Mid-depth South Atlantic ocean circulation and chemical stratification during MIS-10 to 12: implications for atmospheric CO₂

A. J. Dickson (1) , M. J. Leng (2) , M. A. Maslin (1)

1 Environmental Change Research Centre
2 NERC Isotope Geosciences Laboratory

A detailed record of benthic foraminifera carbon isotopes from the South East Atlantic margin shows little glacial-interglacial variability between MIS-12 to MIS-10, suggesting that Glacial North Atlantic Intermediate Water (GNAIW) consistently penetrated to at least 30° S. Millennial-scale increases in either the mass or flux of GNAIW over the core site occur alongside reductions in Lower North Atlantic Deep Water recorded in North Atlantic sediment cores and show that the lower and intermediate limb of the Atlantic deepwater convective cell oscillated in anti-phase during previous glacial periods. In addition, a 500 yr resolution record of the Cape Basin intermediate-deep ?¹³C gradient shows that a reduction in deep Southern Ocean ventilation at the end of MIS-11 was consistent with a modelled CO₂ drawdown of ~21?30 ppm. Further increases in the Southern Ocean chemical divide during the transition into MIS-10 were completed before minimum CO₂ levels were reached, suggesting that other mechanisms such as alkalinity changes were responsible for the remaining ~45 ppm drawdown.

Domaines: Interfaces continentales, environnement; Sciences de la Terre

A. J. Dickson, M. J. Leng, M. A. Maslin. Mid-depth South Atlantic ocean circulation and chemical stratification during MIS-10 to 12: implications for atmospheric CO₂. Climate of the Past Discussions, 2008, 4 (3), pp.667-695. ⟨hal-00298224⟩