How glacial landscape evolution has impacted Scandinavian Ice Sheet dynamics and dimensions

The topography and bathymetry of Scandinavia have been molded by ice across numerous glacial cycles during the Quaternary. In this study, we explore the interplay between this changing morphology and the Scandinavian Ice Sheet (SIS). Using a higher-order ice-sheet model, we simulate the SIS over a glacial cycle on three different topographies, representing different stages of Quaternary glacial landscape evolution. By subjecting these simulations to identical climate conditions, we isolate the effects of landscape morphology on the evolution and dynamics of the ice sheet. Our findings indicate that early Quaternary glaciations in Scandinavia were restricted in both extent and volume by the pre-glacial bathymetry. It was only as glacial deposits filled a depression in the North Sea and expanded the Norwegian shelf that the ice sheet could expand further. This is illustrated by our middle to late Quaternary simulation (around 0.5 million years ago), where a filled bathymetry facilitated both a faster and further southward expansion, resulting in a relative increase in both ice-sheet volume and extent. Additionally, our study highlights that the formation of The Norwegian Channel acted as a barrier to southward ice-sheet expansion. This limitation only allowed the ice sheet to advance into the southern North Sea close to glacial maxima. Notably, our experiments suggest that distinct segments of The Norwegian Channel may have formed in different stages during glacial periods after the bathymetry was sufficiently filled with glacial sediments. These results underscore the importance of considering changes in landscape morphology over time when interpreting ice-sheet history based on ice-volume proxies and when interpreting climate variability from past ice-sheet extents.