Present-day sediment dynamics and provenance of the Gornergletscher

Glacial erosion processes shape the Earth’s surface. Nevertheless, the processes that drive glacial erosion and the subsequent export of sediments are poorly understood and quantified. These processes include ice sliding, which controls erosion by abrasion and quarrying, and meltwater availability, which is essential to flush out sediment stocks that form a protective layer of sediments impeding bedrock erosion. Mapping glacial erosion rates can help understand the role of these different processes through the spatial relationships between the subprocesses and erosion rates. Here we report timeseries of glacial erosion rate maps inferred from the inversion of suspended sediment loads and their provenance. Geographically, we focus on the Gornergletscher complex (VS, Switzerland) where we collected data for the summer of 2017. The erosion rate timeseries are then compared to records of temperature, precipitation and estimates of discharge and turbidity of the meltwater river. Erosional activity seems to increase with rising temperatures and meltwater discharge, leading to an increased proportion of suspended sediments coming from the north-eastern (and occasionally western) side of the glacier. Interestingly, the peak in sediments from the north-eastern side is always preceded by a peak in sediments from the western side of the glacier. Sediments of these two zones are predominant in the suspended load signal when the maximal temperature at the Equilibrium Line Altitude (ELA) is above 10°C and on the rising limb of the hydrograph. Furthermore, the obtained erosion rate maps suggest that sliding velocities are not the only explanatory factor of the erosion rate patterns. We therefore postulate from these preliminary results that the present-day sediment output of the Gornergletscher complex is largely influenced by short term variations in temperature and meltwater availability.