The ice content of palsas and peat plateaus, estimated with high-frequency induced polarisation

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Palsas and peat Pleateaus are specific landforms that are shaped by processes in permanently frozen ground. They cover extensive areas in subarctic regions in Canada, European Russia, Siberia and Northern Fennoscandia. The landforms store a significant amount of Carbon and Nitrogene, which might be released into Earth’s atmosphere by global warming. Therefore, they may contribute to feedback mechanisms and accelerate climate change. Ice content in frozen ground is an essential quantitiy that controls how sensitive frozen ground is to a temperature increase. Ice content is also a key parameter for any numerical simulation trying to predict the degradation of palsas and peat plateaus under climate change conditions. At the same time, ice content and its spatial variation is difficult to measure at a reolution required to understand the details of degradation processes. In this project, we will apply an innovative geophysical method, high-frequency induced polarisation, to determine ice content under specific palsas and peat plateaus in Fennoscandia. The method determines the frequency-dependent electrical properties (electrical conductivity and permittivity) in a frequency range between 1Hz and 250kHz. Since the electric permittivity of frozen water exhibits a characteristic behavior in that frequency range, the method is suitable to estimate ice content. Recently, it was demonstrated that ice content estimation is possible und real conditions at the field scale. We will carry out measurements at four selected in Northern Norway and determine ice content and its spatial variation. At one site, we will carry out repetitive surveys in order to capture the variation of subsurface conditions with time, which is known to be quite rapid. Our results will provide a basis to advance the prediction of the fate of palsas and peat plateaus in the context of global warming. The data will constitute a step towards closing the gap between the requirements of numerical simulation, and the lack of actual ground information. The studied sites in Fennoscandia are representative of large subarctic regions, and therefore the contributions to the understanding of permafrost degradation will be of global relevance.