浮遊性有孔虫群集と表層水塊の関係に基づく過去2万7千年間の下北沖の古環境変動復元(<特集>西太平洋におけるIMAGESコアを用いた高時間解像度の環境復元)

概要

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Planktonic foraminiferal assemblage provides the information about water mass properties. We investigate the fossil foraminiferal fauna using factor analysis to reconstruct the changes in water masses and the outflow/inflow timing of the Oyashio and Tsugaru currents across the Tsugaru Strait off Shimokita (41°33.9'N, 141°52.1'E) in the northwestern North Pacific over the last 26,900 years. In the study area, the Oyashio Current affected both surface and subsurface (below the pycnocline) waters during 26.9-15.7 thousand calendar years before present (cal. kyr BP). Vertical mixing and subsurface warming resulted from the flow of the Oyashio Current into the Japan Sea around 15.7-10.6 cal. kyr BP. The Tsugaru Current started to enter into the Pacific about 11.2-10.6 cal. kyr BP and formed two water masses condition of the surface layer under the influence of the Tsugaru and the subsurface layers of the Oyashio Current during 10.6-9.0 cal. kyr BP. The increasing of inflow of the Tsushima/Tsugaru Current enforced surface layer warming and the stratification of water column. Finally, the subsurface layer started to warm at 6.2 cal. kyr BP. The timings of outflow/inflow of the Oyashio and Tsugaru currents in this study are compatible with the results at the Japan Sea sites.
日本古生物学会の論文
2006-03-28