L’evolution del glaciers du massif de Chambeyron (Ubaye, Alps du Sud francaises) en liaison avec les changements climatiques des 10 dernières années

The evolution of cirque glaciers (Massif de Chambeyron, France), with respect to the climatic change during the last ten years

Abstract

Located in the upper Ubaye Valley, the Massif of Chambeyron shelters the four most southern glaciers in the French Alps (0,5 Km² together). The submediterranean climate, dry in winter (accumulation season), hot in summer (ablation season) has not been favourable to the glaciers during the last ten years. Measurements were performed on the two Marinet cirque glaciers: — a cross profile on the Eastern glacier which shows an important lowering of the glacial level (4,04 m between 1984 and 1988), — by the means of theodolit measurements a study gives valuable information on the surface velocities of the Western Marinet glacier. The velocities decrease from 4,17 m/year in 1984 to 2,04 m/year in 1990 and 4 to 6 m of glacier ice melted during the same time. The front as in slight retreat. On a morphological point of view, the glacial retreat allows the appearing of rock bars. On another hand, the surface of the glacier becomes more and more debris-covered near the front. Another consequence of the climatic warming consists in thermal changes in the basal ice of polythermal glaciers (i.e. cold basal ice). Cracks appeared last years on the steep Pointe de Chauvet glacier generating the fear of a fall down like the one which happened in 1989 at the upper Coolidge glacier (Viso).