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Université de Fribourg

Twenty years of European mountain permafrost dynamics—the PACE legacy

Etzelmüller, Bernd ; Guglielmin, Mauro ; Hauck, Christian ; Hilbich, Christin ; Hoelzle, Martin ; Isaksen, Ketil ; Noetzli, Jeanette ; Oliva, Marc ; Ramos, Miguel

In: Environmental Research Letters, 2020, vol. 15, no. 10, p. 104070

This paper reviews and analyses the past 20 years of change and variability of European mountain permafrost in response to climate change based on time series of ground temperatures along a south–north transect of deep boreholes from Sierra Nevada in Spain (37°N) to Svalbard (78°N), established between 1998 and 2000 during the EU-funded PACE (Permafrost and Climate in Europe) project. In...

Université de Fribourg

Seismic monitoring in the Gugla rock glacier (Switzerland): ambient noise correlation, microseismicity and modelling

Guillemot, Antoine ; Helmstetter, Agnès ; Larose, Éric ; Baillet, Laurent ; Garambois, Stéphane ; Mayoraz, Raphaël ; Delaloye, Reynald

In: Geophysical Journal International, 2020, vol. 221, no. 3, p. 1719–1735

A network of seismometers has been installed on the Gugla rock glacier since October 2015 to estimate seismic velocity changes and detect microseismicity. These two processes are related to mechanical and structural variations occurring within the rock glacier. Seismic monitoring thus allows a better understanding of the dynamics of rock glaciers throughout the year. We observed seasonal...

Université de Fribourg

Estimating glacier-bed overdeepenings as possible sites of future lakes in the de-glaciating Mont Blanc massif (Western European Alps)

Magnin, F. ; Haeberli, W. ; Linsbauer, Andreas ; Deline, P. ; Ravanel, L.

In: Geomorphology, 2020, vol. 350, p. 106913

De-glaciating high mountain areas result in new landscapes of bedrock and debris where permafrost can degrade, persist or even newly form in cases, and of new lakes in glacier bed overdeepenings (GBOs) becoming ice-free. These landscapes with new lakes in close neighborhood to over-steepened and perennially frozen slopes are prone to chain reaction processes (e.g. rock-ice avalanches into...

Université de Fribourg

Direct observations of a three million cubic meter rock-slope collapse with almost immediate initiation of ensuing debris flows

Walter, Fabian ; Amann, Florian ; Kos, Andrew ; Kenner, Robert ; Phillips, Marcia ; Preux, Antoine de ; Huss, Matthias ; Tognacca, Christian ; Clinton, John ; Diehl, Tobias ; Bonanomi, Yves

In: Geomorphology, 2020, vol. 351, p. 106933

Catastrophic collapse of large rock slopes ranks as one of the most hazardous natural phenomena in mountain landscapes. The cascade of events, from rock- slope failure, to rock avalanche and the near-immediate release of debris flows has not previously been described from direct observations. We report on the 2017, 3.0 × 106 m3 failure on Pizzo Cengalo in Switzerland, which led to human...

Université de Fribourg

Petrophysical joint inversion applied to alpine permafrost field sites to image subsurface ice, water, air, and rock contents

Mollaret, Coline ; Wagner, Florian M. ; Hilbich, Christin ; Scapozza, Cristian ; Hauck, Christian

In: Frontiers in Earth Sc-ience, 2020, vol. 8, p. -

Quantification of ground ice is crucial for understanding permafrost systems and modeling their ongoing degradation. The volumetric ice content is however rarely estimated in permafrost studies, as it is particularly difficult to retrieve. Standard borehole temperature monitoring is unable to provide any ice content estimation, whereas non-invasive geophysical techniques, such as refraction ...

Université de Fribourg

Monitoring rock glacier kinematics with satellite synthetic aperture radar

Strozzi, Tazio ; Caduff, Rafael ; Jones, Nina ; Barboux, Chloé ; Delaloye, Reynald ; Bodin, Xavier ; Kääb, Andreas ; Mätzler, Eva ; Schrott, Lothar

In: Remote Sensing, 2020, vol. 12, no. 3, p. 559

Active rock glaciers represent the best visual expression of mountain permafrost that can be mapped and monitored directly using remotely sensed data. Active rock glaciers are bodies that consist of a perennially frozen ice/rock mixture and express a distinct flow-like morphology indicating downslope permafrost creep movement. Annual rates of motion have ranged from a few millimeters to...

Université de Fribourg

Quantitative imaging of water, ice and air in permafrost systems through petrophysical joint inversion of seismic refraction and electrical resistivity data

Wagner, Florian ; Mollaret, Coline ; Günther, Thomas ; Kemna, Andreas

In: Geophysical Journal International, 2019, vol. 219, no. 3, p. 1866–1875

Quantitative estimation of pore fractions filled with liquid water, ice and air is crucial for a process-based understanding of permafrost and its hazard potential upon climate- induced degradation. Geophysical methods offer opportunities to image distributions of permafrost constituents in a non-invasive manner. We present a method to jointly estimate the volumetric fractions of liquid water,...