Thickness evolution of the Scandinavian Ice Sheet during the Late Weichselian in Nordfjord, western Norway: evidence from ice-flow modeling

AbstractThis work attempts to explain the fan-like landform assemblages observed in satellite images of the area covered by the former Scandinavian ice sheet (SIS). These assemblages have been interpreted as evidence of large ice streams within the SIS. If this interpretation is correct, then it calls into doubt current theories on the formation of ice streams. These theories regard soft sediment and topographic troughs as being the key determinants of ice-stream location. Neither can be used to explain the existence of ice streams on the flat, hard-rock area of the Baltic Shield. Initial results from a three-dimensional, thermomechanical ice-sheet model indicate that interactions between ice flow, form and temperature can create patterns similar to those mentioned above. The model uses a realistic, 20 km resolution gridded topography and a simple parameterization of accumulation and ablation. It produces patterns of maximum ice-sheet extent, which are similar to those reconstructed from the area’s glacial geomorphology. Flow in the maximum, equilibrium ice sheet is dominated by wedges of warm, low-viscosity, fast-flowing ice. These are separated by areas of cold, slow-flowing ice. This patterning appears to develop spontaneously as the modelled ice sheet grows.

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Late Weichselian thermal state at the base of the Scandinavian Ice Sheet

10.5194/cp-2019-49 ◽

2019 ◽

Cited By ~ 1

Author(s):

Dmitry Y. Demezhko ◽

Anastasia A. Gornostaeva ◽

Alexander N. Antipin

Keyword(s):

Thermal State ◽

Ice Sheet ◽

Ground Surface ◽

Substantial Part ◽

Temperature Pattern ◽

Glacial Cycle ◽

Surface Temperatures ◽

Scandinavian Ice Sheet ◽

Late Weichselian ◽

The Last Glacial

Abstract. Geothermal estimates of the ground surface temperatures for the last glacial cycle in Northern Europe has been analyzed. During the Middle and Late Weichselian (55–12 kyr BP) a substantial part of this area was covered by the Scandinavian Ice Sheet. The analysis of geothermal data has allowed reconstructing limits of the ice sheet extension and its basal thermal state in the Late Weichselian. Ground surface temperatures outside the ice sheet were extremely low (from −8 to −18 °C). Within the ice sheet, there were both thawed and frozen zones. The revealed temperature pattern is generally consistent with the modern one for the ground surface temperatures in Greenland that makes it possible to consider these ice sheets as analogues. The anomalous climatically induced surface heat flux and orbital insolation of the Earth varied consistently outside the glaciation and independently within the limits of the ice sheet.

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Ice-flow patterns and precise timing of ice sheet retreat across a dissected fjord landscape in western Norway

Quaternary Science Reviews ◽

10.1016/j.quascirev.2019.04.032 ◽

2019 ◽

Vol 214 ◽

pp. 139-163 ◽

Cited By ~ 4

Author(s):

Jan Mangerud ◽

Anna L.C. Hughes ◽

Tone Herfindal Sæle ◽

John Inge Svendsen

Keyword(s):

Ice Sheet ◽

Flow Patterns ◽

Ice Flow ◽

Precise Timing ◽

Western Norway

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Late Weichselian base temperatures of the Scandinavian ice sheet

10.5194/cp-2019-49-rc2 ◽

2019 ◽

Author(s):

Anonymous

Keyword(s):

Ice Sheet ◽

Scandinavian Ice Sheet ◽

Late Weichselian

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Genesis of the glaciotectonic thrust-fault complex at Halk Hoved, southern Denmark.

Bulletin of the Geological Society of Denmark ◽

10.37570/bgsd-2012-60-05 ◽

2012 ◽

Vol 60 ◽

pp. 61-80

Author(s):

Tillie M. Madsen

Keyword(s):

Pore Water Pressure ◽

Water Pressure ◽

Ice Sheet ◽

Thrust Fault ◽

Complex Deformation ◽

North East ◽

Macro Scale ◽

Scandinavian Ice Sheet ◽

Late Weichselian ◽

Southern Fringe

The coastal cliff of Halk Hoved, southern Jutland, Denmark, is a major glaciotectonic complex formed by proglacial deformation of the North-East (NE) advance from the Scandinavian Ice Sheet in Late Weichselian. We describe and interpret the pre-, syn- and post-tectonic sedimentary successions and macro-scale architecture of this complex. Initially, the Lillebælt Till Formation (unit 1) and the overlying glaciofluvial sediments (unit 2) were deposited during the Warthe glaciation in Late Saalian. During the NE advance towards the Main Stationary Line (MSL) in Late Weichselian, these sediments were pushed along a décollement surface whereby a thrust-fault complex was formed. In a cross section the complex extends for more than 900 m and consists of eighteen c. 15–20 m thick thrust sheets stacked by piggyback thrusting. Accumulated displacement amounts to at least 235 m along thrust faults dipping at 30–40° towards N-NE, resulting in at least 24% glaciotectonic shortening of the complex. Deformation was presumably facilitated by elevated pore-water pressure in the Lillebælt Till Formation. As the compressive stress exceeded the shear strength of the weakened till, failure occurred, and a décollement horizon formed along the lithological boundary between the Lillebælt Till Formation and the underlying aquifer. During deformation, piggyback basins formed wherein sediments of hyperconcentrated flow (unit 3) and glaciolacustrine diamicton (unit 4) were deposited. The whole thrust-fault complex and the intervening sediments were truncated subglacially as the NE advance finally overrode the complex. Following the retreat of the NE advance, a succession of glaciofluvial sediments (unit 5) and finally the East Jylland Till Formation (unit 6) were deposited during the advance of the Young Baltic Ice Sheet. The Halk Hoved thrust-fault complex is a prominent example of glaciotectonism at the southern fringe of the Scandinavian Ice Sheet.

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Tephrochronological evidence of a later Younger Dryas ice-sheet maximum in central Norway

10.5194/egusphere-egu21-11404 ◽

2021 ◽

Author(s):

Simon A. Larsson ◽

Stefan Wastegård ◽

Fredrik Høgaas

Keyword(s):

Radiocarbon Dating ◽

Ice Sheet ◽

Younger Dryas ◽

Coastal Lake ◽

Cold Event ◽

Western Norway ◽

Scandinavian Ice Sheet ◽

Marine Fossils ◽

Ice Sheet Dynamics ◽

Southern Norway

The Scandinavian Ice Sheet responded time-transgressively to the Younger Dryas (Greenland Stadial 1) cold event with large regional variations. Around Trondheimsfjorden in central Norway, the Tautra Moraines and the Hoklingen Moraines have long been assumed to have formed by glacial readvances during this event, as they have been dated to c. 12.7 and 11.6 cal. ka BP respectively (Olsen et al., 2015), mainly based on radiocarbon dating of often marine fossils. The Tautra Moraines, being the outer ridges of the two, should thus represent the maximum ice-sheet extent in this region during the Younger Dryas.This ice-front position established a pro-glacial lake west of present-day Leksvik village on the Fosen peninsula (Selnes, 1982), which covered the Lomtj&#248;nnin lakes and Lomtj&#248;nnmyran fens, and drained through a spillway via Lake R&#248;rtj&#248;nna. Some 20 km inland (northeast) from this location, inside the Tautra Moraines, the location of the Dam&#229;smyran bog was covered by the ice sheet at that time.By examining sediments from these sites for occurrences of volcanic ashes (visible and cryptotephra), combined with radiocarbon dating, we find that the ice front remained at the Tautra Moraines until the late Younger Dryas, contrary to the previous chronology (and overriding the suggested formation age of the Hoklingen Moraines). These findings comply with several recent reconstructions of the deglaciation at other sites in western (Lohne et al., 2012; Mangerud et al., 2016) and southern Norway (Romundset et al., 2019) and are a strong example of the usefulness of tephrochronology in the reconstruction of past ice-sheet dynamics.&#160;ReferencesLohne, &#216;.S., Mangerud, J. & Svendsen, J.I. (2012) Timing of the Younger Dryas glacial maximum in Western Norway. Journal of Quaternary Science, vol. 27, pp. 81&#8211;88.Mangerud, J., Aarseth, I., et al. (2016) A major re-growth of the Scandinavian Ice Sheet in western Norway during Aller&#248;d&#8211;Younger Dryas. Quaternary Science Reviews, vol. 132, pp. 175&#8211;205.Olsen, L., H&#248;gaas, F. & Sveian, H. (2015) Age of the Younger Dryas ice-marginal substages in Mid-Norway&#8212;Tautra and Hoklingen, based on a compilation of 14C-dates. Norges geologiske unders&#248;kelse Bulletin, vol. 454, pp. 1&#8211;13.Romundset, A., Lakeman, T.R. & H&#248;gaas, F. (2019) Coastal lake records add constraints to the age and magnitude of the Younger Dryas ice-front oscillation along the Skagerrak coastline in southern Norway. Journal of Quaternary Science, vol. 34, pp. 112&#8211;124.Selnes, H. (1982) Paleo-&#248;kologiske unders&#248;kelser omkring israndavsetninger p&#229; Fosenhalv&#248;ya, Midt-Norge. Thesis at the Department of Botany, University of Trondheim.

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Ice sheet unzipping in the mountain-piedmont region of west-central Sweden: complex late-deglaciation of the Scandinavian ice sheet

10.5194/egusphere-egu21-6517 ◽

2021 ◽

Author(s):

Robin Blomdin ◽

Gustaf Peterson Becher ◽

Colby Smith ◽

Carl Regnéll ◽

Christian Öhrling ◽

...

Keyword(s):

Regional Scale ◽

Ice Sheets ◽

Ice Sheet ◽

Spatial Density ◽

Ice Flow ◽

Westward Expansion ◽

West Central ◽

Scandinavian Ice Sheet ◽

Elevation Model ◽

Piedmont Region

Regional-scale glacial geomorphological maps provide important empirical data for reconstructions of former ice sheets, which may serve as analogues for the behaviour of modern ice sheets under climate warming. In particular, the extensive LiDAR-derived record of former ice sheet beds, provides an outstanding archive from which to infer former ice sheet behaviour. The stacking together and analysis of, tens of thousands of individual landforms, based on their spatial coherency, provides a powerful tool to reconstruct ice flow dynamics, temporally evolving ice divide positions and the &#8220;unzipping&#8221; of ice sheets into separate masses during deglaciation. In this study, we develop a glacial geomorphological dataset focussing on the mountain-piedmont region of J&#228;mtland in west-central Sweden. We focus on this region because it is where the last (Weichselian) ice sheet is believed to have unzipped into separate domes and was inundated by vast ice dammed lakes. J&#228;mtland also records a complex temporal evolution of subglacial processes and was formerly mapped without the benefit of a LiDAR-based elevation model. The dataset was created by mapping in GIS and covers an area of 50&#160;000 km2 and almost 88&#160;000 landforms, including glacial lineations, crag-and-tails, ice marginal moraines, lateral meltwater channels, eskers, and glacial lake shorelines. We use this unique dataset&#8211;in terms of spatial density and resolution&#8211;and quantitatively analyse cross-cutting relationships to establish a relative ice flow chronology. Our key findings include 1) a previously unmapped landform system, formed by the Early-to-Middle Weichselian westward expansion of a mountain centred ice sheet, and 2) a complex early Holocene deglaciation sequence with ice sheet unzipping occurring in southern and east-central J&#228;mtland. The ice sheet split into a larger sheet retreating northward and a smaller ice sheet remaining southeast of the mountain piedmont. Our results provide new insights into the late deglaciation of the Scandinavian Ice Sheet.

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