Internal structure and palsa development at Orravatnsrustir Palsa Site (Central Iceland), investigated by means of integrated resistivity and ground-penetrating radar methods

The natural cyclical development of palsas makes it difficult to use visible signs of decay as reference points for environmental change. Thus, to determine the actual development stage of a palsa, investigations of the internal structure are crucial. Our study presents 2-D and 3-D electrical resistivity imaging (ERI) and 2-D ground-penetrating radar (GPR) results, measurements of surface and subsurface temperatures, and of the soil matric potential from Orravatnsrustir Palsa Site in Central Iceland. By a joint interpretation of the results, we deduce the internal structure (i.e., thickness of thaw zone and permafrost, ice/water content) of five palsas of different size and shape. The results differentiate between initial and mature development stages and show that palsas of different development stages can exist in close proximity. While internal characteristics indicate undisturbed development of four palsas, one palsa shows indications of environmental change. Our study shows the value of the multimethod geophysical approach and introduces measurements of the soil matric potential as a promising method to assess the current state of the subsurface.

Automated summary

Our study used a multi-method geophysical approach to investigate the internal structure of palsas in Central Iceland, showing differences between initial and mature development stages. We also introduced measurements of the soil matric potential as a promising method to assess the current state of the subsurface, highlighting the importance of this approach in understanding environmental changes.