion in a periglacial environment has been evaluated over a large area of the western Swiss Alps, using data from the ERS-1 and ERS-2 satellites. About 280 active rock glaciers with different classes of velocities have been identified on the analysed interferograms. The velocities range from a few centimetres per year to several meters per year. This data was validated by some differential GPS measurements and compared to numerous field observations. The resulting classification permits a better description of the full range of rock glaciers velocities and dynamics. Therefore, ERS InSAR reveals to be an efficient remote sensing technique, not only for inventorying active rock glaciers over a wide area, but also to estimate and categorize their displacement velocities.
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On July 10, 1990, part of the historical terminal moraine of the Dolent glacier collapsed. This event triggered a debris flow of approximately 40'000 m3 which endangered a campsite and a village in the Val Ferret, Valais, Swiss Alps. Investigations were carried out in cooperation with cantonal authorities and supported within the framework of the National Research Programme 31 on "Climate Change and Natural Catastrophes". The aims were to determine the triggering factors of the debris flows and to investigate whether a degradation of the permafrost could explain the instability of the moraine. Seismic refraction, D.C. resitivity mapping and surface thermal measurements were performed. Results show that there is no permafrost in equilibrium with the present climate in the moraine but degraded permafrost cannot be excluded in the deeper layers. The triggering factors of the debris flows are not yet clear. The instability of the moraine was not induced by an extreme rainfall event. There are number of possible explanation of the debris flow, in particular a combination of the following processes: a slow outburst of a water-pocket in the glacier, snowmelt which soaked the moraine with water and/or modified hydrogeological parameters in the moraine. The partial collapse of the moraine remains and unforeseeable phenomenon which can occur again at any time during the summer months and threaten the mountain communities in this region. The investigation of such phenomena is of importance in terms of the physical processes involved and in terms of the associated risk analysis.
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New evidence combined with a detailed re-evaluation of postglacial fault movements, seismic activity and shoreline sequences suggests that the period of deglaciation and the early Holocene was more seismically active than the mid to Late Holocene. It is proposed that the large-scale lateral displacements formerly proposed can not be justified, rather all postglacial fault movements appear to be limited to metre-scale vertical movements along pre-existing fault lines. In addition, it is argued that the Younger Dryas ice advance may have produced localised crustal redepression but not the more widespread impact formerly proposed. Both tectonic and postglacial rebound stresses, however, may be needed to explain the contemporary seismotectonics of the Scottish Highlands.
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The thermal condition of high-alpine mountain flanks can be an important determinant of climate change impact on slope stability and correspondingly down-slope hazard regimes. In this study we analyze time-series from 17 shallow temperature-depth profiles at two field sites in steep bedrock and ice. Extending earlier studies that revealed the topographic variations in temperatures, we demonstrate considerable differences of annual mean temperatures for variable surface characteristics and depths within the measured profiles. This implies that measurements and model related to compact and near-vertical bedrock temperatures may deviate considerably from conditions in the majority of bedrock slopes in mountain ranges that are usually non-vertical and fractured. For radiation-exposed faces mean annual temperatures at depth are up to 3 °C lower and permafrost is likely to exist at lower elevations than reflected by estimates based on near-vertical homogeneous cases. Retention of a thin snow cover and ventilation effects in open clefts are most likely responsible for this cooling. The measurements presented or similar data could be used in the future to support the development and testing of models related to the thermal effect of snow-cover and fractures in steep bedrock.
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Estimates of permafrost distribution in mountain regions are important for the assessment of climate change effects on natural and human systems. In order to make permafrost analyses and the establishment of guidelines for e.g. construction or hazard assessment comparable and compatible between regions, one consistent and traceable model for the entire Alpine domain is required. For the calibration of statistical models, the scarcity of suitable and reliable information about the presence or absence of permafrost makes the use of large areas attractive due to the larger data base available. We present a strategy and method for modelling permafrost distribution of entire mountain regions and provide the results of statistical analyses and model calibration for the European Alps. Starting from an integrated model framework, two statistical sub-models are developed, one for debris-covered areas (debris model) and one for steep bedrock (rock model). They are calibrated using rock glacier inventories and rock surface temperatures. To support the later generalization to surface characteristics other than those available for calibration, so-called offset terms have been introduced into the model that allow doing this in a transparent and traceable manner. For the debris model a generalized linear mixed-effect model (GLMM) is used to predict the probability of a rock glacier being intact as opposed to relict. It is based on the explanatory variables mean annual air temperature (MAAT), potential incoming solar radiation (PISR) and the mean annual sum of precipitation (PRECIP), and achieves an excellent discrimination (area under the receiver-operating characteristic, AUROC Combining double low line 0.91). Surprisingly, the probability of a rock glacier being intact is positively associated with increasing PRECIP for given MAAT and PISR conditions. The rock model is based on a linear regression and was calibrated with mean annual rock surface temperatures (MARST). The explanatory variables are MAAT and PISR. The linear regression achieves a root mean square error (RMSE) of 1.6 Å°C. The final model combines the two sub-models and accounts for the different scales used for model calibration. The modelling approach provides a theoretical basis for estimating mountain permafrost distribution over larger mountain ranges and can be expanded to more surface types and sub-models than considered, here. The analyses performed with the Alpine data set further provide quantitative insight into larger-area patterns as well as the model coefficients for a later spatial application. The transfer into a map-based product, however, requires further steps such as the definition of offset terms that usually contain a degree of subjectivity.
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Advanced methodologies such as core drilling, borehole logging/monitoring, geophysical tomography, high-precision photogrammetry, laser altimetry, GPS/SAR surveying, miniature temperature data logging, geotechnical laboratory analyses, numerical modelling, or GIS-based simulation of spatial distribution patterns in complex topography at regional to global scales have created a rapidly increasing knowledge basis concerning permafrost in cold mountain ranges. Based on a keynote presentation about mountain permafrost at CFG8 in Obergurgl 2012, a brief summary is provided concerning primary research frontiers and the long-term challenge related to the increasing probability of far-reaching flood waves in high-mountain regions originating at newly forming lakes as a consequence of large rock falls and landslides from destabilising steep rock walls with conditions of warming and degrading permafrost often in combination with de-buttressing by vanishing glaciers. Research is especially intense in the densely populated European Alps.
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The processes leading to a glacier instability depend on the thermal properties of the contact between the glacier and its bedrock. Assessing the stability of temperate glacier (i.e. the glacier can slide on its bedrock) remains problematic. In order to scrutinize in more detail the processes governing such "sliding" instabilities, a numerical model designed to investigate gravitational instabilities in heterogeneous media was further developed to account for the presence of water at the interface between the bedrock and the glacier for Allalingletscher. This model made it possible to account for various geometric configurations, interaction between sliding and tension cracking and water flow at the bedrock. We could show that both a critical geometrical configuration of the glacier tongue and the existence of a distributed subglacial drainage network were the main causes of the Allalingletscher catastrophic break-off. Moreover, the analysis of the modelling results diagnosed the phenomenon of recoupling of the glacier to its bed followed by a pulse of subglacial water flow as a potential new precursory sign of the final break-off in 1965. This model casts a gleam of hope for a better understanding of the ultimate rupture process resulting from such glacier sliding instabilities.
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A large rock avalanche occurred at 03:27:30 PDT, 6 August 2010, in the Mount Meager Volcanic Complex southwest British Columbia. The landslide initiated as a rock slide in Pleistocene rhyodacitic volcanic rock with the collapse of the secondary peak of Mount Meager. The detached rock mass impacted the volcano's weathered and saturated flanks, creating a visible seismic signature on nearby seismographs. Undrained loading of the sloping flank caused the immediate and extremely rapid evacuation of the entire flank with a strong horizontal force, as the rock slide transformed into a debris flow. The disintegrating mass travelled down Capricorn Creek at an average velocity of 64 m s-1, exhibiting dramatic super-elevation in bends to the intersection of Meager Creek, 7.8 km from the source. At Meager Creek the debris impacted the south side of Meager valley, causing a runup of 270 m above the valley floor and the deflection of the landslide debris both upstream (for 3.7 km) and downstream into the Lillooet River valley (for 4.9 km), where it blocked the Lillooet River river for a couple of hours, approximately 10 km from the landslide source. Deposition at the Capricorn-Meager confluence also dammed Meager Creek for about 19 h creating a lake 1.5 km long. The overtopping of the dam and the predicted outburst flood was the basis for a night time evacuation of 1500 residents in the town of Pemberton, 65 km downstream. High-resolution GeoEye satellite imagery obtained on 16 October 2010 was used to create a post-event digital elevation model. Comparing pre- and post-event topography we estimate the volume of the initial displaced mass from the flank of Mount Meager to be 48.5 × 106 m3, the height of the path (H) to be 2183 m and the total length of the path (L) to be 12.7 km. This yields H/L = 0.172 and a fahrböschung (travel angle) of 9.75°. The movement was recorded on seismographs in British Columbia and Washington State with the initial impact, the debris flow travelling through bends in Capricorn Creek, and the impact with Meager Creek are all evident on a number of seismograms. The landslide had a seismic trace equivalent to a M = 2.6 earthquake. Velocities and dynamics of the movement were simulated using DAN-W. The 2010 event is the third major landslide in the Capricorn Creek watershed since 1998 and the fifth large-scale mass flow in the Meager Creek watershed since 1930. No lives were lost in the event, but despite its relatively remote location direct costs of the 2010 landslide are estimated to be in the order of 10 M CAD.
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By subtracting surface topographies from 1979, 1994, 2000 and 2008, we measured ice-thinning rates increasing from 1 m a–1 (1979–94) to >4 m a–1 (2000–08) on the tongue of Mer de Glace, French Alps. The relative contributions of changes in surface mass balance and ice fluxes to this acceleration in the thinning are estimated using field and remote-sensing measurements. Between 1979–94 and 2000–08, surface mass balance diminished by 1.2 m w.e. a–1, mainly because of atmospheric warming. Mass-balance changes induced by the growing debris-covered area and the evolving glacier hypsometry compensated each other. Meanwhile, Mer de Glace slowed down and the ice fluxes through two cross sections at 2200 and 2050 m a.s.l. decreased by 60%. Between 1979–94 and 2000–08, two-thirds of the increase in the thinning rates was caused by reduced ice fluxes and one-third by rising surface ablation. However, these numbers need to be interpreted cautiously given our inability to respect mass conservation below our upper cross section. An important implication is that large errors would occur if one term of the continuity equation (e.g. surface mass balance) were deduced from the two others (e.g. elevation and ice-flux changes).
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The mechanisms that control climate-dependent rockfall from permafrost mountain slopes are currently poorly understood. In this study, we present the results of an extensive rock slope monitoring campaign at the Matterhorn (Switzerland) with a wireless sensor network. A negative dependency of cleft expansion relative to temperature was observed at all clefts for the dominant part of the year. At many clefts this process is interrupted by a period with increased opening and shearing activity in the summer months. More specific, this period lasts from sustained melting within the cleft to the first freezing in autumn. Based on these empirical findings we identify two distinct process regimes governing the cleft motion observed. Combining current theories with laboratory evidence on rock slope movement and stability, we postulate that (1) the negative temperature-dependency is caused by thermomechanical forcing and is reinforced by cryogenic processes during the freezing period and, (2) the enhanced movement in summer originates from a hydro-thermally induced strength reduction in clefts containing perennial ice. It can be assumed that the irreversible part of the process described in (1) slowly modifies the geometric settings and cleft characteristics of permafrost rock slopes in the long term. The thawing related processes (2) can affect stability within hours or weeks. Such short-term stability minima may activate rock masses subject to the slow changes and lead to acceleration and failure.
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P-wave refraction seismics is a key method in permafrost research but its applicability to low-porosity rocks, which constitute alpine rock walls, has been denied in prior studies. These studies explain p-wave velocity changes in freezing rocks exclusively due to changing velocities of pore infill, i.e. water, air and ice. In existing models, no significant velocity increase is expected for low-porosity bedrock. We postulate, that mixing laws apply for high-porosity rocks, but freezing in confined space in low-porosity bedrock also alters physical rock matrix properties. In the laboratory, we measured p-wave velocities of 22 decimetre-large lowporosity (<10 %) metamorphic, magmatic and sedimentary rock samples from permafrost sites with a natural texture (>100 micro-fissures) from 25 �C to −15 �C in 0.3 �C increments close to the freezing point. When freezing, pwave velocity increases by 11–166% perpendicular to cleavage/ bedding and equivalent to a matrix velocity increase from 11–200% coincident to an anisotropy decrease in most samples. The expansion of rigid bedrock upon freezing is restricted and ice pressure will increase matrix velocity and decrease anisotropy while changing velocities of the pore infill are insignificant. Here, we present a modified Timur’s twophase- equation implementing changes in matrix velocity dependent on lithology and demonstrate the general applicability of refraction seismics to differentiate frozen and unfrozen low-porosity bedrock.
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The characteristics and instability of recently exposed valley-side moraines are described. The presence of an ice-core, largely of glacial origin, is a major contributing factor in their instability by encouraging mass wasting on the moraine proximal slopes. An inventory of the spatial distribution and magnitude of mass wasting events over two field seasons indicates that the most unstable slopes are those closest to the glacier and, presumably, most recently deglaciated. The temporal distribution of mass wasting events indicates that they are triggered by the accumulation of rain water and/or water from ablation at the ice-core surface.