Influence of local vs. regional settings on glaciation patterns in the French Alps

Abstract

To complement the work led by glaciologists, geographers should explain the distribution of glaciers at different scales. Indeed, various local effects can interfere with regional climatic parameters to generate variations in glacier sensitivity. In this paper, we propose a method to explore the influences of various parameters (topography, relative location, topoclimate, etc.) on glacierisation, at two complementary scales (regional and local). Firstly, the level of equilibrium line altitude (ELA) of 217 glaciers located in the French Alps is explained by coupling a F-test on the influence of region belonging with a multiscalar principal component analysis (PCA). Secondly, the variables identified as influencing the ELA at a local scale (longitude, curvature and incoming solar radiation) are integrated into a geographically weighted regression (GWR) to predict the altitude of instantaneous glacierisation (AIG) at any given point. AIG is then mapped all over the French Alps, and partial correlation maps between AIG and explanatory variables are also provided. Finally, it is useful to identify the structures of spatial organisation, which show a subdivision between glaciers evolving under the influence of a humid climate (Belledonne-Grandes Rousses and Mont-Blanc), and other glaciers, set in drier conditions, and where local effects (curvature and incoming solar radiation) partly compensate for the low-level of precipitation.