Snow is a critical component of the Andean hydrological system, supporting water supply for drinking, irrigation, hydropower, and industry. Persistent cloud cover and limited in situ observations have hindered long-term assessments of snow dynamics across the Andes, the world’s longest mountain range. Here, we present a continent-scale analysis of snow persistence (SP) and snowline elevation from 2000 to 2025 using daily MODIS Terra–Aqua products enhanced with advanced temporal and spatial cloud-reduction algorithms. Cloud persistence was reduced from 49% to 29%, substantially increasing the usable observational record for snow detection, although cloud-related limitations remain in tropical and southern Patagonia regions. Our results reveal that snow responses are strongly heterogeneous along the mountain chain. There is a marked and spatially coherent decline in SP between 29 °S and 36 °S, where an area equivalent to approximately 80,000 km 2 of snow cover has been lost over the past 26 years. In this region, the snowline rose by 5–15 m yr ⁻¹ , reaching cumulative increases of up to 500 m. At the watershed scale, only basins in the Central Andes (29 °S – 36 °S) exhibit statistically significant SP declines and rising snowlines, while tropical watersheds show minimal snow presence and southern Patagonia displays mixed patterns partially influenced by persistent cloud cover. The accelerating loss of seasonal snow in the central Andes has profound implications for water security in regions where snowmelt is a dominant hydrological input. Our results underscore the need for higher-resolution multispectral and radar observations, expanded ground-based monitoring, and integrative modeling approaches to quantify snow water equivalent and anticipate future changes. Collectively, this study provides one of the most comprehensive assessments to date of Andean snow dynamics and highlights the central Andes as a hotspot of cryospheric sensitivity to ongoing climate change.
Saavedra et al. (Tue,) studied this question.