Shrinking Snow Cover in the Sierra Nevada de Santa Marta: A Multisensor Satellite Assessment of Seasonal and Perennial Snow (2015–2024)

The Sierra Nevada de Santa Marta (SNSM) hosts the northernmost and most vulnerable tropical glaciers in South America. Despite extensive documentation of long-term glacier retreat, recent assessments of seasonal and perennial snow cover remain scarce. This study analyzes snow-cover dynamics in the SNSM for the 2015–2024 period using multispectral satellite data from Sentinel-2 and Landsat 8/9. Snow presence was quantified using the Normalized Difference Snow Index (NDSI) and summarized through a probabilistic Snow-Cover Frequency (SCF) framework, allowing the estimation of total and perennial snow-covered areas above 4,800 meters above see level (m a.s.l). Results reveal strong interannual variability in total snow cover but a sustained and statistically significant decline in perennial snow extent. Total snow-covered area decreased from 15.29 km² in 2015 to 6.19 km² in 2024, while perennial snow cover contracted by approximately 60% over the same period. Spatial analyses indicate a progressive upward migration and fragmentation of snow-covered areas, with persistent snow increasingly confined to small, topographically sheltered zones near the highest peaks. Overall, this study provides new evidence of an accelerated recent decline of the SNSM cryosphere and underscores the value of sustained, high-frequency remote sensing for monitoring tropical snow dynamics in rapidly changing mountain environments.