CONICET | Buscador de Institutos y Recursos Humanos

The semi-arid Andes of Argentina host the largest permafrost distribution in the Southern Hemisphere outside Antarctica, dominated by rock glaciers that constitute the most common periglacial landform of this region. Rock glaciers develop impressive forms up to several kilometres in length and covering surface areas up to 3 km2, even outranging ice glaciers in cumulated size and number. The altitudinal range of intact rock glaciers varies between 3500 and 5000 m a. s. l., with rock glacier density being lower in the dryer North (30-31°S) than in the South of the semi-arid Andes (31-33°). The highest rock glacier concentration is located between 32°S and 33°S. Intact rock glaciers (309 km2) cover more surface areas as ice glaciers (240 km2), and as debris-covered glaciers (104 km2).Within the permafrost body and the seasonally frozen active layer rock glaciers potentially store large amounts of water. Due to their significant size and wide distribution, rock glaciers are assumed to be important water reservoirs and sources for this part of the Andes and their foreland. However, our knowledge about their composition and ice content is very limited. In general, the internal rock glacier hydrology changes according to the thermal ground conditions. During frost periods (winter) the active layer acts as seasonal water storage due to interstitial ice contents. Whereas in thaw periods (summer), the active layer becomes an aquifer and water is released and contributes to seasonal runoff. Beneath the active layer rock glacier permafrost features two hydrological functions: Ice-rich permafrost bodies and massive ground ice act as long-term water storage and as aquiclude. Furthermore, the ice content of rock glacier permafrost influences the permafrost degradation and its distribution due to latent heat effects.We assess the hydrological significance of rock glacier permafrost by a combination of field geophysics (electrical resistivity tomography (ERT), refraction seismic tomography (RST), ground penetrating radar (GPR)) and four phase modelling. The latter will be used to estimate the volumetric ice contents of the active layer and the permafrost bodies. Ice contents are quantified at the talus-derived rock glacier ?Dos Lenguas? (30°S) and the giant debris rock glacier system ?Morenas Coloradas? (32.5°S). First results of the geophysical long and cross sections (survey lines > 3 km) indicate heterogeneous ice content distributions that are closely related to surface characteristics of the rock glaciers. In addition, high resolution digital elevation models (DEM) of both rock glaciers are derived by structure-from-motion techniques using images taken from unmanned aerial vehicles (UAV). The interrelation of surface morphology and material composition will be finally used for sophisticated quantification of water storage capacities of both rock glaciers