988 Surface water changes in the Ryukyu Trench slope region, western margin of the North Pacific during the last 320, 000 years

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概要

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• Two piston cores taken from the Ryukyu Trench slope, western margin of the North Pacific, contain a micropaleontologic record of the last 105, 000 years (covering the period from isotope Stage 5 to Stage 1) and 320, 000 years (covering the period from Stage 8 to Stage 1), respectively. Planktic foraminiferal assemblages are examined to reconstruct the past surface water conditions. The surface water during interglacial stages 5 and 7 was similar to the postglacial situation, when the studied region was dominated by warmer waters associated with the Kuroshio Current. During glacial stages 2, 3, 4, 6 and 8, the Kuroshio-related warm water was weaker; alternatively the influence of the temperate water which currently occupies the northern part of the Western North Pacific Central Water was stronger. In these glacial stages, the temperate water affected this region more intensely than it does today. However, the polar front characterized by the Oyashio Current has never attained this area during the last 320, 000 years. During stages 2, 4 and 6, the surface water was eutrophic; the primary productivity in DCM (deep chlorophyll maximum) layer was probably enhanced during stages 2 and 8. The sea surface temperature is estimated based on percentage frequency data of planktic foraminifera, using transfer function FP12-E. The estimated paleo-SST are 27-29℃ for summer and 18-26℃ for winter. As a result, glacial-interglacial fluctuations of the estimated SST are 1-2℃ for summer and 4-5℃ for winter; seasonal contrast during interglacials is similar to that of today and slightly greater during glacials. The decline of winter SST during glacial periods is believed to have been caused not only by the southward displacement of the temperate water mass, but also by the upward transporting of the cooler water from the underlying water column.

• 日本古生物学会の論文
• 1995-06-30

著者

• Oda Motoyoshi

  Department Of Geology Kumamoto University

• Oda Motoyoshi

  Department Of Earth Sciences Kumamoto University

• Oda Motoyoshi

  Department Of Earth Science Faculty Of Science Kumamoto University

• Xu Xuedong

  Department of Earth Science, Kumamoto University

• Xu Xuedong

  Department Of Earth Sciences Kumamoto University

• Xu Xuedong

  Department Of Earth Science Kumamoto University

関連論文

• Mid-Quaternary Paleoceanographic Trend in Near-shore Waters of the Northwest Pacific : A Case Study Based on an Offshore Well
• AMS-^C ages of three piston cores from the Nishi-Shichitou Ridge, Northwest Pacific
• Chronology of two piston cores from the East China Sea
• Chronology of four piston cores from the west flank of the Nishi-Shichitou Ridge, Northwest Pacific.
• Vertical Distribution of Living Planktic Foraminifera in the North Equatorial Current Domain
• 988 Surface water changes in the Ryukyu Trench slope region, western margin of the North Pacific during the last 320, 000 years
• New Planktic Foraminiferal Transfer Functions for the Kuroshio : Oyashio Current Region off Japan

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