According to the Intergovernmental Panel on Climate Change, the Earth's temperatures should increase from 1.8°C to 4.2°C within the 21st century. From all the subsurface materials, permafrost is certainly one of the most sensitive to climate changes, because it is strongly dependent on climatic conditions. In this context, the localization and

characterization of permafrost in steep sedimentary terrains is of great importance.

The proposed study aims therefore to fill in the important gap in the knowledge of the permafrost-related parameters in talus slopes located within the alpine periglacial belt.

Two main objectives can be outlined: (1) analysis of the internal structure of talus slopes

and cartography of the lateral extension of permafrost in talus slopes; (2) determination and evaluation of the factors controlling the permafrost characteristics in talus slopes.

The study focuses on four talus slopes located in the Western Swiss Alps (Valais). Each

selected talus slope presents different characteristics (size, surface topography, lithology,

etc.). However, the main difference lies in the variation of the subsurface porosity: this

parameter plays a major role in the ability for air to circulate through a debris accumulation.

In order to fulfill the objectives, a combination of different field investigation techniques is necessary. The methodologies are mainly focused to both collecting vertical thermal

measurements in 20-m deep boreholes aligned longitudinally along the talus slopes and

on recording 2D geophysical data. In this context, electrical resistivity tomography,

seismic refraction tomography and electromagnetic methods are combined. Classical surface thermal measurements (BTS, continuous logging) complete and constrain the geophysical results. The drilling of boreholes allows us to validate the surface geophysical information and to study the thermal regime of the investigated talus. A major contribution of boreholes will also be the study of reversible upslope-downslope air advection within the ground, which is a key factor controlling the presence and the spatial extension of permafrost in talus slopes.

This study will open new perspectives to fulfil an important gap in the knowledge on

permafrost distribution and structure in alpine talus slopes. In particular, the main

objective is to model the permafrost distribution and related processes within the studied slopes. The project will also improve the knowledge on the potential use of geophysical

methods in alpine

Project location

Publications

Scapozza, C., Lambiel, C., Reynard, E., Baron, L. and Marescot, L. (2009). Verification of Geophysical Models of the Permafrost Distribution withinan Alpine Talus Slope Using Borehole Information, Valais, Swiss Alps. In Geophysical Research Abstracts.EGU2009-9444	Info
Lambiel, C. et Pieracci, K. (2008). Permafrost distribution in talus slopes located within the alpine periglacial belt, Swiss Alps. Permafrost and Periglacial Processes, 19(3): 293-304. Doi:10.1002/ppp.624	Info