An oceanic origin for the increase of atmospheric radiocarbon during the Younger Dryas

Variations in carbon-14 to carbon-12 ratio in the atmosphere (Delta C-14(atm)) provide a powerful diagnostic for elucidating the timing and nature of geophysical and anthropological change. The ( Atlantic) marine archive suggests a rapid Delta C-14(atm) increase of 50% at the onset of the Younger Dryas (YD) cold reversal (12.9-11.7 kyr BP), which has not yet been satisfactorily explained in terms of magnitude or causal mechanism, as either a change in ocean ventilation or production rate. Using Earth-system model simulations and comparison of marine-based radiocarbon records from different ocean basins, we demonstrate that the YD Delta C-14(atm) increase is smaller than suggested by the marine archive. This is due to changes in reservoir age, predominantly caused by reduced ocean ventilation.