Destabilisation of Creeping Permafrost: The Plator Rock Glacier Case Study (Central Italian Alps)

Abstract

The Plator rock glacier is the first such landform identified in the Italian Alps that shows destabilised behaviour. Analysis of six sets of sequential orthophotographs from 1981 to 2012 reveals an exceptional advance of the rock glacier front (92.1 m) and a horizontal velocity up to 4 m a‐1 in different zones. The spatial variability of kinematics was evaluated by tracking sets of ‘tracer’ boulders on the rock glacier through time. Its velocity has progressively increased from the rooting zone to the tongue, with complex trends associated with distinct morphological features. Destabilisation likely occurred between 1954 and 1981, probably due to the relatively low elevation of the tongue, which resulted in warm permafrost conditions. Field observations reveal the presence of a large rock fall deposit, which occurred before 1981, and suggest that the debris overload could have triggered destabilisation. Since June 2015, an intensive monitoring programme has been implemented on the rock glacier, as the tongue is expected to travel over a steeper slope segment within the next 3 to 5 years, which could evolve in a catastrophic movement. Copyright © 2016 John Wiley & Sons, Ltd.

Recent Acceleration of a Rock Glacier Complex, Ádjet, Norway, Documented by 62 Years of Remote Sensing Observations

“…The results provide information about the displacement of a rock glacier complex having rates that are comparable to advances of frozen debris lobes in Alaska (Darrow et al, ) and destabilized rock glaciers in the Swiss and Central Italian Alps (Delaloye et al, ; Scotti et al, ). The long time series and complementarity of methods document the temporal fluctuations of displacement rates.…”

Permafrost Favorability Index: Spatial Modeling in the French Alps Using a Rock Glacier Inventory

“…Therefore, the currently active rock glaciers are believed to be representative for the climatic conditions of the colder periods of recent centuries, e.g., the Little Ice Age (LIA) (Lambiel and Reynard, 2001;Cossart et al, 2010). Although rock glaciers have been demonstrated to be sensitive to climate change, the response time is estimated to be of several decades to centuries (Scapozza et al, 2010;Scotti et al, 2017). As consequence, the present model likely reflects the permafrost favorability in climatic conditions that are no longer valid in the present climate, and even less so in warmer future climate.…”

“…In addition, observations of accelerating and destabilizing rock glaciers are interpreted as potential signals of ice-rich permafrost degradation (Roer et al, 2008;Delaloye and Morard, 2011;Ramelli et al, 2011;Delaloye et al, 2013;Scotti et al, 2017). In the French Alps two recent cases of geomorphological phenomena linked to permafrost degradation received particular attention: the collapse of the Bérard rock glacier in 2006 (Bodin et al, 2016), and the active layer detachment of the Lou rock glacier that resulted in a destructive debris flow, damaging the town of Lanslevillard in August 2015 (Schoeneich et al, 2017).…”

Rock‐glacier dams in High Asia

“…Yet, rock glaciers seem capable of building dams or even impounding lakes in mountain rivers of High Asia (Figure 1), thus disrupting the downstream motion of sediment, covering large tracts of valley floor with ice-rich debris, and forming potential sources of catastrophic outburst floods. However, recent studies reported increasing rock-glacier activity and advance rates into river valleys in response to atmospheric warming (Sorg et al, 2015), or even the sudden collapse of rock glaciers producing debris flows (Iribarren Anacona et al, 2015;Bodin et al, 2016;Scotti et al, 2017). However, recent studies reported increasing rock-glacier activity and advance rates into river valleys in response to atmospheric warming (Sorg et al, 2015), or even the sudden collapse of rock glaciers producing debris flows (Iribarren Anacona et al, 2015;Bodin et al, 2016;Scotti et al, 2017).…”

“…The pioneering work by Costa and Schuster (1988) on natural dams formed by landslides, glaciers, dunes or lava flows discloses little about rock glaciers as potential obstacles to river flow; neither do more recent reviews concerning the forms, dynamics, and distribution of rock glaciers in mountainous terrain (Janke, 2013;Scotti et al, 2013;Jones et al, 2018b). However, recent studies reported increasing rock-glacier activity and advance rates into river valleys in response to atmospheric warming (Sorg et al, 2015), or even the sudden collapse of rock glaciers producing debris flows (Iribarren Anacona et al, 2015;Bodin et al, 2016;Scotti et al, 2017). Clearly, the geomorphic impact of rock glaciers on rivers, and especially whether and how rock glaciers divert, disturb, or even completely block sediment and water fluxes, deserves detailed enquiry.…”