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  • 1. Adrielsson, L
    et al.
    Alexanderson, H
    Interactions between the Greenland Ice Sheet and the Liverpool Land coastal ice cap during the last two glaciation cycles2005Inngår i: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 20, nr 3, s. 269-283Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The sedimentary record from the Ugleelv Valley on central Jameson Land, East Greenland, adds new information about terrestrial palaeoenvironments and glaciations to the glacial history of the Scoresby Sund fjord area. A western extension of a coastal ice cap on Liverpool Land reached eastern Jameson Land during the early Scoresby Sund glaciation (approximate to the Saalian). During the following glacial maximum the Greenland Ice Sheet inundated the Jameson Land plateau from the west. The Weichselian also starts with an early phase of glacial advance from the Liverpool Land ice cap, while polar desert and ice-free conditions characterised the subsequent part of the Weichselian on the Jameson Land plateau. The two glaciation cycles show a repeated pattern of interaction between the Greenland Ice Sheet in the west and an ice cap on Liverpool Land in the east. Each cycle starts with extensive glacier growth in the coastal mountains followed by a decline of the coastal glaciation, a change to cold and arid climate and a late stage of maximum extent of the Greenland Ice Sheet. Copyright (c) 2005 John Wiley T Sons, Ltd.

  • 2. Andresen, C S
    et al.
    Björck, S
    Bennike, O
    Bond, G
    Holocene climate changes in southern Greenland: evidence from lake sediments2004Inngår i: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 19, nr 8, s. 783-795Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A Holocene lake sediment record is presented from Lake N14 situated on Angissoq island 15 km off the main coast of southern Greenland. The palaeoclimatic development has been interpreted on the basis of flux and percentage content of biogenic silica, clastic material, organic material and sulphur as well as sedimentation rate, moss content and magnetic susceptibility. A total of 43 radiocarbon dates has ensured a reliable chronology. It is argued that varying sediment composition mainly reflects changing precipitation. By analogy with the present meteorological conditions in southern Greenland, Holocene climate development is inferred. Between 11550 and 9300 cal. yr BP temperature and precipitation increase markedly, but this period is climatically unstable. From 9300 yr BP conditions become more stable and a Holocene climatic optimum, characterised by warm and humid conditions, is observed from 8000 to 5000 cal. yr BP. From 4700 cal. yr BP the first signs of a climatic deterioration are observed, and from 3700 cal. yr BP the climate has become more dry and cold. Superimposed on the climatic long-term trend is climate variability on a centennial time-scale that increases in amplitude after 3700 cal. yr BP. A climatic scenario related to the strength and position of the Greenland high-pressure cell and the Iceland low-pressure cell is proposed to explain the Holocene centennial climate variability. A comparison of the Lake N14 record with a terrestrial as well as a marine record from the eastern North Atlantic Ocean suggests that the centennial climate variability was uniform over large areas at certain times. Copyright (C) 2004 John Wiley Sons, Ltd.

  • 3. Andrén, Thomas
    et al.
    Björck, J
    Johnsen, S
    Correlation of Swedish glacial varves with the Greenland (GRIP) oxygen isotope record1999Inngår i: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 14, nr 4, s. 361-371Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A mean varve thickness curve has been constructed for a part of the Swedish varve chronology from the northwestern Baltic proper. The mean varve thickness curve has been correlated with the delta(18)O record from the GRIP ice-core using the Younger Dryas-Preboreal climate shift. This climate shift was defined by pollen analyses. The Scandinavian ice-sheet responded to a warming at the end of the Younger Dryas, ca. 10 995 to 10 700 clay-varve yr BP. Warming is recorded as a sequence of increasing mean varve thickness and ice-rafted debris suggesting intense calving of the ice front. The Younger Dryas-Preboreal climatic shift is dated to ca. 10 650 clay-varve yr BP, about 40 yr after the final drainage of the Baltic Ice Lake. Both the pollen spectra and a drastic increase in varve thickness reflect this climatic shift. A climate deterioration, correlated with the Preboreal oscillation, is dated to ca. 10 440 to 10 320 clay-varve yr BP and coincides with the brackish water phase of the Yoldia Sea stage. The ages of the climatic oscillations at the Younger Dryas-Preboreal transition show an 875 yr discrepancy compared with the GRIP record, suggesting a large error in the Swedish varve chronology in the part younger than ca. 10 300 clay-varve yr BP.

  • 4. Bourne, A. J.
    et al.
    Davies, S. M.
    Abbott, P. M.
    Rasmussen, S. O.
    Steffensen, J. P.
    Svensson, A.
    Revisiting the Faroe Marine Ash Zone III in two Greenland ice cores: implications for marine-ice correlations2013Inngår i: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 28Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Nineteen new Icelandic tephra layers are identified in NGRIP and NEEM ice spanning Greenland Interstadial-9 (GI-9) and the early phase of GI-8 (similar to 38 000-40 500 b2k). Fourteen tephras are identified in the NGRIP record and five direct correlatives are identified in NEEM, thus indicating the occurrence of 14 separate volcanic events. With two exceptions, the tephras are tholeiitic basalt in composition and despite having very similar geochemical signatures can, in most cases, be discriminated from one another using their TiO2 values. All of these tephra layers fall within the compositional range of the Faroe Marine Ash Zone III (FMAZ III) deposit previously identified in ocean cores from the Faroes region and previously correlated to NGRIP 2066.95m by Davies et al. (2010). Thus, the FMAZ III in the marine realm is most likely a complex ash zone that represents a series of closely timed Grimsvotn eruptions that, as yet, can only be stratigraphically separated in the high-resolution ice-core records. The geochemical signatures and stratigraphic positions of the new ice-core layers means that the FMAZ III tephra deposit, as currently defined in the marine realm, cannot be correlated to NGRIP 2066.95m or any other ice-core tephra horizons preserved during this interval. Copyright (C) 2013 John Wiley & Sons, Ltd.

  • 5. ESPER, JAN
    et al.
    DÜTHORN, ELISABETH
    KRUSIC, PAUL J.
    TIMONEN, MAURI
    BÜNTGEN, ULF
    Northern European summer temperature variations over the Common Era from integrated tree-ring density records2014Inngår i: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 29, nr 5, s. 487-494Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Tree-ring chronologies of maximum latewood density are most suitable to reconstruct annually resolved summer temperature variations of the late Holocene. The two longest such chronologies have been developed in northern Europe stretching back to the 2nd century BC, and the 5th century AD. We show where similarities between the two chronologies exist, and combine portions of both into a new summer temperature reconstruction for the Common Era. To minimize the transfer of potential biases, we assess the contribution of the candidate reconstructions’ measurements, and exclude data (i) from exceptionally young and old trees, and (ii) produced by different laboratory technologies. Our new composite reconstruction reveals warmer conditions during Roman, Medieval and recent times, separated by prolonged cooling during the Migration period and Little Ice Age. Twentieth century warmth, as indicated in one of the existing density records, is reduced in the new reconstruction, also affecting the overall, millennial-scale, cooling trend over the late Holocene (−0.30 °C per 1000 years). Due to the reduced biological memory, typical for tree-ring density measurements, the new reconstruction is most suitable for evaluating the rate and speed of abrupt summer cooling following large volcanic eruptions.

  • 6. MANGERUD, Jan
    et al.
    ASTAKHOV, Valery
    JAKOBSSON, Martin
    Svendsen, JOHN INGE
    Huge Ice-age lakes in Russia2001Inngår i: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 16, nr 8, s. 773-777Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]
    During an early phase of the Last Ice Age (Weichselian, Valdaian), about 90 000 yr ago, an ice sheet formed over the shallow Barents and Kara seas. The ice front advanced on to mainland Russia and blocked the north-flowing rivers (Yenissei, Ob, Pechora, Dvina and others) that supply most of the freshwater to the Arctic Ocean. The result was that large ice-dammed lakes were formed between the ice sheet in the north and the continental water divides to the south. Here we present reconstructions and calculations of the areas and volumes of these lakes. The lake on the West Siberian Plain was nearly twice as large as the largest lake on Earth today. The well-mapped Lake Komi in northeast Europe and a postulated lake in the White Sea Basin would also rank before the present-day third largest lake. The lakes overflowed towards the south and thus the drainage of much of the Eurasian continent was reversed. The result was a major change in the water balance on the continent, decreased freshwater supply to the Arctic Ocean, and increased freshwater flow to the Aral, Caspian, Black and Baltic seas. A sudden outburst of the lakes’ water to the Arctic Ocean when the ice sheet thinned is postulated.
  • 7. Olsen, Jesper
    et al.
    Kjaer, Kurt H.
    Funder, Svend
    Larsen, Nicolaj K.
    Ludikova, Anna
    High-Arctic climate conditions for the last 7000 years inferred from multi-proxy analysis of the Bliss Lake record, North Greenland2012Inngår i: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 27, nr 3, s. 318-327Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The Arctic is more vulnerable to climate change than are mid latitudes. Therefore, palaeolimnological studies from the High Arctic are important in providing insights into the dynamics of the climate system. Here we present a multi-proxy study from one of the world's northernmost lakes: Bliss Lake, Peary Land, Greenland. The early Holocene (10 850-10 480 cal. a BP) is characterized by increased erosion and gradually more marine conditions. Full marine conditions developed from 10 480 cal. a BP until the lake was isolated at 7220 cal. a BP. From its marine isolation at 7220 cal. a BP Bliss Lake becomes a lacustrine environment. Evidence from geochemical proxies (delta C-13 and total organic carbon) suggests that warmer conditions prevailed between 7220 and 6500 cal. a BP, corresponding to the Holocene thermal maximum, and from 3300 until 910 cal. a BP. From 850 to 500 cal. a BP colder climate conditions persisted. The transition from warmer to colder climate conditions taking place around 850 cal. a BP may be associated with the transition from the Medieval Warm Period to the Little Ice Age. Copyright (C) 2011 John Wiley & Sons, Ltd.

  • 8. Rubensdotter, L
    et al.
    Rosqvist, G
    The effect of geomorphological setting on Holocene lake sediment variability, northern Swedish Lapland2003Inngår i: Journal of Quaternary Science, ISSN 0267-8179, E-ISSN 1099-1417, Vol. 18, nr 8, s. 757-767Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Comparison of catchment geomorphology and lithostratigraphical analysis of sediments in two small neighbouring alpine lakes show that the minerogenic influx into the lakes has varied significantly during the Holocene, despite similarities in environmental setting. One lake contains a homogeneous organic-rich sediment sequence whereas the sediment of the other lake is laminated and has a higher minerogenic content. X-ray radiographs are used to visualise lithostratigraphical structures and provide high-resolution density data. We find that moderate differences in geomorphology and process activity in the lakeshore region around alpine lakes can significantly affect the lake sediment composition. Minerogenic sediment accumulation rates vary strongly over time, owing to different depositional processes, which complicate temporal reconstructions. We also find that non-glacial processes deposit minerogenic sediment layers with similar characteristics (high density, low organic content) as layers interpreted as having a glaciofluvial origin. This has implications for palaeoclimate studies based on proglacial lacustrine sediment. Our results indicate that erosion of surface sediments in the catchments characterised the early Holocene. A low and constant minerogenic inflow indicates that stable environmental conditions (with little fluvial erosion) were established in the catchments during the middle Holocene. The variability in sediment composition increased again in the late Holocene, possibly as a result of short-term climate fluctuations superimposed on a general climate deterioration trend. Copyright (C) 2003 John Wiley Sons, Ltd.

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