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  • 2010-2014  (105)
  • 2000-2004  (15)
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  • 11
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    Forcing of wet phases in southeast Africa over the past 17,000 years (2011)
    Macmillan Publishers
    In:  EPIC3Nature, Macmillan Publishers, 480(7378), pp. 509-512, ISSN: 0028-0836
    Details
    Publication Date: 2019-07-17
    Description: Intense debate persists about the climatic mechanisms governing hydrologic changes in tropical and subtropical southeast Africa since the Last Glacial Maximum, about 20,000 years ago. In particular, the relative importance of atmospheric and oceanic processes is not firmly established. Southward shifts of the intertropical convergence zone (ITCZ) driven by high-latitude climate changes have been suggested as a primary forcing whereas other studies infer a predominant influence of Indian Ocean sea surface temperatures on regional rainfall changes. To address this question, a continuous record representing an integrated signal of regional climate variability is required, but has until now been missing. Here we show that remote atmospheric forcing by cold events in the northern high latitudes appears to have been the main driver of hydro-climatology in southeast Africa during rapid climate changes over the past 17,000 years. Our results are based on a reconstruction of precipitation and river discharge changes, as recorded in a marine sediment core off the mouth of the Zambezi River, near the southern boundary of the modern seasonal ITCZ migration. Indian Ocean sea surface temperatures did not exert a primary control over southeast African hydrologic variability. Instead, phases of high precipitation and terrestrial discharge occurred when the ITCZ was forced southwards during Northern Hemisphere cold events, such as Heinrich stadial 1 (around 16,000 years ago) and the Younger Dryas (around 12,000 years ago), or when local summer insolation was high in the late Holocene, that is, during the past 4,000 years.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
    Format: application/pdf
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  • 12
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    Long chain 1,13- and 1,15-diols as a potential proxy for palaeotemperature reconstruction (2012)
    ELSEVIER SCIENCE BV
    In:  EPIC3Geochimica et Cosmochimica Acta, ELSEVIER SCIENCE BV, 84, pp. 204-216, ISSN: 00167037
    Details
    Publication Date: 2019-07-17
    Description: Although commonly reported in marine and freshwater environments, little is known about the biological sources of long chain alkyl 1,13- and 1,15-diols, and factors controlling their distributions. Here we analyzed the occurrence and distribution of these lipids in a comprehensive set of marine surface sediments and compare their distributions with environmental conditions like sea surface temperature (SST), salinity and nutrient concentrations. Fractional abundances of the C28 1,13-, C30 1,13- and C30 1,15-diols show a strong correlation with SST and based on these results, we propose the Long chain Diol Index (LDI), which expresses the C30 1,15-diol abundance relative to those of C28 1,13-, C30 1,13- and C30 1,15-diols. The LDI shows a strong linear correlation with SST (LDI = 0.033 � SST + 0.095; R2 = 0.969, n = 162) over a temperature range of �3 to 27 �C. Long chain diol distributions in sediments from the South Atlantic close to the Congo River outflow (West Africa) provided a 43 kyr LDI SST record. This record reflects several known climatic events and shows similarities with an alkenone- derived SST record obtained using the same suite of sediments, both in trend and in terms of absolute SST. This confirms the potential of the LDI as a proxy for palaeo-SST reconstruction.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 13
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    Organic-geochemical proxies of sea surface temperature in surface sediments of the tropical eastern Indian Ocean (2014)
    Pergamon-Elsevier
    In:  EPIC3Deep Sea Research Part I: Oceanographic Research Papers, Pergamon-Elsevier, 88, pp. 17-29, ISSN: 0967-0637
    Details
    Publication Date: 2014-06-25
    Description: In this study we reconstruct sea surface temperatures (SSTs) using two lipid-based biomarker proxies (alkenone unsaturation index View the MathML sourceU37K′ and TEX86 index based on glycerol dibiphytanyl glycerol tetraethers) in 36 surface sediment samples from the Indonesian continental margin off west Sumatra and south of Java and the Lesser Sunda Islands. Comparison of measured temperatures (World Ocean Atlas 09) to reconstructed temperatures suggests that SST estimates based on View the MathML sourceU37K′ reflect the SE monsoon SST in the upwelling area south of Java and the Lesser Sunda Islands. Estimates based on TEX86 using the calibration for temperatures 〉20 °C (View the MathML sourceTEX86H) are up to 2 °C lower than View the MathML sourceU37K′-based SSTs. This offset is possibly related to either one or a combination of two factors: (i) the depth habitats of the source organisms and (ii) different seasonal production and/or seasonality of export associated with phytoplankton blooming triggered by primary productivity. In the non-upwelling area off west Sumatra, the alkenone-based SSTs are cooler than measured temperatures during the entire year, likely reflecting the limitations of the View the MathML sourceU37K′ proxy beyond 28 °C, while reconstructed temperatures based on View the MathML sourceTEX86H are consistent with mean annual SST.
    Repository Name: EPIC Alfred Wegener Institut
    Type: Article , isiRev
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  • 14
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    Forcing of tropical Atlantic sea surface temperatures during the mid-Pleistocene transition (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-25
    Description: 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.
    Description: 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.
    Description: The Dutch scientific funding organization (NWO) is thanked for financial support (project 75019617).
    Keywords: Sea surface temperatures ; Mid-Pleistocene transition ; Tropical Atlantic
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 15
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    Correction to “Forcing of tropical Atlantic sea surface temperatures during the mid-Pleistocene transition” (2010)
    American Geophysical Union
    Details
    Publication Date: 2022-05-26
    Description: 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.
    Keywords: Sea-surface temperatures ; Mid-Pleistocene transition ; Tropical Atlantic
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 16
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    (Supplementary Table B) Data for locations employed as representatives of potential catchment areas (2012)
    PANGAEA
    Details
    Publication Date: 2023-03-03
    Keywords: Aridity index; Calculated; Center for Marine Environmental Sciences; Distance; Evapotranspiration, potential; LATITUDE; LONGITUDE; MARUM; Precipitation, annual mean; Temperature, annual mean
    Type: Dataset
    Format: text/tab-separated-values, 390 data points
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  • 17
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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
    Publication Date: 2023-03-03
    Keywords: Aridity index; Center for Marine Environmental Sciences; Evapotranspiration, potential; LATITUDE; LONGITUDE; MARUM; Precipitation, annual mean; Temperature, annual mean
    Type: Dataset
    Format: text/tab-separated-values, 304 data points
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 18
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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
    Publication Date: 2023-03-03
    Description: 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.
    Keywords: Center for Marine Environmental Sciences; MARUM
    Type: Dataset
    Format: application/zip, 2 datasets
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  • 19
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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
    Publication Date: 2023-03-03
    Description: 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.
    Keywords: Center for Marine Environmental Sciences; MARUM
    Type: Dataset
    Format: application/zip, 3 datasets
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  • 20
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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
    Publication Date: 2023-03-03
    Description: 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.
    Keywords: Center for Marine Environmental Sciences; MARUM
    Type: Dataset
    Format: application/zip, 3 datasets
    Location Call Number Limitation Availability
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    DATA PANGAEA
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