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Glacier retreat due to climate change is significant and well investigated on a
regional scale. Much less is known about local effects, especially in the proglacial
area. This thesis focuses on glacial changes and new methods to tackle the processes
therein. The glacial changes within the catchment of the river Fagge, in the upper
Kaunertal valley, are investigated by combining different direct glaciological, geodetic
and geophysical methods. Alongside long-term monitoring of glacier flow velocities
at adjacent glaciers, the investigation focuses on the glacier tongue of Gepatschferner.
In addition to the direct measurements of the ice motion and the determination of the
surface mass balance, the ice thickness and the thickness of subglacial sediments is
measured with vibroseismic soundings. Changes in total area, elevation and volume
are calculated from multiple high-resolution digital elevation models from airborne
laser scans. These detailed glaciological investigations are part of the joint project
PROSA, which focuses on the geomorphodynamics of the entire proglacial system
and aims at balancing the sediment budget therein.
The presented cumulative doctoral thesis consists of three publications and additional
results from the glaciological part of PROSA. This includes long-term
monitoring of glacier flow velocities (Paper 1), detailed investigations of the process
development of a surface depression at the tongue of Gepatschferner (Paper 2), and
an approach at closing the balances of ice, water and sediments on the glacier tongue
(Paper 3).
It turned out that the formation of circular and funnel-shaped surface depressions
occurs as a consequence of increased glacier retreat rates. Additionally, the process
of the depression development in turn increases the retreat rates. This exemplary
development was caused by the evacuation of subglacial sediments after a heavy
precipitation event and by decreasing glacier dynamics as a result of negative glacier
mass balances. Beside the mass balances, the horizontal motion and especially the
vertical motion of the glacier provide valuable information on the glacier state, such
as measured in the long-term program on Kesselwandferner. The magnitudes of the
mass exchanges showed the influence of extreme events, which exceed mean daily
and even annual turnovers, as well as the role of the melt water production at the
glacier tongue of Gepatschferner and its severe effect on the glacial runoff regime of
the river Fagge.