| 1. |
- Abbott, Peter M., et al.
(author)
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A detailed framework of Marine Isotope Stages 4 and 5 volcanic events recorded in two Greenland ice-cores
- 2012
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In: Quaternary Science Reviews. - : Elsevier BV. - 0277-3791 .- 1873-457X. ; 36, s. 59-77
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Journal article (peer-reviewed)abstract
- Sulphate records from Greenland ice-cores indicate that Marine Isotope Stages 4 and 5 were charactensed by a higher incidence of large volcanic eruptions than other periods during the last glacial period, however, few investigations have focused on tephra deposits associated with these volcanic eruptions and the nature and origin of the events. Here we present a detailed tephrochronological framework of the products of 15 volcanic events spanning this interval: the majority of which have been preserved as cryptotephra horizons within the Greenland records. The major element compositions of individual glass shards within these horizons indicate that 13 of the eruptions originated from Iceland and 6 of these events can be correlated to the specific volcanic systems of Katla, Grimsvotn, Grimsvotn-Kverkfjoll and either Reykjanes or Veidivotn-Bardarbunga. For the remaining Icelandic horizons a source from either the rift zone or a flank zone can be suggested based on rock suite affinities. Two horizons have been correlated to a source from the Jan Mayen volcanic system which represents the first discovery of material from this system within any Greenland ice-cores. The robust geochemical characterisations, independent ages for these horizons (derived from the GICCO5 ice-core chronology) and stratigraphic positions relative to the Dansgaard-Oeschger climate events recorded in the Greenland ice-cores represent a critical framework that provides new information on the frequency and nature of volcanic events occurring in the North Atlantic region during MIS 4 and 5. This framework can now be utilised in the assessment of the differential timing and rate of response to the millennial-scale climatic events that characterised this period, through the use of the tephra horizons as time-synchronous tie-lines to other palaeoclimatic sequences.
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| 2. |
- Berggren, Ann-Marie, 1969-, et al.
(author)
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A 600-year annual 10Be record from the NGRIP ice core, Greenland
- 2009
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In: Geophysical Research Letters. - 0094-8276 .- 1944-8007. ; 36, s. L11801-
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Journal article (peer-reviewed)abstract
- Despite the extensive use of 10Be as the most significant information source on past solar activity, there has been only one record (Dye-3, Greenland) providing annual resolution over several centuries. Here we report a new annual resolution 10Be record spanning the period 1389-1994 AD, measured in an ice core from the NGRIP site in Greenland. NGRIP and Dye-3 10Be exhibits similar long-term variability, although occasional short term differences between the two sites indicate that at least two high resolution 10Be records are needed to assess local variations and to confidently reconstruct past solar activity. A comparison with sunspot and neutron records confirms that ice core 10Be reflects solar Schwabe cycle variations, and continued 10Be variability suggests cyclic solar activity throughout the Maunder and Spörer grand solar activity minima. Recent 10Be values are low; however, they do not indicate unusually high recent solar activity compared to the last 600 years.
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| 3. |
- Davies, Siwan M, et al.
(author)
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Identification of the Fugloyarbanki tephra in the NGRIP ice-core: a key tie-point for marine and ice-core sequences during the last glacial period
- 2008
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In: Journal of Quaternary Science. - : Wiley. - 0267-8179 .- 1099-1417. ; 23:5, s. 409-414
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Journal article (peer-reviewed)abstract
- A visible tephra horizon in the NGRIP ice core has been identified by geochemical analysis as the Fugloyarbanki Tephra, a widespread marker horizon in marine cores from the Faroe Islands area and the northern North Atlantic. An age of 26 740 ± 390 yr b2k (1σ uncertainty) is derived for this tephra according to the new Greenland Ice Core Chronology (GICC05) based on multi-parameter counting of annual layers. Detection of this tephra for the first time within the NGRIP ice core provides a key tie-point between marine and ice-core records during the transition between MIS 3 and 2. Identification of this volcanic event within the Greenland records demonstrates the future potential of using tephrochronology to precisely correlate palaeoarchives in widely separated localities that span the last glacial period, as well as providing a potential method for examining the extent of the radiocarbon marine reservoir effect at this time.
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| 4. |
- Johnsen, Sigfus J., et al.
(author)
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A "deep" ice core from east Greenland
- 1992
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In: MoG Geoscience. ; 29
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Journal article (peer-reviewed)abstract
- Pilot studies on the Renland peninsula in Scoresbysund Fjord, East Greenland, indicated that the relatively small and separate Renland ice cap meets most of the criteria defining a favourable ice-core drill-site. In 1988, a Nordic expedition recovered a continuous surface-to-bedrock ice core from the summit. This relatively short core reaches deep into the past, probably throughout the last glaciation and through most of the preceding interglacial, Eem, 125,000 years B.P. The core contains detailed information on temporal changes of the coastal environment, and serves as a valuable complement to the new deep ice cores being drilled in Central Greenland. Core analyses suggest that (1) during Eemian time the East Greenland climate was at least 5ÔC warmer than now, and the precipitation 20% higher; (2) during the last glacial period, the precipitation decreased to a minimum, perhaps only 20% of the present value; (3) the post-glacial climatic optimum was 2,5ÔC warmer than now; (4) the long-term variability of the record is relatively low, due to isostatic movements in the area; and (5) from 70,000 years B.P. the Greenland glacial climate alternated between two quasi-stable stages. The latter point may reflect a chaotic feature of climate. If so, climate predictions will be difficult to access.
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| 5. |
- Ruth, Urs, et al.
(author)
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Ice core evidence for a very tight link between North Atlantic and east Asian glacial climate
- 2007
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In: GEOPHYSICAL RESEARCH LETTERS. ; 34:L03706
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Journal article (peer-reviewed)abstract
- Corresponding millennial-scale climate changes havebeen reported from the North Atlantic region and from eastAsia for the last glacial period on independent timescalesonly. To assess their degree of synchrony we suggestinterpreting Greenland ice core dust parameters as proxiesfor the east Asian monsoon systems. This allows comparingNorth Atlantic and east Asian climate on the same timescalein high resolution ice core data without relative datinguncertainties. We find that during Dansgaard-Oeschgerevents North Atlantic region temperature and east Asianstorminess were tightly coupled and changed synchronouslywithin 5–10 years with no systematic lead or lag, thusproviding instantaneous climatic feedback. The tight linkbetween North Atlantic and east Asian glacial climate couldhave amplified changes in the northern polar cell to largerscales. We further find evidence for an early onset of aYounger Dryas-like event in continental Asia, which givesevidence for heterogeneous climate change within east Asiaduring the last deglaciation.
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| 6. |
- Sjolte, Jesper, et al.
(author)
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Modelling the response of stable water isotopes in Greenland precipitation to orbital configurations of the previous interglacial
- 2014
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In: Tellus. Series B: Chemical and Physical Meteorology. - : Stockholm University Press. - 0280-6509 .- 1600-0889. ; 66
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Journal article (peer-reviewed)abstract
- The relation between delta O-18 of precipitation and temperature has been used in numerous studies to reconstruct past temperatures at ice core sites in Greenland and Antarctica. During the past two decades, it has become clear that the slope between delta O-18 and temperature varies in both space and time. Here, we use a general circulation model driven by changes in orbital parameters to investigate the Greenland delta O-18-temperature relation for the previous interglacial, the Eemian. In our analysis, we focus on changes in the moisture source regions, and the results underline the importance of taking the seasonality of climate change into account. The orbitally driven experiments show that continental evaporation over North America increases during summer in the warm parts of the Eemian, while marine evaporation decreases. This likely flattens the Greenland delta O-18 response to temperature during summer. Since the main climate change in the experiments occurs during summer this adds to a limited response of delta O-18, which is more strongly tied to temperature during winter than during summer. A south-west to north-east gradient in the delta O-18-temperature slope is also evident for Greenland, with low slopes in the south-west and steeper slopes in the north-east. This probably reflects the proportion of continental moisture and Arctic moisture arriving in Greenland, with more continental moisture in the south-west and less in the north-east, and vice versa for the Arctic moisture.
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| 7. |
- Steffensen, Jörgen Peder, et al.
(author)
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High-Resolution Greenland Ice Core Data Show Abrupt Climate Change Happens in Few Years
- 2008
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In: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 321, s. 680-684
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Journal article (peer-reviewed)abstract
- The last two abrupt warmings at the onset of our present warm interglacial period, interrupted bythe Younger Dryas cooling event, were investigated at high temporal resolution from the NorthGreenland Ice Core Project ice core. The deuterium excess, a proxy of Greenland precipitationmoisture source, switched mode within 1 to 3 years over these transitions and initiated a moregradual change (over 50 years) of the Greenland air temperature, as recorded by stable waterisotopes. The onsets of both abrupt Greenland warmings were slightly preceded by decreasingGreenland dust deposition, reflecting the wetting of Asian deserts. A northern shift of theIntertropical Convergence Zone could be the trigger of these abrupt shifts of Northern Hemisphereatmospheric circulation, resulting in changes of 2 to 4 kelvin in Greenland moisture sourcetemperature from one year to the next.
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| 8. |
- Walker, Mike, et al.
(author)
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Formal definition and dating of the GSSP (Global Stratotype Section and Point) for the base of the Holocene using the Greenland NGRIP ice core, and selected auxiliary records
- 2009
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In: Journal of Quaternary Science. - : Wiley. - 1099-1417 .- 0267-8179. ; 24:1, s. 3-17
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Research review (peer-reviewed)abstract
- The Greenland ice core from NorthGRIP (NGRIP) contains a proxy climate record across the Pleistocene-Holocene boundary of unprecedented clarity and resolution. Analysis of an array of physical and chemical parameters within the ice enables the base of the Holocene, as reflected in the first signs of climatic warming at the end of the Younger Dryas/Greenland Stadial 1 cold phase, to be located with a high degree of precision. This climatic event is most clearly reflected in an abrupt shift in deuterium excess values, accompanied by more gradual changes in delta O-18, dust concentration, a range of chemical species, and annual layer thickness. A timescale based on multi-parameter annual layer counting provides an age of 11 700 calendar yr b2k (before AD 2000) for the base of the Holocene, with a maximum counting error of 99 yr. A proposal that an archived core from this unique sequence should constitute the Global Stratotype Section and Point (GSSP) for the base of the Holocene Series/Epoch (Quaternary System/Period) has been ratified by the International Union of Geological Sciences. Five auxiliary stratotypes for the Pleistocene-Holocene boundary have also been recognised. Copyright (C) 2008 John Wiley & Sons, Ltd.
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| 9. |
- Walker, Mike, et al.
(author)
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The Global Stratotype Section and Point (GSSP) for the base of the Holocene Series/Epoch (Quaternary System/Period) in the NGRIP ice core
- 2008
-
In: Episodes. - 0705-3797. ; 31:2, s. 264-267
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Journal article (peer-reviewed)abstract
- The Greenland ice core from NorthGRIP (NGRIP) contains a proxy climate record across the Pleistocene-Holocene boundary of unprecedented clarity and resolution. Analysis of an array of physical and chemical parameters within the ice enables the base of the Holocene, as reflected in the first signs of climatic warming at the end of the Younger Dryas/Greenland Stadial 1 cold phase, to be located with a high degree of precision. This climatic event is most clearly reflected in an. abrupt shaft in deuterium excess values, accompanied by more gradual changes in delta O-18, dust concentration, a range of chemical species, and annual layer thickness. A timescale based on multi-parameter annual layer counting provides an age of 11,700 yr b2k (before AD2000) for the base of the Holocene, with, an estimated 2 sigma uncertainty of 99 yr: It is proposed that an archived core from this unique sequence should constitute the Global Stratotype Section and Point (GSSP) for the base of the Holocene Series/Epoch (Quaternary System/Period).
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| 10. |
- Willerslev, Eske, et al.
(author)
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Ancient biomolecules from deep ice cores reveal a forested Southern Greenland
- 2007
-
In: Science. - : American Association for the Advancement of Science (AAAS). - 1095-9203 .- 0036-8075. ; 317:5834, s. 111-114
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Journal article (peer-reviewed)abstract
- It is difficult to obtain fossil data from the 10% of Earth's terrestrial surface that is covered by thick glaciers and ice sheets, and hence, knowledge of the paleoenvironments of these regions has remained limited. We show that DNA and amino acids from buried organisms can be recovered from the basal sections of deep ice cores, enabling reconstructions of past flora and fauna. We show that high-altitude southern Greenland, currently lying below more than 2 kilometers of ice, was inhabited by a diverse array of conifer trees and insects within the past million years. The results provide direct evidence in support of a forested southern Greenland and suggest that many deep ice cores may contain genetic records of paleoenvironments in their basal sections.
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