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

Abstract

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 Orravatnsrústir 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.

Long‐Term, High‐Resolution Permafrost Monitoring Reveals Coupled Energy Balance and Hydrogeologic Controls on Talik Dynamics Near Umiujaq (Nunavik, Québec, Canada)

“…Zhang et al, 2014), Eurasia (Iwahana et al, 2012;Wünnemann et al, 2008;Y. Zhang et al, 2021), Scandinavia (Emmert & Kneisel, 2021;Saemundsson et al, 2012;Westin & Zuidhoff, 2001), and parts of northern Europe (Pissart, 2000). The observations presented in this study provide field-based insights into the processes that govern how these features likely will change over time in unsaturated environments dominated by mineral soils (gelisols), which comprise a large fraction of the surficial soils of the Arctic and subarctic, particularly in the continuous and discontinuous permafrost zones (Tarnocai et al, 2009).…”

“…Lithalsas, such as the one considered here, are characterized by a negligible organic matter cover (i.e., in areas outside of peatlands), perennially unsaturated conditions (with the exception of short periods of time following spring snowmelt or high magnitude rainfall events), and snow cover redistribution to prevent the insulation of the top of the mound (Harris, 1993; Wolfe et al., 2014). These raised periglacial landforms located in non‐wetland environments have been documented worldwide, such as Canada (Allard et al., 1986, 1996; Calmels & Allard, 2008; Deslauriers et al., 2021; Paul et al., 2021; Wolfe et al., 2014; Wolfe & Morse, 2017; Y. Zhang et al., 2014), Eurasia (Iwahana et al., 2012; Wünnemann et al., 2008; Y. Zhang et al., 2021), Scandinavia (Emmert & Kneisel, 2021; Saemundsson et al., 2012; Westin & Zuidhoff, 2001), and parts of northern Europe (Pissart, 2000). The observations presented in this study provide field‐based insights into the processes that govern how these features likely will change over time in unsaturated environments dominated by mineral soils (gelisols), which comprise a large fraction of the surficial soils of the Arctic and subarctic, particularly in the continuous and discontinuous permafrost zones (Tarnocai et al., 2009).…”

Best practices for using electrical resistivity tomography to investigate permafrost

“…Note that total percentages exceed 100%, as some studies presented the results of more than one type of survey. 3D surveying has been used in permafrost research to examine heterogeneous 3D landforms such as ice wedge polygons, 43 rock glaciers, 145 and palsas 146 . 3D approaches also have the advantage of being able to estimate permafrost volume 134,143 …”

“…3D surveying has been used in permafrost research to examine heterogeneous 3D landforms such as ice wedge polygons, 43 rock glaciers, 145 and palsas. 146 3D approaches also have the advantage of being able to estimate permafrost volume. 134,143 7.4 | 3D surveying: a case study from Switzerland ERT's utility in estimating permafrost distribution and quantifying changes in frozen bedrock.…”

An overview of multimethod imaging approaches in environmental geophysics

“…Many studies have employed multiple geophysical methods to image the characteristics, and derive the formation and thermo-hydrological functioning of permafrost environments. For instance, Emmert and Kneisel (2021) combine ERT and GPR data to investigate the internal structure of palsas, i.e., peat mounds underlain by permafrost, in central Iceland. Based on their data they could assign the studied palsas to different development stages, highlighting recent changes in environmental conditions that impacted and changed the trajectory of palsa development.…”