Glacial carbon cycle changes by Southern Ocean processes with sedimentary amplification

Abstract

It is recognized that changes in atmospheric carbon dioxide concentrations associated with climate changes during the Pleistocene glacial-interglacial cycle were mainly caused by changes in the ocean carbon cycle. To investigate the mechanism of this carbon cycle change, we have conducted numerical experiments on the glacial oceans using a three-dimensional ocean general circulation model. In addition to changes in the solubility of carbon dioxide at the sea surface, ocean circulation, and dust-induced iron fertilization, which have been well constrained by previous modeling studies, we found that the enhanced salinity stratification and iron fertilization including glaciogenic dust in the Southern Ocean amplified the response of carbonate compensation, contributing to increased carbon storage in the deep ocean and a consequent decrease in atmospheric CO2 concentration. Considering these processes, the deep-water properties of the glacial period with low oxygen and low carbon isotope ratios are reproduced more closely to observations than in previous model experiments, supporting the validity of the ocean carbon cycle field reproduced by the present model experiments.