Stages of glacial retreat in the French Alps since the termination of the Little Ice Age

Marie Gardent (1) , Philip Deline (1)

1 EDYTEM - Environnements, Dynamiques et Territoires de Montagne

Since the end of the Little Ice Age (LIA), and especially since the 1980s, one of the most obvious impacts of climate change in mountain areas is the glacial retreat. However, this generalized shrinkage of the glaciers took place with periods of retreat, stagnation, and advance, that are accurately known at local scale for several well documented glaciers but not at the regional scale of the French Alps. The most recent data about French alpine glacier extension are from IGN topographical maps and the Vivian's database, both dating from the end of the 1960s. Although IGN starts recently to update glacier surface areas on its maps, up to now there is no complete and accurate set of data about the present glacier extension in the French Alps. Furthermore, France is up to now missing in international databases like GLIMS or GlobGlacier. In order to fill this gap, an inventory of the post-LIA and present French glaciers is in progress since 2010, integrated in a GIS. Based on present maps, orthophotos and DEMs, it lists the French Alps glaciers, maps their limits, and implements a database. Proglacial margins are geomorphologically mapped using present orthophotos, completed by field check. This is needed because of low quality orthophotos, and debris- or snow-covered glacier margins, and to complete the maps derived from orthophotos or DEM. By crossing this database with former documents (e.g. ancient maps and terrestrial photos), it allows the reconstruction of the stages of the glacier retreat since the end of LIA, the survey of the present glacier extensions, and the quantification of the glacier retreat rates since 150 years. This work takes place in the EU-funded project GlaRiskAlp (Alcotra France-Italy). The inventory should be merged with the ones in Valley of Aosta and Piemonte (Italy), and integrate international databases. It will be used as a base for the recognition of areas in the Western Alps prone to hazards related with the glacial retreat.

Marie Gardent, Philip Deline. Stages of glacial retreat in the French Alps since the termination of the Little Ice Age. XVIII th INQUA congress, 2011, Berne, Switzerland. ⟨halsde-00879516⟩