Signals of an increasing drought condition in the Central Andes

The tropical glaciers of the Central Andes, particularly those in the Cordillera Real and surroundings, have been experiencing accelerated retreat since 1980. Dendrochronology based studies reach the same conclusions. These facts may profoundly impact communities living in the Andean high mountains and even in big cities like La Paz. This study examines the environmental changes in the Lake Tuni catchment and its associated glaciers (Condoriri, Jist'aña and Huayna-Potosí), located in the Cordillera Real Mountain range, 20-50 km northeast of La Paz. We employed a multi-proxy analysis based on the glacier´s dynamics, historical regional meteorological data, climate indices, and the geochemistry retrieved from a well-dated sedimentary record from Lake Tuni. The remote sensing data reveals a significant acceleration in glacier retreat beginning in the 1990s, with a pronounced worsening observed in the early 2000s while the sedimentary record shows a decline in runoff since 2000, characterized by a reduction in the terrigenous composition and magnetic susceptibility of sediments and a dominance of pollens of plants typical of drier conditions. Additionally, since the 1980s, increasing microcharcoal, dust, and wind-blown minerals from ice-free proglacial areas have darkened glacier surfaces, potentially accelerating melt. These indicators suggest a reduced availability of meltwater, which is critical for local water resources. Our findings imply that since the 1990s, the timing of glacier retreat has coincided with significant reductions in precipitation and changes in regional hydrology. We attribute these changes to altered Southern Amazon basin hydrology where vast areas of deforestation were created in the same period. This study highlights the extreme vulnerability of the Central Andes ecosystem, where the interplay and timing of climate change and land use by humans create unprecedented challenges. The continued retreat of these glaciers poses significant risks to water security for Andean communities, underscoring the urgent need for integrated, multidisciplinary approaches to enhance climate resilience in the region.