This paper presents an analysis of the internal structure, hydrogeology and dynamics of a large, complex, multilobate and multiroot rock glacier combining electrical resistivity tomography (ERT), hydrochemical data and differential interferometry synthetic aperture radar (DInSAR). The rock glacier consists of a series of overlapping lobes that represent different advancing stages with different degrees of conservation. The ERT surveys characterize the active layer and the upper part of the permafrost layer, the latter showing a heterogeneous geometry and electrical resistivity values ranging from 7 to 142 kΩm. Hydrochemical data argue for both the existence of different disconnected water flow pathways inside the rock glacier and the remarkable ionic concentrator effect of this landform. The horizontal displacement from October 2014 to April 2017 shows greatest magnitudes in the upper sector of both tongues, reaching speeds of up to 150 cm/year. The active frontal sector shows a displacement rate of 2-4.5 cm/year. This study contributes to knowledge of the material properties of rock glaciers, which are considered to represent important reservoirs/ water resources, and their influence on the distribution of mountain permafrost, hydrology, and dynamics. Finally, to the best of our knowledge, the possible influence of the metal content of the ground on the resistivity values recorded for mountain permafrost is highlighted for the first time.
<p>Within the extensive periglacial belt of the dry Andean high mountain range (17&#176;30&#8217;S to 35&#176;S), the most visible expression of creeping mountain permafrost is the occurrence of rock glaciers, which have been studied systematically in the last decades (e.g. Schrott, 1996; Trombotto et al., 1999; Halla et al. 2021). Active, inactive and relict rock glaciers are included in regional and national inventories (e.g. IANIGLA-CONICET 2018), whereas the spatial distribution, internal structure and ice content within block- and talus slopes have not been explored. Thus, there is a lack of explanatory approaches and analytical data on their local and regional distribution patterns and formative controls, despite these landforms being widespread and characteristic elements in the Upper Agua Negra catchment (ca. 30&#176;S 69&#176;W, Province San Juan, Argentina) and covering more than 70&#160;% of its area. We hypothesize that the permafrost bodies and the seasonally frozen active layer of these periglacial landforms store significant amounts of ice and contribute to runoff during summer months, rendering them important water reservoirs and decisive components of the water balance in the high-Andean desert landscape. Especially in light of global climate change, understanding the spatial distribution of potentially ice-rich permafrost landforms is imperative to assess available water resources, water quality and their evolution.</p> <p>A holistic inventory of key cryogenic landforms with focus on block- and talus slopes will be compiled for the Agua Negra catchment. Using field and remote sensing-based geomorphological mapping (based on e.g. 12&#160;m resolution TanDEM-X and 1&#160;m Pl&#233;iades data), published data and statistical modeling techniques, the spatial heterogeneity of cryospheric landforms and their formation controls will be analyzed. Our regional inventory will complement the existing &#8220;Inventario Nacional de Glaciares y Ambiente Periglacial&#8221; (IANIGLA-CONICET 2018) and will further provide the basis for a first assessment of the hydrological importance of these cryogenic landforms.</p> <p>Halla, C., Bl&#246;the, J.H., Tapia Baldis, C., Trombotto Liaudat, 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.</p> <p>IANIGLA-CONICET, Ministerio de Ambiente y Desarrollo Sustentable de la Naci&#243;n (2018). IANIGLA-Inventario Nacional de Glaciares y Ambiente Periglacial. Informe de la subcuenca del r&#237;o Blanco. Cuenca del r&#237;o San Juan, p. 62.</p> <p>Trombotto, D., Buk, E., &#160;Hern&#225;ndez, J., 1999. Rock glaciers in the Southern Central Andes (appr. 33&#176; S.L.), Mendoza, Argentina: a review. Bamberger Geographische Schriften, Selbstverlag des Faches Geographie an der Universit&#228;t Bamberg, Germany, 19, 145-173.</p> <p>Schrott, L., 1996. Some geomorphological-hydrological aspects of rock glaciers in the Andes (San Juan, Argentina). Zeitung f&#252;r Geomorphologie, Supplementband 104, 161-173.</p>
<p>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 35&#186; and 27&#186;S), 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.</p><p>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.</p><p>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.</p><p><em>Halla, C., Bl&#246;the, 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.</em></p>
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