Younger Dryas: A data to model comparison to constrain the strength of the overturning circulation

The University of Victoria Earth System Climate Model (UVic ESCM) is used to compare simulated time series of radiocarbon during the Younger Dryas (YD) with paleoceanographic records. I find that only a complete shut-down and recovery of the Atlantic Meridional Overturning Circulation (AMOC) can simulate both the rise in atmospheric CO₂ concentrations seen in ice core records and the peak and subsequent decrease in atmospheric Δ¹⁴C comparable to the peak recorded in the varved sediments of the Cariaco Basin. Simulated radiocarbon profiles in the western North Atlantic match well with data from deep-sea corals at the beginning of the YD, whereas planktonic/benthic foraminifera records match best with a transient state during the rapid recovery of the AMOC. The steepness of the increase in atmospheric Δ¹⁴C at ~12.9 ka cal could not be simulated with oceanic circulation changes only because the response time of the climate system is too slow.