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

Abstract

Abstract. 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 km2. 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 km2 in 1952, was reduced to 5.91 km2 in 2001 (−25.5 %) before collapsing to 4.21 km2 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.

Ice aprons on steep high-alpine slopes: insights from the Mont-Blanc massif, Western Alps

“…The combination of the current IA high retreat rates, the reduction of their albedo accelerating melting, their reduced thicknesses and the acceleration of global warming leads concern with regard to a very large number of IAs disappearing in the short term. At the present rate (Kaushik and others, 2022 b ), the IAs in the MMB would lose another half of their surface area within 20 years. IAs thus seem to be among the most vulnerable components of the mountain cryosphere.…”

“…Although some international glacier inventories have existed since the mid-1970s, like the World Glacier Inventory (WGMS, 1989) or the Randolph Glacier Inventory (RGI), no data were available for IAs partly because IAs are not glaciers and therefore not systematically contained in these inventories. First steps have been made in the MBM by Guillet and Ravanel (2020) and Suvrat and others (2022 b ) while thickness losses also become significant as indicated by first observations and measurements, affecting the stability of recently deglaciated and permafrost-affected rock walls. The interactions between IAs and permafrost need to be better understood.…”

“…Paul and others, 2013). The work has recently been completed by Kaushik and others (2022 b ) by including the years 1952 and 2001 from ortho-images IGN. The total surface area of IAs in 1952 was 7.93 km 2 and then dropped to 5.91 km 2 in 2001, 4.92 km 2 in 2012 and 4.21 km 2 in 2019 (Fig.…”

“…IAs are small ice masses located in mainly concave topographies (Kaushik and others, 2022 b ). The loss of surface is therefore related to the loss of thickness.…”