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  • PANGAEA  (443)
  • American Geophysical Union  (2)
  • AMER GEOPHYSICAL UNION  (1)
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  • 1
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    Miocene to Pliocene development of surface and subsurface temperatures in the Benguela Current system (2011)
    AMER GEOPHYSICAL UNION
    In:  EPIC3Paleoceanography, AMER GEOPHYSICAL UNION, 26, ISSN: 0883-8305
    Details
    Publikationsdatum: 2019-07-17
    Beschreibung: The initiation of the Benguela upwelling has been dated to the late Miocene, but estimates of its sea surface temperature evolution are not available. This study presents data from Ocean Drilling Program (ODP) Site 1085 recovered from the southern Cape Basin. Samples of the middle Miocene to Pliocene were analyzed for alkenone-based (U37 K", SSTUK) and glycerol dialkyl glycerol tetraether (GDGT) based (TEX86, TempTEX) water temperature proxies. In concordance with global cooling during the Miocene, SSTUK and TempTEX exhibit a decline of about 8°C and 16°C, respectively. The temperature trends suggest an inflow of cold Antarctic waters triggered by Antarctic ice sheet expansion and intensification of Southern Hemisphere southeasterly winds. A temperature offset between both proxies developed with the onset of upwelling, which can be explained by differences in habitat: alkenone!producing phytoplankton live in the euphotic zone and record sea surface temperatures, while GDGT!producing Thaumarchaeota are displaced to colder subsurface waters in upwelling!influenced areas and record subsurface water temperatures. We suggest that variations in subsurface water temperatures were driven by advection of cold Antarctic waters and thermocline adjustments that were due to changes in North Atlantic deep water formation. A decline in surface temperatures, an increased offset between temperature proxies, and an increase in primary productivity suggest the establishment of the Benguela upwelling at 10 Ma. During the Messinian Salinity Crisis, between 7 and 5 Ma, surface and subsurface temperature estimates became similar, likely because of a strong reduction in Atlantic overturning circulation, while high total organic carbon contents suggest a “biogenic bloom.” In the Pliocene the offset between the temperature estimates and the cooling trend was reestablished.
    Repository-Name: EPIC Alfred Wegener Institut
    Materialart: Article , isiRev
    Format: application/pdf
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    ARTIKEL (OA)
  • 2
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    Forcing of tropical Atlantic sea surface temperatures during the mid-Pleistocene transition (2010)
    American Geophysical Union
    Details
    Publikationsdatum: 2022-05-25
    Beschreibung: Author Posting. © American Geophysical Union, 2004. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 19 (2004): PA4029, doi:10.1029/2003PA000892.
    Beschreibung: We compare a new mid-Pleistocene sea surface temperature (SST) record from the eastern tropical Atlantic to changes in continental ice volume, orbital insolation, Atlantic deepwater ventilation, and Southern Ocean front positions to resolve forcing mechanisms of tropical Atlantic SST during the mid-Pleistocene transition (MPT). At the onset of the MPT, a strong tropical cooling occurred. The change from a obliquity- to a eccentricity-dominated cyclicity in the tropical SST took place at about 650 kyr BP. In orbital cycles, tropical SST changes significantly preceded continental ice-volume changes but were in phase with movements of Southern Ocean fronts. After the onset of large-amplitude 100-kyr variations, additional late glacial warming in the eastern tropical Atlantic was caused by enhanced return flow of warm waters from the western Atlantic driven by strong trade winds. Pronounced 80-kyr variations in tropical SST occurred during the MPT, in phase with and likely directly forced by transitional continental ice-volume variations. During the MPT, a prominent anomalous long-term tropical warming occurred, likely generated by extremely northward displaced Southern Ocean fronts. While the overall pattern of global climate variability during the MPT was determined by changes in mean state and frequency of continental ice volume variations, tropical Atlantic SST variations were primarily driven by early changes in Subantarctic sea-ice extent and coupled Southern Ocean frontal positions.
    Beschreibung: The Dutch scientific funding organization (NWO) is thanked for financial support (project 75019617).
    Schlagwort(e): Sea surface temperatures ; Mid-Pleistocene transition ; Tropical Atlantic
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Format: application/pdf
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    ARTIKEL (OA)
  • 3
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    Correction to “Forcing of tropical Atlantic sea surface temperatures during the mid-Pleistocene transition” (2010)
    American Geophysical Union
    Details
    Publikationsdatum: 2022-05-26
    Beschreibung: Author Posting. © American Geophysical Union, 2005. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Paleoceanography 20 (2005): PA1019, doi:10.1029/2005PA001134.
    Schlagwort(e): Sea-surface temperatures ; Mid-Pleistocene transition ; Tropical Atlantic
    Repository-Name: Woods Hole Open Access Server
    Materialart: Article
    Format: application/pdf
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    ARTIKEL (OA)
  • 4
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    (Supplementary Table B) Data for locations employed as representatives of potential catchment areas (2012)
    PANGAEA
    Details
    Publikationsdatum: 2023-03-03
    Schlagwort(e): Aridity index; Calculated; Center for Marine Environmental Sciences; Distance; Evapotranspiration, potential; LATITUDE; LONGITUDE; MARUM; Precipitation, annual mean; Temperature, annual mean
    Materialart: Dataset
    Format: text/tab-separated-values, 390 data points
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    DATA PANGAEA
  • 5
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    (Supplementary Table A ) Locations employed for calculation of continental environmental conditions with WebWIMP Modelling program and values obtained as displayed in Fig. 1 (2012)
    PANGAEA
    Details
    Publikationsdatum: 2023-03-03
    Schlagwort(e): Aridity index; Center for Marine Environmental Sciences; Evapotranspiration, potential; LATITUDE; LONGITUDE; MARUM; Precipitation, annual mean; Temperature, annual mean
    Materialart: Dataset
    Format: text/tab-separated-values, 304 data points
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    DATA PANGAEA
  • 6
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    Hydrogen isotopic composition of sediment cores from a transect off western Africa (2013)
    PANGAEA
    In:  Supplement to: Collins, James A; Schefuß, Enno; Mulitza, Stefan; Prange, Matthias; Werner, Martin; Tharammal, Thejna; Paul, André; Wefer, Gerold (2013): Estimating the hydrogen isotopic composition of past precipitation using leaf-waxes from western Africa. Quaternary Science Reviews, 65, 88-101, https://doi.org/10.1016/j.quascirev.2013.01.007
    Details
    Publikationsdatum: 2023-03-03
    Beschreibung: The hydrogen isotopic composition of plant leaf-wax n-alkanes (dDwax) is a novel proxy for estimating dD of past precipitation (dDp). However, vegetation life-form and relative humidity exert secondary effects on dDwax, preventing quantitative estimates of past dDp. Here, we present an approach for removing the effect of vegetation-type and relative humidity from dDwax and thus for directly estimating past dDp. We test this approach on modern day (late Holocene; 0-3 ka) sediments from a transect of 9 marine cores spanning 21°N-23°S off the western coast of Africa. We estimate vegetation type (C3 tree versus C4 grass) using d13C of leaf-wax n-alkanes and correct dDwax for vegetation-type with previously-derived apparent fractionation factors for each vegetation type. Late Holocene vegetation-corrected dDwax (dDvc) displays a good fit with modern-day dDp, suggesting that the effects of vegetation type and relative humidity have both been removed and thus that dDvc is a good estimate of dDp. We find that the magnitude of the effect of C3 tree - C4 grass changes on dDwax is small compared to dDp changes. We go on to estimate dDvc for the mid-Holocene (6-8 ka), the Last Glacial Maximum (LGM; 19-23 ka) and Heinrich Stadial 1 (HS1; 16-18.5 ka). In terms of past hydrological changes, our leaf-wax based estimates of dDp mostly reflect changes in wet season intensity, which is complementary to estimates of wet season length based on leaf-wax d13C.
    Schlagwort(e): Center for Marine Environmental Sciences; MARUM
    Materialart: Dataset
    Format: application/zip, 2 datasets
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    DATA PANGAEA
  • 7
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    Distribution and stable isotopic compositions of hydrogen and carbon of plant-wax derived n-C29 and -C31 alkanes in terrestrial, coastal and offshore surface sediments (2013)
    PANGAEA
    In:  Supplement to: Leider, Arne; Hinrichs, Kai-Uwe; Schefuß, Enno; Versteegh, Gerard J M (2013): Distribution and stable isotopes of plant wax derived n-alkanes in lacustrine, fluvial and marine surface sediments along an Eastern Italian transect and their potential to reconstruct the hydrological cycle. Geochimica et Cosmochimica Acta, 117, 16-32, https://doi.org/10.1016/j.gca.2013.04.018
    Details
    Publikationsdatum: 2023-03-03
    Beschreibung: Reconstructing terrestrial water budgets is of prime importance for understanding past climate and environment. To shed more light on how plant-wax derived n-alkanes may be used for this purpose we investigated the distribution and stable isotopic compositions of hydrogen (dD) and carbon (d13C) of plant-wax derived n-C29 and -C31 alkanes in terrestrial, coastal and offshore surface sediments in relation to hydrology along a NW-SE transect east of the Italian Apennines from the Po River to the Eastern Gulf of Taranto. The plant wax average chain length increases southward and may relate to increasing temperature and/or aridity. The plant wax dD of the terrestrial and coastal samples also increases southward and mainly reflects changes in the dD of precipitation. The d13C of plant waxes is primarily interpreted in terms of C3 vegetation changes rather than varying contributions by C4 plants. The plant wax d13C-dD composition of the Po River and Apennine rivers differs considerably from that in southern Italy, and suggests a mainly southern source for plant waxes in marine sediments of the Gulf of Taranto. This calibration provides a basis for the reconstruction of past changes in the Italian water balance and n-alkane source areas.
    Schlagwort(e): Center for Marine Environmental Sciences; MARUM
    Materialart: Dataset
    Format: application/zip, 3 datasets
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    DATA PANGAEA
  • 8
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    Compound specific stable isotopes, BIT, pollen and spores of Miocene to Pliocene sediments of ODP Hole 175-1085A (2013)
    PANGAEA
    In:  Supplement to: Dupont, Lydie M; Rommerskirchen, Florian; Mollenhauer, Gesine; Schefuß, Enno (2013): Miocene to Pliocene changes in South African hydrology and vegetation in relation to the expansion of C4 plants. Earth and Planetary Science Letters, 375, 408-417, https://doi.org/10.1016/j.epsl.2013.06.005
    Details
    Publikationsdatum: 2023-03-03
    Beschreibung: Pollen and stable carbon (d13C) and hydrogen (dD) isotope ratios of terrestrial plant wax from the South Atlantic sediment core, ODP Site 1085, is used to reconstruct Miocene to Pliocene changes of vegetation and rainfall regime of western southern Africa. Our results reveal changes in the relative amount of precipitation and indicate a shift of the main moisture source from the Atlantic to the Indian Ocean during the onset of a major aridification 8 Ma ago. We emphasise the importance of declining precipitation during the expansion of C4 and CAM (mainly succulent) vegetation in South Africa. We suggest that the C4 plant expansion resulted from an increased equator-pole temperature gradient caused by the initiation of strong Atlantic Meridional Overturning Circulation following the shoaling of the Central American Seaway during the Late Miocene.
    Schlagwort(e): Center for Marine Environmental Sciences; MARUM
    Materialart: Dataset
    Format: application/zip, 3 datasets
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    DATA PANGAEA
  • 9
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    Sedimentary climate indicators of sediment core MD08-3167 and GeoB1711-4, southwestern Africa (2014)
    PANGAEA
    In:  Supplement to: Collins, James A; Schefuß, Enno; Govin, Aline; Mulitza, Stefan; Tiedemann, Ralf (2014): Insolation and glacial–interglacial control on southwestern African hydroclimate over the past 140 000 years. Earth and Planetary Science Letters, 398, 1-10, https://doi.org/10.1016/j.epsl.2014.04.034
    Details
    Publikationsdatum: 2023-03-03
    Beschreibung: The past climate evolution of southwestern Africa is poorly understood and interpretations of past hydrological changes are sometimes contradictory. Here we present a record of leaf-wax dD and View the MathML source taken from a marine sediment core at 23°S off the coast of Namibia to reconstruct the hydrology and C3 versus C4 vegetation of southwestern Africa over the last 140 000 years (140 ka). We find lower leaf-wax dD and higher View the MathML source (more C4 grasses), which we interpret to indicate wetter Southern Hemisphere (SH) summer conditions and increased seasonality, during SH insolation maxima relative to minima and during the last glacial period relative to the Holocene and the last interglacial period. Nonetheless, the dominance of C4 grasses throughout the record indicates that the wet season remained brief and that this region has remained semi-arid. Our data suggest that past precipitation increases were derived from the tropics rather than from the winter westerlies. Comparison with a record from the Congo Basin indicates that hydroclimate in southwestern Africa has evolved in antiphase with that of central Africa over the last 140 ka.
    Schlagwort(e): Center for Marine Environmental Sciences; MARUM
    Materialart: Dataset
    Format: application/zip, 9 datasets
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    DATA PANGAEA
  • 10
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    Isotopic composition of terrestrial plant waxes (dD and δ¹³C of n-alkanes) of sediment core SO188_342 from the Northern Bay of Bengal for the last 18 ka (2014)
    PANGAEA
    In:  Supplement to: Contreras-Rosales, Lorena Astrid; Jennerjahn, Tim C; Tharammal, Thejna; Meyer, Vera D; Lückge, Andreas; Paul, André; Schefuß, Enno (2014): Evolution of the Indian Summer Monsoon and terrestrial vegetation in the Bengal region during the past 18 ka. Quaternary Science Reviews, 102, 133-148, https://doi.org/10.1016/j.quascirev.2014.08.010
    Details
    Publikationsdatum: 2023-03-03
    Beschreibung: The Indian Summer Monsoon (ISM) is a major global climatic phenomenon. Long-term precipitation proxy records of the ISM, however, are often fragmented and discontinuous, impeding an estimation of the magnitude of precipitation variability from the Last Glacial to the present. To improve our understanding of past ISM variability, we provide a continuous reconstructed record of precipitation and continental vegetation changes from the lower Ganges-Brahmaputra-Meghna catchment and the Indo-Burman ranges over the last 18,000 years (18 ka). The records derive from a marine sediment core from the northern Bay of Bengal (NBoB), and are complemented by numerical model results of spatial moisture transport and precipitation distribution over the Bengal region. The isotopic composition of terrestrial plant waxes (dD and d13C of n-alkanes) are compared to results from an isotope-enabled general atmospheric circulation model (IsoCAM) for selected time slices (pre-industrial, mid-Holocene and Heinrich Stadial 1). Comparison of proxy and model results indicate that past changes in the dD of precipitation and plant waxes were mainly driven by the amount effect, and strongly influenced by ISM rainfall. Maximum precipitation is detected for the Early Holocene Climatic Optimum (EHCO; 10.5-6 ka BP), whereas minimum precipitation occurred during the Heinrich Stadial 1 (HS1; 16.9-15.4 ka BP). The IsoCAM model results support the hypothesis of a constant moisture source (i.e. the NBoB) throughout the study period. Relative to the pre-industrial period the model reconstructions show 20% more rain during the mid-Holocene (6 ka BP) and 20% less rain during the Heinrich Stadial 1 (HS1), respectively. A shift from C4-plant dominated ecosystems during the glacial to subsequent C3/C4-mixed ones during the interglacial took place. Vegetation changes were predominantly driven by precipitation variability, as evidenced by the significant correlation between the dD and d13C alkane records. When compared to other records across the ISM domain, precipitation and vegetation changes inferred from our records and the numerical model results provide evidence for a coherent regional variability of the ISM from the Last Glacial to the present.
    Schlagwort(e): Center for Marine Environmental Sciences; Leibniz Centre for Tropical Marine Research; MARUM; ZMT
    Materialart: Dataset
    Format: application/zip, 2 datasets
    Standort Signatur Einschränkungen Verfügbarkeit
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    DATA PANGAEA
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