70 Years of Glacier Loss on the Nevados de Chillán volcanic complex, Chile

Abstract. Glaciers on the Nevados de Chillán volcanic complex are rapidly retreating, with anticipated consequences for agroforestry, tourism, and regional human and ecological security. Quantifying their mass balance is critical for understanding current meltwater contributions and for anticipating future water availability as these glaciers continue to shrink. Here we estimate the geodetic mass balance of all 28 documented glaciers on the Nevados de Chillán complex. An uncrewed aerial vehicle (UAV) campaign conducted in March 2024 provided updated elevation data for 11 glaciers on the complex, allowing calculation of volume change from 1954–2024 (70 years). For the remaining 17 glaciers, we analyzed airplane and satellite digital elevation models (DEMs) to estimate volume change from 1954–2000 (46 years). Our results show a clear acceleration in glacier mass loss after 2000 for the glaciers surveyed with UAV data. Mean annual specific mass balance of the Cerro Blanco subcomplex accelerated from -0.41 ± 0.33 m w.e. y^-1 (1954–2024) to -0.60 ± 0.29 m w.e. y^-1 (2000–2024), while that of the Las Termas subcomplex increased from -0.13 ± 0.32 m w.e. y^-1 (1954–2024) to -0.36 ± 0.18 m w.e. y^-1 (2000–2024). Regional water resource planning should consider how increasing glacier melt rates on the Nevados de Chillán complex will impact the timing and volume of future water availability.