The Anthropogenic Influence on Glacier Retreat in Central Chile

Abstract. Glaciers in the Andes mountain range have retreated since the mid-20th century. This change has been attributed to climate change and the effects of local pollution. Some glaciers subjected to similar meteorological conditions and the same influence of climate change are found to exhibit significantly different retreat rates, which cannot be explained by climatological factors alone. In the Maipo River basin, located in central continental Chile, two glaciers with similar climatic and geomorphological characteristics, the Paloma Oeste Glacier (POG) and the Bello Glacier (BG), exhibit significantly different levels of ablation. We implement two multivariable regression models, one per glacier, to identify the importance of specific climatic and anthropogenic variables in glacier surface area retreat. These models incorporate a temperature-related variable and precipitation (indicative of climate change), surface-level Black Carbon concentration (BC, indicative of anthropogenic activity) and the large-scale climate indices PDO and Niño 3.4 (related to climate variability) as covariates. The results indicate that the glacier surface change is more sensitive to the surface BC concentration and the Niño 3.4 index than to precipitation, PDO, or temperature for both glaciers. However, since the surface BC concentration in POG is more than 40 times higher than in BG, the area retreat is significantly higher in POG than in BG. Between 2000 and 2020, 49 % of the area retreat of POG is explained by BC pollution, while 97 % of BG’s retreat is explained by climatic effects (climate change and climate variability). Furthermore, when analyzing the causes of glacier retreat in POG before and during sustained drought conditions, often referred to as the Central Chile Megadrought (2010–2020), we found a change in the relative importance of BC surface concentrations. Before the Megadrought, BC is identified as the leading cause of glacier retreat in POG, accounting for a 53 %. However, the climatic effects (61 %) on glacier retreat during the Megadrought become more relevant than the impact of BC (39 %). These results highlight the spatiotemporal varying influence of climatic and anthropogenic factors on glacier retreat, emphasizing the significant contribution of climate change, particularly during sustained drought conditions.