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  • Center for Marine Environmental Sciences; MARUM  (3)
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  • 1
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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
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 2
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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
    Publication Date: 2023-03-03
    Description: 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.
    Keywords: Center for Marine Environmental Sciences; MARUM
    Type: Dataset
    Format: application/zip, 9 datasets
    Location Call Number Limitation Availability
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    DATA PANGAEA
  • 3
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    Abrupt shifts of the Sahara-Sahel boundary during Heinrich stadials demonstrated on a sediment core transect (2013)
    PANGAEA
    In:  Supplement to: Collins, James A; Govin, Aline; Mulitza, Stefan; Heslop, David; Zabel, Matthias; Hartmann, Jens; Röhl, Ursula; Wefer, Gerold (2013): Abrupt shifts of the Sahara–Sahel boundary during Heinrich stadials. Climate of the Past, 9(3), 1181-1191, https://doi.org/10.5194/cp-9-1181-2013
    Details
    Publication Date: 2023-06-15
    Description: Relict dune fields that are found as far south as 14° N in the modern-day African Sahel are testament to equatorward expansions of the Sahara desert during the Late Pleistocene. However, the discontinuous nature of dune records means that abrupt millennial-timescale climate events are not always resolved. High-resolution marine core studies have identified Heinrich stadials as the dustiest periods of the last glacial in West Africa although the spatial evolution of dust export on millennial timescales has so far not been investigated. We use the major-element composition of four high-resolution marine sediment cores to reconstruct the spatial extent of Saharan-dust versus river-sediment input to the continental margin from West Africa over the last 60 ka. This allows us to map the position of the sediment composition corresponding to the Sahara-Sahel boundary. Our records indicate that the Sahara-Sahel boundary reached its most southerly position (13° N) during Heinrich stadials and hence suggest that these were the periods when the sand dunes formed at 14° N on the continent. Heinrich stadials are associated with cold North Atlantic sea surface temperatures which appear to have triggered abrupt increases of aridity and wind strength in the Sahel. Our study illustrates the influence of the Atlantic meridional overturning circulation on the position of the Sahara-Sahel boundary and on global atmospheric dust loading.
    Keywords: Center for Marine Environmental Sciences; MARUM
    Type: Dataset
    Format: application/zip, 8 datasets
    Location Call Number Limitation Availability
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    DATA PANGAEA
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