3:45 PM - 4:00 PM
[BPT04-08] Boron isotope-based seasonal paleo-pH reconstruction for the Southeast Atlantic – Multispecies approach using habitat preference of planktonic foraminifera
Keywords:carbon cycle, ocean carbonate chemistry, atmospheric pCPO2, boron isotopes, seasonality, foraminifera
To test the applicability of the season-adjusted calibrations, we used a core drilled on the Walvis Ridge in the Southeast Atlantic spanning the last 330,000 years to reconstruct changes in surface-water pCO2. The reconstruction based on G. bulloides, reflecting the austral spring season, yields values closely following the Vostok ice-core data, indicating that surface-water pCO2 was close to equilibrium with the atmosphere during the cooler spring season. In contrast, pCO2 estimated from δ11BCc of O. universa, T. sacculifer and G. ruber that predominantly lived during the warmer seasons, exhibits up to ~58 ppmv higher values than the Vostok ice-core data, with larger deviations during interglacials than during glacials.
This is probably due to the higher austral fall temperatures, as shown by Mg/Ca to be on average 4.3 °C higher than during the cooler spring season, accounting for an increase in pCO2 of 4 % per 1 °C. Our results show that paleo-pH estimates based on δ11BCc contain a significant seasonal signal reflecting the habitat preference of the recording foraminifera species.