Abstract

The International Panel for Climate Change (2001) indicated that average global surface air temperature increased by 0.6±0.2 °C since the late 19th century and is projected to increase by 1.4–5.8 °C over the period 1990–2100 (approx 0.2 to 0.5 °C per decade) and some climate models for the European Alps predict higher/more intense precipitation in winter. Suspended sediment fluxes from the Glacier Noir and Glacier Blanc catchments were monitored at the proximal and distal ends of the 0.75 km² the Pre de Madame Carle proglacial zone in the Ecrins National Park, France. A 10-min turbidity and discharge record, supplemented by 5-hourly automated water sampling were used to determine 10-min suspended sediment loads for a 12-d period during the summer 2005 melt season. Total suspended sediment input at the proximal end of the Pre de Madame Carle proglacial zone was estimated at 13 537 ± 0.47 t (13 139 ± 0.46 t from the Torrent du Glacier Noir + 397 ± 0.006 t from the Torrent du Glacier Blanc) and the total output at the distal end was 4263 ± 0.23 t giving a total storage of 9274 ± 0.49 t (68% of input) over this period. Net accumulation occurred for 91.2% and net erosion for 8.8% of the period respectively. The net erosion or ‘sediment flush’ events were a direct result of two rainstorm events (of 4-hr and 12-hr duration) lasting 6.7% of the monitoring period with sediment flush occurring for 8.8% of the period.

These findings are important in the light of climate prediction models which suggest a future with higher/more intense precipitation in winter. If the findings of this study are extrapolated, they could have a major impact on our understanding of the stability of Alpine proglacial zones as fine sediment stores. Additionally, recently reported changes in suspended sediment loads during warmer climate scenarios (Stott & Mount, in press) combined with the likelihood that proglacial zones will expand in a future warmer climate, makes these findings timely and important.

Keywords: suspended sediment budget, proglacial zone, climate warming, turbidity, rainstorms.