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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Discussion papers
https://doi.org/10.5194/cp-2018-98
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/cp-2018-98
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 20 Aug 2018

Research article | 20 Aug 2018

Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Climate of the Past (CP) and is expected to appear here in due course.

Understanding the mechanisms behind high glacial productivity in the southern Brazilian margin

Rodrigo da C. Portilho-Ramos1,2, Tainã M. L. Pinho3, Cristiano M. Chiessi3, and Cátia F. Barbosa4 Rodrigo da C. Portilho-Ramos et al.
  • 1MARUM - Center for Marine Environmental Sciences, University of Bremen, Leobener Strasse, 28359 Bremen, Germany
  • 2Institute of Geosciences, University of São Paulo, Rua do Lago 562, CEP 05508-080, São Paulo, Brazil
  • 3School of Arts, Sciences and Humanities, University of São Paulo, Rua Arlindo Bettio 1000, CEP03828-000, São Paulo, Brazil
  • 4Departamento de Geoquímica, Universidade Federal Fluminense, Rua Outeiro São João Baptista S/N, CEP 24020-141, Niterói, Rio de Janeiro, Brazil

Abstract. This study explores the mechanisms behind the high glacial productivity in the southern Brazilian margin during the last 70 kyr. Therefore, we use planktonic foraminifera assemblage and subsurface temperatures derived through the Modern Analogue Technique. We show that enhanced glacial productivity was driven by the synergy of two mechanisms operating in different seasons: (i) a high productivity upwelling during short austral summer events; and (ii) the persistent presence of the Plata Plume Water due to prolonged austral winter conditions. We suggest that the upwelling systems in the southern Brazilian margin were more productive during the last glacial period due to the enhanced Si supply for diatom production through high-Si thermocline waters preformed in the Southern Ocean. We hypothesize that orbital forcing did not have a major influence on changes in upwelling during the last glacial period. However, the more frequent northward intrusions of the Plata Plume Water were modulated by austral winter insolation at 65 °S through changes in the strength of alongshore SW-winds. After the Last Glacial Maximum, the reduced Si content of thermocline waters decreased upwelling productivity, while lower austral winter insolation decreased the influence of the Plata Plume Water over the southern Brazilian margin, reducing regional productivity.

Rodrigo da C. Portilho-Ramos et al.
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Rodrigo da C. Portilho-Ramos et al.
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