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

Type Article
Date 2017-04
Language English
Author(s) Campos Marilia C.1, Chiessi Cristiano M.1, Voigt Ines2, Piola Alberto R.3, 4, 5, Kuhnert HenningORCID2, Mulitza StefanORCID2
Affiliation(s) 1 : Univ Sao Paulo, Sch Arts Sci & Humanities, BR-03828000 Sao Paulo, Brazil.
2 : Univ Bremen, MARUM Ctr Marine Environm Sci, D-28359 Bremen, Germany.
3 : Serv Hidrog Naval, C1270ABV, Buenos Aires, DF, Argentina.
4 : Univ Buenos Aires, FCEN, Dept Ciencias Atmosfera & Oceanos, C1428 EHA, Buenos Aires, DF, Argentina.
5 : Consejo Nacl Invest Cient & Tecn, CNRS, Inst Franco Argentino Estudios Clima & Sus Impact, C1428EGA, Buenos Aires, DF, Argentina.
Source Climate Of The Past (1814-9324) (Copernicus Gesellschaft Mbh), 2017-04 , Vol. 13 , N. 4 , P. 345-358
DOI 10.5194/cp-13-345-2017
WOS© Times Cited 7
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 (delta C-13), i.e. delta(CO2atm)-C-13, presumably due to out-gassing from the ocean. However, information on the preceding Heinrich Stadials during the last glacial period is scarce. Here we present delta C-13 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 delta C-13 decreases are most likely related to millennial-scale periods of weakening of the Atlantic meridional overturning circulation and the consequent increase (decrease) in CO2atm (delta(CO2atm)-C-13). 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 delta C-13 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 delta C-13 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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Figure 1: Stable oxygen isotope values of G. ruber and G. inflata Figure 1: Stable oxygen isotopic delta 18 O) records from sediment core GeoB6212-1. 2 371 KB Open access
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