海底堆積物からみた氷期・間氷期の海洋環境の変化

概要

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The environmental changes that occurred during deglaciation, revealed by deep sea sediments, are reviewed with special reference to deepwater circulation. New paleoceanographic tracers developed during the last decade show that global changes of deepwater properties occurred after the last glacial maximum. In the Atlantic, Cd/Ca and δ13C records show that the formation of North Atlantic Deep Water (NADW) decreased or stopped and that the Antarctic Ocean was the dominant source of deepwater in glacial time. The tracers also show that the deepwater was nutrient-rich and the intermediate water was nutrient-poor (bottom-heavy state) compared to the present condition. In the Pacific deepwater, paleochemistry has been less constrained due to paucity of data. Some δ13C records from the Pacific, however, were compiled, and they show that a "bottom-heavy state" may have occurred as in the Atlantic. More systematic investigations, including extensive coring programs, are required, especially in the southern ocean, in order to construct a global ocean model and to solve the mystery of the postglacial increase in atmospheric CO2 levels.
日本第四紀学会の論文