Detecting glacier-scale mass-balance heterogeneity using ASTER DEM differencing

Abstract. Glaciers in the Southern Andes show substantial spatial variability in mass balance, reflecting the combined effects of spatial variations in climate forcing and differences in glacier geometry. This study analyses elevation change patterns and climatic drivers for two contrasting glacier systems in southern Chile: the Queulat Glacier Complex and the stratovolcano Melimoyu. Elevation changes from 2000 to 2026 were derived from multi-temporal digital elevation models and analysed using a hypsometric approach to resolve elevation-dependent mass balance.

The results present a pronounced contrast between the two glacier systems. The Queulat Glacier Complex experiences consistently negative mass balance throughout the study period, with a rate of mass loss increasing from approximately −0.23 ± 0.39 to −0.63 ± 0.19 m w.e./yr. In contrast, Melimoyu maintained positive or near-balanced conditions in the early 2000s, followed by a transition to slightly negative mass balance in recent years. Elevation-dependent analyses show that mass loss in Queulat is predominantly associated with extensive low-elevation glacier tongues, while Melimoyu is characterised by a top-heavy hypsometry with a large accumulation area at high elevations.

Examination of downscaled ERA5 reanalysis data shows a consistent regional warming and a decrease in solid precipitation over the study period, while differences in total precipitation between the two sites remain small. This suggests that the contrasting glacier behaviour is not primarily driven by differences in climatic forcing, but rather by differences in glacier geometry and elevation distribution, which modulate the sensitivity to warming.

These results underline the key role of hypsometry and spatial glacier structure in determining individual glacier responses to climate change. The study indicates that glaciers under similar climatic conditions can exhibit substantially different mass-balance trajectories due to their geometry.