Landslide-like developement of rockglaciers detected with ERS-1/2 SAR interferometry
Reynald Delaloye(1), Tazio Strozzi(2), Christophe Lambiel(3) and Eric Perruchoud(1)
(1) University of Fribourg, Ch. du Musee 4, 1700 Fribourg, Switzerland
(2) Gamma Remote Sensing, Worbstr. 225, 3073 Gümligen, Switzerland
(3) University of Lausanne, Quartier Dorigny, 1015 Lausanne, Switzerland
Perennially frozen ground supersaturated with ice may be affected by slow deformation – the so-called permafrost creep. The process leads to the formation of rockglaciers that are large masses of ice/rock debris mixture acting as sediments conveyors. In the Alps, active rockglaciers are numerous above 2200 to 2500 m a.s.l. Their deformation rate lies typically in the order of 0.1 to 1.0 m/year. In response to the rapid increase in air temperature that occurred in the European Alps during the 1980s and the high level of temperature since that time, permafrost has warmed of about 0.5 to 1°C and rockglaciers are moving significantly faster. In the worst cases a dramatic increase of the deformation rate has initiated a “surge” process, that is the development of landslide-like mass wasting affecting part or whole of the rockglacier.
Recent analysis of ERS-1/2 differential SAR interferograms for inventorying mass wasting in the periglacial belt of the Valais Alps (Switzerland) has evidenced – what was not expected before - that at least 10 rockglaciers were affected by very rapid movement in 1995-1999. For these rockglaciers obvious signals have been detected on 1-day interferograms both in summer and winter time indicating a displacement of about 2-5 m/year in the satellite line-of-sight. Ongoing terrestrial surveys (differential GPS) on several of these very rapidly moving rockglaciers confirm both the magnitude order of the displacement (locally up to more than 7 m/year) and the spatial pattern of the area affected by the surge. They also show that the mass wasting processes are still active. New data provided by the ALOS PALSAR and TerraSAR-X satellites should allow the detection of the current activity of these very rapidly moving rockglaciers.
Keywords: ESA European
Space Agency - Agence spatiale europeenne,
observation de la terre, earth observation,
satellite remote sensing,
teledetection, geophysique, altimetrie, radar,
chimique atmospherique, geophysics, altimetry, radar,