Citation link: http://nbn-resolving.de/urn:nbn:de:gbv:46-diss000106647
|Title:||Application and quality of X-Ray fluorescence core scanning in reconstructing late Pleistocene NW African continental margin sedimentation patterns and paleoclimate variations||Other Titles:||Anwendungen und Qualitätsbeurteilung von XRF-Analysen zur Rekonstruktion spät-Pleistozäner Sedimentations- und Klima-Änderungen am NW Afrikanischen Kontinentalrand||Authors:||Tjallingii, Rik||Supervisor:||Bickert, Torsten Röhl, Ursula||1. Expert:||Wefer, Gerold||2. Expert:||Stein, Rüdiger||Institution:||Universität Bremen||Faculty:||FB5 Geowissenschaften||Keywords:||NW Africa, Cape Blanc, XRF core scanner, end member modeling, eolian dust, aridity, vegetation cover, productivity, upwelling.||Issue Date:||12-Feb-2007||Abstract:||
Abrupt climate changes during the last glacial-interglacial cycle known as Dansgaard-Oeschger (D-O) oscillations. Although, it is evident that these climate changes are most severe in the North Atlantic realm, the forcing of the D-O climate oscillations is still controversial. Feedback mechanisms between ocean heat transport, atmospheric circulation, and low latitude climate changes are thought to play an important role in the continuation, amplification, and possibly initiation of D-O climate oscillations. However, the role low-latitude climate zones and their potential to influence or initiate high-latitude climate change is still unknown. The region off Cape Blanc (Northwest Africa) is situated between the North Atlantic mid latitudes and the equatorial Atlantic, and is a key region to study climate forcing in the subtropics.Millennial-scale changes of the terrigenous sediment composition based on non-destructive XRF core scanning and grain-size variations of the terrigenous sediment fraction indicate coherent high- and low- climate variations during the last glacial-interglacial cycle. Water corrected X-Ray Fluorescence (XRF) Core Scanner measurements are used to obtaining chemical changes of the eolian dust input. End member modeling of the terrigenous fraction reveal two eolian end members, and a hemipelagic end member. Additionally, opal and organic matter accumulations are used to reconstruct upwelling intensities and surface water productivity off Cape Blanc. These data indicate increased continental aridity, trade wind intensities, and upwelling intensities accompanied by reduced surface water productivity associated with North Atlantic Heinrich events and extreme Greenland stadial events. Moreover, both the eolian contributions off Cape Blanc and simulations of the vegetation (obtained from the Atmosphere-Ocean-Vegetation model CLIMBER 2) indicate that Northwest African humidity is forced by the strength of the African Monsoon during interglacial conditions.
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