The Role of Ice-Sheet Topography in the Alpine Hydro-Climate at Glacial Times

Abstract

Abstract. In this study, we investigate the sensitivity of the glacial Alpine hydro-climate to northern hemispheric and local ice-sheet changes. Bridging the scale gap by using a chain of global and regional climate models, we perform sensitivity simulations of up to 2 km horizontal resolution over the Alps for the Last Glacial Maximum (LGM) and the Marine Isotope Stage 4 (MIS4). In winter, we find wetter conditions in the southern part of the Alps during LGM compared to present day, to which dynamical processes, i.e., changes in the wind speed and direction, substantially contribute. During summer, we find the expected drier conditions in most of the Alpine region during LGM, as thermodynamics suggests drier conditions under lower temperatures. The MIS4 climate shows enhanced winter precipitation compared to the LGM, which is explain by its warmer climate compared to the LGM – thus, again explained by thermodynamics. The sensitivity simulations of the northern hemispheric ice-sheet changes show that an increase of the ice-sheet thickness leads to a significant intensification of glacial Alpine hydro-climate conditions, which is mainly explained by dynamical processes. Changing only the Fennoscandian ice sheet is less influential on the Alpine precipitation, whereas modifications in the local Alpine ice-sheet topography significantly alter the Alpine precipitation, in particular we find a reduction of summer precipitation at the southern face of the Alps when lowering the Alpine ice sheet. The findings demonstrate that the northern hemispheric and local ice-sheet topography play an important role in regulating the Alpine hydro-climate and thus permits a better understanding of the precipitation patterns in the complex Alpine terrain at glacial times.

Last Glacial Maximum glacier fluctuations on the northern Alpine foreland: Geomorphological and chronological reconstructions from the Rhine and Reuss glacier systems

“…The aim of this study is to gain an understanding of the behavior of the Rhine and Reuss glaciers during the LGM by reconstructing their ice margins at various points in time. Such data are required to understand large-scale atmospheric patterns and thus forcing mechanisms in Alps paleoclimate, specifically the impact of the Laurentide ice sheet on paleoprecipitation (Luetscher et al, 2015;Monegato et al, 2017;Višnjević et al, 2020;Gribenski et al, 2021;Del Gobbo et al, 2022;Velasquez et al, 2022). This is an issue of some significance as different approaches have led to markedly divergent interpretations with respect to moisture delivery trajectories.…”

“…Either a situation similar to today's, dominated by westerlies throughout the LGM (Višnjević et al, 2020) or an early phase of dominant meridional moisture transport (Luetscher et al, 2015;Spötl et al, 2021) are discussed. Finally, chronologically well constrained, mapped LGM ice extents provide critical points of validation and ground truthing for Alpine ice cap modelling results (Becker et al, 2016;Seguinot et al, 2018;Imhof et al, 2019) and the regional climate model input functions (Velasquez et al, 2020(Velasquez et al, , 2021(Velasquez et al, , 2022.…”