Behavior of the monitored Morenas Coloradas rock glacier in the new environmental system of global warming

D. TROMBOTTO LIAUDAT; ESTEFANÍA BOTTEGAL

Wellington

Simposio; The Cryosphere in a Changing Climate; 2017

Sponsored by the International Glaciological Society (IGS), the International Association of Cryospheric Sciences (IACS), and the Climate and Cryosphere (CliC) project.

Until 2008 (Trombotto & Borzotta, 2009), the MorenasColoradas rock glacier (31°/32° S), in the Central Andes showed dissimilarsituations at its different monitoring sites, which were explained by variousfactors, not only external ones, related to the climatic variability and height(thermal diffusivity of the cryotic body, α = <0.2×10−6m2/s), but also to thermal-hydrological situations whichdestabilized its internal cryogenic structure. In the lower monitoring site, ona plunged terrace of the cryoform ?nose?, Balcón I (3560 m ASL), a transitionlayer even showed signs of aggradation of permafrost. Long term studies ofsurficial drillings showed, however, that the air isotherm of 0 °C was higherin altitude than the active front of the lithoglacier and that the cryogenicprofile of the 90ies has risen at least 40 m in altitude into the site calledBalcón I superior (3590 m ASL). At the monitoring area of Balcón I and Balcón Isuperior, the geodesic measurement points revealed important cryodynamicactivity in the period 2013-2015, where the largest displacement wasapproximately 2.5 m in S direction (downslope). Balcón II however, moved muchless, in the order of 0.50 m.  Geodesic measurements have also been madein inactive lobes with results very close to 0 m. The present studies allow todeduce that the largest cryogenic sedimentary movements are superficial, thatis to say, they are located in the active layer and are due to internalmovements produced by melting water coming from the top of the cryoform, andfrom both sides of the upper basin of the valley. Thermokarst expressdegradation of dead ice that was integrated into the cryoform up to 3770 m ASLapproximately (Balcón II). In active layer ?overthrusts?, processes of islandice, which melts at higher altitudes, interact, or inject the open cryogenicsedimentary structure. Other geodetic measurements show superficial movementsthat may express changes in the deep structure. The latter are due to energychanges by heat exchange between the external environment and the cryoform as awhole, which results in a new dynamic situation.