It has been thought that about 9Oppm decrease of atmospheric CO₂ in the last glacial maximum was attributed to the change in oceanic processes. In order to explain this decrease quantitatively, change in three processes (solubility pump, biological pump, alkalinity pump) and these effect on atmospheric CO₂ in the last glacial period should be clarified. Although various kinds of paleoceanographical analysis on sea floor sediments and numerical simulation based on these results with some assumptions have been carried out, quantitative conclusion has not been suggested yet. In this review paper, biological pump and, especially, alkalinity pump in the last glacial period are focused on and update of interpretation with respect to the effect of oceanic change on atmospheric CO₂ is introduced, taking into account for ocean carbonate chemistry.