[B-PT03] Biomineralization and Geochemistry of Proxies

[BPT03-08] Evidence for late-glacial oceanic carbon redistribution and discharge from the Pacific Southern Ocean

★Invited Papers

*Shinya Iwasaki¹, Lester Lembke-Jene², Kana Nagashima³, Helge Wolfgang Arz⁴, Naomi Harada⁵, Katsunori Kimoto³, Frank Lamy² (1.MARUM, 2.AWI, 3.JAMSTEC, 4.IOW, 5.AORI)

Keywords:Planktonic foraminifera, carbonate dissolution, deglaciation, ocean carbon cycle

Southern Ocean deep-water circulation plays an important role in the global carbon cycle. On geological time-scales, upwelling along the Chilean continental margin likely contributed to the deglacial atmospheric carbon dioxide rise, but little quantitative evidence exists of carbon storage. Here, we use a new X-ray Micro-Computer-Tomography method to assess foraminiferal test dissolution as proxy for paleo-carbonate ion concentrations ([CO₃^2–]). Our subantarctic Southeast Pacific sediment core depth transect shows significant deep-water [CO₃^2–] variations during the Last Glacial Maximum and Deglaciation (10 – 22 ka BP). We provide evidence for an increase in [CO₃^2–] during the early deglacial period (15-19 ka BP), followed by a ca. 40 µmol kg^–1 reduction in Lower Circumpolar Deepwater (CDW). This decreased Pacific to Atlantic export of low-carbon CDW contributed to significantly lowered carbon storage within the Southern Ocean, highlighting the importance of a dynamic Pacific–Southern Ocean deep-water reconfiguration for shaping late-glacial oceanic carbon storage, and subsequent deglacial oceanic-atmospheric CO₂ transfer.