Changes in deep Pacific circulation and carbon storage during the Pliocene-Pleistocene transition

• Published in: Earth and planetary science letters 2023-03, Vol.605, p.118020, Article 118020
• Main Authors: Jian, Zhimin, Dang, Haowen, Yu, Jimin, Wu, Qiong, Gong, Xun, Stepanek, Christian, Colin, Christophe, Hu, Lili, Lohmann, Gerrit, Zhou, Xiaoli, Wan, Sui
• Format: Article
• Language: English
• Subjects: benthic foraminiferal B/Ca; deep Pacific carbon storage; deep Pacific circulation; Earth Sciences; foraminiferal εNd; intensification of Northern Hemisphere Glaciation; Sciences of the Universe
• ISSN: 0012-821X; 1385-013X
• DOI: 10.1016/j.epsl.2023.118020

The global climate has been gradually cooling over the Cenozoic and is punctuated by the intensification of Northern Hemisphere Glaciation (NHG) from the latest Pliocene to earliest Pleistocene (∼3.1–2.5 millions of years ago, Ma). A decline of atmospheric CO2 is supposed as a prerequisite for the NHG, but the associated carbon-cycle processes remain elusive. Here we combine foraminiferal records of neodymium isotope and boron-calcium ratio, and simulations of an Earth system model, to investigate changes in the water-mass composition and carbonate-ion concentration of the deep Pacific Ocean during the NHG. Our proxy records have revealed a significant expansion of southern-sourced waters with increased respired carbon storage into the deep Pacific during the NHG. These changes may be explained by strengthened deep-water formation and biological-pump efficiency in the Southern Ocean due to Antarctic sea-ice growth, as suggested by our model experiments and evidence from the Sub-Antarctic region. These results provide key clues for quantifying the role of the dissolved inorganic carbon content of deep Pacific waters in modulating atmospheric CO2 during the NHG. •Neodymium isotope and boron-calcium ratio records are reconstructed from 4 to 2 Ma in the deep Pacific.•εNd record and Earth System Model experiments reveal increased southern-sourced waters during the NHG.•B/Ca record suggests an increased deep Pacific carbon sequestration during the NHG.