Permafrost evolution in a Mountain Cathment Near Santiago de Chile

Abstract

The Chilean Central Andes near Santiago are a semi-arid region with substantial frozen water reserves in theirhigh altitude cryosphere. Millions of people depend on the Andean cryosphere for freshwater supply. Over thelast sixty years, global warming has altered the mountains’ water balance, as the temperature rose, precipitationdecreased, and deglacierization exposed hundreds of square kilometers. The distribution of solid water stored insoil permafrost and the potential effects of climate change on it are unknown.Here, we map favorable spots for permafrost occurrence at the “Monos de Agua” catchment, Aconcagua basinat 33?S, between 3600 and 5100 m a.s.l.. We identify these “cold spots” based on ground surface temperature andincoming solar radiation between 2017 and 2019. We suggest that these locations currently present permafrostand frozen water might actually be there. We confirmed a body of frozen water at one of these cold spots using anelectrical resistivity survey.Our mapping suggests that at least 15 ± 7% of the catchment’s surface is underlain by permafrost. Permafrostoccurrence begins around 3600 m a.s.l. with low probability and only at locations with favorable conditions oflow exposure and isolation. Permafrost occurrence probability increases with altitude, with the largest fractionpresent above 4200 m a.s.l.Our results suggest that the permafrost area in this region will decrease between 13 and 87% by the end of thecentury under the future global warming RCP scenarios. This event represents new challenges for the hydrologicalmemory and water security planning in the Chilean Central Andes.