Reconstruction of the late Vistulian Fennoscandian Ice Sheet - based on numerical modelling and sensitivity analyses

This study presents a modelled reconstruction of the past ice dynamics of the Fennoscandian Ice Sheet, paying particular attention to the interactions between the ice sheet margin in Poland and the Baltic and Norwegian Channel Ice Streams. The focus is on the Late Vistulian time period, 24 – 12 ka BP, a key stage of the Last Glacial Period, characterized by significant climatic fluctuations and a dynamic evolution of the ice sheets over Northern Europe. In our reconstruction we use a numerical model constrained by empirical data, such as glacial landforms, glacial and postglacial deposits, and geochronology, to test the relationship between the modelled extent of the Fennoscandian Ice Sheet and its climatic and basal boundary conditions. A series of simulations were carried out for the Fennoscandian and British–Irish ice sheets with a spatial resolution of 10 km. These simulations applied and modified climates from the Paleoclimate Modelling Intercomparison Project – Phase 4 (PMIP4), and in tandem explored the importance of basal friction conditions on ice behaviour in this region. The modelling results reveal the existence of ice streams with diverse spatiotemporal characteristics. Their widths range from several tens to several hundreds of kilometres, while velocities vary from a few hundred to more than 1000 meters per year. The dynamic behaviour of these ice streams strongly controls the southern extent of the Fennoscandian Ice Sheet during deglaciation, forming pronounced lobate outlets reaching several hundred kilometres in length and several hundred meters in thickness at the Southern margin. Significantly, adjustments impacting friction beneath one ice stream alters its behaviour in such a way that it then influences the dynamics of other ice streams. In particular, there is a significant interplay such that when we reduce activity of Norwegian Channel Ice Stream, the ice divide between the Baltic Ice Stream and the Norwegian Channel Ice Stream migrates. As a consequence, this changes the behavior of Baltic Ice Stream and the extent of the ice at the ice sheet margin in Poland. This is the first time the two major outlets of the Fennoscandian Ice Sheet have been shown to be so strongly linked in controlling the wider southern margin of the ice sheet.

Funding sources: This research was funded by the National Science Centre (NCN) under grant no. 2024/08/X/ST10/00193 and 2015/17/D/ST10/01975.

 

Acknowledgements: Numerical analyses were carried out using the computing cluster provided by the Faculty of Mathematics and Computer Science, Adam Mickiewicz University, Poznań, Poland.