Spectral Index for classifying glacier debris distribution and thickness using Multispectral UAV imagery: A case study at Juncal Norte Glacier, Central Andes of Chile

Abstract. Understanding of debris-covered glaciers is crucial for predicting melt dynamics in high-mountain regions. Juncal Norte Glacier, located on the northwestern slope of Nevado Juncal in central Chile, has experienced a marked retreat—losing 22% of its surface area between 1955 and 2022. As it recedes, its lower tongue has become increasingly covered by supraglacial debris, a process that appears to have accelerated in recent years. This study proposes a spectral index (SI) derived from UAV-based multispectral imagery to classify debris thickness and its spatial distribution at Juncal Norte Glacier tongue. Data was collected during three UAV flights in February 2025 using high-resolution sensors. The classification relies on the green, red, red edge, and near-infrared (NIR) bands, enabling detailed surface mapping of the glacier’s ablation zone, with a spatial resolution of 11 cm/pixel. Preliminary results indicate that the method captures fine-scale debris heterogeneity and identifies zones of bare ice and varying debris thickness. Future work will focus on refining the spectral approach and integrating the results into geodetic mass balance estimates to improve glacier change assessments.