Observing decreasing snow cover and increasing surface temperature across the Andes with remotely sensed and reanalysis data

Abstract Mountain environments are at risk of water insecurity and ecosystemic disruption due to elevation dependent warming (EDW) and its impact on the cryosphere. Although past studies have investigated temperature and snow cover trends independently across the Andes, none have established their inter-relationship based on both remotely sensed and reanalysis datasets. This study leverages the available temperature and snow cover records from ERA5-Land (1950–2023) and a suite of remotely sensed data (primarily MODIS) from the past two decades (2003–2023) to highlight warming hotspots across the Cordillera and spatiotemporal relationships between temperature (air and surface) and snow cover by elevation band. Particular attention is given to the extratropical Southern Andes (25°S–38°S), whose snow-dominated mountain hydrology is uniquely vulnerable—confirmed by in-situ discharge gauges for sampled catchments in its eastern slopes. Results reveal the strong dependence of discharge on snow cover in the summertime, but more variability with respect to its relationship to year-round temperatures. Snow cover area appears to be especially sensitive to temperatures in the wintertime at higher elevations (3–5 km); however, the most significant trends in concurrent snow cover decrease and temperature increase emerge for the austral fall and spring (May and September – November). Trends with greater magnitudes for the modern period (2003–2022/3) compared to the historical climatology (1950–2000) demand greater attention with significant implications for future water management across the Andes.