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

A detailed record of benthic foraminifera carbon isotopes from the intermediate-depth South East Atlantic margin shows little glacial-interglacial variability between MIS-12 to MIS-10, suggesting that Northern Atlantic deep-waters consistently penetrated to at least 30 degrees S. Millennial-scale increases in either the mass or flux of northern-sourced deepwaters over the core site occurred 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 delta C-13 gradient shows that a reduction in deep Southern Ocean ventilation at the end of MIS-11 was consistent with a modelled CO2 drawdown of similar to 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 similar to 45 ppm drawdown.