| 1. |
- Briner, Jason P., et al.
(author)
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Configuration of the Scandinavian Ice Sheet in southwestern Norway during the Younger Dryas
- 2023
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In: Norwegian Journal of Geology. - 2387-5844. ; 103
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Journal article (peer-reviewed)abstract
- The extent of the Scandinavian Ice Sheet in southwestern Norway is precisely located during the well-characterized Younger Dryas re-advance. However, the thickness of the ice sheet is less well constrained inland from the terminal position. Some exceptions include lateral moraines traced inland and up to 1000 m a.s.l. along Hardangerfjorden. Here, we apply 10Be dating in two areas: (1) bedrock and boulders in the high-relief landscapes near the Younger Dryas margin around the Bergen urban area, and (2) boulders from an upland 1600 m a.s.l. much farther (120 km) inland. We find that coastal summits ranging from ~400 to ~680 m a.s.l. and located only ~10–15 km up-flow from the ice margin, were covered by the Scandinavian Ice Sheet during the Younger Dryas. The scatter in the 10Be age population of 22 boulder samples is best explained by isotopic inheritance owing to inefficient subglacial erosion during the foregoing glaciation. Most of the 11 bedrock samples also exhibit inheritance, pointing to the source of inheritance in boulders and implying inefficient subglacial erosion during the last glaciation even in valley-bottoms near Bergen. Regional glacial striae compilations suggest that ice flow during maximum Younger Dryas ice-sheet configurations was for the most part cross-valley, with potentially low basal slip rates. Five new 10Be ages from the inland site help to constrain ice height far inland. We combine these new results with prior information to generate a cross profile of the Younger Dryas ice sheet in southern Norway.
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| 2. |
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| 3. |
- Gowan, Evan J., et al.
(author)
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A new global ice sheet reconstruction for the past 80000 years
- 2021
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In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 12:1
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Journal article (peer-reviewed)abstract
- The evolution of past global ice sheets is highly uncertain. One example is the missing ice problem during the Last Glacial Maximum (LGM, 26000-19000 years before present) - an apparent 8-28 m discrepancy between far-field sea level indicators and modelled sea level from ice sheet reconstructions. In the absence of ice sheet reconstructions, researchers often use marine delta O-18 proxy records to infer ice volume prior to the LGM. We present a global ice sheet reconstruction for the past 80000 years, called PaleoMIST 1.0, constructed independently of far-field sea level and delta O-18 proxy records. Our reconstruction is compatible with LGM far-field sea-level records without requiring extra ice volume, thus solving the missing ice problem. However, for Marine Isotope Stage 3 (57000-29000 years before present) - a pre-LGM period - our reconstruction does not match proxy-based sea level reconstructions, indicating the relationship between marine delta O-18 and sea level may be more complex than assumed. The configuration of past ice sheets, and therefore sea level, is highly uncertain. Here, the authors provide a global reconstruction of ice sheets for the past 80,000 years that allows to test proxy based sea level reconstructions and helps to reconcile disagreements with sea level changes inferred from models.
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| 4. |
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| 5. |
- Haflidason, Haflidi, et al.
(author)
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The Lastglacial and Holocene seismostratigraphy and sediment distribution of Lake Bolshoye Shchuchye, Polar Ural Mountains, Arctic Russia
- 2019
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In: Boreas. - : Wiley. - 0300-9483 .- 1502-3885. ; 48:2, s. 452-469
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Journal article (peer-reviewed)abstract
- Seismostratigraphical studies of the 11.8-km(2)-large and similar to 140-m-deep Lake Bolshoye Shchuchye, Polar Ural Mountains, reveal up to 160-m-thick acoustically laminated sediments in the lake basin. Using a dense grid of seismic lines, the spatial and temporal distributions of the sedimentary history have been reconstructed. Three regional seismic horizons have been identified and correlated with the well-dated 24-m-long sediment core retrieved from the lake. Isopach maps constructed from the seismic data show four phases of sedimentation. A contour map of the deepest regional seismic reflector represents the earliest hemipelagic sedimentation in the lake. Three contour maps represent time intervals covering the last 23cal. ka based on the well-dated core stratigraphy from the lake. The detailed time constraints on the upper stratigraphical units in the lake allow calculation of the lake's development in terms of sediment fluxes and the denudation rates from the Last Glacial Maximum (LGM) to the present. The sedimentation in Lake Bolshoye Shchuchye has been dominated by hemipelagic processes during at least the last 24cal. ka BP only locally interrupted by delta progradation and slope processes. A major shift in the sediment accumulation at c.18.7cal. ka BP is interpreted to mark the end of the local glacial maximum, greatly reduced denudation and the onset of the deglaciation period; this also demonstrates how fast the glaciers melted and possibly disappeared at the end of the LGM. The denudation rate during the Holocene is only a fifth of the LGM rate. The age of the oldest stratified sediments in Lake Bolshoye Shchuchye is not well constrained, but estimated as c. 50-60 ka.
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| 6. |
- Hughes, Anna L. C., et al.
(author)
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The last Eurasian ice sheets - a chronological database and time-slice reconstruction, DATED-1
- 2016
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In: Boreas. - : Wiley. - 0300-9483 .- 1502-3885. ; 45:1, s. 1-
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Journal article (peer-reviewed)abstract
- We present a new time-slice reconstruction of the Eurasian ice sheets (British-Irish, Svalbard-Barents-Kara Seas and Scandinavian) documenting the spatial evolution of these interconnected ice sheets every 1000 years from 25 to 10 ka, and at four selected time periods back to 40 ka. The time-slice maps of ice-sheet extent are based on a new Geographical Information System (GIS) database, where we have collected published numerical dates constraining the timing of ice-sheet advance and retreat, and additionally geomorphological and geological evidence contained within the existing literature. We integrate all uncertainty estimates into three ice-margin lines for each time-slice; a most-credible line, derived from our assessment of all available evidence, with bounding maximum and minimum limits allowed by existing data. This approach was motivated by the demands of glaciological, isostatic and climate modelling and to clearly display limitations in knowledge. The timing of advance and retreat were both remarkably spatially variable across the ice-sheet area. According to our compilation the westernmost limit along the British-Irish and Norwegian continental shelf was reached up to 7000 years earlier (at c. 2726 ka) than the eastern limit on the Russian Plain (at c. 20-19 ka). The Eurasian ice sheet complex as a whole attained its maximum extent (5.5 Mkm(2)) and volume (similar to 24 m Sea Level Equivalent) at c. 21 ka. Our continental-scale approach highlights instances of conflicting evidence and gaps in the ice-sheet chronology where uncertainties remain large and should be a focus for future research. Largest uncertainties coincide with locations presently below sea level and where contradicting evidence exists. This first version of the database and time-slices (DATED-1) has a census date of 1 January 2013 and both are available to download via the Bjerknes Climate Data Centre and PANGAEA (www.bcdc.no; http://doi.pangaea.de/10.1594/PANGAEA.848117).
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| 7. |
- Mangerud, Jan, et al.
(author)
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Did the Eurasian ice sheets melt completely in early Marine Isotope Stage 3? New evidence from Norway and a synthesis for Eurasia
- 2023
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In: Quaternary Science Reviews. - 0277-3791. ; 311
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Journal article (peer-reviewed)abstract
- We describe glaci-lacustrine sediments buried under thick tills in Folldalen, south-east Norway, a site located close to the former centre of the Scandinavian Ice Sheet. Thus, the location implies that the ice sheet had melted when the sediments were deposited. The exposed ground was occupied by arctic vegetation. The best age estimate from 20 quartz luminescence dates is 55.6 ± 4.6 ka. Due to possible incomplete bleaching, an age in the younger part of the time range is most probable. We conclude that the Scandinavian Ice Sheet melted almost completely away early in Marine Isotope Stage (MIS) 3. Our review shows that the other Eurasian ice sheets also disappeared in that period. In north-western Germany, there were forests, containing warmth-demanding trees early in MIS 3, indicating a summer climate only slightly cooler than at present, thus supporting the evidence that the adjacent ice sheets had melted. The melting of the Eurasian ice sheets contributed to 50–100% of the sea-level rise from MIS 4 to MIS 3, implying that the much larger North American ice sheets did not melt much. In contrast, the Eurasian ice sheets contributed only about 30% to the sea-level drop from MIS 3 to MIS 2, meaning that the North American ice sheets during that period expanded strongly.
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| 8. |
- Regnéll, Joachim, 1956-, et al.
(author)
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Ice-dammed lakes of Scandinavia : A key to the pattern and chronology of the final decay of the Scandinavian ice-sheet
- 2021
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Conference paper (other academic/artistic)abstract
- Here we present the use of ice-dammed lake-related landforms and sediments for reconstructing the final phases of decay of the Scandinavian Ice Sheet.In the late stages of the deglaciation, extensive glacial lakes were dammed between the easterly retreating Scandinavian Ice Sheet and the water divide within the mountains to the west. Using high-resolution airborne LiDAR-data, shorelines and other landforms relating to these ice-dammed lakes have now been discovered over larger areas and in greater numbers than previously known, opening a treasure trove of palaeoglaciological information of vast potential for reconstructing the final decay phase of the Scandinavian Ice Sheet.The geomorphological imprint of the ice-dammed lakes is of particular importance in northern Scandinavia, as geological evidence pertaining unequivocally to the final ice sheet decay is sparse. Its interpretation is complicated since the ice sheet is thought to have mainly been cold-based during final decay, inhibiting sliding at the ice-bed interface and limiting the construction (or destruction) of landforms indicative of the changing shape and flow of the ice sheet. Furthermore, dated sediment sequences marking the onset of ice-free conditions are woefully few in northern Scandinavia. Likewise, available cosmogenic nuclide exposure dates provide high age uncertainty and inadequate geographical cover, leaving the timing and location of final ice sheet decay still elusive.Using examples from northern and central Scandinavia, we show that ice-dammed lakes are an intricate part of the deglacial dynamics and show how mapping and dating them offer a solution to these problems. Even with a frozen ice-bed interface, surface melting and meltwater drainage creates landforms unequivocally associated with ice sheet decay: drainage channels, dammed lake shorelines, and deltas. Meltwater drainage routes and ice-dammed lakes are therefore powerful tools for reconstructing a disintegrating ice sheet; a ponded lake reveals the location of its requisite ice-dam, and drainage pathways reveal ice-free conditions. A dated sequence of ice-dammed lake sediments can therefore constrain both ice and lake coverage at that time for a much larger area than the dated site itself. Furthermore, the extent of different ice-dammed lake stages and their requisite ice-damming positions enables the pattern of ice margin change to be traced, and the relative age of ice-marginal positions determined using cross-cutting relations. The shorelines’ present-day tilts are also used to inform patterns and magnitudes of postglacial isostatic uplift, information otherwise lacking from the continental interior but of particular importance for modelling former ice sheet volumes and understanding the crustal response to ice sheet loading. Reconstructing the extents and timing of ice-dammed lakes and the study of related landforms and deposits can therefore greatly improve our understanding of the final decay of the Scandinavian Ice Sheet and provide potential analogues for the predicted future behaviours of modern ice sheets.
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| 9. |
- Regnéll, Joachim, et al.
(author)
-
Ice-dammed lakes of Scandinavia : A key to the pattern and chronology of the final decay of the Scandinavian ice-sheet
- 2021
-
Conference paper (other academic/artistic)abstract
- Here we present the use of ice-dammed lake-related landforms and sediments for reconstructing the final phases of decay of the Scandinavian Ice Sheet. In the late stages of the deglaciation, extensive glacial lakes were dammed between the easterly retreating Scandinavian Ice Sheet and the water divide within the mountains to the west. Using high-resolution airborne LiDAR-data, shorelines and other landforms relating to these ice-dammed lakes have now been discovered over larger areas and in greater numbers than previously known, opening a treasure trove of palaeoglaciological information of vast potential for reconstructing the final decay phase of the Scandinavian Ice Sheet. The geomorphological imprint of the ice-dammed lakes is of particular importance in northern Scandinavia, as geological evidence pertaining unequivocally to the final ice sheet decay is sparse. Its interpretation is complicated since the ice sheet is thought to have mainly been cold-based during final decay, inhibiting sliding at the ice-bed interface and limiting the construction (or destruction) of landforms indicative of the changing shape and flow of the ice sheet. Furthermore, dated sediment sequences marking the onset of ice-free conditions are woefully few in northern Scandinavia. Likewise, available cosmogenic nuclide exposure dates provide high age uncertainty and inadequate geographical cover, leaving the timing and location of final ice sheet decay still elusive. Using examples from northern and central Scandinavia, we show that ice-dammed lakes are an intricate part of the deglacial dynamics and show how mapping and dating them offer a solution to these problems. Even with a frozen ice-bed interface, surface melting and meltwater drainage creates landforms unequivocally associated with ice sheet decay: drainage channels, dammed lake shorelines, and deltas. Meltwater drainage routes and ice-dammed lakes are therefore powerful tools for reconstructing a disintegrating ice sheet; a ponded lake reveals the location of its requisite ice-dam, and drainage pathways reveal ice-free conditions. A dated sequence of ice-dammed lake sediments can therefore constrain both ice and lake coverage at that time for a much larger area than the dated site itself. Furthermore, the extent of different ice-dammed lake stages and their requisite ice-damming positions enables the pattern of ice margin change to be traced, and the relative age of ice-marginal positions determined using cross-cutting relations. The shorelines’ present-day tilts are also used to inform patterns and magnitudes of postglacial isostatic uplift, information otherwise lacking from the continental interior but of particular importance for modelling former ice sheet volumes and understanding the crustal response to ice sheet loading. Reconstructing the extents and timing of ice-dammed lakes and the study of related landforms and deposits can therefore greatly improve our understanding of the final decay of the Scandinavian Ice Sheet and provide potential analogues for the predictedfuture behaviours of modern ice sheets.
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| 10. |
- Svendsen, John Inge, et al.
(author)
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Glacial and environmental changes over the last 60000years in the Polar Ural Mountains, Arctic Russia, inferred from a high-resolution lake record and other observations from adjacent areas
- 2019
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In: Boreas. - : Wiley. - 0300-9483 .- 1502-3885. ; 48:2, s. 407-431
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Journal article (peer-reviewed)abstract
- Our knowledge about the glaciation history in the Russian Arctic has to a large extent been based on geomorphological mapping supplemented by studies of short stratigraphical sequences found in exposed sections. Here we present new geochronological data from the Polar Ural Mountains along with a high-resolution sediment record from Bolshoye Shchuchye, the largest and deepest lake in the mountain range. Seismic profiles show that the lake contains a 160-m-thick sequence of unconsolidated lacustrine sediments. A well-dated 24-m-long core from the southern end of the lake spans the last 24cal. ka. From downward extrapolation of sedimentation rates we estimate that sedimentation started about 50-60 ka ago, most likely just after a large glacier had eroded older sediments from the basin. Terrestrial cosmogenic nuclide (TCN) exposure dating (Be-10) of boulders and Optically Stimulated Luminescence (OSL) dating of sediments indicate that this part of the Ural Mountains was last covered by a coherent ice-field complex during Marine Isotope Stage (MIS) 4. A regrowth of the glaciers took place during a late stage of MIS 3, but the central valleys remained ice free until the present. The presence of small- and medium-sized glaciers during MIS 2 is reflected by a sequence of glacial varves and a high sedimentation rate in the lake basin and likewise from Be-10 dating of glacial boulders. The maximum extent of the mountain glaciers during MIS 2 was attained prior to 24cal. ka BP. Some small present-day glaciers, which are now disappearing completely due to climate warming, were only slightly larger during the Last Glacial Maximum (LGM) as compared to AD 1953. A marked decrease in sedimentation rate around 18-17cal. ka BP indicates that the glaciers then became smaller and probably disappeared altogether around 15-14cal. ka BP.
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