Refined modeling and 14C plateau tuning reveal consistent patterns of glacial and deglacial 14C reservoir ages of surface waters in low-latitude Atlantic

Modeling studies predict that changes in radiocarbon (C-14) reservoir ages of surface waters during the last deglacial episode will reflect changes in both atmospheric C-14 concentration and ocean circulation including the Atlantic Meridional Overturning Circulation. Tests of these models require the availability of accurate C-14 reservoir ages in well-dated late Quaternary time series. We here test two models using plateau-tuned C-14 time series in multiple well-placed sediment core age-depth sequences throughout the lower latitudes of the Atlantic Ocean. C-14 age plateau tuning in glacial and deglacial sequences provides accurate calendar year ages that differ by as much as 500-2500years from those based on assumed global reservoir ages around 400years. This study demonstrates increases in local Atlantic surface reservoir ages of up to 1000years during the Last Glacial Maximum, ages that reflect stronger trades off Benguela and summer winds off southern Brazil. By contrast, surface water reservoir ages remained close to zero in the Cariaco Basin in the southern Caribbean due to lagoon-style isolation and persistently strong atmospheric CO2 exchange. Later, during the early deglacial (16ka) reservoir ages decreased to a minimum of 170-420 (14)Cyears throughout the South Atlantic, likely in response to the rapid rise in atmospheric pCO(2) and Antarctic temperatures occurring then. Changes in magnitude and geographic distribution of C-14 reservoir ages of peak glacial and deglacial surface waters deviate from the results of Franke et al. (2008) but are generally consistent with those of the more advanced ocean circulation model of Butzin et al. (2012).