Synchronous records of pCO₂ and Δ¹⁴C suggest rapid, ocean-derived pCO₂ fluctuations at the onset of Younger Dryas

Steinthorsdottir, Margret, de Boer, Agatha M., Oliver, Kevin I.C., Muschitiello, Francesco, Blaauw, Maarten, Reimer, Paula J. and Wohlfarth, Barbara (2014) Synchronous records of pCO₂ and Δ¹⁴C suggest rapid, ocean-derived pCO₂ fluctuations at the onset of Younger Dryas. Quaternary Science Reviews, 99, 84-96. (doi:10.1016/j.quascirev.2014.06.021).

Abstract

Just before the onset of the Younger Dryas (YD) cold event, several stomatal proxy-based pCO₂ records have shown a sharp increase in atmospheric CO₂ concentration (pCO₂) of between ca 50 and 100 ppm, followed by a rapid decrease of similar or even larger magnitude. Here we compare one of these records, a high-resolution pCO₂ record from southern Sweden, with the IntCal13 record of radiocarbon (Δ¹⁴C). The two records show broadly synchronous fluctuations at the YD onset. Specifically, the IntCal13 record documents decreasing Δ¹⁴C just before the YD onset when pCO₂ peaks, consistent with a source of “old” CO₂ from the deep ocean. We propose that this fluctuation occurred due to a major ocean flushing event. The cause of the flushing event remains speculative but could be related to the hypothesis of the glacial ocean as a thermobaric capacitor. We confirm that the earth system can produce such large multi-decadal timescale fluctuations in pCO₂ through simulating an artificial ocean flushing event with the GENIE Earth System Model. We suggest that sharp transitions of pCO₂ may have remained undetected so far in ice cores due to inter-firn gas exchange and time-averaging. The stomatal proxy record is a powerful complement to the ice core records for the study of rapid climate change.

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