Ninth International Conference on Permafrost ... - IARC Research

Temperatures in Alpine Rock Walls During the Warm Winter 2006–2007 in Austriaand Its Significance for Mountain Permafrost: Preliminary ResultsAndreas Kellerer-PirklbauerInstitute of Geography and Regional Science, University of Graz, AustriaMichael AvianInstitute of Remote Sensing and Photogrammetry, Graz University of Technology, AustriaGerhard Karl Lieb, Matthias RieckhInstitute of Geography and Regional Science, University of Graz, AustriaIntroductionIn a large part of Europe temperatures during autumnand winter 2006–2007 reached a record high. The autumnof 2006 (Sept., Oct., and Nov.) was more than 3°C warmerfrom the northern side of the Alps to southern Norwayif compared to the 1971–2000 average (WMO 2007).The extreme temperature anomaly also affected the highmountains of Austria and caused record temperature valuesat the Sonnblick Observatory located in the high mountainsof central Austria (3106 m a.s.l., 47°03′N, 12°57′E; cf.Fig. 1). At this observatory, the period September 2006to June 2007 was substantially warmer than the average.Deviations from the mean monthly values of the normalperiod 1961–1990 are in the range of +2.6°C (Nov. 2006)and +4.9°C (April 2007) with a mean value of +3.2°C forthis 10-month period (ZAMG 2007). Comparable extremeatmospheric temperature anomalies are reported to affectnear-surface permafrost conditions to depths exceeding 10 m(Isaksen et al. 2007). In particular, monitoring temperaturechanges in bedrock gives a good indication for the effectsof air temperature anomalies on ground thermal conditions(Smith & Riseborough 1996). For this reason, continuoustemperature measurements in alpine rock walls for monitoringthe effects of climate change on bedrock temperatures(including permafrost) in central and eastern Austria wereinitiated in summer 2006 within the project ALPCHANGE.Measurements at 9 rock wall sites (RWS) distributed over 5study areas (SAs) recorded the exceptionally warm 9-monthperiod from 01.10.2006 to 30.06.2007. Preliminary resultsare presented here.Study Areas and InstrumentationFour of the 5 SAs are located in the Hohe Tauern Range,where the highest mountains of Austria reach almost 3800m a.s.l. At each of the 4 SAs (Dösen Valley, HintereggenValley, Hinteres Langtal Cirque, and Pasterze Glacier; Fig.1, Table 1), 2 RWS with opposed aspects were instrumentedwith 3 temperature sensors for each rock wall. The fifth SAis located in the eastern part of the Niedere Tauern Range(Hochreichart Cirque), where only one north-facing rockwall at an elevation of 1960 m a.s.l. was instrumented. The9 RWS are located at elevations between 2220 and 2775 ma.s.l. (3 of them are probably affected by permafrost). All 9RWS were drilled in different metamorphic bedrock types(Table 1).To measure bedrock temperatures, 16 mm wide boreholeswere drilled at each site 40 cm horizontally into the bedrockby using HILTI drilling equipment connected to an externalpower set. Due to technical problems, the boreholes at thesites DOV-A, HEV-A, and HEV-B (Table 1) did not reachthe intended 40 cm depth. To measure near rock surfacetemperature, a sensor was installed at 3 cm. The other sensorswere installed at depths of 10 and 40 cm (slightly less at the3 RWS mentioned above) as suggested by Matsuoka (1994).At all RWS, the measurements were recorded every 30minutes on three-channel miniature temperature dataloggers/MTLs (M-Log6, Ge oPr e c i s i o n). All datasets cover at leastthe period 01.10.2006 to 30.06.2007. The three sensors areFigure 1. Locations of the 5 study areas in Austria and the SonnblickObservatory. For abbreviations refer to Table 1.Table 1. Characteristics of the 9 alpine rock wall sites, wheretemperature is monitored since summer/early autumn 2006.SA=study area (DOV=Dösen Valley, HEV=Hintereggen Valley,HLC=Hinteres Langtal Cirque, HRC=Hochreichart Cirque,PAG=supraglacial slopes flanking the tongue of PasterzeGlacier); RWS=rock wall site; Bedrock types: GGN=graniticgneiss, AGN=augengneiss, MS=mica schist, GN=Gneiss, CMS=calcareous mica schist; Depths=depths of sensors in borehole.SA RWS Lat. Long.Alt. Bed- DepthsAspect(m asl) rock. (cm)DOV DOV-A 46°59′N 13°17′E 2630 S GGN 3,10,32DOV-B 1 46°59′N 13°17′E 2640 N GGN 3,10,40HEV HEV-A 46°55′N 13°23′E 2505 W AGN 3,10,30HEV-B 1 46°55′N 13°23′E 2530 E AGN 3,10,30HLC HLC-A 46°59′N 12°47′E 2725 SW MS 3,10,40HLC-B 1 46°59′N 12°47′E 2700 NE MS 3,10,40HRC HRC-A 47°22′N 14°41′E 1960 N GN 3,10 2 ,40 2PAG PAG-A 47°05′N 12°44′E 2220 SW CMS 3,10,40PAG-B 47°05′N 12°44′E 2250 NE CMS 3,10,401probably with permafrost occurrence (Lieb 1998)2sensor that partly malfunctioned (no data presented in Table 2)131