中更新世气候转型期西太平洋暖池的快速气候变化研究

西太平洋暖池 中更新世气候转型 快速气候变化 热带驱动 XRF岩芯扫描
金海燕 2009-01 项目
【英文摘要】Based on the paleoceanographic studies of the pelagic sediment of ODP Site 807, which recoverd from the Ontong-Java plateau, a continuous stratigraphy of the western equatorial Pacific during the mid-Pleistocene was reconstructed. Our results implied that the final formation of the asymmetric East-West pattern in the equatorial Pacific was occurred at ~1.6 Ma B.P. and should be much more resulted from the vibrant subsurface water change, which was related to the deep water reorganization in the Southern Ocean. Analysis on the increasing sampling interval during the 600-1200 kyr B.P. in this core, with an average time resolution reached ~500 yr/sample, showed that the mid-Pleistocene transition was refleced not only by the periodicity changes on the orbital scale, but also by the variation character on the millennial scale. Moreover, the calculated SSTs derived from the Mg/Ca ratio of planktonic foraminiferal shells changed synchronously with the northern hemisphere ice sheet growth, which indicated that the rapid climate change in the tropical ocean had a teleconnection with the high latitude ice sheet volume. Our results further confirmed by the high resolution paleoceanograhic records at ODP Site 1144 in the South China Sea, including stable isotopes, Mg/Ca-derived SSTs, geochemical data from XRF core scanner, etc. All the results in this study would be helpful to better understand and give more evidence of the mid-Pleistocene transition and the tropical forcing in the global climate system..
【中文摘要】本次研究通过对翁通-爪哇海台大洋钻探ODP 807站开展古海洋学研究,建立起西太平洋中更新世连续的地层古环境序列。研究揭示赤道太平洋东-西向的不对称格局在更新世约1.6百万年最终形成,且主要表现在次表层水的变化上,可能与南大洋深部水的重组有关。在此基础上,对中更新世距今60-120万年时间段进行样品加密分析,时间分辨率达~500年/样,发现中更新世气候转型不仅表现在轨道周期的变化上,同时也体现在千年尺度快速气候波动的变化特征上,且采用浮游有孔虫Mg/Ca比值恢复的表层海水古温度与北半球冰盖体积的增减基本呈同步变化的趋势,说明热带海区的快速气候波动与高纬冰盖的变化有着密切关联。这一结果也得到了南海北部ODP1144站高分辨率古海洋学记录(稳定同位素、Mg/Ca比值古温度、XRF元素岩芯扫描等)的进一步证实。该项研究为探讨中更新世气候转型以及热带快速气候变化的机制提供了新的科学依据。