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

Tianyu Chen*, Laura F. Robinson, Tao Li, Andrea Burke, Xu Zhang, Joseph A. Stewart, Nicky J. White, Timothy D.J. Knowles

*Corresponding author for this work

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Abstract

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.
Original languageEnglish
Pages (from-to)631-636
Number of pages6
JournalNature Geoscience
Volume16
Early online date26 Jun 2023
DOIs
Publication statusPublished - 1 Jul 2023

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