(Avian et al. 2007). The morphology of the glacier tongue is peculiar: its right side
(as seen in the flow direction) is strongly debris-covered, whereas the left side is
relatively debris-free and bare ice occurs at the surface. The accelerated glacier
recession has important paraglacial implications (Ballantyne 2002) on the vicinity
of the glacier, e.g. by the exposure of unstable rock walls prone to rock fall events
(Kellerer-Pirklbauer et al. 2012) or by the development of a chaotic and highly
dynamic proglacial area where large volumes of sediments are stored (Geilhausen
et al. 2011).
The specific aim of this study is to analyze glaciological and related paraglacial
changes at Pasterze Glacier and its surroundings in the two time periods 2003–2006
and 2006–2009. We used high-resolution aerial photographs and products derived
therefrom, such as topographic line information, digital elevation models (DEMs)
and orthophotos. We (a) quantified changes of the entire glacier regarding surface
extent, elevation and volume, and (b) analyzed glacier velocities and the extent of
the supraglacial debris cover at the glacier tongue. In a further step (c) we quantified
major glacier-related morphological changes such as the evolution of rock windows
in the massive icefall of Pasterze Glacier and a large paraglacial rock fall event.
9.2 The Study Area
Pasterze Glacier is a valley glacier located in the central part of the Hohe Tauern
Range, Austria (Fig. 9.1). The glacier catchment consists of different metamorphic
rocks which are part of the Penninic tectonic unit. These rocks are predominantly
calcareous mica schist and prasinite (a type of greenschist derived from basalts)
with some amphibolite from the Jurassic to Cretaceous periods (H€ ock and Pestal
1994). The climatic conditions are largely continental. At an automatic weather
station (AWS) near Pasterze Glacier located at 2,070 m a.s.l. (AWS-MA; see
Fig. 9.1), the annual precipitation in the period 2003–2009 was 1,000 mm and the
mean annual air temperature (MAAT) about 2.1
C (data provided by VERBUNDAustrian Hydro Power). The potential upper timberline can be estimated at 2,150 m
a.s.l. (Lieb 2007). The mean lower limit of discontinuous permafrost depends on
substrate and aspect and is at around 2,900 m a.s.l. on south-facing slopes and
2,600 m a.s.l. on northeast-facing slopes (Kellerer-Pirklbauer et al. 2012).
The glacier has a length of 8.3 km and a maximum ice thickness of about 190 m
considering georadar data (Span et al. 2005) and recent glacier thickness losses
based on own measurements (see below). Together with the nearby Großglockner
(3,798 m), Austria’s highest mountain peak, Pasterze Glacier forms a unique Alpine
landscape which attracts up to a million visitors a year. Glaciological surveys have
been carried out at Pasterze Glacier almost annually since 1878 (initiated by
Ferdinand Seeland) representing one of the longest time series of continuous glacier
monitoring globally (Wakonigg and Lieb 1996). The surveys include measurements of glacier length, surface velocity and surface elevation change. The annual
campaigns have been organized by the Department of Geography and Regional
9 Glaciological Studies at Pasterze Glacier (Austria) Based on Aerial Photographs
175
(as seen in the flow direction) is strongly debris-covered, whereas the left side is
relatively debris-free and bare ice occurs at the surface. The accelerated glacier
recession has important paraglacial implications (Ballantyne 2002) on the vicinity
of the glacier, e.g. by the exposure of unstable rock walls prone to rock fall events
(Kellerer-Pirklbauer et al. 2012) or by the development of a chaotic and highly
dynamic proglacial area where large volumes of sediments are stored (Geilhausen
et al. 2011).
The specific aim of this study is to analyze glaciological and related paraglacial
changes at Pasterze Glacier and its surroundings in the two time periods 2003–2006
and 2006–2009. We used high-resolution aerial photographs and products derived
therefrom, such as topographic line information, digital elevation models (DEMs)
and orthophotos. We (a) quantified changes of the entire glacier regarding surface
extent, elevation and volume, and (b) analyzed glacier velocities and the extent of
the supraglacial debris cover at the glacier tongue. In a further step (c) we quantified
major glacier-related morphological changes such as the evolution of rock windows
in the massive icefall of Pasterze Glacier and a large paraglacial rock fall event.
9.2 The Study Area
Pasterze Glacier is a valley glacier located in the central part of the Hohe Tauern
Range, Austria (Fig. 9.1). The glacier catchment consists of different metamorphic
rocks which are part of the Penninic tectonic unit. These rocks are predominantly
calcareous mica schist and prasinite (a type of greenschist derived from basalts)
with some amphibolite from the Jurassic to Cretaceous periods (H€ ock and Pestal
1994). The climatic conditions are largely continental. At an automatic weather
station (AWS) near Pasterze Glacier located at 2,070 m a.s.l. (AWS-MA; see
Fig. 9.1), the annual precipitation in the period 2003–2009 was 1,000 mm and the
mean annual air temperature (MAAT) about 2.1
C (data provided by VERBUNDAustrian Hydro Power). The potential upper timberline can be estimated at 2,150 m
a.s.l. (Lieb 2007). The mean lower limit of discontinuous permafrost depends on
substrate and aspect and is at around 2,900 m a.s.l. on south-facing slopes and
2,600 m a.s.l. on northeast-facing slopes (Kellerer-Pirklbauer et al. 2012).
The glacier has a length of 8.3 km and a maximum ice thickness of about 190 m
considering georadar data (Span et al. 2005) and recent glacier thickness losses
based on own measurements (see below). Together with the nearby Großglockner
(3,798 m), Austria’s highest mountain peak, Pasterze Glacier forms a unique Alpine
landscape which attracts up to a million visitors a year. Glaciological surveys have
been carried out at Pasterze Glacier almost annually since 1878 (initiated by
Ferdinand Seeland) representing one of the longest time series of continuous glacier
monitoring globally (Wakonigg and Lieb 1996). The surveys include measurements of glacier length, surface velocity and surface elevation change. The annual
campaigns have been organized by the Department of Geography and Regional
9 Glaciological Studies at Pasterze Glacier (Austria) Based on Aerial Photographs
175