Andean Permafrost in Taluses and Blockslopes in the Agua Negra Catchment, Argentina - Distribution and Hydrological Significance

Extensive areas in mountain regions are under permafrost conditions with periglacial processes in the arid Andes of Argentina being mostly associated with high mountain permafrost. The most visible expression of creeping mountain permafrost within the periglacial altitudinal belt (between 35º and 27ºS), is the occurrence of rock glaciers. Beside snow and ice melting, active layer thawing and degrading permafrost contribute to river runoff; an essential resource in the arid Andes and their forelands. Halla et al. (2021) calculated for the first time rock glacier ice content using geophysical methods and four-phase modeling. Besides rock glaciers, taluses (including protalus ramparts) and blockslopes are widespread above an altitude of 4000 m a.s.l., with a first quantitative assessment revealing a surface coverage of about 73 %. We hypothesize that beside rock glaciers, taluses and blockslopes present a high potential for ice content, having a comparable or even more significant importance as valuable water reserves. However, taluses and blockslopes have not yet been properly investigated and little research has focused on the permafrost distribution and stratigraphy of these landforms.

This study determines the characteristics and the influence of climatic, topographical, and lithological conditions on the permafrost, using a multi-method approach: Electrical Resistivity Tomography (ERT), Seismic Refraction Tomography (SRT), hydrological monitoring along the course of Agua Negra river (discharge, water sampling), and UAV-, as well as spaceborne remote sensing analysis. While the use of ERT is beneficial due to the contrasting electrical resistivities of lithological media, water and ice, SRT complements the data with detailed p-wave based information on the upper layer. Hydrological monitoring aids in distinguishing different water resources and in estimating their contributions to runoff. In addition, the repeated application of remote sensing techniques allows for an acquisition of high resolution digital elevation models with models of difference providing insight in the magnitude, timing and spatial pattern of vertical and horizontal surface changes.

The possibility of determining with greater precision the distribution of permafrost in the arid Andes will lead to a more accurate estimation of solid-state water reserves stored in periglacial landforms in arid Andean catchments.

Halla, C., Blöthe, J.H., Tapia Baldis, C., Trombotto, D., Hilbich, C., Hauck, C., Schrott, L., 2021. Ice content and interannual water storage changes of an active rock glacier in the dry Andes of Argentina. The Cryosphere, 15, 1187-1213.