Ground temperature variations in a talus slope influenced by permafrost: a comparison of field observations and model simulations

Abstract

Abstract.Variations in surface and near-surface ground temperatures (GST) dominate the evolution of the ground thermal regime over time and represent the upper boundary condition for the subsurface. Focusing on the Lapires talus slope in the south-western part of the Swiss Alps, which partly contains massive ground ice, and using a joint observational and modelling approach, this study compares and combines observed and simulated GST in the proximity of a borehole. The aim was to determine the applicability of the physically based subsurface model COUP to accurately reproduce spatially heterogeneous GST data and to enhance its reliability for long-term simulations. The reconstruction of GST variations revealed very promising results, even though twodimensional processes like the convection within the coarse-blocky sediments close to the surface or ascending air circulation throughout the landform ("chimney effect") are not included in the model. For most simulations, the model bias revealed a distinct seasonal pattern mainly related to the simulation of the snow cover. The study shows that, by means of a detailed comparison of GST simulations with ground truth data, the calibration of the upper boundary conditions -which are crucial for modelling the subsurface -could be enhanced.

Estimating Permafrost Distribution in the Maritime Southern Alps, New Zealand, Based on Climatic Conditions at Rock Glacier Sites

“…Brazier et al, 1998), facilitating the existence of permanently frozen ground at lower altitudes. Establishing the underlying climatic controls would require physical models that include all energy fluxes above maritime permafrost occurrences (e.g., Luetschg et al, 2008;Staub et al, 2015). Such energy balance studies, accompanied by long-term ground temperature, surface temperature, and snow cover monitoring, would further allow exploring the effect of maritime snow conditions on long-term subsurface temperature evolution.…”

Soil Moisture Data for the Validation of Permafrost Models Using Direct and Indirect Measurement Approaches at Three Alpine Sites

“…The modeled processes of water infiltration into the frozen soil were implemented and described by Stähli et al (1996) and a complete description and test of water infiltration is given by Scherler et al (2010). The model has already been used in many studies focussing on various purposes, including soil moisture (e.g., Noroozvalashedi et al, 2012;Wu and Jansson, 2013) and permafrost (Engelhardt et al, 2010;Marmy et al, 2013Marmy et al, , 2015Scherler et al, 2013Scherler et al, , 2014Staub et al, 2015). Other studies specifically applied the COUP model to simulate the soil moisture in frozen grounds (Scherler et al, 2010;Xarpell et al, 2010;Python, 2015).…”

“…The model has already shown good ability to simulate ground temperature regimes, precise snow conditions and soil moisture. However limitations exist regarding 2-or 3-dimensional processes, such as energy transfer by subsurface convection in blocky surface layers (Scherler et al, 2014) or 2D air circulation in ventilated talus slopes (Staub et al, 2015).…”

“…The COUP model is currently used in permafrost research for process modeling and long-term transient modeling of the permafrost evolution (Scherler et al, 2010(Scherler et al, , 2014 as well as for sensitivity studies (Engelhardt et al, 2010;Marmy et al, 2013;Staub et al, 2015), whereas the 4PM was selected for its ability to determine the spatial variability of ice content in the ground, which was found to be one of the key factors controlling the sensitivity of mountain permafrost to climate changes (e.g., Harris et al, 2009;Scherler et al, 2013).…”

Introduction to the special issue of Geographica Helvetica: "Mapping, measuring and modeling in geomorphology"

“…monitoring-based data acquisition) and the development of numerical models to predict the occurrence and rate of such processes. Staub et al (2015) monitor ground surface and near-surface temperatures within talus slopes in mountain environments and thereafter compare observed with modelled data. The outcome of this work has allowed them to predict spatial and temporal variations of permafrost in sensitive mountain environments under a range of ongoing and future climate change scenarios.…”