Formation of glacial lakes - a recent dynamic process in the Hohe Tauern National Park

Abstract Due to climate change in high alpine environments, the surface-topography in the vicinity of glaciers changes very rapidly and in the case where glaciers expose natural basins after their retreat, “new” glacial lakes emerge. These dynamic processes are quite obvious in the Hohe Tauern Mountain Range, especially in the Stubach Valley and the Obersulzbach Valley, both situated in the Salzburgian part of the Hohe Tauern National Park. Two proglacial lakes, Unterer Eisboden See and Obersulzbach See, have consequently been monitored by the Hydrological Service of Salzburg in cooperation with Salzburg University, Department of Geography & Geology since the early 90s. Modern and classical methods e.g. multi-temporal (aerial) photography, orthophoto interpretation, repeated terrestrial laser-scanning, ground penetration radar as well as bathymetry were used in an interdisciplinary ap-proach to document the development of the lakes in front of the termini of Stubacher Sonnblickkees and Obersul-zbachkees. Additionally, parameters like precipitation, temperature, water level, discharge and conductivity were registered in order to analyze the dominant on-going processes in the water cycle. Regular daily water level fluctuations and even a glacial lake outburst flood (GLOF) in July 2006 were monitored at Unterer Eisboden See. In order to calculate suspended and solute sediment fluxes at Obersulzbach See, gauging stations to measure sediment concentrations and turbidity were also installed. As both lakes also represent the development of new ecosystems, hydrobiological probing and monitoring were also started. In order to estimate the maximum possible extension of the two pro glacial lakes, ground radar measurements were carried out and surface models were combined with bathymetry. This interdisciplinary work on both the above mentioned lakes offers various possibilities to understand dynamic processes (e.g. the influence on the downstream hydrological and geomorphological system due to discharge mod-ifications, suspended sediment trapping, decoupling effects and long term sediment storage) in protected areas under global change conditions.