Spectral induced polarization measurements at different mountain permafrost landforms with varying ice contents

SUMMARY Understanding the spatial variability of ice content in frozen ground is key to design adequate measures to manage different ecosystems in frame of climate change. To-date investigations in frozen ground require the analysis of borehole data or the collection of multiple geophysical data. Here we propose the use of spectral induced polarization (SIP) as a technique that provides in quasi real-time information about changes in ice content in the subsurface. We demonstrate that exploring the frequency dependence in electrical conductivity and polarization (capacitive) properties in the frequency range between 0.1 and 75 Hz provides direct information about their relative variations in ice content. Our study is based on measurements conducted at nine representative permafrost sites in the European Alps with varying landforms and ice contents, including a pure ice and an unfrozen reference. We use the phase frequency effect ($\phi {\rm FE}$) parameter as a parameter describing both the amplitude of the polarization and its frequency dependence to compare the response associated to the different sites. Our results show the lowest $\phi {\rm FE}$ in sites with low ice content, while increases in this parameter are associated with higher ice content. We evaluate the correlation between SIP parameters and validation ground ice contents for all sites and observe a clear correlation between $\phi {\rm FE}$ and volumetric ice content. The $\phi {\rm FE}$ results exhibit distinct landform-specific patterns, with the highest values found in rock glaciers, intermediate values in frozen talus slopes, lower values in bedrock permafrost and the lowest in unfrozen talus slopes, reducing interpretation ambiguities in electrical resistivity results for assessing ice content.