西太平洋暖池核心区MIS 7期以来的古生产力变化:类ENSO式过程的响应

对取自热带西太平洋暖池核心区的WP7岩心进行了底栖有孔虫和钙质超微化石研究。在利用氧同位素曲线对比和AMS14C测年数据进行地层划分的基础上,依据底栖有孔虫和钙质超微化石指标,分析了距今近250ka以来区域生产力和上层海水结构的演变特征,探讨了其控制因素和所指示的古海洋学意义。计算结果显示WP7岩心所在的暖池核心区约在距今250ka以来初级生产力在冰期(MIS6期、4期和2期)高,在间冰期(MIS7期、5期、3期和1期)低,表明该区古生产力在长的轨道时间尺度上受北半球高纬度冰量变动的影响。钙质超微化石下透光带属种Flori-sphaera profunda百分含量指示的温跃层深度变化表明冰期温跃层浅、间冰期温跃层加深,这说明类ENSO式变化导致的冰期—间冰期温跃层深度波动可能是MIS7期以来暖池核心区古生产力在冰期高而在间冰期显著降低的直接控制因素。

Variations of paleoproductivity in the nuclear region of western Pacific warm pool since MIS 7:response to ENSO-like process

Deep-sea Core WP7 (3°56'S,156°E,and water depth 1 580 m) retrieved from the nuclear region of western Pacific warm pool (WPWP) was selected for benthic foraminifera and calcareous nannofossil study.On the basis of the AMS 14C data and comparison with SPECMAP δ18O the stratigraphy of Core WP7 was established.Withbenthic foraminifera and nannofossil indexes,the variations of paleoproductivity and upper water structure were reconstructed and their control factors and paleoceangraphic implications in this region during the last 250 ka BP were discussed.Results showed that the primary productivity was higher in glacial periods (MIS 6,4 and 2) and lower in interglacial periods (MIS 7,5,3 and 1),which indicated the controlling influence of the Northern Hemisphereice volume changes on the productivity of WPWP.The down core changes of Florisphaeraprof unda percentage content implied that the thermocline was shallower in glacial periods and deeper in interglacial periods,which might be the direct controlling factors of WPWP productivity changes.It is speculated that the glacial-interglacial fluctuation of the depth of thermocline was induced by the super-ENSO variation.