Keywords Pasterze Glacier • Glacier change • Glacier recession •
Photogrammetric mapping • Geomorphological mapping
9.1 Introduction
Glaciers in the European Alps have lost around 50 % of their volume between the
end of the Little Ice Age (LIA, ~1850 AD) and 1975, approx. 10 % in the period
1975–2000, and again 10 % in the period 2000–2009 (Haeberli et al. 2007, 2013a).
These values highlight the strong influence of the first decade of this century on
glacier recession in the European Alps. Furthermore, projected future atmospheric
warming will cause almost complete deglaciation in the European Alps within a
matter of decades. However, predicting this evolution gets more complicated when
considering various feedbacks such as size effects (small/large glaciers), thermal
aspects (temperature/cold firn/ice areas), albedo, insulation (debris cover), surface
elevation (glacier surface lowering into warmer climate) and process changes (ice
collapse; lake formation) (Haeberli et al. 2013a, b; Vaughan et al. 2013). Glaciers
that persist tend to be (i) small ice patches on very high and/or radiation-sheltered
locations or (ii) mighty glacier tongues with large ice thickness which need longer
time periods to melt (Zemp et al. 2006; Haeberli et al. 2013b).
This study focuses on Pasterze Glacier, the largest glacier of the Eastern
European Alps with a present (2009) area of 17.3 km
2 . As all other glaciers in the
Alps, it has more or less continuously receded since the end of the LIA maximum
(~1850 AD), interrupted by relatively short periods of minor advances and stagnations. During the LIA maximum the glacier covered 26.5 km
2 (Paschinger 1969)
and has thus lost about one third of its area during the past 160 years.
Atmospheric warming is the driving force behind glacial recession. Temperatures in the Alps increased by about +2
C over the last 100 years (Auer et al. 2007).
The warming is indicated by long-term climatic observations at the Meteorological
Observatory Hoher Sonnblick (Sch€ oner et al. 2000) located approx. 16 km to the
east of Pasterze Glacier. During the last few years accelerated recession and decline
of the glacier tongue has been observed (Avian et al. 2007; Kellerer-Pirklbauer
et al. 2008) accompanied by a considerable increase in the areal extent of the
supraglacial debris cover (Kellerer-Pirklbauer 2008). Ongoing mass balance studies
at Pasterze Glacier applying the glaciological method confirm the observed mass
loss (ZAMG 2013).
The glaciological and geomorphological changes examined in this paper are
largely connected to the specific topographical setting of the glacier. The upper part
is separated from the lower one by a distinct icefall known as ‘Hufeisenbruch’
(German for ‘horseshoe’). The icefall has changed its appearance substantially
since the 1990s with a steady increase in bedrock outcrops (hereafter termed
‘rock windows’) within the icefall on the one hand and a steady decrease in the
glacier motion through the icefall on the other. Rapid glacier disintegration created
circular collapse structures which occur more frequently at the glacier tongue
174
V. Kaufmann et al.
Photogrammetric mapping • Geomorphological mapping
9.1 Introduction
Glaciers in the European Alps have lost around 50 % of their volume between the
end of the Little Ice Age (LIA, ~1850 AD) and 1975, approx. 10 % in the period
1975–2000, and again 10 % in the period 2000–2009 (Haeberli et al. 2007, 2013a).
These values highlight the strong influence of the first decade of this century on
glacier recession in the European Alps. Furthermore, projected future atmospheric
warming will cause almost complete deglaciation in the European Alps within a
matter of decades. However, predicting this evolution gets more complicated when
considering various feedbacks such as size effects (small/large glaciers), thermal
aspects (temperature/cold firn/ice areas), albedo, insulation (debris cover), surface
elevation (glacier surface lowering into warmer climate) and process changes (ice
collapse; lake formation) (Haeberli et al. 2013a, b; Vaughan et al. 2013). Glaciers
that persist tend to be (i) small ice patches on very high and/or radiation-sheltered
locations or (ii) mighty glacier tongues with large ice thickness which need longer
time periods to melt (Zemp et al. 2006; Haeberli et al. 2013b).
This study focuses on Pasterze Glacier, the largest glacier of the Eastern
European Alps with a present (2009) area of 17.3 km
2 . As all other glaciers in the
Alps, it has more or less continuously receded since the end of the LIA maximum
(~1850 AD), interrupted by relatively short periods of minor advances and stagnations. During the LIA maximum the glacier covered 26.5 km
2 (Paschinger 1969)
and has thus lost about one third of its area during the past 160 years.
Atmospheric warming is the driving force behind glacial recession. Temperatures in the Alps increased by about +2
C over the last 100 years (Auer et al. 2007).
The warming is indicated by long-term climatic observations at the Meteorological
Observatory Hoher Sonnblick (Sch€ oner et al. 2000) located approx. 16 km to the
east of Pasterze Glacier. During the last few years accelerated recession and decline
of the glacier tongue has been observed (Avian et al. 2007; Kellerer-Pirklbauer
et al. 2008) accompanied by a considerable increase in the areal extent of the
supraglacial debris cover (Kellerer-Pirklbauer 2008). Ongoing mass balance studies
at Pasterze Glacier applying the glaciological method confirm the observed mass
loss (ZAMG 2013).
The glaciological and geomorphological changes examined in this paper are
largely connected to the specific topographical setting of the glacier. The upper part
is separated from the lower one by a distinct icefall known as ‘Hufeisenbruch’
(German for ‘horseshoe’). The icefall has changed its appearance substantially
since the 1990s with a steady increase in bedrock outcrops (hereafter termed
‘rock windows’) within the icefall on the one hand and a steady decrease in the
glacier motion through the icefall on the other. Rapid glacier disintegration created
circular collapse structures which occur more frequently at the glacier tongue
174
V. Kaufmann et al.