Water content and ground temperature variations in the active layer of a rock glacier in the Central Andes of San Juan, Argentina

Abstract

This paper analyses the response of the active layer between 2018 and 2020 in a typical rock glacier in the Central Andes of Argentina, in terms of volumetric water content and ground temperature variations. The period 2018–2020 coincided with the warmest and driest years of the last fourth decades in the Central Andes, reflected also in the reduced cooling periods, and decreased extent and duration of snow coverage. We performed sedimentological studies and calculations of thermal properties, along with measurements of water content and soil temperature in the top meter of soil within the active layer. Afterward, using the Coupled Heat and Mass Transfer Model for the Soil–Plant–Atmosphere System (COUP) model software, a number of selected parameters were adjusted to get the best correlation between measured and simulated data, using air temperature and precipitation datasets from global reanalysis models as inputs. This numerical model allowed to interpret the physical processes driven by thermal and hydrological fluxes within the active layer of rock glaciers in the Central Andes. During the autumn, we observed upward migration of moisture controlled by cryosuction at the freezing front. Maximum soil water content and downward moisture migration take place in the end of winter and during the spring, starting with snowmelt and seasonal ice thawing. However, the upper part of the active layer remained much drier than saturation over the simulation period (2018–2019). From the hydrological balance analysis, it is deduced that the studied soil profile receives some inflow of groundwater during spring and summer. Results contribute to better understand the Andean cryo-lithozone and may be a reference to study other rock glaciers using little and accessible equipment.