氷期の海洋炭素循環シミュレーション

抄録

Over the past 800,000 years, atmospheric partial pressure of carbon dioxide (pCO₂) during glacial periods was lower by about 90 ppmv than during interglacial periods. Changes in the ocean carbon cycle are recognized as the primary driver of the glacial-interglacial changes in atmospheric pCO₂. The changes in the ocean carbon cycle would result from multiple processes, including changes in CO₂ solubility, the redistribution of carbon by ocean biological pumps and ocean circulation, and carbonate sedimentation processes although the quantitative contribution of individual oceanic processes remains controversial. This paper reviews previous modeling studies of the glacial ocean carbon cycle, with a particular focus on environmental changes in the Southern Ocean. During glacial periods, geological records have shown that there were physical changes in sea ice, stratification, and ocean circulation, as well as biogeochemical changes in the ecosystem in the Southern Ocean. As the Southern Ocean is a region where deep waters ventilate to the surface ocean, its environmental changes affect the carbon cycle of the entire ocean and atmospheric pCO₂. By presenting a comprehensive study of these changes in comparison with the constraints of geological records, we discuss current challenges and prospects for understanding the mechanisms of past changes in the ocean carbon cycle.