RECENT PERIGLACIAL STUDIES ON ROCK GLACIERS OF THE CENTRAL ANDES, MENDOZA, ARGENTINA

FRÖJD, CHRISTINA; TROMBOTTO LIAUDAT DARÍO; BOTTEGAL, ESTEFANIA; SILEO, NOELIA; PECKER MARCOSIG, IVANNA; DAPEÑA, CRISTINA

Queenstown

Congreso; 1st SOUTHERN HEMISPHERE CONFERENCE ON PERMAFROST; 2019

International Permafrost Association Southern Hemisphere Regional Conference on Permafrost

Different periglacial studies related to mountain permafrost were carried out in the Central Andes of Mendoza, Argentina, in the last years. These studies were made especially on rock glaciers. Most important research includedmonitoring of soil temperatures in active layers and the determination of the top and base mountain permafrost to observe climatic changes as well as the impact of global warming on the Andean cryospheric system. Other studies have involved hydrochemistry and an overview of how groundwater interacts with cryoforms. Hydrological studies in Mendoza are considered strategic because the region is semiarid and needs to improve the management of the resource wáter for human activities in the oasis as well as for drinking water in a changing environment. ExpandingAndean wetlands at high altitudes are studied in order to analyse the C storage. The region corresponds to the most southern part of the Dry Andes. Important investigated valleys with permafrost are located in the basin of the Vallecitos river with a Surface of 44.95 km². The basin belongs to the Cordón del Plata mountain range, Cordillera Frontal (32˚57´S, 69˚22´ W). Sub-basins show > 60% of periglacial environment with possible permafrost occurrence from ~3600 m asl on upwards. The heads of the valley are occupied by debris-covered glaciers. At present, the glacier área has decreased considerably, or even vanished. Thermokarst are also present in the covered glacier area but also in some parts of the rock glaciers indicating ice degradation and at the same time the occurrence of subterranean glacial ice. At the Morenas Coloradas rock glacier, regional studies were carried out between 1989 and 1992, where the terminal parthas been monitored continuously since 1999. This rock glacier showed different temperature characteristics at three monitoring sites in active layers, Balcón I (3560 m asl), Balcón I Superior (3590 m asl) and Balcón II (3770 m asl). As a consequence of the thermal changes of the active layers, the rock glacier shows abrupt movements, particularly in its terminal part. Thus geodesic measurings were made and resulted in different speeds and directions. At the monitoring área of Balcón I Superior, which lies on a superimposed lobe, the geodesic measuring points revealed significantkinematic activity in the period May 2015 – February 2016, when the largest displacement was approximately 2 m to the South, developing an advance of the front over Balcón I. At Balcón II however, the points moved much les, in the order of 0.30 m/yr. On the other hand, at the Stepanek rock glacier a seasonal hydrochemical monitoring was carried out between 2013 and 2017. The objective was to explain groundwater and surface water Flow, hydrochemistry and to understand the interaction between groundwater and the rock glacier. The Stepanek rock glacier fills the valley and its permafrost affects the water flow. The isotopic results of the water samples strongly indicate that there is an intra-permafrost water influence from the rock glacier, in response of the degradation of permafrost and meltingof ground ice. Due to lithological factors, the Andean periglacial environment may indicate altitudinal differences in the hydrogeochemical results. Elevated values of Ni2+, Cd2+ and Zn2+ were detected in the meltwater runoff. The hydrogeochemical and isotopic research allows the interpretation of different water paths across the rock glacier. It isexpected that this becomes more important in the future due to further global warming.