Indicators of present global warming through changes in active layer-thickness, estimation of thermal diffusivity and geomorphological observations in the Morenas Coloradas rockglacier, Central Andes of Mendoza, Argentina

Temperature profiles from the active layer have been analysed for 2 sites on the composed rockglacier Morenas Coloraclas. Cordon del Plata, Mendoza, Argentina, using monitoring data collected between 1989 and 2008 in order to characterize the impact of global warming in the cryolithozone of the Dry Andes at these latitudes (32 degrees-33 degrees S). A significant change in the active layer and suprapermafrost of this rockglacier of the Cordon del Plata is registered at the monitoring sites. The observed changes imply direct consequences for the cryogenic environment and the Andean creeping permafrost. The nose of the Morenas Coloradas rockglacier for example (Balcon I, 3560 m a.s.l.), already expresses inactivity; the permafrost table is found at great depth (7.5-9 m). Data collected at Balcon I and II allow to estimate the theoretical thermal diffusivity alpha at the active layer of Morenas Coloraclas. Thermal diffusivity may be decisive for the study of cryogenic dynamics at other altitudes and latitudes in the region where data are still scarce. Low alpha values (<0.2 x 10(-6)m(2)/s) correlate with occurrence of freezing and ice at low altitudes. While the glaciers are turning into small insignificant bodies in the high mountains, the periglacial level with creeping permafrost and linked with rockglaciers is expanding altitudinally, passing a transitional rooting area which is indirectly feeding the rockglaciers with their covered or dead ice. The ice of glacigenic origin contributes to the genesis of this type of permafrost. As the permafrost table is found at greater depths, the rockglaciers need to be monitored in order to define a balance between the upper periglacial level (in terms of altitude) with mountain continuous-quasi continuous permafrost and the lower periglacial level to where the lowest fronts of creeping permafrost are reaching. The variations of the cryogenic structure of the rockglaciers of the Cordon del Plata caused by warming processes, will have direct consequences for the volume of frozen sediments and therefore for the hydrology of the entire region, a fact that has to be taken into account for future socio-economic programs of the respective provincial governments. (C) 2008 Elsevier B.V. All rights reserved.