Session: Glacial Climates (LGM, Last deglaciation, Ice sheet uncertainties, Glacial-interglacial cycles)
Author: Akitomo Yamamoto / firstname.lastname@example.org / University of Tokyo
Co-author: Ayako Abe-Ouchi, University of Tokyo;
Paleoproxy records suggest that weakening of the Atlantic Meridional Overturning Circulation (AMOC) during Heinrich events was associated with the atmospheric CO2 increase of 10−20 ppm over 1000 years (Ahn and Brook, 2008). However the mechanism of CO2 increase and this linkage to the AMOC have remained unclear. In this study, the response of deep ocean circulation and ocean biogeochemical properties to glacial freshwater perturbations in the northern North Atlantic are investigated using a coupled atmosphere−ocean circulation model MIROC and offline ocean biogeochemical model. In associate with the AMOC weakening from 26 Sv to 6 Sv and the decrease in global export production by 20%, the atmospheric CO2 increases by 4.5 ppmv. Preliminary analyses show that the carbon reservoir of the upper ocean (above 2000m) except the Southern Ocean decreases resulting in atmospheric CO2 increase. On the other hand, enhanced export production in the Southern Ocean increases the carbon reservoir of the deep ocean leading to atmospheric CO2 reduction. We will also discuss the response of biological pump in the Southern Ocean and changes in carbon isotope in this presentation.