Preprints
https://doi.org/10.5194/egusphere-2024-2486
https://doi.org/10.5194/egusphere-2024-2486
14 Aug 2024
 | 14 Aug 2024

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

Karlijn Ploeg and Arjen Peter Stroeven

Abstract. The prospect of alarming levels of future sea level rise in response to the melting of the Antarctic and Greenland ice sheets affirms an urgency to better understand the dynamics of these retreating ice sheets. The history and dynamics of the ephemeral ice sheets of the Northern Hemisphere, such as the Fennoscandian Ice Sheet, reconstructed from glacial geomorphology, can thus serve as a useful analogue. The recent release of a 1 m LiDAR-derived national elevation model reveals an unprecedented record of the glacial geomorphology in Sweden. This study aims to offer new insights and precision regarding ice retreat in the Torneträsk region of northwestern Sweden, and the influence of ice-dammed lakes and faulting on the dynamics of the ice sheet margin during deglaciation. Using an inversion model, mapped glacial landforms are ordered in swarms representing spatially and temporally coherent ice sheet flow systems. Ice-dammed lake traces such as raised shorelines, perched deltas, spillways, and outlet channels, are particularly useful for pin-pointing precise locations 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 low-relief areas. Eight ice-dammed lake stages are outlined for the Torneträsk Basin, the lowest of which yield lake extents more extensive than previously identified. The three youngest stages released a total of 26 km3 of glacial lake outburst floods (GLOFs) through Tornedalen, changing the valley morphology and depositing thick deltaic sequences in Ancylus Lake at its highest postglacial shoreline at around 10 cal ka BP. The Pärvie Fault, the longest-known glacially-induced fault in the Sweden, offsets the six oldest lake stages in the Torneträsk Basin. Cross-cutting relationships between glacial landforms and fault scarp segments are indicative of the Pärvie Fault rupturing multiple times during the last deglaciation and, indeed, before deglaciation. Precise dating of the two bracketing raised shorelines or the ages of the corresponding GLOF sediments would pinpoint the age of this rupture 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 rupture or re-activation of faults through glacial isostatic adjustment.

Publisher's note: Copernicus Publications remains neutral with regard to jurisdictional claims made in the text, published maps, institutional affiliations, or any other geographical representation in this preprint. The responsibility to include appropriate place names lies with the authors.
Karlijn Ploeg and Arjen Peter Stroeven

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2024-2486', Colby A. Smith, 30 Aug 2024
    • AC1: 'Reply on RC1', Karlijn Ploeg, 25 Oct 2024
  • RC2: 'Comment on egusphere-2024-2486', Benjamin Boyes, 16 Sep 2024
    • AC2: 'Reply on RC2', Karlijn Ploeg, 25 Oct 2024
Karlijn Ploeg and Arjen Peter Stroeven
Karlijn Ploeg and Arjen Peter Stroeven

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Short summary
Mapping of glacial landforms using LiDAR data shows that the retreating margin of the Fennoscandian Ice Sheet dammed a series of lakes in the Torneträsk Basin during deglaciation. These lakes were more extensive than previously thought and produced outburst floods. We show that sections of the Pärvie Fault, the longest glacially-activated fault of Sweden, ruptured at different times, both underneath and in front of the ice sheet, and during the existence of ice-dammed lake Torneträsk.