中更新世以来地中海溢出流演化及其对全球变化的影响

The significance of Mediterranean Outflow Water (MOW) on the North Atlantic circulation and climate has been broadly recognized. The consequent variation of MOW flux may affect the density of the North Atlantic Deep Water, thus stabilize or destabilize thermohaline circulation and so trigger climate change. The IODP Expedition 339 (2011.11-2012.1) recovered 5.5 km of core from the Gulf of Cadiz and the west Iberian margin, which provide important materials to reveal the long-term MOW evolution. As part of the post-cruise study, this research will work on the sediments of Site U1391, which is under the influence of modern distinct MOW and reconstruct the Middle-Late Pleistocene surface and deep water property through detailed analyses of planktonic and benthic foraminifera fauna, foraminiferal stable isotopes and Mg/Ca ratios, in addition to relevant data from sedimentological, down-hole logging and magnetic analyses. The results will be compared with those from other sites of IODP, to disclose the MOW evolution on a long-term scale (0- 1.3 MaBP), especially its character during the MPR and Δ13Cmax, and to disclose its influence on the North Atlantic circulation and global climate.

地中海溢出流对北大西洋环流和全球气候的重要性已经被广泛认识，其流量的变化甚至影响到全球温盐环流的稳定性和触发气候突然变化。IODP339航次的执行为揭示地中海溢出流在长世时间尺度上的演化特征提供了宝贵材料。研究将通过对IODP339航次 U1391站位柱状样沉积物进行详细的微体古生物群落、有孔虫壳体氧碳稳定同位素及微量元素等分析，在部分关键时期如末次冰期旋回、中布容事件等进行高分辨率采样分析，结合沉积学、岩性录井、古地磁等其他资料的综合研究，并与航次其他站位的古海洋学研究结果比较，重建中更新世以来地中海溢出流的演化过程，尤其是通过研究中更新世气候转型过程及最近几个大洋碳同位素重值期地中海溢出流及区域上升流特征，揭示其对北大西洋环流与气候变化的影响意义，深入对全球大洋环流系统的认识。

研究对IODP339航次U1391站位中更新世以来沉积物岩心进行了详细的微体古生物、AMS14C测年、有孔虫氧碳稳定同位素及微量元素等的综合分析，通过对钻孔沉积物中底栖有孔虫研究，利用有孔虫群落对水体环境变化反映灵敏的优势，详细阐述了底栖有孔虫特征属种及群落组合变化过程，首次揭示了晚更新世冰期/间冰期旋回及长时间尺度(0.9 Ma以来)地中海溢出流强度演化历史。在冰期/间冰期尺度上，地中海溢出流具有典型的旋回性变化特征，冰期弱、间冰期强；而在长时间尺度上，存在40万年的周期性变化，以MIS1期、9-11期、19-21期为强，尤其以MIS11期高于现在20m的海平面格局下，地中海溢出流显著增强。研究为认识晚第四纪冰期旋回中地中海溢出流演化特征及其对北大西洋深部环流形成与气候变化具有重要意义，深入了对全球大洋环流系统的认识。