Explications et synthèse des variations de l'hydrographie sous-glaciaire du glacier d'Argentière, Mont-Blanc, grâce aux mesures de l'écoulement du glacier sur son lit rocheux de 1970 à 1998

Explanation and synthesis of hydrographic variations under the Argentière glacier (Mont-Blanc), thanks to glacier flow measurement on its rock bed from 1970 to 1998

Chamonix-Glaciologie, Association scientifique 1901

Abstract

The French and Swiss company Emosson has for goal at the Argentière glacier to take the water under the glacier at a higher altitude from the dam. The first mission is to understand and prevent the hydrographic flow under the glacier. After 25 years in the right side, the stream suddenly changed his way in november 98 after an important volume of stonning water to go back to the left side, talweg of the valley.

We are showing here that with the help of the sliding velocity measures of the glacier on its bed rock and measures taken above, we can detect the causes of the hydrographic fluctuations. We explain this flow variations by a slowing down of the glacier sliding caused by the decreasing at 2400 m since 1985.

The sliding velocity appears as the motor of this dynamics and the principal cause of the flow variations under the glacier.

With a fondamental point of view, ten years of sliding velocity measurements show that the sliding glacier appears to be regular and faster in the summer period. But sometimes, progressive acceleration during important thunder storm only in automn are measured and illustrated here. These stonning events are very important in the hydrographic fluctuations when the conditions under the glacier have changed.