Permafrost Distribution Modeling in the Semi-Arid Chilean Andes

Abstract

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.

DInSAR for a Regional Inventory of Active Rock Glaciers in the Dry Andes Mountains of Argentina and Chile with Sentinel-1 Data

“…This work focuses on the detection of active periglacial phenomena, and not on the determination of their magnitude of displacement. Therefore, the range of detectable displacement, from 2.2 cm/year to 170 cm/year, almost covers the entire displacement values recorded in the literature for the observed phenomena [5,10,19]. In particular, rock glaciers do not exceed point displacements of more than 300-400 cm/year [22].…”

“…On the other hand, an inactive rock glacier is not in thermal equilibrium with the environment and slowly loses its internal ice as it melts, introducing new water to the active part of hydrologic cycle. Furthermore, both Roer and Nyenhuis [9] and Azócar [10] have shown that the geomorphological, geomorphometric, and environmental or ecological parameters are more useful to discriminate between active or relict rock glaciers than between active or inactive glaciers. Moreover, some of the parameters used are in situ measurements, an important constraint for regional applications.…”

“…Second, assessment of the degree of activity in these types of inventories is usually based on geomorphological criteria. This approach is qualitative, subjective, and, as can be seen in the papers of Roer and Nyenhuis and in the Master's thesis of Azócar [9,10], has a greater relevance in the discrimination between active rock glaciers and relict rock glaciers than in discerning between active and inactive.…”

Evaluating sources of uncertainty and variability in rock glacier inventories

“…Despite general awareness on the limitations involved with drawing clear‐cut boundaries between active, inactive and relict categories, this classification scheme is the most widely adopted in rock glacier studies (e.g. Imhof, ; Putnam and Putnam, ; Angillieri, ; Scapozza and Mari, ; Lilleøren and Etzelmüller, ; Scotti et al, ; Azócar, ; Bornet, ; Onaca et al, ).…”

Pedoclimate monitoring in the periglacial high mountain soils of the Atacama Desert, northern Chile

“…Mountain pedoclimate is recognized as a phenomenon that may influence slope stability and hydrology, but knowledge about its characteristics and response to climatic change is still very limited, especially for low latitudes. In the high Andes, this lack of knowledge is greater, and the Central Andes cryosphere is a zone of growing interest . Long‐term in situ measurements of periglacial processes north of 30°S in the Andes are still missing, and permafrost outside rock glaciers remains unexplored .…”