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  • 2010-2014  (5)
  • 2014  (3)
  • 2013  (2)
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  • 2010-2014  (5)
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  • 2014  (3)
  • 2013  (2)
  • 2012  (3)
  • 1
    facet.materialart.
    Unbekannt
    Palynological analyses of the sediments around the Miocene/Pliocene boundary in ODP Hole 151-911A (2014)
    PANGAEA
    In:  Supplement to: Grøsfjeld, Kari; De Schepper, Stijn; Fabian, Karl; Husum, Katrine; Baranwal, Soma; Andreassen, Karin; Knies, Jochen (2014): Dating and palaeoenvironmental reconstruction of the sediments around the Miocene/Pliocene boundary in Yermak Plateau ODP Hole 911A using marine palynology. Palaeogeography, Palaeoclimatology, Palaeoecology, 414, 382-402, https://doi.org/10.1016/j.palaeo.2014.08.028
    Details
    Publikationsdatum: 2024-01-09
    Beschreibung: The late Neogene evolution of the Arctic to Subarctic region is poorly understood due to few available records and poor age control. At the margin of the Arctic Ocean, Yermak Plateau Ocean Drilling Program (ODP) Hole 911A is strategically located for establishing a stratigraphic framework for the Arctic. Here we present dinoflagellate cyst and acritarch data from 24 stratigraphic levels in the lower part (474.26-505.64 metres below the seafloor (mbsf)) of ODP Hole 911A. The marine palynomorphs indicate a latest Miocene to earliest Pliocene age (between 5.8 and 5.0 Ma) for the base of the hole based on the co-occurrence of the dinoflagellate cyst Barssidinium evangelineae and acritarch Lavradosphaera crista. Our age estimate for the sediments can possibly be further refined to 5.0-5.33 Ma based on the presence of Achomosphaera andalousiensis suttonensis, which apparently has a range restricted to the Pliocene. An age close to the Miocene/Pliocene boundary agrees with the planktonic foraminifer data. Together with recently available magnetostratigraphic data, the base of the hole is likely to be placed at ~5.2 Ma. This new chronostratigraphy is a first step towards a better understanding of the late Neogene palaeoenvironment for the Yermak Plateau and also for the wider Arctic to Subarctic region. The terrestrial and fresh water palynomorphs were most likely redistributed and/or displaced from the shelf towards deeper parts of the basin during contourite deposition under the influence of the West Spitsbergen Current. The in situ marine dinoflagellate cyst assemblage contains a mixture of cool water and thermophilic taxa, indicating sea-ice free, cool-temperate, warmer than present conditions at the Yermak Plateau. Rivers were likely the source for the freshwater influence.
    Schlagwort(e): 151-911A; Achomosphaera andalousiensis andalousiensis; Achomosphaera andalousiensis suttonensis; Acritarcha; Acritarcha, standard error; Acritarcha indeterminata; Acritarcha per unit mass; Amiculosphaera umbraculum; Barssidinium evangelineae; Barssidinium graminosum; Barssidinium pliocenicum; Barssidinium spp.; Bitectatodinium raedwaldii; Bitectatodinium tepikiense; Botryococcus spp.; Brigantedinium spp.; Cymatiosphaera invaginata; Cymatiosphaera spp.; DEPTH, sediment/rock; Dinoflagellate cyst; Dinoflagellate cyst, standard error; Dinoflagellate cyst indeterminata; Dinoflagellate cyst per unit mass; Dinoflagellate cyst reworked; Dinoflagellate cyst reworked, standard error; Dinoflagellate cyst reworked per unit mass; DRILL; Drilling/drill rig; Dry mass; DSDP/ODP/IODP sample designation; Echinidinium euaxum; Filisphaera filifera; Filisphaera microornata; Foraminifera, linings; Habibacysta tectata; Impagidinium aculeatum; Impagidinium pallidum; Impagidinium patulum; Impagidinium sp.; Impagidinium spp.; Invertocysta lacrymosa; Invertocysta tabulata; Joides Resolution; Laboratory code/label; Lavradosphaera crista; Lavradosphaera lucifer; Leg151; Lejeunecysta mariae; Lejeunecysta spp.; Lingulodinium machaerophorum; Lycopodium clavatum, standard deviation; Lycopodium clavatum markers counted; Lycopodium clavatum spores per tablet; Lycopodium tablets; Nematosphaeropsis labyrinthus; North Greenland Sea; Number of taxa; Ocean Drilling Program; ODP; Operculodinium? eirikianum crebrum; Operculodinium? eirikianum eirikianum; Operculodinium centrocarpum; Operculodinium sp.; Pediastrum spp.; Pentapharsodinium dalei; Protoceratium reticulatum; Sample code/label; Selenopemphix dionaeacysta; Spiniferites elongatus; Spiniferites falcipedius; Spiniferites spp.; Sumatradinium sp.; Tasmanites; Trinovantedinium glorianum; Trinovantedinium variabile
    Materialart: Dataset
    Format: text/tab-separated-values, 1521 data points
    Standort Signatur Einschränkungen Verfügbarkeit
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    DATA PANGAEA
  • 2
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    Unbekannt
    Subglacial roughness of the former Barents Sea ice sheet (2013)
    Wiley
    In:  EPIC3Journal of Geophysical Research-Earth Surface, Wiley, 118(4), pp. 2546-2556, ISSN: 0148-0227
    Details
    Publikationsdatum: 2016-11-15
    Beschreibung: The roughness of a glacier bed has high importance for the estimation of the sliding velocity and can also provide valuable insights into the dynamics and history of ice sheets, depending on scale. Measurement of basal properties in present-day ice sheets is restricted to ground-penetrating radar and seismics, with surveys retrieving relatively coarse data sets. Deglaciated areas, like the Barents Sea, can be surveyed by shipborne 2-D and 3-D seismics and multibeam sonar and provide the possibility of studying the basal roughness of former ice sheets and ice streams with high resolution. Here, for the first time, we quantify the subglacial roughness of the former Barents Sea ice sheet by estimating the spectral roughness of the basal topography. We also make deductions about the past flow directions by investigating how the roughness varies along a 2-D line as the orientation of the line changes. Lastly, we investigate how the estimated basal roughness is affected by the resolution of the basal topography data set by comparing the spectral roughness along a cross section using various sampling intervals. We find that the roughness typically varies on a similar scale as for other previously marine-inundated areas in West Antarctica, with subglacial troughs having very low roughness, consistent with fast ice flow and high rates of basal erosion. The resolution of the data set seems to be of minor importance when comparing roughness indices calculated with a fixed profile length. A strong dependence on track orientation is shown for all wavelengths, with profiles having higher roughness across former flow directions than along them.
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , isiRev
    Standort Signatur Einschränkungen Verfügbarkeit
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    ARTIKEL (OA)
  • 3
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    Unbekannt
    The effect of sedimentation in a subglacial lake on the dynamics of an artificial ice stream (2013)
    In:  EPIC3AGU Fall Meeting, San Francisco, 2013-12-09-2013-12-13
    Details
    Publikationsdatum: 2016-12-13
    Beschreibung: As ice flows over a subglacial lake, the drop in bed resistance leads to an increase in ice velocity and a subsequent lowering of the ice surface in the vicinity of the upstream lake edge. Conversely, at the downstream end of the lake a small hump is observed as the ice velocity decreases near the point of contact with land. There are two contributions arising from the ice/lake interaction: (1) changes in the thermal regime that propagate downwards with the advection of ice and (2) the increase in flow speeds caused by basal sliding over the lake surface. Sediment transport from upstream areas into subglacial lakes changes their size, thus reducing the area of the ice/lake interface. Here, we aim to study the effect that this reduction in size has on the flow dynamics and the surface elevation of an artificial ice stream and the temporal evolution of this effect. To this end, we use a full-Stokes, polythermal ice flow model, implemented into the commercial finite element software COMSOL Multiphysics. An enthalpy gradient method is used in order to account for the evolution of temperature and water content within the ice. This conceptual model uses prescribed boundary velocity and temperature profiles and a Weertman-type sliding law with a fixed parameter combination. In order to separate the effect of the slow thermal contribution from the fast mechanical one, we will present sensitivity tests that additionally involve a thermally-constant flow.
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Conference , notRev
    Standort Signatur Einschränkungen Verfügbarkeit
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    ARTIKEL (OA)
  • 4
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    Unbekannt
    Effect of early Pliocene uplift on late Pliocene cooling in the Arctic–Atlantic gateway (2014)
    In:  EPIC3Earth and Planetary Science Letters, 387, pp. 132-144, ISSN: 0012-821X
    Details
    Publikationsdatum: 2015-10-03
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , isiRev
    Standort Signatur Einschränkungen Verfügbarkeit
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    ARTIKEL (OA)
  • 5
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    Unbekannt
    Arctic Ocean glacial history (2014)
    PERGAMON-ELSEVIER SCIENCE LTD
    In:  EPIC3Quaternary Science Reviews, PERGAMON-ELSEVIER SCIENCE LTD, 92, pp. 40-67, ISSN: 0277-3791
    Details
    Publikationsdatum: 2016-02-02
    Beschreibung: While there are numerous hypotheses concerning glacialeinterglacial environmental and climatic regime shifts in the Arctic Ocean, a holistic view on the Northern Hemisphere’s late Quaternary ice-sheet extent and their impact on ocean and sea-ice dynamics remains to be established. Here we aim to provide a step in this direction by presenting an overview of Arctic Ocean glacial history, based on the present state-of-the-art knowledge gained from field work and chronological studies, and with a specific focus on ice-sheet extent and environmental conditions during the Last Glacial Maximum (LGM). The maximum Quaternary extension of ice sheets is discussed and compared to LGM. We bring together recent results from the circum-Arctic continental margins and the deep central basin; extent of ice sheets and ice streams bordering the Arctic Ocean as well as evidence for ice shelves extending into the central deep basin. Discrepancies between new results and published LGM ice-sheet reconstructions in the high Arctic are highlighted and outstanding questions are identified. Finally, we address the ability to simulate the Arctic Ocean ice sheet complexes and their dynamics, including ice streams and ice shelves, using presently available ice-sheet models. Our review shows that while we are able to firmly reject some of the earlier hypotheses formulated to describe Arctic Ocean glacial conditions, we still lack information from key areas to compile the holistic Arctic Ocean glacial history.
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , isiRev
    Format: application/pdf
    Standort Signatur Einschränkungen Verfügbarkeit
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    ARTIKEL (OA)
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