末次盛冰期以来南海西南海区对快速气候变化的响应特征

以南海西南巽他陆坡CG2岩心为材料,通过浮游有孔虫Globigerinoides ruber壳体的δ18O和Mg/Ca重建了近24ka以来的表层海水温度(SST)和盐度(SSS),结合浮游有孔虫定量统计数据分析了末次盛冰期(LGM)以来南海西南海区上部水体环境的演化特征。研究表明,在YD、H1、8.2ka冷事件期间,巽他陆架海区盐度变高,浮游有孔虫暖水种丰度减少,温跃层变浅。相比其他开放大洋站位末次冰消期的缓慢变暖,南海西南海区Bølling早期以及YD事件后期升温迅速,且H1期间具有明显的降温,是典型的"格陵兰式"升温,可能南海受东亚季风的影响强烈。东亚夏季风的强弱变化造成了海水盐度频繁的波动,在H1、YD期间,东亚夏季风突然减弱,盐度变高,B/A暖期夏季风增强,盐度变低,比较发现在这些气候事件期间,东、西太平洋站位的盐度变化特征几乎是一致的。LGM以来热带西太平洋海区的上层海水环境变化,与热带辐合带(ITCZ)的纬向移动及其相关的东亚季风异常有密切联系。

RESPONSE OF THE SOUTHWESTERN SOUTH CHINA SEA TO THE RAPID CLIMATE CHANGES SINCE THE LAST GLACIAL MAXIMUM

Changes in the sea surface temperature (SST) and salinity (SSS) over the last 24ka have been estimated from sediment core CG2 located in the Sunda slope by means of Mg/Ca ratio and oxygen isotopes of the planktonic foraminifera Globigerinoides ruber, combined with the quantitative statistical data of planktonic foraminifera. Our results imply that the sea surface salinity, abundance of warm-water species and the depth of thermocline have obvious responses to the rapid climate change. Compared with the slowly deglacial warming of the open Pacific, the SST record in the southwestern SCS shows a deglacial warming interrupted by a cooling event coeval with H1, followed by marked Bølling and late YD SST increasing, which suggest a ‘Greenland type’ of deglacial warming. Their difference between the two regions might be caused by the reason that the SCS is more strongly affected by the East Asian monsoon. In the eastern and western equatorial Pacific, however, salinity variations were almost the same as those during the rapid climate change events. The variation in the upper water environment of the western tropical Pacific was closely linked with the latitudinal shifts of the intertropical convergence zone (ITCZ) and the East Asian monsoon anomaly since the LGM.