Gerhard Karl Lieb

THE RESPONSE OF PARTIALLY DEBRIS-COVERED VALLEY GLACIERS TO CLIMATE CHANGE: THE EXAMPLE OF THE PASTERZE GLACIER (AUSTRIA) IN THE PERIOD 1964 TO 2006

Abstract. Long‐term observations of partly debris‐covered glaciers have allowed us to assess the impact of supra‐glacial debris on volumetric changes. In this paper, the behaviour of the partially debris‐covered, 3.6 km2 tongue of Pasterze Glacier (47°05′N, 12°44′E) was studied in the context of ongoing climate changes. The right part of the glacier tongue is covered by a continuous supra‐glacial debris mantle with variable thicknesses (a few centimetres to about 1 m). For the period 1964–2000 three digital elevation models (1964, 1981, 2000) and related debris‐cover distributions were analysed. These datasets were compared with long‐term series of glaciological field data (displacement, elevation change, glacier terminus behaviour) from the 1960s to 2006. Differences between the debriscovered and the clean ice parts were emphasised. Results show that volumetric losses increased by 2.3 times between the periods 1964–1981 and 1981–2000 with significant regional variations at the glacier tongue. Such variations are controlled by the glacier emergence velocity pattern, existence and thickness of supra‐glacial debris, direct solar radiation, counter‐radiation from the valley sides and their changes over time. The downward‐increasing debris thickness is counteracting to a compensational stage against the common decrease of ablation with elevation. A continuous debris cover not less than 15 cm in thickness reduces ablation rates by 30–35%. No relationship exists between glacier retreat rates and summer air temperatures. Substantial and varying differences of the two different terminus parts occurred. Our findings clearly underline the importance of supra‐glacial debris on mass balance and glacier tongue morphology.

CLIMATE CHANGE AND ROCK FALL EVENTS IN HIGH MOUNTAIN AREAS: NUMEROUS AND EXTENSIVE ROCK FALLS IN 2007 AT MITTLERER BURGSTALL, CENTRAL AUSTRIA

Kellerer‐Pirklbauer, A., Lieb, G.K.,Avian, M. and Carrivick, J., 2012. Climate change and rock fall events in high mountain areas: numerous and extensive rock falls in 2007 at Mittlerer Burgstall, Central Austria. Geografiska Annaler: Series A, Physical Geography, 94, 597ndash;78. doi:10.1111/j.1468‐0459.2011.00449. Abstract Landslides in alpine areas are becoming more frequent. In 2007, a number of rock fall events occurred on the sharp SE‐ridge of the mountain Mittlerer Burgstall (2933 ma.s.l., 47°06′ 07″ N; 12° 42′ 36″ E) completely changing the shape of the mountain. Before the events, the SE‐ridge was sharp with steep rock faces on both sides. The mountain was a nunatak surrounded by two glacier tongues of Pasterze Glacier during the Little Ice Age. In this paper we use geomorphological mapping, permafrost distribution modelling, glacier reconstruction, surface and near‐surface ground temperature data, air temperature data, and airborne laserscanning data to assess these multiple rock fall events. Results show that the entire area of detachment covers 3100 m2. The areas of transportation and deposition cover 85-000m2 partly contributing to the supraglacial debris cover of Pasterze Glacier. The volume of all rock fall deposits is about 56-000m3. Permafrost modelling and ground temperature monitoring indicate that the area of detachment is located near the lower limit of discontinuous permafrost. Permafrost is relatively warm and thin at the summit area of Mittlerer Burgstall with a mean temperature of only –1.0°C at 1.8 m depth in 2007–2010. Substantial surface lowering of the glacier tongues surrounding the mountain on both sides (by −250 and −70 m since the Little Ice Age) changed the stress and strain field in the bedrock. Furthermore, the generally highly fractured bedrock favoured slope instability. The triggering event for the rock falls were most likely the effects of the warm winter of 2006/07 which was 2.2–4.8°C warmer compared to the seven winters before. A monitoring programme regarding future rock falls at Mittlerer Burgstall is ongoing.

Recent and Holocene dynamics of a rock glacier system: The example of Langtalkar (Central Alps, Austria)

The Hinteres Langtalkar rock glacier (Gössnitztal, Hohe Tauern, Austria) has been part of a complex transportation system of debris and ice since the beginning of the Holocene and shows the highest creep rates of all rock glaciers measured in the Hohe Tauern Range. Results of movement analysis show that the entire rock glacier behaves very differently at different zones and that sudden temporal and spatial changes of velocity rates are a typical feature. Zones with high rates occur close to rather inactive zones and zones with low rates have rapidly accelerated within recent years. The increase in movement rates over time is probably caused by topography. These studies – especially the measurement of surface velocities and elevational changes – allow a differentiation of the rock glacier and a first attempt of a morphogenetic interpretation. In this context, it is important that the innermost part of the cirque was covered by a small cirque glacier during the Little Ice Age advance. This cirque glacier created a moraine complex which contributes to the material supply of the rock glacier. A first estimation of transportation rates is possible with the help of the measurement results available, leading to an estimation of a probable age of at least 4000 years.

Velocity Changes of Rock Glaciers and Induced Hazards

Recent observations and geodetic measurements in the European Alps show that changes are occurring on rock glacier dynamics, ranging from moderate velocity variations to strong acceleration or even total collapse. These changes can be related to the ground temperature and to climate warming. In most cases, rock glaciers do not represent any serious hazard, except the instability of their surface and local rockfalls at the steep front. The surface movements, though moderate, can nevertheless cause damages to sensible infrastructures like cableways or buildings, if these are not designed to adapt to surface movements. The strong accelerations observed on some rock glaciers, however, induce a change of magnitude, and may threaten in some cases downslope areas. Thus, the presence of active or inactive rock glaciers with high ice content must be considered not only with regard to present conditions and dynamics, but with respect to possible evolutions due to climate change.

UAS-Based Change Detection of the Glacial and Proglacial Transition Zone at Pasterze Glacier, Austria

Glacier-related applications of unmanned aircraft systems (UAS) in high mountain regions with steep topography are relatively rare. This study makes a contribution to the lack of UAS applications in studying alpine glaciers in the European Alps. We transferred an established workflow of UAS-based change detection procedures to Austria’s largest glacier, the Pasterze Glacier. We focused on a selected part of the glacier tongue and its proglacial vicinity to obtain detailed knowledge of (i) the behavior of a lateral crevasse field, (ii) the evolution of glacier surface structures and velocity fields, (iii) glacier ablation behavior and the current glacier margin, and (iv) proglacial dead ice conditions and dead ice ablation. Based on two UAS flight campaigns, accomplished in 2016 (51 days apart), we produced digital elevation models (DEMs) and orthophotos with a ground sampling distance (GSD) of 0.15 m using Structure-from-Motion (SfM) photogrammetry. Electrical resistivity tomography (ERT) profiling was additionally conducted in the proglacial area. Results indicate distinct changes in the crevasse field with massive ice collapses, rapid glacier recession, surface lowering (mean of −0.9 m), and ice disintegration at the margins, calculated degree day factors on the order of −7 to −11 mm d−1·°C−1 for clean ice parts, and minimal changes of the debris-covered dead ice in the proglacial area. With this contribution we highlight the benefit of UAS in comparison to commonly used terrestrial methods and satellite-related approaches.

Glaciological Studies at Pasterze Glacier (Austria) Based on Aerial Photographs

This chapter describes and analyses glacier recession observed at Pasterze Glacier, Hohe Tauern Range, Austria, for the time period 2003–2009. Pasterze Glacier is the largest glacier of the entire Eastern Alps, and it is highly indicative of ongoing glacier melt in the Alps. We evaluated three glacier stages (2003, 2006 and 2009) and the glaciological changes between them. The quantitative analysis is based on aerial surveys carried out during the summer of these years. The photogrammetric workflow provided high resolution datasets, such as digital elevation models and orthophotos of each stage. We evaluated the extent, surface elevation, flow velocity field, supraglacial debris cover, and geomorphological changes at the glacier surface and the adjacent paraglacial environment. The main numerical results can be summarized as follows: the glacier covered 17.3 ± 0.1 km2 in 2009, the mean surface elevation change was −1.31 ± 0.07 m a−1 for the period 2003–2009, the glacier surface flow velocity in two test areas at the glacier tongue decelerated from 2003–2006 to 2006–2009 (−4 % and −31 %), and the debris cover of the glacier tongue increased from 63 % (2003) to 72 % (2009). We conclude that Pasterze Glacier is far from equilibrium and that its glacier tongue will turn into a large dead ice body in the near future.

Slovenes in Italy: A Fragmented Minority

Abstract The study examines the Slovenian-speaking minority in the northern Italian autonomous region of Friuli-Venezia Giulia. It explores the spatial fragmentation in the Slovenian settlement area in Italy and analyzes the socio-economic and demographic processes that exert influence on the minority. The work is based on the critical evaluation of the current status of research, of statistical data from the state censuses and results of own research on site. The Slovenian-language population in the entire region is currently estimated at about 46,000 people. The main settlement area is the eastern border region of Friuli-Venezia Giulia, which is characterized by different cultural and regional identities. While the Slovenian-speaking population of Friuli focuses more on its cultural and regional distinctions, the majority of the Slovenian-language group in Venezia Giulia considers itself a “national minority.”

Land Use in the Drava Basin: Past and Present

Current land use in the Drava River Basin (DRB) and its recent changes are detected from the data of the CORINE Land Cover (CLC) inventory, which allows a multitemporal analysis for the time period 1990–2012. Further data, like a DEM, were taken from the European Environmental Agency database. In order to provide a good overview, 11 land use classes were defined. Their distribution as well as their changes are shown in maps and analyzed statistically. The most striking results are (i) the clear dominance of the land use class forests (46% of the DRB), (ii) a pronounced differentiation of land use between the eastern and the western part of the catchment, both for natural and cultural reasons, and (iii) a relatively satisfactory environmental status, reflected among others by a high proportion of protected areas.

Die Pasterze, Österreichs größter Gletscher, und seine lange Messreihe in einer Ära massiven Gletscherschwundes

Der Beitrag beschaftigt sich mit der Pasterze, die als groster Gletscher Osterreichs seit mehr als 150 Jahren eine hohe offentliche Wertschatzung geniest. Die wissenschaftliche Erforschung reicht bis ins 19. Jh. zuruck und brachte die Einrichtung eines jahrlichen Gletscher-Monitorings bereits 1879. Die Messreihe der Langenanderungen ist daher die langste der Alpen. Das gegenwartige Gletscher-Monitoring umfasst neben der Messung der Langenanderung auch die Messung der Hohe und Bewegung der Gletscheroberflache an Profilen. Die graphisch veranschaulichten Messergebnisse werden interpretiert und diskutiert. Erganzend werden ausgewahlte Folgeprozesse des Gletscherschwundes, inklusive einiger Erkenntnisse zur holozanen Klimageschichte, dargelegt. Der starke Gletscherschwund wird auch in absehbarer Zukunft weitergehen, was u. a. zur Abtrennung der Gletscherzunge fuhren wird.

Detection of land-cover and land-use change in the Hohe Tauern National Park (Austria) using an object-based classification approach: first results

Land-cover and land-use (LCLU) change reflects environmental as well as social changes. High-mountain environments such as the Hohe Tauern Range (Austria) and its National Park are very sensitive to these changes. Remotely sensed data are ideally suited to detect and analyze land-cover and land-use changes on different spatial and temporal scales. In this study a Landsat Thematic Mapper (TM) time-series from 1988 to 2003, aerial photographs and auxiliary GIS data were used detect land-cover and land-use changes in the National Park and its surroundings. The objective of the study was to develop and test a transferable method for change detection in comparable high-mountain environments. After applying a series of pre-processing steps, object-based image analysis, on the basis of Definiens Developer, was used to extracted land-cover and land-use information from the Landsat images. To generate meaningful image objects, a multiresolutions segmentation algorithm was combined with image object merging. The resultant image objects were then classified by using a hierarchically organized classification method. In a further step the resultant outputs of the land-cover and landuse classifications build the basis for the post-classification change detection. Moreover the advantages and disadvantages of the developed method, the first results as well as future adaptations of the method and applications are discussed in this paper.