Ninth International Conference on Permafrost ... - IARC Research

Preparatory Work for a Permanent Geoelectrical Measurement Station forPermafrost Monitoring at the Hoher Sonnblick, AustriaMichael AvianInstitute of Remote Sensing and Photogrammetry, Graz University of Technology, AustriaAndreas Kellerer-PirklbauerInstitute of Geography and Regional Science, University of Graz, AustriaIntroductionAlexander RömerDepartment of Geophysics, Geological Survey of AustriaRobert SupperDepartment of Geophysics, Geological Survey of AustriaThe thermal and distributional state of permafrost inalpine environments is widely discussed in recent times dueto hazardous geomorphic events threatening infrastructure,tourism, or residents. Subterrain processes in environmentsinfluenced by permafrost degradation might cause severeproblems to alpine infrastructure (e.g., alpine huts, cablecars).However, such processes are not fully understood sofar.The meteorological observatory at the top of the HoherSonnblick (3106 m a.s.l., 47°03′N, 12°57′E, Fig.1) has facedproblems of permafrost degradation since the 1990s, leadingto intense protection activities during the last years. Thisobservatory has been operating continuously since 1886,presenting one of the longest records of meteorological datain the entire alpine arc. Data from this observatory indicatea rise of the mean annual air temperature (MAAT) by 1.6°Csince 1886 (Auer et al. 2002), which is substantially abovethe global average of 0.74°C (IPCC 2007). The summit areaof Hoher Sonnblick is stage of several investigations thatfocus on the relationship between recent climate change andalterations of a mountain permafrost body in a mountain topdetritus environment. One of the most important projectsinvestigates the thermal state of the uppermost 20 m of thesummit area monitored at three boreholes—each equippedwith 25 temperature sensors—aligned along a south-facingslope (Fig. 2). These three boreholes are the first permafrostboreholes installed within Austria and will therefore deliverimportant temperature data relevant for the mountainpermafrost distribution of the Eastern Alps. However, notemperature data are published so far (Staudinger & Schöner2008, pers. com.).In order to get more information about the spatialdistribution and temporal changes of the subsurfacetemperature conditions within shorter periods at HoherSonnblick, the installation of a permanent geoelectricalmeasurement profile is currently carried out. Logistical andtechnical information regarding the relevant preparatorywork is presented here.MethodsGeoelectrical investigations of areas underlain bypermafrost have been carried out at numerous study areasFigure 1. Location of the study area Hoher Sonnblick withinAustria, as well as the Austrian part of the European Alps (grey).in the Alps (e.g., Hauck et al. 2003, Kneisel 2004). Hilbichet al. (2008) report from repeated electrical resistivitytomography (ERT) measurements coupled with boreholetemperature data at Schilthorn (Switzerland), therebyfocusing on active layer dynamics. The application of ERTallows the determination of specific electrical resistivitywithin the subsurface structure. This parameter is mainlydependent on porosity, water saturation, conductivity of porefluid and clay content. Minor influence is given by particleshape and pore geometry.Two measurements have been carried out manually sofar (August 2006 and March 2007) but are planned to beremote controlled in the next project stage. So this test stageverifies the capability of the GEOMON4D for remotecontrolledmeasurements of geoelectric pseudo-sections.Several requirements have to be considered: high-resolutionmeasurements, possibility of snapshots of the underground,high reliability, and quick availability of data.Preparatory Work and OutlookThe first ERT measurements, consisting of 16 electrodesat a spacing of 1 m, were carried out in August 2006 witha Sting RI (AGI) multi-electrode and the GEOMON4Dsystem for comparison. Within the second campaign inMarch 2007, a permanent profile with 41 electrodes at 0.5 mspacing and 20 m length was installed near the profile of thefirst campaign. Three thousand measurements were carriedout, each sampled for 1000 times. Furthermore, a lightning11