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Climate of the Past An interactive open-access journal of the European Geosciences Union
doi:10.5194/cp-2016-59
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
20 Jun 2016
Review status
A revision of this discussion paper was accepted for the journal Climate of the Past (CP) and is expected to appear here in due course.
Glacial δ13C decreases in the western South Atlantic forced by millennial changes in Southern Ocean ventilation
Marília C. Campos1, Cristiano M. Chiessi1, Ines Voigt2, Alberto R. Piola3,4, Henning Kuhnert2, and Stefan Mulitza2 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 presumably originated by outgassing from the Southern Ocean. However, information on the preceding Heinrich Stadials during the last glacial period is scarce. Here we present stable carbon isotopic data (δ13C) 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 intensification in Southern Ocean deep water ventilation presumably associated with a weak Atlantic meridional overturning circulation. After reaching the upper water column of the Southern Ocean, the δ13C depletion would be transferred equatorward via central and thermocline waters. 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 during the last glacial period also originated in the ocean and reached the atmosphere by outgassing from the Southern Ocean. The temporal evolution of δ13C during Heinrich Stadials 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, giving us confidence that such structure is a pervasive feature of Heinrich Stadial 2 and, possibly, also Heinrich Stadial 3.

Citation: Campos, M. C., Chiessi, C. M., Voigt, I., Piola, A. R., Kuhnert, H., and Mulitza, S.: Glacial δ13C decreases in the western South Atlantic forced by millennial changes in Southern Ocean ventilation, Clim. Past Discuss., doi:10.5194/cp-2016-59, in review, 2016.
Marília C. Campos et al.
Marília C. Campos et al.

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Short summary
Abrupt climate change events of the last deglaciation were accompanied by increases in atmospheric CO2 presumably originated by outgassing from the Southern Ocean. We present new planktonic foraminiferal stable carbon isotopic data from the western South Atlantic that suggest that the CO2 added to the atmosphere during abrupt climate change events of the last glacial period also originated in the ocean and reached the atmosphere by outgassing from the Southern Ocean.
Abrupt climate change events of the last deglaciation were accompanied by increases in...
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