摘要
通过对南海西部越南岸外17954—3柱状样中浮游和底栖有孔虫的定量分析,结合碳酸钙、有机碳和稳定同位素数据,获得南海西部上升流区近20万年来的古海洋学记录,进而讨论了晚第四纪东亚夏季风的变迁。结果表明,在间冰期,尤其是末次间冰期,越南岸外出现表层海水古温度低、温跃层浅、生产力高,同时底层海水富营养的现象,说明上升流的存在,且该上升流有从氧同位素5期(MIS5期)向1期逐渐减弱的趋势。结合南海现代海流及生产力分布的研究,推断该上升流由东亚夏季风驱动,其强弱的变化说明,东亚夏季风在近20万年来有间冰期增强、冰期减弱,且从MIS5期向MIS1期递减的特征。
The Asian monsoon system is of primary importance in our understanding ofglobal climate evolution. Coastal upwelling, the main oceanographic phenomena drivenby monsoonal winds, has been a point of vigorous discussion in paleoceanographyrecently. Being the region where the East Asian summer monsoon originates, theSouth China Sea(SCS) is the main studied area for reconstructing the East Asianmonsoon evolution. Previous studies were concentrated on the northern and easternpo of the SCS, with emphasis on the changes in the surface and deep cireulation,paleotemperature, carbonate cycle and productivity. The western SCS, however, wasmuch less studied. In face there is potential summer monsoonal upwelling off theVietnam coast based on the modem oceangraphic observations.Quantitative analysis of planktic and benthic foraminifers in Core 17954-3 off theVietnam coast in the western South China Sea integrated with the data of CaCO_3,organic carbon and productivity as well as Uk~'_37, estimated sea surface temperature (SST),has been carried out to monitor the variations of the coastal upwelling and hencereconstruct the East Asian summer monsoon evolution over the last 200 000 years.Our observations indicate that during the interglacial stages, the upper water colummis characterized by the conditions of low SST(Fig. 1) shallow thermocline(Fig.2) andhigh paleoproductivity (Fig. 3). This result convinces us that the existence of thecoastal upwelling there during the interglacial stages. Prticularly, the intensity of theupwelling gradually decreased from marine isotopic stage (MIS) 5 to MIS 1. Basedon the studies of the surface circulation and the distribution of productivity in themodem SCS, we suggest that the coastal upwelling at Site 17954-3 is driven by theEast Asian summer monsoon. The changes of the upwelling reflect the variations ofthe East Asian summer monsoon, which intensified at interglacial stages and graduallydecreased from the MIS 5 to MIS 1.
出处
《第四纪研究》
CAS
CSCD
北大核心
1999年第6期518-525,共8页
Quaternary Sciences
基金
国家自然科学基金!49776290
关键词
上升流
东亚
夏季风
晚第四纪
越南
季风
coastal upwelling, East Asian summer monsoon. late Quaternary,offshore Vietham coast