Recovering environmental information from steep Alpine ice – development of a lightweight decametric ice corer and first use at Grandes Jorasses (4208 m a.s.l., Mont-Blanc massif)

Ice aprons are very small (generally < 0.1 km2) and thin (generally < 10 m) perennial ice bodies located on steep slopes with a quasi-stationary shear regime, frozen to steep permafrost rock slopes. They occupy – mainly above the glacier equilibrium line altitude – a very small fraction of the ice-covered surface but, with their quasi-stationary shear regime, contain ice that is multi-centennial to multi-millennial in age, making them a potentially important glacial heritage. In order to study these ice masses in their full thickness, a lightweight 10 m long ice corer was specially developed and successfully deployed on the northern face of Grandes Jorasses (4208 m a.s.l.) in July 2023. This article describes the technical characteristics of the ice corer and how it was used on a large ice apron of one of the largest rock faces in the Alps. It also presents the strategies we intend to use to analyse the extracted 8.8 and 6.0 m long ice cores.