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| Titel |
Palaeoceanographic productivity changes in the Eastern Equatorial Atlantic since the penultimate glaciation |
| VerfasserIn |
Rachael Lem, Jim Marshall, Melanie Leng, Fabienne Marret |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250138291
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| Publikation (Nr.) |
 EGU/EGU2017-1267.pdf |
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| Zusammenfassung |
| A 150,000 year multiproxy record from the eastern equatorial Atlantic, offshore Gabon, has
been investigated in order to examine the effects of changing glacial – interglacial climate on
marine productivity.
Higher δ13C values of the benthic foraminifera Planulina wuellerstorfi are documented
during the penultimate glaciation (150 -130 kyr BP) in comparison to the Last Glacial
Maximum [LGM] (24.5 – 19 kyr BP). In conjunction with higher CaCO3 and larger
variability in the isotopic difference between surface and bottom waters during the
penultimate glaciation, this suggests that the eastern equatorial Atlantic was much more
productive at this time than the LGM, most likely driven by increased nutrient input through
strong bottom water upwelling.
The benthic δ18O and planktonic δ18O record of Globigerinoides ruber (white) infer that
both the surface and bottom waters were warmer during the penultimate glaciation than
the LGM. The sea surface temperature [SST] record assimilated through Mg/Ca
analysis of the G. ruber evidences much lower SSTs during the last deglaciation in
comparison with other regional records, and with the present day SST, which together
with high Fe input, we attribute this to a greatly enhanced discharge of the Ogooué
River.
Bulk coccolith carbonate δ13C demonstrates a shift towards lower δ13C values from the
penultimate glaciation towards present day which does not dovetail the other proxies. The
δ18O coccolith record mirrors that of G. ruber during the two glacial periods, but presents
much higher isotopic values during the interglacials. We interpret this as a shift in seasonality
in the calcification of the coccoliths between glacial and interglacial periods, which in
combination with the long term decline in δ13C values reflects a change in the
habitat preferences of this phytoplankton over the last glacial – interglacial cycle. |
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