Effects of topographic and meteorological parameters on the surface area loss of ice aprons in the Mont Blanc massif (European Alps)

Ice aprons (IAs) are part of the critical components of the Alpine cryosphere. As a result of the changing climate over the past few decades, deglaciation has resulted in a surface decrease of IAs, which has not yet been documented, except for a few specific examples. In this study, we quantify the effects of climate change on IAs since the mid-20th century in the Mont Blanc massif (western European Alps). We then evaluate the role of meteorological parameters and the local topography in the behaviour of IAs. We precisely mapped the surface areas of 200 IAs using high-resolution aerial and satellite photographs from 1952, 2001, 2012 and 2019. From the latter inventory, the surface area of the present individual IAs ranges from 0.001 to 0.04 km(2). IAs have lost their surface area over the past 70 years, with an alarming increase since the early 2000s. The total area, from 7.93 km(2) in 1952, was reduced to 5.91 km(2) in 2001 (-25.5 %) before collapsing to 4.21 km(2) in 2019 (-47 % since 1952). We performed a regression analysis using temperature and precipitation proxies to better understand the effects of meteorological parameters on IA surface area variations. We found a strong correlation between both proxies and the relative area loss of IAs, indicating the significant influence of the changing climate on the evolution of IAs. We also evaluated the role of the local topographic factors in the IA area loss. At a regional scale, factors like direct solar radiation and elevation influence the behaviour of IAs, while others like curvature, slope and size of the IAs seem to be rather important on a local scale.