Abstract ID: 3.9177 | Accepted as Poster | Poster | TBA | TBA

Glacier-fed lakes in proglacial environments allow insights into sediment dynamics and climate change adaptation of high mountains. These newly formed lakes influence the sediment cascade by collecting significant amounts of sediment from meltwater streams and paraglacial processes at the lake fringe. Proglacial lakes represent sediment traps that have a significant impact on sediment budgets and sediment availability in downstream fluvial systems, with implications for river ecology and bedload changes. Lake Sulzsee emerged 25 years ago from the retreating Obersulzbach glacier (Hohe Tauern, Austria) and has been intensively monitored with respect to lake evolution and sediment dynamics. Here, we document the phases of lake evolution associated with paraglacial adjustment of the lake shores and lake sedimentation patterns. We combined repeated bathymetric surveys and ground-penetrating radar for lake mapping and lake sediment quantification. Multitemporal surface change detection using high-resolution laser scanning data was used to quantify paraglacial sediment dynamics around the lake. Field and remote sensing mapping provided insight into geomorphological processes and ice-melt dynamics. We observed significant sedimentation within this 35 m deep lake mainly in a large delta and along the steep slopes towards the northern shore. After glacier retreat, sediment input is dominated by meltwater streams from the remaining glacier areas, surface erosion by debris and slush flows, and by shallow debris slides from the northern lake slopes. Individual large boulders on the lakebed represent the deposition of drop stones from the melting glacier. In recent years and decades after glacier retreat from the lake, bathymetry and open water volume changed significantly due to delayed melt of buried ice. We reconstruct the melting of ice preserved at the lakebed for over 20 years, leading to a delayed expansion of the lake area by more than 30% and a subsidence of the lakebed of up to 20 m. Onshore sediment dynamics along the northern slope show hotspots of erosion and significant deposition along the footwall and within the lake. On this slope, moraine deposits and till cover have partly been removed with bedrock now exposed indicating partial sediment depletion and an early end of the paraglacial adjustment in this part of the proglacial area.