Detailed detection of active layer freeze–thaw dynamics using quasi-continuous electrical resistivity tomography (Deception Island, Antarctica)

Abstract

Abstract. Climate-induced warming of permafrost soils is a global phenomenon, with regional and site-specific variations which are not fully understood. In this context, a 2-D automated electrical resistivity tomography (A-ERT) system was installed for the first time in Antarctica at Deception Island, associated to the existing Crater Lake site of the Circumpolar Active Layer Monitoring – South Program (CALM-S) – site. This setup aims to (i) monitor subsurface freezing and thawing processes on a daily and seasonal basis and map the spatial and temporal variability in thaw depth and to (ii) study the impact of short-lived extreme meteorological events on active layer dynamics. In addition, the feasibility of installing and running autonomous ERT monitoring stations in remote and extreme environments such as Antarctica was evaluated for the first time. Measurements were repeated at 4 h intervals during a full year, enabling the detection of seasonal trends and short-lived resistivity changes reflecting individual meteorological events. The latter is important for distinguishing between (1) long-term climatic trends and (2) the impact of anomalous seasons on the ground thermal regime. Our full-year dataset shows large and fast temporal resistivity changes during the seasonal active layer freezing and thawing and indicates that our system setup can resolve spatiotemporal thaw depth variability along the experimental transect at very high temporal resolution. The largest resistivity changes took place during the freezing season in April, when low temperatures induce an abrupt phase change in the active layer in the absence of snow cover. The seasonal thawing of the active layer is associated with a slower resistivity decrease during October due to the presence of snow cover and the corresponding zero-curtain effect. Detailed investigation of the daily resistivity variations reveals several periods with rapid and sharp resistivity changes of the near-surface layers due to the brief surficial refreezing of the active layer in summer or brief thawing of the active layer during winter as a consequence of short-lived meteorological extreme events. These results emphasize the significance of the continuous A-ERT monitoring setup which enables detecting fast changes in the active layer during short-lived extreme meteorological events. Based on this first complete year-round A-ERT monitoring dataset on Deception Island, we believe that this system shows high potential for autonomous applications in remote and harsh polar environments such as Antarctica. The monitoring system can be used with larger electrode spacing to investigate greater depths, providing adequate monitoring at sites and depths where boreholes are very costly and the ecosystem is very sensitive to invasive techniques. Further applications may be the estimation of ice and water contents through petrophysical models or the calibration and validation of heat transfer models between the active layer and permafrost.

An overview of multimethod imaging approaches in environmental geophysics

“…Yet, measuring the geological and hydrological properties and processes of those permafrost environments, both in the Arctic and in Alpine settings, is difficult due to inaccessibility, sensitive ecosystems, and the harsh environmental conditions, which is causing a data gap associated with those properties and processes. Geophysical techniques are known to complement point observations and to assess the intermediate depths (1 -10's of m) at spatial and temporal resolutions critical to understanding the impact of climate change on permafrost hydrological dynamics (Kneisel et al, 2008;Dafflon et al, 2017;Minsley et al, 2012;Farzamian et al, 2020). This is because electrical and seismic properties of soils and rocks, particularly at temperatures below freezing, are highly sensitive to variations in temperature and thus ice content (Wu et al, 2017;Dou et al, 2016).…”

Identifying mountain permafrost degradation by repeating historical ERT-measurements

“…Compared to regular and continuous measurements, for example by automated ERT systems (e.g. Farzamian et al, 2020;Hilbich et al, 2011;Supper et al, 2014), this is a cost-effective application that can provide a high gain in knowledge. Applying a direct comparison of historical and re-measured ERT profiles, our study aims to identify warming induced permafrost degradation on periglacial landforms in two regions of the European Alps over the past decade.…”

Active Layer and Permafrost Investigations Using Geophysical and Geocryological Methods—A Case Study of the Khanovey Area, Near Vorkuta, in the NE European Russian Arctic

“…Geophysical surveys, as ground-penetrating radar (GPR) and electrical resistivity tomography (ERT), have been extensively used to study active layer and permafrost features. However, although the GPR technique performs well only for low clay contents in the subsoil (e.g., Arcone and Delaney, 1982;Palacky, 1988;Delaney et al, 1990;Doolittle et al, 1990;Arcone et al, 1998;Hinkel et al, 2001), the ERT method enables the characterization of both the active layer and the underlying permafrost for almost all soil textures (e.g., Kasprzak, 2015;Seppi et al, 2015;Kasprzak et al, 2017;Léger et al, 2017;Picotti et al, 2017;Francese et al, 2019;Farzamian et al, 2020;Isaev et al, 2020). In addition, electromagnetic induction methods have been successfully used to estimate the thickness of permafrost (e.g., Isaev et al, 2020).…”