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Terrigenous input off northern South America driven by changes in Amazonian climate and the North Brazil Current retroflection during the last 250 ka

Texto completo
Govin, A. [1] ; Chiessi, C. M. [2] ; Zabel, M. [1] ; Sawakuchi, A. O. [3] ; Heslop, D. [4] ; Hoerner, T. [1] ; Zhang, Y. [1] ; Mulitza, S. [1]
Número total de Autores: 8
Afiliação do(s) autor(es):
[1] Univ Bremen, MARUM Ctr Marine Environm Sci, D-28359 Bremen - Germany
[2] Univ Sao Paulo, Sch Arts Sci & Humanities, Sao Paulo - Brazil
[3] Univ Sao Paulo, Inst Geosci, Dept Sedimentary & Environm Geol, Sao Paulo - Brazil
[4] Australian Natl Univ, Res Sch Earth Sci, Canberra, ACT - Australia
Número total de Afiliações: 4
Tipo de documento: Artigo Científico
Fonte: Climate of the Past; v. 10, n. 2, p. 843-862, 2014.
Citações Web of Science: 24

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 degrees N along the northern South American margin. The Amazon River is the sole source of terrigenous material for sites at 5 and 9 degrees N, while the core at 12 degrees 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 degrees N) and of Amazon material ({''}%-Amazon{''}, at 12 degrees N) within the terrigenous fraction. The %-Andes and %-Amazon records exhibit significant precessional variations over the last 250 ka that are more pronounced during inter-glacials 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 degrees 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 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. (AU)

Processo FAPESP: 12/17517-3 - Resposta da porção oeste do Oceano Atlântico às mudanças na circulação meridional do Atlântico: variabilidade milenar a sazonal
Beneficiário:Cristiano Mazur Chiessi
Linha de fomento: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Jovens Pesquisadores
Processo FAPESP: 11/06609-1 - Proveniência, transporte e estocagem de sedimentos nos rios amazônicos
Beneficiário:André Oliveira Sawakuchi
Linha de fomento: Auxílio à Pesquisa - Regular