Monitoring Ongoing Deglaciation in the Andes of Central Chile by Intensive Field Surveys, Remote Sensing and Modeling

Since 2013 an intensive monitoring program has been undertaken on mountain glaciers located at the upper Olivares basin, one of the main tributaries to the Maipo river. This is the most important water source for Santiago, Chile's capital that together with the surrounding metropolitan area have more than 7 million inhabitants. These water resources have been under stress during the recent decade due to a Mega Drought affecting Central Chile. A combination of declining precipitations and increasing atmospheric temperatures in the high Andes resulted in the rise of the regional snowline altitude. These climatic trends are the main driving factors explaining ongoing glacier wastage in the Central Andes of Chile. In order to monitor these glacier changes and their possible consequences on water runoff, we implemented a network of automatic weather stations, gauge stations, time-lapse cameras, mass balance stakes and many other sensors that are continuously measuring variables that allow estimating the annual mass, energy and water balance. Area changes since the Little Ice Age have been mapped and volumetric losses were estimated by repeated LiDAR and GPS surveys. Ice dynamics and ice fluxes were also measured on several glaciers. The combination of all the available data have been used to run a Minimal Glacier Model aiming to evaluate the possible future glacier responses to different IPCC climate change scenarios. Preliminary results indicate that glaciers have lost up to 68% of the 1955 total area. The annual mass balances have been persistently negative and since 2013, the accumulated mass balance ranges between -9 and -6 m of water equivalent. All glaciers have experienced strong ice thinning with mean rates between -1 and -2 m per year. Melting ice runoff is restricted to the austral summer, especially between December and March, when glaciers contribute a critical part to the low stream flow that prevails in the dry summers. The modeled predictions indicate that glaciers will undergo further shrink during the rest of this century without a significant increase in runoff.