Détermination de l'épaisseur des glaciers de Sarenne (Alpes) et de Chacaltaya (Bolivie) par prospection radar au sol à 50 MHz

Determination of the Sarenne and Chacaltaya glaciers thickness using ground penetrating radar at 50 MHz

¹ IRD, Institut de Recherche pour le Développement, ex-ORSTOM, Programme NGT
² Université Pierre et Marie Curie, Paris 6, UMR 7619 Sisyphe
³ IHH, Instituto de Hidráulica e Hidrología, UMSA, La Paz, Bolivie
⁴ CEMAGREF, Etna, Grenoble

Abstract

Geophysical survey have been conducted on the temperate glaciers of Sarenne (Alps) and Chacaltaya (Bolivia) using Ground Penetrating Radar (GPR) at medium frequency range (50 MHz), in order to evaluate the ice thickness. The results clearly show the reflection at the top of the bedrock at depths over 40 metres for Sarenne. For Chacaltaya, the ice thickness reaches 16 metres only. However, if intermediate reflectors are present, they can attenuate or even overshadow the deep reflection on the bedrock. Those reflectors are attributed to some blacks of rock, crevasses or liquid water. Except for these restrictions, those surveys confirm the interest of GPR at 50 MHz to detect quickly and accurately the bedrock topography for this type of temperate glacier when the thickness remains low.