Asynchronous warming and δ18O evolution of deep Atlantic water masses during the last deglaciation

However, changes in the relative contributions of NADW and AABW and their properties are poorly constrained by marine records, including delta O-18 of benthic foraminiferal calcite (delta O-18(c)) .

Here, we use an isotope-enabled ocean general circulation model with realistic geometry and forcing conditions to simulate the deglacial water mass and delta O-18 evolution. Model results suggest that, in response to North Atlantic freshwater forcing during the early phase of the last deglaciation, NADW nearly collapses, while AABW mildly weakens. Rather than reflecting changes in NADW or AABW properties caused by freshwater input as suggested previously, the observed phasing difference of deep delta O-18(c) likely reflects early warming of the deep northern North Atlantic by similar to 1.4 degrees C, while deep Southern Ocean temperature remains largely unchanged.