562 resultados para Niels Bohr
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Stable oxygen and carbon isotope and sedimentological-paleontological investigations supported by accelerator mass spectrometry 14C datings were carried out on cores from north of 85°N in the eastern central Arctic Ocean. Significant changes in accumulation rates, provenance of ice-rafted debris (IRD), and planktic productivity over the past 80,000 years are documented. During peak glacials, i.e., oxygen isotope stages 4 and 2, the Arctic Ocean was covered by sea ice with decreased seasonal variation, limiting planktic productivity and bulk sedimentation rates. In early stage 3 and during Termination I, major deglaciations of the circum-Arctic regions caused lowered salinities and poor oxygenation of central Arctic surface waters. A meltwater spike and an associated IRD peak dated to ~14-12 14C ka can be traced over the southern Eurasian Basin of the Arctic Ocean. This event was associated with the early and rapid deglaciation of the marine-based Barents Sea Ice Sheet. A separate Termination Ib meltwater event is most conspicuous in the central Arctic and is associated with characteristic dolomitic carbonate IRD. This lithology suggests an origin of glacial ice from northern Canada and northern Greenland where lower Paleozoic platform carbonates crop extensively out.
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On the basis of 52 sediment cores, analyzed and dated at high resolution, the paleoceanography and climate of the Last Glacial Maximum (LGM) were reconstructed in detail for the Fram Strait and the eastern and central Arctic Ocean. Sediment composition and stable isotope data suggest three distinct paleoenvironments: (1) a productive region in the eastern to central Fram Strait and along the northern Barents Sea continental margin characterized by Atlantic Water advection, frequent open water conditions, and occasional local meltwater supply and iceberg calving from the Barents Sea Ice Sheet; (2) an intermediate region in the southwestern Eurasian Basin (up to 84-85°N) and the western Fram Strait characterized by subsurface Atlantic Water advection and recirculation, a moderately high planktic productivity, and a perennial ice cover that breaks up only occasionally; and (3) a central Arctic region (north of 85°N in the Eurasian Basin) characterized by a low-salinity surface water layer and a thick ice cover that strongly reduces bioproduction and bulk sedimentation rates. Although the total inflow of Atlantic Water into the Arctic Ocean may have been reduced during the LGM, its impact on ice coverage and halocline structure in the Fram Strait and southwestern Eurasian Basin was strong.
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Includes bibliographies.
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Mode of access: Internet.
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Mode of access: Internet.
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Original Danish words by C. C. T. Andersen, with German translation.
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Text, in part, by B.S. Ingemann.
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Faber's poem, in Danish, precedes the corresponding composition.
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The volume includes songs by Niels Gade, Edvard Grieg, Agathe Gröndahl, Halfdan Kjerulf, Christian Sinding and others.
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Mode of access: Internet.
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Mode of access: Internet.
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Reissued from Flaxland plates.
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Mode of access: Internet.
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Mode of access: Internet.
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Mode of access: Internet.