Understanding the role of anthropogenic emissions in glaciers retreat in the central Andes of Chile.

Glaciers in Chilean Central Andes have significatively retreated, at least, in the last 60 years. From 2004 to 2014, the largest retreat in the area (-0.15 km2 yr-1) was observed at Olivares Alpha Glacier (OAG). Previous glacier fluctuation studies proposed that two open-pit mines distant 7 km from the glacier could be the cause of its enhanced retreat. However, this had not been yet tested due to the lack of measured data. Here, we investigated the impact that major air pollutants emitted by local mining activities could have on the differences observed in OAG glacial retreat compared with a glacier of similar size and altitude with no nearby anthropogenic sources: Bello Glacier (BG), which has a reported lower retreat (-0.02 km2 yr-1). Results revealed a link between anthropogenic air pollutants and glacial retreat rates, meaning that glacial retreat is decoupled from climatic and glaciological factors. Considering that both glaciers are located in the same climatic setting, the anthropogenic air pollutants deposited onto the OAG surface appear to be forcing positive feedback in which the pollutants deposition best explain the differences in the glacier retreat. With the results of this study, it has been calculated that the impact of mining in OAG could be responsible for 82% of its total retreat since between 2004 and 2014, and only the remaining 18% would correspond to the impact of climate change.