EUROCORES_TOPOEUROPE_1.Call_Sediment Budget for glacier forefield (SediBud Pasterze) (SedyMONT)

Within the ESF-Eurocores programme TOPO-EUROPE ("4-D Topography Evolution in Europe: Uplift, Subsidence and Sea level Change") the CRP (collaborative research project) SedyMONT ("Timescales of sediment dynamics, climate and topographic change in mountain landscapes") encompasses six IPs (individual projects) and two APs (associated projects). The CRP analyses timescales and mechanisms of sediment production and transfer and identifies their effects in selected European mountain landscapes. In this context, the project (IP 02) will establish a sediment budget for the Pasterze forefield in the Austrian Alps, where sediment discharge and landscape development is controlled by changing glacial and permafrost conditions in recent times. Sediment budgets commonly identify, differentiate and quantify sediment transfer processes and storages and clarify to what extent these components are coupled to each other. As retreating Alpine glaciers expose landscapes with unconsolidated and potentially unstable landforms (e.g. moraine slopes), glacier forefields react very sensitive to changing climatic conditions with rapid topographic modification. Therefore, sediment budget studies on relative short time scales within glacier forefield landsystems are of specific scientific interest. The study area is located near Austria`s highest peak (Großglockner 3.798m) within the High Tauern range. Due to the withdrawal of the Pasterze glacier, a natural sediment sink has developed in the proglacial area since the late 1950s, taken over by a (Sander) lake and infilled by glacifluvial sedimentation. First geophysical findings indicate sediment thicknesses of about 12 to 30 m. The main objectives of the project are to establish a highly resoluted and spatio-temporal differentiated sediment budget for this proglacial area and to develop future sedimentation scenarios with regard to an improved water management for the Margaritze reservoir just below the Sander. This implies the identification, spatial distribution and quantification of various sediment storage types and dominant processes controlling sediment input, transfer and output. Therefore, variations of glacial and glacifluvial sediment load (bed-, suspended- and solute load) with respect to runoff are of major importance. A methodological focus is on evaluating suitable combinations of geophysical techniques in terms of resolution, internal structure, and depth to bedrock for different substrata (fine and water saturated sediments in the Sandur Lake and blocky material within the talus slopes). Structured in several working packages, the applied methods and techniques range from orthophoto-interpretation, detailed geomorphologic field-mapping, geophysical prospecting, discharge monitoring, repeated laser scanning, GIS analyses and a final WebGIS implementation. The project will be characterised by both, an intensive cooperation within the CRP (e.g. meetings, workshops) and an exchange with national and international colleagues outside the programme. Due to the intensive fieldwork, the realisation of the project demands one PhD-position and a project accompanying reimbursement of work on an hourly basis promoting young researchers to a high international scientific level (doctoral and diploma theses).

The objective of the collaborative research project SedyMONT (Timescales of Sediment Dynamics, Climate and Topographic Change in Mountain Landscapes; ESF EUROCORES TOPO-EUROPE programme) was to determine which landscape forming processes have adapted to ongoing climate change and to what extent. The topographic response to climate change is poorly understood due to its complex and scale depended nature and quantitative metrics of timescales and controls of sediment dynamics are prerequisites to predict a climate-driven landscape response. This requires the identification of sediment sources, intermediate storage, transport and yield in different mountain environments. The outlined Austrian subproject investigated three glacier forefields in the Austrian Alps (Pasterze, Obersulzbachkees and Ödenwinkelkees) where landscape change and sediment discharge are controlled by modern glaciation and deglacierization. The recently deglaciated landscape is out of equilibrium with current climate, therefore highly sensitive to climate change and susceptible to erosion and rapid modification. The proglacial metamorphosis is of importance to assess the implications of accelerated deglacierization and discharge modifications on sediment transfer from mountain to piedmont zones. For example, the lifespan and economic feasibility of hydropower schemes depend on sedimentation rates controlled by sediment flux from upstream areas. We found that sediment storage activity decreases in both intensity and areal extent with increasing distance from the glacier and becomes confined to meltwater channels. The degree of process domain interaction in the proglacial zone and the topography of the recently deglaciated valley floor are key controls on sediment discharge because they affect the quantity of hillslope sediment supply and the transport capacity of the meltwater stream. In two of the study sites, glacial retreat has exposed natural bedrock basins and proglacial lakes have formed. These lakes have strongly reduced the connectivity between glacial sediment production and downstream sediment fluxes because of sediment trapping and decoupling effects. It is generally assumed that climate change and accelerated glacier melt will raise sediment discharge from proglacial zones. In the light of our findings, we address the topographic consequences of climate change with basin exposure and proglacial lake formation in expanding proglacial zones. A number of proglacial lakes have formed during the 20th century as a result of glacial retreat. We hypothesize an increasing likelihood that natural bedrock basins capable of forming proglacial lakes will be exposed in the near future because many (valley) glaciers have receded in convergence zones of combining ice flows from multiple directions where glacier-bed overdeepening is common. This raises the question of how the proglacial zone will take control on sediment yields if sediment production sites will be disconnected from the sediment transfer system. Scenarios of future sediment flux from any proglacial zone would depend critically on the potential development of a proglacial lake.