A. Godio

A. Santilano

A. Vergnano

F. Pace

G. Romano

I. Baneschi

L. Capozzoli

L. Franceschi

M. Doveri

M. Menichini

English

PORTO@iris (Publications Open Repository TOrino - Politecnico di Torino)

11 February 2024POLITECNICO DI TORINORepository ISTITUZIONALEHydro-Geophysical characterization of the arctic environment, Ny-Ålesund (Svalbard) / Vergnano, A.; Pace, F.; Romano,G.; Godio, A.; Santilano, A.; Capozzoli, L.; Baneschi, I.; Franceschi, L.; Menichini, M.; Doveri, M.. - ELETTRONICO. -(2023). (Intervento presentato al  convegno The 41st National Conference of the GNGTS tenutosi a Bologna nel 7-9Febbraio 2023) [10.13120/2tf2-1j75].OriginalHydro-Geophysical characterization of the arctic environment, Ny-Ålesund (Svalbard)Publisher:PublishedDOI:10.13120/2tf2-1j75Terms of use:Publisher copyright(Article begins on next page)This article is made available under terms and conditions as specified in the  corresponding bibliographic description inthe repositoryAvailability:This version is available at: 11583/2979387 since: 2023-06-15T10:19:00ZGNGTSGruppo Nazionale di Geofisica della Terra SolidaBOOK OF ABSTRACTS  41st NATIONAL CONFERENCE7-9 FEBRUARY 2023BOLOGNA22° CONVEGNO NAZIONAL ESession 3.2 ___ GNGTS 2023Hydro-Geophysical characterization of thearctic environment, Ny-Ålesund (Svalbard)A. Vergnano1, F. Pace1, G. Romano2, A. Godio1, A. Santilano3, L. Capozzoli4, I.Baneschi3, L. Franceschi3, M. Menichini3, M. Doveri31 Department of Environment, Land and Infrastructure Engineering (DIATI), Politecnico di Torino,Torino, Italy2 Department of Earth and GeoEnvironmental sciences, University of Bari Aldo Moro, Bari, Italy3 Institute of Geosciences and Earth Resources - National Research Council (IGG-CNR), Pisa, Italy4 Institute of Methodologies for Environmental Analysis-National Research Council (IMAA-CNR),Potenza, ItalyIntroductionThe Arctic research station in Ny-Ålesund (Svalbard, Norway) is an international base for severalresearch fields. It shines for hydrogeological studies, being situated in a little basin in which theentire water cycle from glaciers to sea can be studied in an area of a few kilometers squared.Hydrogeological studies are easily linked to other research fields, such as geophysics,geochemistry, geomorphology, and biology, making multidisciplinary research possible andvaluable.Few geophysical campaigns have been carried out in Svalbard (Ross et al. 2007; Kasprzak et al.2017). The Ny-Ålesund area lacks geophysical subsoil characterization as well, even if someexploratory drillings were made in the first half of the 20th century for coal mining purposes. Thearea is geophysically interesting and challenging, because of the presence of permafrost, springs,and old coal mines; spatial heterogeneity in geophysical properties is also expected because ofgeologic faults and geomorphologic features linked to the past ice movement. To explore thesubsoil in arctic tundra environments, past research has successfully employed two geophysicaltechniques, Electrical Resistivity Tomography (ERT) and Ground Penetrating Radar (GPR) (Leger etal., 2017; Hauck and Kneisel, 2008, Sjöberg et al. 2015), which allowed the researchers to detectfrozen/unfrozen areas and to distinguish the active layer from permafrost.The ICEtoFLUX project and the geophysical campaignsThe research project ICEtoFLUX (“HydrologIcal changes in ArctiC Environments and water-drivenbiogeochemical FLUXes”) was financed by Arctic Research Program “PRA” 2022-2024 and dealswith the hydrological characterization of the arctic environment. The project goal is to quantifythe hydrological dynamics and the interactions between the glacier and the river basin with amultidisciplinary approach that includes hydrological, geochemical, microbiological andSession 3.2 ___ GNGTS 2023geophysical measures. The long-term aim is to understand the temporal evolution of thepermafrost and the effects of climate change on the sub-permafrost aquifer.The geophysical surveys took place in the summer of 2022 and focused on ERT and GPRacquisitions. The investigated areas were the Bayelva basin (on the left in Fig. 1) and the minearea (on the right). In the eastern part of the investigated area within the Bayelva basin,geophysical acquisitions overlapped the alignment of four piezometers (2 m deep) realized by theICEtoFLUX project for the physical-chemical and hydrological monitoring of the active layer. TheERT profiles were acquired with 10 m of spacing between the electrodes in order to characterizethe deep features, such as the permafrost thickness and the sub-permafrost aquifer. Moreover, 1m of electrode spacing was adopted in specific areas to inspect, with higher resolution, the activelayer and the supra-permafrost aquifer. Around 8.3 km of electric lines were carried out. TheseERT profiles are shown in Fig. 1 (yellow lines).GPR measurements with 40 MHz and 400 MHz antennas were carried out in the area of theClimate Change Tower, close to the four piezometers aforementioned, for a total of around 2 kmof GPR lines. Coincident ERT and GPR profiles with different acquisition settings were designedalong the line of piezometers in order to correlate the geophysical results with the geochemicaldata and water table information coming from the piezometer monitoring (see Fig. 1).Fig. 1 – Map of the geophysical campaign carried out in Ny-Ålesund (Svalbard) in the summer of 2022. The ERTprofiles are plotted in yellow and the GPR profiles in green. The investigated area on the west is the Bayelva riverbasin, while that on the east is the former mine. The piezometers are indicated with white numbers. The red cross isa recent borehole (48.5 m deep). The blue circle indicates the position of a spring (Haldorsen and Heim, 1999).Session 3.2 ___ GNGTS 2023ResultsThe ERT and GPR profiles along the piezometer #1 here presented were acquired with 1 m ofelectrode spacing and 400 MHz of frequency.The electric data inversion was carried out using the software Res2dinvx64 Version 4.0 (GeotomoSoftware, Loke and Barker, 1996). The inversion results including topography gave a misfit of3.9%; the resistivity model is plotted in Fig. 2a. The dashed line in figure 2a shows the interfacebetween the active layer, which is electrically less resistive (around 400 Ohm m), and theunderlying layers that can be associated to the permafrost (ρ > 1.0 kOhm m). A more detailedreconstruction of the transition between the active layer and the permafrost is retrieved by theGPR results, of the B-scan acquired along the same profile (Fig. 2b). In the radargram, thecontinuity of the main reflector, located at a depth of approximately 2 meters below the groundsurface, clearly marks the top of the permafrost (black dashed line in Fig. 2b), allowing todelineate its morphology.The reliability of the response of ERT and GPR methods and their complete integrability istestified by the good agreement of the results. Overlapping the ERT and the GPR profiles in Fig. 2,the top of the permafrost (black dashed line in figure 2a exactly falls in the transition zonebetween the less resistive layer (active layer) and the more resistive one (permafrost).The resistivity distribution and radargrams of the other ERT and GPR lines, which investigateddeeper subsoil structures, showed a more complex framework with strong local heterogeneities,which can be explained by hydrological evidence suggested by the piezometers monitoring interms of very different water quantity and physical-chemical features (electrical conductivity andtemperature) in space and time.These results will be further interpreted along with hydrological and geochemical data, withadditional geological/geomorphological information provided by the project partners.ConclusionThis novel characterization of the subsurface properties of a vast area in Ny-Ålesund providesmany geophysical models useful to better understand the hydrogeology and hydrologicalprocesses of the area. Thanks to the 1m spaced ERT measurements and 400 MHz GPR, the activelayer and its local discontinuities are correlated to the time series of piezometers. With the other(10m spaced) ERT surveys, deeper frozen permafrost areas are distinguished from unfrozenpermafrost zones, allowing to map supra- and sub-permafrost aquifers. The preliminaryinterpretation of the ERT section obtained by commercial software will be updated by using theopen-source software ResIPy for a more quantitative interpretation of the petrophysics of theactive layer and permafrost. Correlations with climate will be developed in the piezometers area,and future time-lapse geophysical measurements will map yearly or seasonal changes in thepermafrost in Ny-Ålesund.Session 3.2 ___ GNGTS 2023Fig. 2 a) the resistivity model of the ERT crossing the piezometer #1 (the northernmost in Fig. 1, 1 m electrodespacing); b) the GPR result for the piezometer line (400 MHz antenna). The meaning of the black dashed lines isexplained in the main text.ReferencesHaldorsen, S. and Heim, M. (1999) ‘An arctic groundwater system and its dependence uponclimatic change: an example from Svalbard’, Permafrost and Periglacial Processes, 10(2), pp.137–149. Available at:https://doi.org/10.1002/(SICI)1099-1530(199904/06)10:2<137::AID-PPP316>3.0.CO;2-#.Hauck, C. and Kneisel, C. (2008) Applied geophysics in periglacial environments. Cambridge, UK ;New York: Cambridge University Press.Kasprzak, M. et al. (2017) ‘On the potential for a bottom active layer below coastal permafrost:the impact of seawater on permafrost degradation imaged by electrical resistivity tomography(Hornsund, SW Spitsbergen)’, Geomorphology, 293, pp. 347–359. Available at:https://doi.org/10.1016/j.geomorph.2016.06.013.Leger, E. et al. (2017) ‘Quantification of Arctic Soil and Permafrost Properties UsingGround-Penetrating Radar and Electrical Resistivity Tomography Datasets’, IEEE Journal ofSelected Topics in Applied Earth Observations and Remote Sensing, 10(10), pp. 4348–4359.Available at: https://doi.org/10.1109/JSTARS.2017.2694447.Loke, M.H. and Barker, R.D. (1996) ‘Rapid least-squares inversion of apparent resistivitypseudosections by a quasi-Newton method1’, Geophysical Prospecting, 44(1), pp. 131–152.Available at: https://doi.org/10.1111/j.1365-2478.1996.tb00142.x.Session 3.2 ___ GNGTS 2023Ross, N. et al. (2007) ‘Internal Structure of Open System Pingos, Adventdalen, Svalbard: The Useof Resistivity Tomography to Assess Ground-Ice Conditions’, Journal of Environmental andEngineering Geophysics, 12(1), pp. 113–126. Available at: https://doi.org/10.2113/JEEG12.1.113.Sjöberg, Y. et al. (2015) ‘Geophysical mapping of palsa peatland permafrost’, The Cryosphere,9(2), pp. 465–478. Available at: https://doi.org/10.5194/tc-9-465-2015.Corresponding author: andrea.vergnano@polito.it

Hydro-Geophysical characterization of the arctic environment, Ny-Ålesund (Svalbard)

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Hydro-Geophysical characterization of the arctic environment, Ny-Ålesund (Svalbard)

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