Showing papers by "Arjen P. Stroeven published in 2023"

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

Abstract: 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.

A topographic hinge-zone divides coastal and inland ice dynamic regimes in East Antarctica

Abstract: Abstract The impact of late Cenozoic climate on the East Antarctic Ice Sheet is uncertain. Poorly constrained patterns of relative ice thinning and thickening impair the reconstruction of past ice-sheet dynamics and global sea-level budgets. Here we quantify long-term ice cover of mountains protruding the ice-sheet surface in western Dronning Maud Land, using cosmogenic Chlorine-36, Aluminium-26, Beryllium-10, and Neon-21 from bedrock in an inverse modeling approach. We find that near-coastal sites experienced ice burial up to 75–97% of time since 1 Ma, while interior sites only experienced brief periods of ice burial, generally <20% of time since 1 Ma. Based on these results, we suggest that the escarpment in Dronning Maud Land acts as a hinge-zone, where ice-dynamic changes driven by grounding-line migration are attenuated inland from the coastal portions of the East Antarctic Ice Sheet, and where precipitation-controlled ice-thickness variations on the polar plateau taper off towards the coast.

Last ice sheet recession and landscape emergence above sea level in east central Sweden, evaluated using 14C produced in situ in quartz

Abstract: The aim of this study is to test the Holocene relative sea-level (RSL) curve (or shoreline displacement curve) for east central Sweden using 14C produced in situ in quartz-bearing bedrock (in-situ 14C). The original RSL curve is instead based on radiocarbon dating of organic material from isolation basins. Having an accurate RSL curve is crucial from at least two aspects. In Sweden&#8217;s safety assessments for a planned spent nuclear fuel repository and for the existing repository for low- and intermediate level waste, the RSL curve is used to constrain the emergence above sea level in landscape development models. Also, the RSL is used to constrain model estimates of rates and depths of glacial and subaerial erosion from cosmogenic 10Be and 26Al produced in situ in quartz in bedrock surfaces.Avoiding vein quartz and hydrothermally altered bedrock, five samples of granitoid bedrock were taken along an elevation transect extending southwards from Forsmark, the location of the planned spent nuclear fuel repository. Because all samples derive from bedrock outcrops positioned below the highest postglacial shoreline, they target the timing of progressive landscape emergence above sea level. To further assess the accuracy of in-situ 14C dating, we took an additional five samples from bedrock outcrops 100 km west of Forsmark, above the highest postglacial shoreline. The in-situ 14C concentrations in these samples should reflect local deglaciation ages.The ten new in-situ 14C measurements provide robust age constraints that compare favorably with the original RSL curve derived from radiocarbon&#160;dating of organic material in isolation basins and with the regional deglaciation chronology. Inferences of limited rates and depths of bedrock erosion over the past 1 Myr, inferred from 10Be and 26Al inheritance and which are critically dependent on the RSL curve, therefore glean strong support from these new in-situ 14C measurements.