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  • 1
    E-Resource
    E-Resource
    Data compilation of the research vessel Meteor (1964) (2008)
    Bremerhaven [u.a.] : Alfred Wegener Inst. for Polar and Marine Research (AWI) [u.a.]
    Details Availability
    Keywords: CD-ROM ; Meteor ; Forschungsergebnis
    Type of Medium: Electronic Resource
    Pages: 1 CD-ROM , Begleith. (27 S.) , 12 cm
    Series Statement: WDC-MARE reports 6
    DDC: 550
    Language: English
    Note: Literaturverz. Begleith. S. 14 - 26 , Systemvoraussetzungen: Linux: SUSE, Debian, Ubuntu, Gentoo, Redhat. - Macintosh: Mac OS X. - Solaris: Version 8. - Windows: Windows 2000/XP using Java Runtime Engine JRE 1.4 or higher.
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  • 2
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    Early Holocene planktic foraminifers record species-specific 14 C reservoir ages in Arctic Gateway (2017)
    Elsevier
    In:  Marine Micropaleontology, 135 . pp. 45-55.
    Details
    Publication Date: 2020-02-06
    Description: Highlights • Planktic foraminifera species show an Early Holocene 14C plateau analogous to the atmospheric 14C plateau at 10.2–9.6 cal ka. • Age-calibrated Early Holocene 14C plateau boundaries provide precise age control in 3 sediment cores on a 900 km long transect. • Differences between planktic foraminiferal and atmospheric 14C ages reveal the 14C reservoir age of local surface waters. • Different planktic species document different 14C reservoir ages characteristic of different surface and subsurface waters. To trace spatial variations in Holocene reservoir ages of surface and subsurface waters we studied narrowly spaced 14C records of planktic foraminifera in three high-sedimentation rate cores from the Nordic Seas, the Barents Sea continental margin and eastern Fram Strait. The two northern cores reveal a distinct Early Holocene 14C plateau in dates on the subsurface dweller Neogloboquadrina pachyderma at 9.3–9.1 14C ka. The plateau was tuned to an atmospheric 14C plateau at 9.0–8.7 14C ka that spans 10.2–9.6 calendar ka. These two plateau boundaries provide robust age control points to estimate short-term changes in sedimentation rate and to correlate paleoceanographic signals over 900 km along the West Spitsbergen Current. The difference between planktic and atmospheric 14C plateau ages suggests local 14C reservoir ages of 370–400 yr. Planktic foraminifera species that inhabit different water masses document different reservoir ages. By comparison, the subpolar N. incompta reveals a reservoir age of 150 yr, probably formed in well-mixed Atlantic-sourced waters during winter. The near-surface dweller Turborotalita quinqueloba shows an age of 290 yr in the Fram Strait, but one of 720 yr at the Barents Sea continental margin. The latter age suggests a calcification within old, meltwater-enriched Arctic surface waters admixed by the East Spitsbergen Current. Likewise, we assign an elevated reservoir age of 760 yr on mixed species at a Norwegian Sea site near 71°N to Preboreal meltwaters that spread from northern Norway far west, also documented by the spatial distribution of a coeval δ13C minimum of N. pachyderma.
    Type: Article , PeerReviewed
    Format: text
    Format: text
    DOI: 10.1016/j.marmicro.2017.07.002
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  • 3
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    Glacial-to-deglacial changes in North Atlantic meltwater advection and deep-water formation – Centennial-to-millennial-scale 14 C records from the Azores plateau (2018)
    Elsevier
    In:  Geochimica et Cosmochimica Acta, 236 . pp. 399-415.
    Details
    Publication Date: 2021-02-08
    Description: The last deglacial was marked by tremendous changes in ocean temperature and circulation as well as atmospheric CO2 and 14C. We employed the “14C plateau-tuning technique” to a centennial-scale planktic 14C record of core MD08-3180 retrieved S.W. of the Azores Islands at ∼3060 m water depth to establish both a new standard of absolute age control and a record of past 14C reservoir ages of ocean surface waters. Both δ18O minima of G. bulloides and high planktic reservoir ages of ∼1600 to 2170 yr suggest two major melt water incursions that reached from the Labrador Sea up to the subtropics over Heinrich Stadial 1 (HS-1). In parallel, we established a record of (apparent) benthic ventilation ages that add the planktic 14C reservoir ages together with the benthic-planktic 14C age difference at the site and time of deposition, a sum finally adjusted to past changes in atmospheric 14C that occurred since the time of deep-water formation. Near the Azores apparent deep-water ages of the Last Glacial Maximum were as low as 340–740 yr, which suggests a lateral advection of young North Atlantic Deep Waters (NADW) from subpolar regions south of Iceland, in harmony with recent model simulation and in contrast to a widely assumed major shoaling of glacial deep-water formation. During HS-1, local benthic ventilation ages increased up to 2200–2550 yr, thus suggest an incursion of old southern-source deep waters, an unstable regime that was interrupted by brief pulses of NADW incursion near 16, 15.6 cal. ka, and most salient, near 14.9/14.7 ka.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/j.gca.2018.03.001
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  • 4
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    A link between paleoceanography, early diagenetic cementation, and shear strength maxima in Late Quaternary deep-sea sediments? (1989)
    AGU (American Geophysical Union)
    In:  Paleoceanography, 4 (3). pp. 253-269.
    Details
    Publication Date: 2018-10-02
    Description: Near-surface sediments from the equatorial east Atlantic and the Norwegian Sea exhibit pronounced shear strength maxima in profiles from the peak Holocene and Pleistocene. These semi-indurated layers start to occur at 8–102 cm below the sediment surface and can be explained neither by the modal composition nor by the effective overburden pressure of the sediments. However, scanning electron microscope and microprobe data exhibit micritic crusts and crystal carpets, which are clearly restricted to (undisturbed) samples from indurated layers and form a manifest explanation for their origin. The minerals precipitated comprise calcite, aragonite, and in samples more proximal to the African continent SiO2 needles, and needles of as yet unidentified K-Mg-Fe-Al silicates, crusts of which dominate the indurated layers in the Norwegian Sea. By their stratigraphic position in deep-sea sediments the carbonate-based shear strength maxima are tentatively ascribed to dissolved adjacent pteropod layers from the early Holocene and hence to short-lived no-analogue events of early diagenesis. Possibly, they have been controlled by a reduced organic carbon flux, leading to increased aragonite preservation in the deep sea.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/PA004i003p00253
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  • 5
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    Benthic isotope evidence for changes of the Mediterranean outflow during the Late Quaternary (1987)
    AGU (American Geophysical Union)
    In:  Paleoceanography, 2 (6). pp. 543-559.
    Details
    Publication Date: 2016-09-05
    Description: A suit of sediment cores close to and south of the Strait of Gibraltar (12°-36°N, 500–2800 m water depth) were analyzed for stable isotopes in epibenthic foraminifers Cibicidoides wuellerstorfi and Planulina ariminensis. During peak glacial times, the data exhibit higher δ13C values of up to 1.6‰ at intermediate depths near the Strait of Gibraltar (36°N). The values decrease to the south as evidenced by our data, but also to the north as revealed by data of intermediate depth cores north of 38°N (in Duplessy et al. [1987]). Thus, the distribution pattern of δ13C provides crucial evidence for an increased influence of nutrient depleted Mediterranean Outflow Water (MOW) on the glacial northeast Atlantic hydrography. During oxygen isotope Terminations I and II, the meridional carbon isotope gradient indicates a significantly decreased but still active MOW. As deduced from the δ18O fluctuations, the temperatures of the MOW in the Atlantic were lower during glacial times by as much as 5°C. During glacial times and during Termination I the maximum δ13C values of the MOW correlate with minimum values of the North Atlantic Deep Water (NADW) and vice versa. This inverse response to climatic change of the carbon isotope signals of both water masses indicates, that the supply of saline MOW to the north Atlantic may be less important for the formation of NADW than previously assumed.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/PA002i006p00543
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  • 6
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    Sonostratigraphic records from equatorial atlantic deep-sea carbonates: Paleoceanographic and climatic relationships (1988)
    Elsevier
    In:  Marine Geology, 83 . pp. 9-20.
    Details
    Publication Date: 2016-09-05
    Description: Paleoceanographic and stratigraphic methods, based on high-resolution compressional wave (p-wave) velocity measurements, have been applied to the studies of late Quaternary deep-sea carbonates in the western and eastern equatorial Atlantic. The measurements provide sonostratigraphic records in which changes in p-wave velocity parallel the changes from a glacial to an interglacial climate: Maxima in p-wave velocity (greater than 1540 m/s) occur during interglacial oxygen isotope stages 1, 5 and 7. Minima (1490 m/s) occur during glacial oxygen isotope stages 2, 4 and 6. Changes in p-wave velocity parallel past changes in carbonate accumulation and sediment coarse fraction, and allow a detailed core to core correlation. From these results two main patterns emerge: (1) In cores from shallower than 4300 m and from well above the present lysocline, large temporal changes in p-wave velocity parallel the production of planktonic foraminifera and the climatic history recorded in the sediments, and (2) below 4300 m, the position of the foraminiferal lysocline in the western equatorial Atlantic, large downcore p-wave velocity fluctuations gradually disappear due to dissolution of carbonate sediments. Dissolution also causes a distinct decrease in p-wave velocity and acoustic reflectivity in surface sediments across the present foraminiferal lysocline. Thus, past changes in the position of the foraminiferal lysocline or calcite compensation depth that caused distinct changes in reflectivity of sediments should lead to distinct reflectors within sediment columns. Their distribution can be utilized to map paleowater masses with different degrees of carbonate saturation.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/0025-3227(88)90048-5
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  • 7
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    Variations in Atlantic surface ocean paleoceanography, 50°-80°N: A time-slice record of the last 30,000 years (1995)
    AGU (American Geophysical Union)
    In:  Paleoceanography, 10 (6). pp. 1063-1094.
    Details
    Publication Date: 2015-08-28
    Description: Eight time slices of surface-water paleoceanography were reconstructed from stable isotope and paleotemperature data to evaluate late Quaternary changes in density, current directions, and sea-ice cover in the Nordic Seas and NE Atlantic. We used isotopic records from 110 deep-sea cores, 20 of which are accelerator mass spectrometry (AMS)-14C dated and 30 of which have high (〉8 cm /kyr) sedimentation rates, enabling a resolution of about 120 years. Paleotemperature estimates are based on species counts of planktonic foraminifera in 18 cores. The δ18O and δ13C distributions depict three main modes of surface circulation: (1) The Holocene-style interglacial mode which largely persisted over the last 12.8 14C ka, and probably during large parts of stage 3. (2) The peak glacial mode showing a cyclonic gyre in the, at least, seasonally ice-free Nordic Seas and a meltwater lens west of Ireland. Based on geostrophic forcing, it possibly turned clockwise, blocked the S-N flow across the eastern Iceland-Shetland ridge, and enhanced the Irminger current around west Iceland. It remains unclear whether surface-water density was sufficient for deepwater formation west of Norway. (3) A meltwater regime culminating during early glacial Termination I, when a great meltwater lens off northern Norway probably induced a clockwise circulation reaching south up to Faeroe, the northward inflow of Irminger Current water dominated the Icelandic Sea, and deepwater convection was stopped. In contrast to circulation modes two and three, the Holocene-style circulation mode appears most stable, even unaffected by major meltwater pools originating from the Scandinavian ice sheet, such as during δ18O event 3.1 and the Bölling. Meltwater phases markedly influenced the European continental climate by suppressing the “heat pump” of the Atlantic salinity conveyor belt. During the peak glacial, melting icebergs blocked the eastward advection of warm surface water toward Great Britain, thus accelerating buildup of the great European ice sheets; in the early deglacial, meltwater probably induced a southward flow of cold water along Norway, which led to the Oldest Dryas cold spell.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/95PA01453
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  • 8
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    Paired d18O signals of Neogloboquadrina pachyderma (s) and Turborotalita quinqueloba show thermal stratification in Nordic Seas (2003)
    Elsevier
    In:  Marine Micropaleontology, 48 . pp. 107-125.
    Details
    Publication Date: 2017-06-22
    Description: The vertical density gradients in the Nordic Seas are crucial for the preconditioning of the surface water to thermohaline sinking in winter. These gradients can be reconstructed from paired oxygen isotope data in tests of different species of planktonic foraminifera, the isotopic signatures of which represent different calcification depths in the water column. Comparison of δ18O values from foraminiferal tests in plankton hauls, sediment traps, and nearby core top samples with the calculated δ18Ocalcite profile of the water column revealed species-specific δ18O vital effects and the role of bioturbational admixture of subfossil specimens into the surface sediment. On the basis of core top samples obtained along a west–east transect across various hydrographic regions of the Nordic Seas, δ18O values of Turborotalita quinqueloba document apparent calcification depths within the pycnocline at 25–75 m water depth. The isotopic signatures of Neogloboquadrina pachyderma (s) reflect water masses near and well below the pycnocline between 70 and 250 m off Norway, where the Atlantic inflow leads to thermal stratification. Here, temperatures in the calcification depth of N. pachyderma (s) differ from sea surface temperature by approximately −2.5°C. In contrast, N. pachyderma (s) calcifies very close to the sea surface (20–50 m) in the Arctic domain of the western Nordic Seas. However, further west N. pachyderma (s) prefers somewhat deeper, more saline water at 70–130 m well below the halocline that confines the low saline East Greenland Current. This implies that the δ18O values of N. pachyderma (s) do not fully reflect the freshwater proportion in surface water and that any reconstruction of past meltwater plumes based on δ18O is too conservative, because it overestimates sea surface salinity. Minimum δ18O differences (〈0.2‰) between N. pachyderma (s) and T. quinqueloba may serve as proxy for sea regions with dominant haline and absent thermal stratification, whereas thermal stratification leads to δ18O differences of 〉0.4 to 〉1.5‰.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1016/S0377-8398(02)00165-2
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  • 9
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    Overview of Glacial Atlantic Ocean Mapping (GLAMAP 2000) (2003)
    AGU (American Geophysical Union)
    In:  Paleoceanography, 18 (2). p. 1030.
    Details
    Publication Date: 2017-05-10
    Description: GLAMAP 2000 presents new reconstructions of the Atlantic's sea surface temperatures (SST) at the Last Glacial Maximum (LGM), defined at both 21,500–18,000 years B.P. (“Last Isotope Maximum”) and 23,000–19,000 years B.P. (maximum glacial sea level low stand and orbital minimum of solar insolation; EPILOG working group; see Mix et al. [2001]). These reconstructions use 275 sediment cores between the North Pole and 60°S with carefully defined chronostratigraphies. Four categories of core quality are distinguished. More than 100 core sections provide a glacial record with subcentennial- to multicentennial-scale resolution. SST estimates are based on a new set of almost 1000 reference samples of modern planktic foraminifera and on improved transfer-function techniques to deduce SST from census counts of microfossils, including radiolarians and diatoms. New proxies also serve to deduce sea ice boundaries. The GLAMAP 2000 SST patterns differ significantly in crucial regions from the CLIMAP [1981] reconstruction and thus are important in providing updated boundary conditions to initiate and validate computational models for climate prediction.
    Type: Article , PeerReviewed
    Format: text
    DOI: 10.1029/2002PA000769
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