Pliocene changes in trade wind intensity in the SE Pacific inferred from grain-size variability


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Cornelia.Saukel [ at ] awi.de

Abstract

The knowledge about the evolution of the southeast Pacific trade wind strength forms one of the missing links in understanding the progression of Pliocene reorganizations in tropical Pacific oceanography, including the shoaling of the thermocline in the tropical eastern Pacific, the amplification of oceanic upwelling and productivity as well as the development of the tropical west-to-east SST gradient. Here we present results from ODP Site 1237 (16°S, 76°W, 140 km off the coast of Peru), which underlies the modern path of eolian transport from the Atacama Desert in northern Chile and Peru. In order to reconstruct long- and short-term changes in dust supply and thus trade wind intensities and continental aridity, we have analyzed the grain-size distributions of the wind-blown sediment fraction (Beckmann-Coulter laser particle sizer) and the geochemical composition of the bulk sediment (ICP-OES measurements and XRF-scans).Grain-size means vary from 2.5 - 4µm around 4 Million years (Ma) to >3 - >8µm between 2 3 Ma, indicating a significant increase in trade wind strength between 4 and 3 Ma. Besides this long-term trend, the data reveal glacial increases in grain sizes, correlating with increases in iron supply and sea surface temperature drops (ODP site 846, Lawrence 2006) in the Pacific cold tongue during the Northern Hemisphere Glaciation. In combination with the geochemical data, grain-size endmembers indicative of dust and volcanic ash layers were identified. This approach enabled us to largely exclude overprints from ash fallout related to volcanic events.



Item Type
Conference (Poster)
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Not peer-reviewed
Publication Status
Published
Event Details
Workshop on Pliocene Climate Change..
Eprint ID
21316
Cite as
Saukel, C. , Stuut, J. B. , Rincón Martinez, D. , Lamy, F. and Tiedemann, R. (2009): Pliocene changes in trade wind intensity in the SE Pacific inferred from grain-size variability , Workshop on Pliocene Climate Change. .


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