Mass exchange and motion of glacier tongues and subglacial sedimenst

With the joint proposal the relief changes in the glacier forefield are investigated by bringing several scientific disciplines together. The project glaciology and geomorphology deals with the contribution of glaciers to the suspended load and bed load transport within the glacial stream by focusing on the relationships of the interacting processes of meltwater production, glacier motion and sediment transport. The subproject glaciology and geomorphology is closely connected to the other subprojects and is conducting fundamental research of intrasystematic feedbacks. The separation of surface and subglacial melting by measurements of the surface ablation and total volume changes derived from laser scans is new. The high temporal and spatial resolution of the measurements at the glacier tongue with a thickness of about 100 meters is new as well as the use of the vibroseismic at the temperate glacier tongue to investigate ice thickness and the properties of the zone of desintegration.

Within the joint project PROSA the surface changes of a rapidly changing proglacial System of the catchment of the upper river Fagge (Kaunertal) are investigated. Subproject 4 focuses on the glacial changes especially those of the glacier terminus of Gepatschferner which is the second biggest glacier in Austria and a glacier terminus at an elevation of 2200 m. The investigations aim on the combination of the fluxes of ice, water and sediments and the identification of dominant processes therein.The glaciological investigations include direct and indirect methods. The localization and extensive analysis is based on high resolution digital elevation models from ALS (Airborne Laser Scan) data. Ice thickness and the thickness of subglacial sediments are measured with geophysical investigations such as ground penetrating radar and vibroseismics. Additionally, the glacier motion is measured with differential GPS and time-lapse photogrammetry and direct measurements of surface ice melt come into operation. These comprehensive investigations are the basis for the determination of area, height, and volume changes of the glaciers and they enable a separation of the individual processes.On the example of the terminus of Gepatschferner, it turned out that extreme events, like a small-scale evacuation of subglacial sediments due to heavy precipitation, can exceed and thus affect the mean annual or daily mass motion on a large-scale by a multiple.