An evaluation of benthic foraminiferal B/Ca and d11B for deep ocean carbonate ion and pH reconstructions

• Published in: Earth and Planetary Science Letters
• Main Authors: Yu, Jimin, Foster, Gavin, Elderfield, H, Broeker, Wally S., Clark, Elizabeth
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Elsevier
• Subjects: Keywords: Atmospheric CO; B/Ca; Benthic foraminifera; Carbonate ions; Caribbean Sea; Deep ocean; Deep Water; Ice core; Ocean circulation; Boron; Boron compounds; Carbonation; Ions; Oceanography; carbon dioxide; epifauna; interglaci d11B; Benthic foraminifer; Carbonate ion; PH; ice core
• Online Access: http://hdl.handle.net/1885/65228; https://doi.org/10.1016/j.epsl.2010.02.029; https://openresearch-repository.anu.edu.au/bitstream/1885/65228/5/Yu_J_2010_An_evaluation.pdf.jpg; https://openresearch-repository.anu.edu.au/bitstream/1885/65228/7/01_Yu_An_evaluation_of_benthic_2010.pdf.jpg

Reliable reconstructions of deep ocean carbonate ion concentration, [CO32-], and pH are crucial to understand mechanisms responsible for the past atmospheric CO2 variations observed in ice cores. However, it is challenging to reconstruct past deep water [CO32-] and pH and literature results from different proxies conflict, warranting careful investigations on possible reasons for the existing inconsistencies. Here, we present the first down core B/Ca and -11B records measured in an epifaunal benthic foraminifer Cibicidoides wuellerstorfi from the Caribbean Sea during the last 160kyr. The two proxies yield quantitatively comparable deep water [CO32-] and pH results, showing high values during glacials relative to inter-glacials (differences in [CO32-] and pH are ~35μmol/kg and ~0.15, respectively), consistent with past ocean circulation changes in the Caribbean Sea. Our data provide convincing evidence that both proxies serve as faithful proxies to estimate deep ocean [CO32-] and pH, despite our incomplete understanding of boron incorporation into foraminiferal carbonates.