Recent glacier variations at the Aconcagua basin, central Chilean Andes

The majority of glaciers in central Chile have receded in recent decades, from >50m to only a few meters per year, mainly in response to an increase in the 0 degrees C isotherm altitude. The Aconcagua river basin (33 degrees S) is one of the major glaciated basins in central Chile, with 121 km(2) of ice in 2003. An earlier inventory using 1955 aerial photographs yielded a total surface area of 151 km implying a reduction in glacier area of 20% (0.63 km(2) a(-1)) over the 48 years. Photographic stereo models, high-resolution satellite images (Landsat, ASTER) and SRTM data have been used to delineate glacier basins. A focus on Glaciar Juncal Norte, one of the largest glaciers in the basin, allows a more detailed analysis of changes. The glacier has exhibited a smaller reduction (14%) between 1955 and 2006, and the resulting elevation changes over this smaller period are not significant. The above reduction rates are lower than in other glaciers of central Chile and Argentina. This trend emphasizes water runoff availability in a river where most of the water in the dry summers is generated by glaciers and snowpack, and where most of the superficial water rights are already allocated. Ongoing hydrological research including modelling of future water runoff will improve our understanding.