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| Titel |
Terrigenous input off northern South America driven by changes in Amazonian climate and the North Brazil Current retroflection during the last 250 ka |
| VerfasserIn |
A. Govin, C. M. Chiessi, M. Zabel, A. O. Sawakuchi, D. Heslop, T. Hörner, Y. Zhang, S. Mulitza |
| 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 ; 10, no. 2 ; Nr. 10, no. 2 (2014-04-28), S.843-862 |
| Datensatznummer |
250116957
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| Publikation (Nr.) |
 copernicus.org/cp-10-843-2014.pdf |
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| Zusammenfassung |
| We investigate changes in the delivery and oceanic transport of Amazon
sediments related to terrestrial climate variations over the last 250 ka. We
present high-resolution geochemical records from four marine sediment cores
located between 5 and 12° N along the northern South
American margin. The Amazon River is the sole source of terrigenous material
for sites at 5 and 9° N, while the core at
12° N receives a mixture of Amazon and Orinoco detrital particles.
Using an endmember unmixing model, we estimated the relative proportions of
Amazon Andean material ("%-Andes", at 5 and 9° N) and
of Amazon material ("%-Amazon", at 12° N) within the
terrigenous fraction. The %-Andes and %-Amazon records exhibit
significant precessional variations over the last 250 ka that are more
pronounced during interglacials in comparison to glacial periods. High
%-Andes values observed during periods of high austral summer insolation
reflect the increased delivery of suspended sediments by Andean tributaries
and enhanced Amazonian precipitation, in agreement with western Amazonian
speleothem records. Increased Amazonian rainfall reflects the
intensification of the South American monsoon in response to enhanced
land–ocean thermal gradient and moisture convergence. However, low
%-Amazon values obtained at 12° N during the same periods seem
to contradict the increased delivery of Amazon sediments. We propose that
reorganizations in surface ocean currents modulate the northwestward
transport of Amazon material. In agreement with published records, the
seasonal North Brazil Current retroflection is intensified (or prolonged in
duration) during cold substages of the last 250 ka (which correspond to
intervals of high DJF or low JJA insolation) and deflects eastward the
Amazon sediment and freshwater plume. |
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