Permafrost Distribution Modeling in the Semi-Arid Chilean Andes
Guillermo F. Azócar1, Alexander Brenning1,2, and Xavier Bodin31Department of Geography and Environmental Management, University of Waterloo, Ontario, Canada 2Department of Geography, Friedrich Schiller University, Jena, Germany 3Laboratoire EDYTEM, Université de Savoie Mont Blanc, CNRS, Le Bourget-du-Lac, France
Received: 25 Apr 2016 – Accepted for review: 09 Jun 2016 – Discussion started: 16 Jun 2016
Abstract. Mountain permafrost and rock glaciers in the dry Andes are of growing interest due to the increase in human activities in this remote area. Empirical models of mountain permafrost distribution based on the spatial analysis of intact and relict rock glaciers and mean annual air temperature (MAAT) have been established as a tool for regional-scale assessments of permafrost favorability across entire mountain ranges; however, this kind of model approach has never been applied for a large portion of the Andes. In the present study, this methodology is applied to map permafrost favorability throughout the semi-arid Andes of central Chile (29° S–32° S), excluding areas of exposed bedrock. After spatially modeling MAAT distribution from scarce temperature records (116 station-years) using a linear mixed-effects model (LMEM), a generalized additive model (GAM) was built to model the activity status of 3524 rock glaciers. A Permafrost Favorability Index (PFI) was obtained by adjusting model predictions for conceptual differences between permafrost and rock glacier distribution. The results indicate that model has an acceptable performance (median AUROC: 0.76). Conditions highly favorable to permafrost presence (PFI ≥ 0.75) are predicted for 1051 km2 of mountain terrain, or 2.7 % of the total area of the watersheds studied. Favorable conditions are expected to occur in 2636 km2, or 6.8 % of the area. Especially in the Elqui and Huasco watersheds in the northern half of the study area, where a substantial surface portion (11.8 % each) was considered to be favorable for permafrost presence, while predicted favorable areas in the southern Limarí and Choapa watersheds are mostly limited to specific sub-watersheds. In the future, local ground-truth observations will be required to confirm permafrost presence in favorable areas, and to monitor permafrost evolution under the influence of climate change.
Azócar, G. F., Brenning, A., and Bodin, X.: Permafrost Distribution Modeling in the Semi-Arid Chilean Andes, The Cryosphere Discuss., doi:10.5194/tc-2016-100, in review, 2016.