| 1. |
- Hubberten, HW, et al.
(författare)
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The periglacial climate and environment in northern Eurasia during the Last Glaciation
- 2004
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 23:11-13, s. 1333-1357
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Forskningsöversikt (refereegranskat)abstract
- This paper summarizes the results of studies of the Late Weichselian periglacial environments carried out in key areas of northern Eurasia by several QUEEN teams (European Science Foundation (ESF) programme: "Quaternary Environment of the Eurasian North"). The palaeoglaciological boundary conditions are defined by geological data on timing and extent of the last glaciation obtained in the course of the EU funded project "Eurasian Ice Sheets". These data prove beyond any doubt, that with the exception of the northwestern fringe of the Taymyr Peninsula, the rest of the Eurasian mainland and Severnaya Zemlya were not affected by the Barents-Kara Sea fee Sheet during the Last Glacial Maximum (LGM). Inversed modelling based on these results shows that a progressive cooling which started around 30 ka BP, caused ice growth in Scandinavia and the northwestern areas of the Barents-Kara Sea shelf, due to a maritime climate with relatively high precipitation along the western flank of the developing ice sheets. In the rest of the Eurasian Arctic extremely low precipitation rates (less than 50 mm yr(-1)), did not allow ice sheet growth in spite of the very cold temperatures. Palaeoclimatic and palaeoenvironmental conditions for the time prior to, during, and after the LGM have been reconstructed for the non-glaciated areas around the LGM ice sheet with the use of faunal and vegetation records, permafrost, eolian sediments, alluvial deposits and other evidences. The changing environment, from interstadial conditions around 30 ka BP to a much colder and drier environment at the culmination of the LGM at 20-15 ka BP, and the beginning of warming around 15 ka BP have been elaborated from the field data, which fits well with the modelling results. (C) 2003 Elsevier Ltd. All rights reserved.
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| 2. |
- Svendsen, JI, et al.
(författare)
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Late quaternary ice sheet history of northern Eurasia
- 2004
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Ingår i: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791. ; 23:11-13, s. 1229-1271
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Forskningsöversikt (refereegranskat)abstract
- The maximum limits of the Eurasian ice sheets during four glaciations have been reconstructed: (1) the Late Saalian (> 140 ka), (2) the Early Weichselian (100-80 ka), (3) the Middle Weichselian (60-50 ka) and (4) the Late Weichselian (25-15 ka). The reconstructed ice limits are based on satellite data and aerial photographs combined with geological field investigations in Russia and Siberia, and with marine seismic- and sediment core data. The Barents-Kara Ice Sheet got progressively smaller during each glaciation, whereas the dimensions of the Scandinavian Ice Sheet increased. During the last Ice Age the Barents-Kara Ice Sheet attained its maximum size as early as 90-80,000 years ago when the ice front reached far onto the continent. A regrowth of the ice sheets occurred during the early Middle Weichselian, culminating about 60-50,000 years ago. During the Late Weichselian the Barents-Kara Ice Sheet did not reach the mainland east of the Kanin Peninsula, with the exception of the NW fringe of Taimyr. A numerical ice-sheet model, forced by global sea level and solar changes, was run through the full Weichselian glacial cycle. The modeling results are roughly compatible with the geological record of ice growth, but the model underpredicts the glaciations in the Eurasian Arctic during the Early and Middle Weichselian. One reason for this is that the climate in the Eurasian Arctic was not as dry then as during the Late Weichselian glacial maximum.
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| 3. |
- Houmark-Nielsen, M, et al.
(författare)
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Southwest Scandinavia, 40-15 kyr BP: palaeogeography and environmental change
- 2003
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Ingår i: Journal of Quaternary Science. - : Wiley. - 1099-1417 .- 0267-8179. ; 18:8, s. 769-786
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Forskningsöversikt (refereegranskat)abstract
- Twelve palaeogeographical reconstructions illustrate environmental changes at the southwest rim of the Scandinavian Ice Sheet 40-15 kyr BP. Synchronised land, sea and glacier configurations are based on the lithostratigraphy of tills and intertill sediments. Dating is provided by optically stimulated luminescence and calibrated accelerator mass spectrometry radiocarbon. An interstadial sequence ca. 40-30 kyr BP with boreo-arctic proglacial fjords and subarctic flora and occasional glaciation in the Baltic was succeeded by a Last Glacial Maximum sequence ca. 3020 kyr BP, with the closure of fjords and subsequent ice streams in glacial lake basins in Kattegat and the Baltic. Steadily flowing ice from Sweden bordered the Norwegian Channel Ice Stream. A deglaciation sequence ca. 20-15 kyr BP indicates the transgression of arctic waters, retreat of the Swedish ice and advance of Baltic ice streams succeeded by a return to interstadial conditions. When ameliorated ice-free conditions prevailed in maritime regions, glaciers advanced through the Baltic and when interstadial regimes dominated the Baltic, glaciers expanded off the Norwegian coast. The largest glacier extent was reached in the North Sea around 29 kyr BP, about 22 kyr BP in Denmark and ca. 18 kyr BP in the Baltic. Our model provides new data for future numerical and qualitative landform-based models. Copyright (C) 2003 John Wiley Sons, Ltd.
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| 4. |
- Kjaer, Kurt, et al.
(författare)
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Ice-flow patterns and dispersal of erratics at the southwestern margin of the last Scandinavian Ice Sheet: signature of palaeo-ice streams
- 2003
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Ingår i: Boreas. - : Wiley. - 1502-3885 .- 0300-9483. ; 32:1, s. 130-148
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Tidskriftsartikel (refereegranskat)abstract
- An extensive set of proxy-data was acquired from eastern and central Denmark in order to study the dynamic behaviour of the southwestern margin of the last Scandinavian Ice Sheet. We examine the last three glacier advances of the Late Weichselian: the Main advance from central Sweden, representing the maximum ice extent at this time (c. 21-20 ka BP), and the two succeeding Baltic advances (c. 18-15 ka BP). Directional properties from tills and glaciotectonic overprints are used to reveal large-scale flowline patterns. Together with the geomorphological outline of ice margins, flowlines were successively more fan-shaped, indicating that the dependence of the subglacial topography increases as ice advances become younger. It is suggested that while the ice thickness decreases. more lobate configurations of ice margins are created as a result. Clast-compositional data derived from the fine-gravel fraction in tills are used to reconstruct dispersal patterns of erratic material. The dispersal patterns during the three advances show a gradually diminishing influence of local Pre-Quaternary bedrocks and older glacial deposits, and progressively longer transport distances of far-travelled erratics. We speculate that the principal factor governing this development is a successively decreasing interaction between the ice and its bed, which influences the concentration of erratics. debris comminution processes and the basal ice velocity. We envisage the Main advance from central Sweden as a slow-flowing inter-stream ice body with high bed interaction compared to the succeeding Baltic advances, which we regard to have been rapid flowing ice streams with limited bed interaction.
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| 5. |
- Parducci, Laura, et al.
(författare)
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Glacial Survival of Boreal Trees in Northern Scandinavia
- 2012
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 335:6072, s. 1083-1086
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Tidskriftsartikel (refereegranskat)abstract
- It is commonly believed that trees were absent in Scandinavia during the last glaciation and first recolonized the Scandinavian Peninsula with the retreat of its ice sheet some 9000 years ago. Here, we show the presence of a rare mitochondrial DNA haplotype of spruce that appears unique to Scandinavia and with its highest frequency to the west-an area believed to sustain ice-free refugia during most of the last ice age. We further show the survival of DNA from this haplotype in lake sediments and pollen of Trondelag in central Norway dating back similar to 10,300 years and chloroplast DNA of pine and spruce in lake sediments adjacent to the ice-free Andoya refugium in northwestern Norway as early as similar to 22,000 and 17,700 years ago, respectively. Our findings imply that conifer trees survived in ice-free refugia of Scandinavia during the last glaciation, challenging current views on survival and spread of trees as a response to climate changes.
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