New multi-phase thermo-geophysical model: Validate ERT-monitoring & assess permafrost evolution in alpine rock walls (Zugspitze, German/Austrian Alps)
Authors: Schroeder Tanja , Scandroglio Riccardo , Stammberger Verena , Wittmann Maximilian , Krautblatter Michael 
Published: March 2020

&lt;p&gt;&lt;span&gt;In the context of climate change, permafrost degradation is a key variable in understanding rock slope failures in high mountain areas. Permafrost degradation imposes a variety of environmental, economic and humanitarian impacts on infrastructure and people in high mountain areas. Therefore, new high-quality monitoring and modelling strategies are needed.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;Electrical Resistivity Tomography (ERT) is the predominant permafrost monitoring technique in high mountain areas. Its high temperature sensitivity for frozen vs. unfrozen conditions, combined with the resistivity-temperature laboratory calibration on Wettersteinkalk (Zugspitze) (Krautblatter et al. 2010) gives us quantitative information on site-specific rock wall temperatures (Magnin &lt;em&gt;et al.&lt;/em&gt; 2015). Long-term ERT-Measurements (2007/2014 &amp;#8211; now) were taken at the Kammstollen along the northern Zugspitze rock face. Two high-resistivity bodies along the investigation area reach resistivity values &amp;#8805;10&lt;sup&gt;4.5&lt;/sup&gt;&lt;/span&gt;&amp;#937;&lt;span&gt;m (&lt;/span&gt;&lt;span&gt;&amp;#8764;&lt;/span&gt;&lt;span&gt;&amp;#8722;0.5 &lt;/span&gt;&lt;span&gt;&amp;#176;&lt;/span&gt;&lt;span&gt;C), indicating frozen rock, displaying a core section with resistivities &amp;#8805;10&lt;sup&gt;4.7&lt;/sup&gt;&lt;/span&gt;&amp;#937;&lt;span&gt;m (&lt;/span&gt;&lt;span&gt;&amp;#8764;&lt;/span&gt;&lt;span&gt;&amp;#8722;2 &lt;/span&gt;&lt;span&gt;&amp;#176;&lt;/span&gt;&lt;span&gt;C) (Krautblatter &lt;em&gt;et al.&lt;/em&gt;, 2010). We can differentiate seasonal variability, seen by laterally aggrading and degrading marginal sections (Krautblatter &lt;em&gt;et al.&lt;/em&gt;, 2010) and singular effects due to environmental factors and extreme weather events.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;Here, we present a new local high-resolution numerical, process-orientated thermo-geophysical model (TGM) for steep permafrost rock walls. The model links apparent resistivities, the ground thermal regime and meteorological forcings as seasonality and long-term climate change to validate the ERT and project future conditions. The TGM comprises a surface energy balance model, conductive energy transport, turbulent and seasonal heat fluxes (sensible, latent, melt and rain heat fluxes) including phase-change, as well as a multi-phase rock wall composition.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;Finally, we can reproduce the natural temperature field in the rock wall, assess the spatial-temporal permafrost evolution in alpine rock walls, validate the ERT measurements via the new TGM and the applicability of the laboratory derived resistivity-temperature relationship by Krautblatter et al. (2010) for natural rock-wall conditions.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;&amp;#160;&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;Krautblatter, M., Verleysdonk, S., Flores-Orozco, A. &amp; Kemna, A. (2010): Temperature- calibrated imaging of seasonal changes in permafrost rock walls by quantitative electrical resistivity &lt;/span&gt;&lt;span&gt;tomography&lt;/span&gt;&lt;span&gt; (Zugspitze, German/Austrian Alps). &lt;em&gt;J. Geophys. Res. &lt;/em&gt;115: F02003.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;&lt;span&gt;Magnin, F., Krautblatter, M., Deline, P., Ravanel, L., Malet, E., Bevington, A. (2015): Determination of warm, sensitive permafrost areas in near-vertical rockwalls and evaluation of distributed models by electrical resistivity tomography. &lt;em&gt;J. Geophys. Res. Earth Surf.&lt;/em&gt;, 120, 745-762.&lt;/span&gt;&lt;/p&gt;