History and dynamics of Fennoscandian Ice Sheet retreat and contemporary ice-dammed lake evolution and faulting in the Torneträsk area, northwestern Sweden

The prospect of future sea level rise due to the melting of Antarctica and Greenland affirms an urgency to better understand the deglaciation dynamics of ephemeral ice sheets. The history and dynamics of Fennoscandian Ice Sheet retreat, reconstructed from glacial geomorphology, can serve as a useful analogue. The recent release of a 1 m LiDAR-derived national elevation model for Sweden reveals new insights, even for well-studied areas such as the Torneträsk region of northwestern Sweden. This study aims to refine the history of retreat and dynamics of the ice sheet margin during deglaciation based on glacial geomorphological mapping. The mapped glacial landforms are, by means of an inversion model, grouped in swarms representing spatially and temporally coherent ice sheet flow systems. Ice-dammed lake traces such as raised shorelines, perched deltas, and outlet channels, allow for the precise identification of ice margins. A strong topographic control on retreat patterns is evident, from ice sheet disintegration into separate lobes in the mountains to orderly retreat in the low-relief areas. Eight ice-dammed lake stages are identified for the Torneträsk basin, of which the lowest stages demonstrate the lake covered a larger extent than previously thought. The lake finally drains through Tornedalen by means of a glacial lake outburst flood. The Pärvie fault, the longest-known glacially-induced fault in the world, offsets the six oldest raised shorelines of Torneträsk. The implication of this new finding is that the Pärvie fault ruptured partially underneath the ice sheet in response to glacial isostatic adjustment to the unloading of the crust. Precise dating of the two bracketing raised shorelines would pinpoint the age of the Pärvie fault. Collectively, this study provides data for better understanding the history and dynamics of the Fennoscandian Ice Sheet during final retreat, such as interactions with ice-dammed lakes and re-activation of faults through glacial isostatic adjustment.