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Electrical Resistivity Tomography surveys to characterize Arctic permaFROST (ERTAFROST)
IADC_id: 30
active
Call year: 2015
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The Arctic region has undergone rising air temperature over the past half-century. In turn, permafrost temperatures have been increasing and active layer depths have thickened in many regions. Thawing of permafrost may result in land surface subsidence. This land surface subsidence, also called thermokarst, alters local hydrology and can potentially influence the rate and the magnitude of permafrost carbon loss and subsequent greenhouse gas emissions, possibly accelerating future climate change. Measurement of the ice content in permafrost is important to understanding the evolution of periglacial landforms, the ecology of permafrost regions, the impact of permafrost thawing on the global carbon inventory and the risk to infrastructure due to frost heave and thaw subsidence. Classical indicators of air temperature, surficial geology and aerial or satellite mapping give only large-scale classification, whereas coring and excavation are highly localized. Geophysical methods have the potential to fill a critical gap between aerial imaging and core sampling. Their main strength has been to identify frozen vs. unfrozen ground, for example, delineating the active layer and the base of permafrost. In particular, geophysical methods such as Electrical Resistivity Tomography (ERT), Electromagnetic (EM) induction methods and Ground Penetrating Radar (GPR) could be powerful and relatively inexpensive tools for effectively map the extent of ice wedges, ice lenses, massive ice, and talik (a layer of year-round unfrozen ground within a permafrost area). Thus, we propose the joint application of such geophysical techniques in some sites in the Arctic, including Ny-Ålesund and Janssonhaugen, western Svalbard (78°10'46''N, 16°28'01''E, 270 m ASL), where a deep borehole (102 m deep) was drilled for measurement of thermal profiles in permafrost, as part of the European Fourth Framework project PACE (Permafrost and Climate in Europe). In this site, permafrost thickness is estimated as approximately 220 m. In addition, in the study areas, electrode arrays could be permanently installed along chosen profiles. This could allow repeated DC tomography measurements at various times of the year, providing information on the spatial and temporal characterization of the active layer in permafrost. The proposed ERT surveys, coupled with GPR and EM measurements, could provide useful information to current knowledge of permafrost conditions in Svalbard.
National/International Cooperation:
ENEA - Agenzia nazionale per le nuove tecnologie, l’energia e lo sviluppo economico sostenibile - Centro Ricerche Casaccia - Roma; Università degli Studi di Bari "Aldo Moro" - Dipartimento di Scienze della Terra e Geoambientali; rn
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