上新世-更新世过渡期是全球气候变化的重要转折时期，其间最重要的气候事件为北半球大冰期（NHG）的形成，但其成因机制仍不明确。西太平洋暖池作为全球热量和水汽的主要源区，通过厄尔尼诺-南方涛动（ENSO）等现象能够影响全球气候变化。而西太平洋暖池的ENSO式模态是否在NHG形成中发挥重要作用仍存在争议。本项目拟选取国际大洋发现计划（IODP）第363航次在西太平洋暖池核心区北部获取的U1490站沉积岩芯为研究材料，通过分析浮游有孔虫表层种和温跃层种壳体的氧碳同位素和Mg/Ca比值，重建上新世-更新世过渡期西太平洋暖池的上层水体温度、盐度和上层水体结构等的演化历史，查明西太平洋暖池的ENSO式变化情况，明确其是否在NHG形成中扮演重要角色。

The Pliocene-Pleistocene transition is an important turning point with the climate event Northern Hemisphere glaciation (NHG). However it is still unclear about the formation mechanism of NHG. As the main source of global heat and water vapor, the western Pacific warm pool (WPWP) may affect global climate through the El niño-Southern Oscillation (ENSO) phenomenon. While the role of the ENSO-like process during the formation period of NHG still remain debate. Our study are based on sediments from Site U1490 retrieved during the International Ocean Discovery Program (IODP) Expedition 363 in the northern core area of WPWP. In this project, temperature, salinity and structure of upper water in the WPWP are reconstructed over the Pliocene-Pleistocene transition, by applying the oxygen and carbon stable isotope and Mg/Ca measurement of surface and thermocline dwelling planktonic foraminiferal species. Furthermore, we ascertain the historical evolution of the ENSO-like process and whether it played an important role in the formation of NHG.