Radiocarbon evidence for the stability of polar ocean overturning during the Holocene

• Published in: Nature Geoscience
• Main Authors: Chen, Tianyu, Robinson, Laura F., Li, Tao, Burke, Andrea, Zhang, Xu, Stewart, Joseph A., White, Nicky J., Knowles, Timothy D.J.
• Other Authors: NERC, University of St Andrews.School of Earth & Environmental Sciences, University of St Andrews.St Andrews Isotope Geochemistry
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2023
• Subjects: GC Oceanography; GE Environmental Sciences; DAS; MCC; GC; GE; Antarctic; Southern Ocean; The Antarctic; Drake Passage; Reykjanes; Antarc*; Antarctica; Iceland; North Atlantic Deep Water; North Atlantic
• Online Access: https://hdl.handle.net/10023/27969; https://doi.org/10.1038/s41561-023-01214-2

Funding: T.C. acknowledges support from the Strategic Priority Research Program of Chinese Academy of Sciences (XDB40010200), Fundamental Research Funds for the Central Universities (020614380116) and National Natural Science Foundation of China (41991325, 41822603 and 42021001). L.F.R. acknowledges support from the Natural Environment Research Council (NE/S001743/1, NE/R005117/1, NE/N003861/1 and NE/X00127X/1). Proxy-based studies have linked the pre-industrial atmospheric pCO2 rise of ∼20 ppmv in the mid- to late Holocene to an inferred increase in the Southern Ocean overturning and associated biogeochemical changes. However, the history of polar ocean overturning and ventilation through the Holocene remains poorly constrained, leaving important gaps in the assessment of the feedbacks between changes in ocean circulation and the carbon cycle in a warm climate state. The deep-ocean radiocarbon content, which provides a measure of ventilation, responds to circulation changes on centennial to millennial time scales. Here we present absolutely dated deep-sea coral radiocarbon records from the Drake Passage, between South America and Antarctica, and Reykjanes Ridge, south of Iceland, over the Holocene. Our data suggest that ventilation in the Antarctic circumpolar waters and North Atlantic Deep Water is surprisingly invariant within proxy uncertainties at our sampling resolution. Our findings indicate that long-term, large-scale polar ocean overturning has not been disturbed to a level resolvable by radiocarbon and is probably not responsible for the millennial atmosphere pCO2 evolution through the Holocene. Instead, continuous nutrient and carbon redistribution within the water column following deglaciation, as well as changes in land organic carbon stock, might have regulated atmospheric CO2 budget during this period. Peer reviewed