Detailed detection of fast changes in the active layer using quasi-continuous electrical resistivity tomography (Deception Island, Antarctica)

• Main Authors: Farzamian, Mohammad, Vieira, Gonçalo, Monteiro Santos, Fernando A., Yaghoobi Tabar, Borhan, Hauck, Christian, Paz, Maria Catarina, Bernando, Ivo, Ramos, Miguel, Pablo, Miguel A.
• Format: Text
• Language: English
• Published: 2019
• Subjects: Crater Lake; Deception Island; Active layer monitoring; Antarc*; Antarctica; Circumpolar Active Layer Monitoring Network; permafrost
• Online Access: https://doi.org/10.5194/tc-2019-39; https://www.the-cryosphere-discuss.net/tc-2019-39/

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 2D 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 Network (CALM-S) I) to evaluate the feasibility of installing and running autonomous ERT monitoring stations in remote and extreme environments such as Antarctica, II) to monitor subsurface freezing and thawing processes on a daily and seasonal basis and to map the spatial and temporal variability of thaw depth, and III) to study the impact of short-lived extreme meteorological events on active layer dynamics. Measurements were repeated at 4-hour intervals during a full year, enabling the detection of seasonal trends, as well as short-lived resistivity changes reflecting individual meteorological events. The latter is important to distinguish 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 set-up can successfully map spatiotemporal thaw depth variability along the experimental transect at very high temporal resolution. Largest resistivity change took place during the freezing season in April when low temperatures induce an abrupt phase change in the active layer in the absence of a snow cover. The seasonal thawing of the active layer is associated with a slower resistivity decrease during October due to the presence of a 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 set-up which enables to detect fast changes in the active layer during short-lived extreme meteorological events. Based on this first complete year-round A-ERT monitoring data set in Deception Island, we believe that this system shows high potential for autonomous applications in remote and harsh polar environments such as Antarctica.