Climate Change and recent variations in small Andean glaciers.

LEIVA, J.C; ; CABRERA, G. A.; LENZANO, M.G. ; BOTTERO; R

Valdivia, Chile

Conferencia; International Glaciological Conference VICC 2010 – Ice and Climate Change: A view from the South.; 2010

CECs- Centro de Estudios Científicos, Chile

Climate Change and recent variations in small Andean glaciers Leiva, J. C., G.A. Cabrera, M.G. Lenzano and R. Bottero Small glaciers in the Andes of Mendoza and San Juan provinces show the impacts of Global Change. In spite of their small size, their contribution to the water discharge of the rivers and streams of the region is very important during drought periods, when the annual snowfall in the Central Andes is scarce. During the last decades they underwent an accelerated shrinking process that will diminish the water availability for the Andean communities and will endanger the irrigated oases situated in the western part of Argentina. In this work we show the recent evolution of a number of small glaciers situated in the Andes between 29 ºS and 33ºS and between the 4500 and 5500 m range. It includes observations on seven small glaciers:  the Los Amarillos glacier and its neighbour the Amarillo glacier, the Brown glaciers, called Superior, Inferior and Norte, the Agua Negra glacier and the Piloto Este glacier, as well as on a larger one: the Las Vacas glacier. The glaciological work conducted on each of these glaciers focused on different aspects and spans over different time intervals between1965 and 2009. In 1965 Colqui began the survey of the front fluctuations of Agua Negra glacier. On this glacier geoelectrical and GPR surveys were performed at the end of the 20th century. On the Piloto glacier mass balance studies started in 1979, the ice depth of this glacier was obtained in 1982 by seismic survey. On the LosAmarillos, Amarillo and Brown glaciers mass balance studies and GPR surveys were performed during the last two years. The analysis of all the obtained data and the comparison of previous terrestrial and aerial photos and satellite images show that these small glaciers have experienced a recession. The Piloto Este mass balance series shows that this glacier is in danger of disappearing in the near future. Moreover, there is no evidence to suggest that the other mentioned small glaciers would behave differently. At the Las  Vacas glacier (a bigger glacier with an area of approximately 18.4km2 ), two of the authors compare the situation of this glacier in the 2001 and 2007, using the digital terrain models (DEM) from Aster stereoscopic images, level 1 A, corresponding to 2001 and 2007, for those years.  The average ice elevation change for the three profiles between 2001 and 2007 is approximately of -35 m. The 2001-2007 las Vacas glacier volume variation is DV01-07 = – 0.64 km3 occurring in a glacial surface of 18.4 km2 in 2001. The applied methodology, perhaps owing to the small number of GCP and in spite that we adjusted both DEM of the zone of interest using tie-points, gives results where the error propagations can be hardly assessed. Nevertheless the longitudinal glacier profiles comparison does not show results incongruent with the regional glaciers behavior. Previous works show that, during drought periods, the glacier contribution reaches up to 60 to 70 % of the total runoff on the Central Andes of Argentina and Chile (Bown et al., 2008; Leiva, 1982, 2002, 2007; Milana et al. 1997; Peña et al 2007). Hence, the observed glacier recession will have strong impacts on the water availability of the region.