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Climate of the Past An interactive open-access journal of the European Geosciences Union
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Volume 13, issue 4 | Copyright
Clim. Past, 13, 345-358, 2017
https://doi.org/10.5194/cp-13-345-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 18 Apr 2017

Research article | 18 Apr 2017

δ13C decreases in the upper western South Atlantic during Heinrich Stadials 3 and 2

Marília C. Campos1, Cristiano M. Chiessi1, Ines Voigt2, Alberto R. Piola3,4, Henning Kuhnert2, and Stefan Mulitza2 Marília C. Campos et al.
  • 1School of Arts, Sciences and Humanities, University of São Paulo, São Paulo, 03828-000, Brazil
  • 2MARUM – Center for Marine Environmental Sciences, University of Bremen, Bremen, 28359, Germany
  • 3Servicio de Hidrografia Naval (SHN), Buenos Aires, C1270ABV, Argentina
  • 4Dept. Ciencias de la Atmósfera y los Océanos, FCEN, Universidad de Buenos Aires, C1428 EHA, and Instituto Franco–Argentino sobre Estudios de Clima y sus Impactos, CNRS/CONICET, C1428EGA, Argentina

Abstract. Abrupt millennial-scale climate change events of the last deglaciation (i.e. Heinrich Stadial 1 and the Younger Dryas) were accompanied by marked increases in atmospheric CO2 (CO2atm) and decreases in its stable carbon isotopic ratios (δ13C), i.e. δ13CO2atm, presumably due to outgassing from the ocean. However, information on the preceding Heinrich Stadials during the last glacial period is scarce. Here we present δ13C records from two species of planktonic foraminifera from the western South Atlantic that reveal major decreases (up to 1‰) during Heinrich Stadials 3 and 2. These δ13C decreases are most likely related to millennial-scale periods of weakening of the Atlantic meridional overturning circulation and the consequent increase (decrease) in CO2atm (δ13CO2atm). We hypothesise two mechanisms that could account for the decreases observed in our records, namely strengthening of Southern Ocean deep-water ventilation and weakening of the biological pump. Additionally, we suggest that air–sea gas exchange could have contributed to the observed δ13C decreases. Together with other lines of evidence, our data are consistent with the hypothesis that the CO2 added to the atmosphere during abrupt millennial-scale climate change events of the last glacial period also originated in the ocean and reached the atmosphere by outgassing. The temporal evolution of δ13C during Heinrich Stadials 3 and 2 in our records is characterized by two relative minima separated by a relative maximum. This w structure is also found in North Atlantic and South American records, further suggesting that such a structure is a pervasive feature of Heinrich Stadial 2 and, possibly, also Heinrich Stadial 3.

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Our new planktonic foraminiferal stable carbon isotopic data from the western South Atlantic show major decreases during abrupt climate change events of the last glacial. These anomalies are likely related to periods of a sluggish Atlantic meridional overturning circulation and increase (decrease) in atmospheric CO2 (stable carbon isotopic ratios). We hypothesize that strengthening of Southern Ocean deep-water ventilation and weakening of the biological pump are responsible for these decreases.
Our new planktonic foraminiferal stable carbon isotopic data from the western South Atlantic...
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