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| Titel |
Climatically-controlled siliceous productivity in the eastern Gulf of Guinea during the last 40 000 yr |
| VerfasserIn |
X. Crosta, O. E. Romero, O. Ther, R. R. Schneider |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1814-9324
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| Digitales Dokument |
URL |
| Erschienen |
In: Climate of the Past ; 8, no. 2 ; Nr. 8, no. 2 (2012-03-07), S.415-431 |
| Datensatznummer |
250005460
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| Publikation (Nr.) |
 copernicus.org/cp-8-415-2012.pdf |
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| Zusammenfassung |
Opal content and diatom assemblages were analysed in core GeoB4905-4 to
reconstruct siliceous productivity changes in the eastern Gulf of Guinea
during the last 40 000 yr. Opal and total diatom accumulation rates
presented low values over the considered period, except during the Last
Glacial Maximum and between 15 000 calendar years Before Present (15 cal. ka
BP) and 5.5 cal. ka BP, the so-called African Humid Period, when
accumulation rates of brackish and freshwater diatoms at the core site were
highest. Conversely, accumulation rates of windblown diatoms exhibited an
opposite pattern with higher values before and after the African Humid
Period and greatest values during Heinrich Events, the Younger Dryas and
since 5.5 cal. ka BP.
Our results demonstrate that siliceous productivity in the eastern Gulf of
Guinea was directly driven by the nutrient load from local rivers, whose
discharges were forced by precipitation changes over western Equatorial
Africa and/or modification of the fluvio-deltaic systems forced by sea level
changes. Precipitation in this region is controlled by the West African
monsoon which is, in turn, partly dependent on the presence and intensity of
the Atlantic Cold Tongue (ACT). Our results therefore suggest that the ACT
was weakened, warmer trade winds were less vigorous, and cloud convection
and precipitation were greater during the AHP though
centennial-to-millennial timescale dry events were observed at ∼10 cal. ka BP, ∼8.5 cal. ka BP and ∼6 cal. ka BP. Conversely, the
ACT was more intense, trade winds were more vigorous and African climate was
more arid during H1, the Younger Dryas and after 5.5 cal. ka BP into the
present. |
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