Increased Amazon freshwater discharge during late Heinrich Stadial 1

Autor(es):Mostrar menos -

Crivellari, Stefano ^[1] ; Chiessi, Cristiano Mazur ^[2] ; Kuhnert, Henning ^[3] ; Haggi, Christoph ^[3] ; Portilho-Ramos, Rodrigo da Costa ^{[1, 3]} ; Zeng, Jing-Ying ^[3] ; Zhang, Yancheng ^[3] ; Schefuss, Enno ^[3] ; Mollenhauer, Gesine ^[4] ; Hefter, Jens ^[4] ; Alexandre, Felipe ^[5] ; Sampaio, Gilvan ^[5] ; Mulitza, Stefan ^[3]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Inst Geosci, Sao Paulo - Brazil

^[2] Univ Sao Paulo, Sch Arts Sci & Humanities, Sao Paulo - Brazil

^[3] Univ Bremen, MARUM Ctr Marine Environm Sci, Bremen - Germany

^[4] Alfred Wegener Inst Polar & Marine Res, Bremerhaven - Germany

^[5] INPE Natl Inst Space Res, Cachoeira Paulista - Brazil

• Tipo de documento: Artigo Científico
• Fonte: QUATERNARY SCIENCE REVIEWS; v. 181, p. 144-155, FEB 1 2018.
• Citações Web of Science: 8

Resumo

The temporal succession of changes in Amazonian hydroclimate during Heinrich Stadial 1 (HS1) (ca. 18-14.7 cal ka BP) is currently poorly resolved. Here we present HS1 records based on isotope, inorganic and organic geochemistry from a marine sediment core influenced by the Amazon River discharge. Our records offer a detailed reconstruction of the changes in Amazonian hydroclimate during HS1, integrated over the basin. We reconstructed surface water hydrography using stable oxygen isotopes (delta O-18) and Mg/Ca-derived paleotemperatures from the planktonic foraminifera Globigerinoides ruber, as well as salinity changes based on stable hydrogen isotope (delta D) of palmitic acid. We also analyzed branched and isoprenoid tetraether concentrations, and compared them to existing bulk sediment In(Fe/Ca) data and vegetation reconstruction based on stable carbon isotopes from n-alkanes, in order to understand the relationship between continental precipitation, vegetation and sediment production. Our results indicate a two-phased HS1 (HS1a and HS1b). During HS1a (18-16.9 cal ka BP), a first sudden increase of sea surface temperatures (SST) in the western equatorial Atlantic correlated with the slowdown of the Atlantic Meridional Overturning Circulation (AMOC) and the associated southern hemisphere warming phase of the bipolar seesaw. This phase was also characterized by an increased delivery of terrestrial material. During HS1b (16.9-14.8 cal ka BP), a decrease in terrestrial input was, however, associated with a marked decline of seawater delta O-18 and palmitic acid delta D. Both isotopic proxies independently indicate a drop in sea surface salinity (SSS). A number of records under the influence of the North Brazil Current, in contrast, indicate increases in SST and SSS resulting from a weakened AMOC during HS1. Our records thus suggest that the expected increase in SSS due to the AMOC slowdown was overridden by a two phased positive precipitation anomaly in Amazonian hydroclimate. (C) 2017 Elsevier Ltd. All rights reserved. (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
• Modalidade de apoio: Auxílio à Pesquisa - Programa de Pesquisa sobre Mudanças Climáticas Globais - Jovens Pesquisadores
• Processo FAPESP: 13/22521-2 - Efeitos das mudanças abruptas da circulação meridional do Atlântico sobre as massas de água profunda: uma abordagem isotópica
• Beneficiário: Stefano Crivellari
• Modalidade de apoio: Bolsas no Brasil - Doutorado Direto