[M-IS08] Paleoclimatology and paleoceanography

[MIS08-P18] Changes in oceanic carbon and oxygen cycle during Heinrich event

*Akitomo Yamamoto¹, Ayako Abe-Ouchi² (1.Japan Agency for Marine-Earth Science and TechnologyAtmosphere and Ocean Research Institute, 2.Atmosphere and Ocean Research Institute, The University of Tokyo)

Keywords:Ocean carbon cycle, dissolved oxygen, Ocean iron cycle, Heinrich event

Weakening of the Atlantic Meridional Overturning Circulation (AMOC) during Heinrich events was often accompanied by the atmospheric CO₂ increase of 10-20 ppm over 1000 years. Previous modeling studies display conflicting atmospheric CO₂ response to an AMOC shut down. On the other hand, recent paleoproxy records suggest that dwindling iron fertilization by dust in the Southern Ocean can contribute millennial-scale CO₂ oscilations (Martínez-García et al., 2014). However, the effect of changes in iron cycle has not been considered in the previous modeling studies.
In this study, we investigate the response of atmospheric CO₂ to changes in ocean circulation and dust-bone iron supply using numerical models. In associate with the AMOC weakening from 26 Sv to 6 Sv, the atmospheric CO₂ decreases by 2 ppm over 1000 years. Combining AMOC weakening and decrease in dust-bone iron supply, the atmospheric CO₂ increases more than 10 ppm. Reduction in export production associated with dwindling iron supply in the Southern Ocean release carbon from the deep sea, contributing to the increase in the atmospheric CO₂. Reduction in export production simultaneously increases dissolved oxygen in the Antarctic Bottomo Water, which is consistent with proxy records. Our results show the significant contribution of changes in dust-bone iron supply to the millennial CO₂ change in the glacial periods.