Constraints on the timing of Atlantic meridional overturning circulation (AMOC) changes during the last deglaciation are fundamental to understanding the climate's rapid response to insolation forcing. However, uncertainty about high-latitude North Atlantic (HLNA) radiocarbon reservoir ages has previously precluded robust age model development for this critical region. HLNA reservoir ages also serve as a proxy for AMOC strength. We present regionally averaged HLNA reservoir ages for 0 to 41 thousand years before the present (kyr BP) based on over 500 radiocarbon dates from 33 North Atlantic cores. An early deglacial increase to >1000 14C yr reservoir ages between 18.5 and 16.5 kyr BP suggests reduced AMOC before peak Heinrich Stadial 1 (HS1) ice-rafted debris (IRD). A rapid decrease in reservoir ages coincident with the IRD maximum at 16 kyr BP indicates strong stratification of the upper water column caused by massive freshwater release. © 2013. American Geophysical Union. All Rights Reserved.

©2014. American Geophysical Union. All Rights Reserved. Benthic δ¹⁸O changes are often assumed to be globally synchronous, but studies comparing 2-9 radiocarbon-dated records over the most recent deglaciation (Termination 1) have proposed differences in the timing of benthic δ¹⁸O change between the Atlantic and Pacific, intermediate and deep, and North and South Atlantic. Because of the relatively small number of records used in these previous studies, it has remained unclear whether these differences are local or regional in scale. Here we present seven regional benthic δ¹⁸O stacks for 0-40 kyr B.P. that include 252 records with independent regional age models constrained by 852 planktonic foraminiferal ¹⁴C dates from 61 of these cores. We find a 4000 year difference between the earliest termination onset in the intermediate South Atlantic at 18.5 (95% confidence interval: 17.9-19.0) kyr B.P. and the latest in the deep Indian at 14.5 (14.1-15.0) kyr B.P. The termination onset occurs at 17.5 kyr B.P. in the intermediate and deep North Atlantic, deep South Atlantic, and deep Pacific. However, throughout the termination deep North Atlantic benthic δ¹⁸O leads the deep Pacific by an average of 1000-year and a maximum of 1700-year. Additionally, the intermediate Pacific termination onset at 16.5 (16.1-16.9) kyr B.P. demonstrates that intermediate-depth benthic δ¹⁸O change was not globally synchronous. These regional stacks provide better age models than a global stack across Termination 1 and potentially important constraints on deglacial ocean circulation changes. Key Points Seven regional benthic δ¹⁸O stacks with ¹⁴C age models Termination 1 onset at 18.5 ka in intermediate South Atlantic and 14.5 ka in deep Indian Deep Pacific lags deep Atlantic by average of 1 kyr during Termination 1

Terrestrial carbon storage is dramatically decreased during glacial periods due to cold temperatures, increased aridity, and the presence of large ice sheets on land. Most of the carbon released by the terrestrial biosphere is stored in the ocean, where the light isotopic signature of terrestrial carbon is observed as a 0.32-0.7‰ depletion in benthic foraminiferal δ13C. The wide range in estimated δ13C change results from the use of different subsets of benthic δ13C data and different methods of weighting the mean δ13C by volume. We present a more precise estimate of glacial-interglacial δ13C change of marine dissolved inorganic carbon using benthic Cibicidoides spp. δ13C records from 480 core sites (more than 3 times as many sites as previous studies). We divide the ocean into eight regions to generate linear regressions of regional δ13C versus depth for the Late Holocene (0-6 ka) and Last Glacial Maximum (19-23 ka) and estimate a mean δ13C decrease of 0.38 ± 0.08‰ (2σ) for 0.5-5 km. Estimating large uncertainty ranges for δ13C change in the top 0.5 km, below 5 km, and in the Southern Ocean, we calculate a whole-ocean change of 0.34 ± 0.19‰. This implies a terrestrial carbon change that is consistent with recent vegetation model estimates of 330-694 Gt C. Additionally, we find that a well-constrained surface ocean δ13C change is essential for narrowing the uncertainty range of estimated whole-ocean δ13C change. ©2014. American Geophysical Union. All Rights Reserved.