Thermal state of permafrost in the Central Andes (27-34° S)

Abstract

The thermal state of permafrost in South America is poorly understood compared to other regions, largely due to a scarcity of in situ data. This study presents the first coordinated regional compilation of borehole temperature records from high-altitude mountain permafrost sites in the Central Andes (3500 to 5250 m; 27-34° S), providing a baseline assessment of ground thermal conditions. Measurements from 53 boreholes along a north-south transect at the Chilean-Argentine border reveal ground thermal characteristics similar to those in other mountain permafrost regions, including high spatial and temporal variability, correlations with altitude and slope aspect, and distinct thermal attributes of rock glaciers. These observations suggest that the ground thermal regime of the Central Andes is shaped by similar processes, a perspective that previously lacked data support. The high temporal variability observed in the short records (< 9 years) reflects short-term microclimatic fluctuations and topo-climatic attributes unique to the Andean cryosphere. These include hyper-arid conditions, intense solar radiation, limited vegetative cover and organic matter, less massive ice (except in rock glaciers), and mountain topography in a Southern Hemisphere location. The susceptibility of the area to regional climatic phenomena (such as Southern Annular Mode (SAM), El Niño-Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO)) suggests that long-term trends can only be determined from extended datasets spanning several decades. This study highlights the need for ongoing ground temperature monitoring and emphasizes the importance of collaboration between industry, governments and scientists to advance understanding of a key climate change indicator in a data-scarce region.