Evolution of paleo-climate and seawater pH from the late Permian to postindustrial periods recorded by boron isotopes and B/Ca in biogenic carbonates

• Published in: Earth-science reviews 2021-04, Vol.215, p.103546, Article 103546
• Main Authors: Wei, Hai-Zhen, Zhao, Yao, Liu, Xi, Wang, Yi-Jing, Lei, Fang, Wang, Wen-Qian, Li, Yin-Chuan, Lu, Hua-Yu
• Format: Article
• Language: English
• Subjects: Atmospheric CO2; Biogenic carbonate; Carbon cycling in ocean-atmosphere system; Ocean acidification; pH proxies
• ISSN: 0012-8252; 1872-6828
• DOI: 10.1016/j.earscirev.2021.103546

Cycling of CO2 between the oceans and the atmosphere has significant impacts on the global climate change. The accurate reconstructions of paleo-pH and atmospheric-oceanic carbon cycling using geochemical tracers (e.g., δ11B, B/Ca) in marine carbonates are reviewed in this work, including the fundamental mechanisms and the remaining challenges in these proxies and the progresses in understanding of evolution of paleo-climate and seawater pH from the late Permian to postindustrial periods. The proxies provide new insight into the evolution of atmospheric CO2 concentrations at time scales from tens of millions to thousands of years, and the direct evidence to the significant ocean acidification during the mass extinction events, and the CO2 cycling in ocean-atmosphere system during the Last Deglaciation and post-industrial periods. On the basis of extensive investigation, it could be concluded that: (i) the carbon dioxide levels and their impacts on Earth surface temperature during the Cenozoic cooling, the Pliocene warmth, and the mid-Pleistocene transition have been evaluated by the combination of multiple proxies; (ii) the benthic/planktonic foraminiferal B/Ca and δ11B data provided consistent implications for global climate variations during the Late Pleistocene, the Late Glacial, Last Glacial Maximum, and the Younger Dryas event; (iii) perturbations of surface ocean pH at the Permo-Triassic (P-T) boundary, the Pliensbachian-Toarcian (Pl-To) boundary, the Cretaceous-Paleogene (K/Pg) boundary and the Palaeocene-Eocene Thermal Maximum (PETM) global warming event were triggered by the large injection of carbon, the short episodic pulses of volcanogenic CO2, the Chicxulub impact, and the volcanism activities of the North Atlantic Igneous Province, respectively; (iv) the ocean acidification in the equatorial and polar Pacific during the Last Deglaciation implied an expanded zone of equatorial upwelling and resultant CO2 emission from higher subsurface dissolved inorganic carbon concentration. The acceleration of modern acidification in post-industrial time was not only driven by anthropogenic CO2 but also varied synchronously with inter-decadal changes in Asian Winter Monsoon Intensity. •The fundamentals and advances in δ11B-pH and B/Ca proxies have been demonstrated.•The evolution of atmospheric CO2 over million-year scale and millennium scale is reviewed.•The significant ocean acidifications and the associated driving forces were clarified.