Rock Glacier Surface Change Detection Based on UAV- and Tristereo Pléiades Data (Agua Negra, Argentina)

Glacial and periglacial landforms in the semi-arid Andes represent an essential water storage and feed regional river runoff. Glacial and periglacial systems are undergoing change; with signs of permafrost degradation such as thermokarst being visible in the study area of the Agua Negra catchment in the Desert Andes of Argentina. Surface changes are often indicators of thawing and freezing processes and/or permafrost degradation. The analysis of surficial changes provides local patterns and indicates potential meltwater contribution to runoff. It is important to understand such changing processes to assess their future input to the hydrological system. Analyses that exceed landform scale are, however, rare due to limited accessibility and high demand on fieldwork and resources.

Glaciers and permafrost in the Agua Negra catchment exist within close proximity, suggesting (de)coupling effects. Glaciers and permafrost features can act as thermal and mechanical entity with water functioning as agent of transient glacier-permafrost interaction. Investigating (de)coupling is essential to better understand landscape (in)stability and changing water storages within the system. We hypothesize that periglacial systems directly interacting with glacial landscapes display diverging surface processes compared to non-glacially impacted periglacial systems. They differ in terms of magnitude and pattern, e.g. due to meltwater (re)routing.

We derive high-resolution digital elevation models (DEMs) for one talus-derived and one glacially impacted rock glacier and assess surface change based on repeated UAV flights in 2017, 2018, 2022 and 2023 for the talus-derived, and 2022 and 2023 for the glacially impacted rock glacier; both georeferenced by DGPS measurements. We increase the spatial scale of the analysis and use tristereo Pléiades data for Pléiades-based surface change detection of two glacially impacted rock glaciers between 2014 and 2022. Here, we use the UAV-based DEMs as validation datasets. We envision that combining the two data sources allows us to investigate change signals over larger spatial areas which might provide new insight in our process-response understanding of the high Andean (peri)glacial landscape and its hydrological significance.

First results from UAV based DEM comparison indicate net negative surface changes of the talus-derived rock glacier. Preliminary analysis of the Pléiades data shows a net negative mass balance of Agua Negra glacier and highlights the need for improved co-registering of the Pléiades data for rock glacier surface change detection.