Earth experienced warm temperatures during the Pliocene followed by a substantial cooling that culminated in an ice age climate at the beginning of the Pleistocene. This warmth had a significant impact on global environments and ocean circulation. The collision of the Indian and Eurasian plates further amplified this climatic pattern. The southern Indian Ocean was severely impacted by these changes in ocean circulation and climatic pattern during the Plio-Pleistocene. We reconstruct paleoceanographic turnovers in the southeastern Indian Ocean during the Plio-Pleistocene using benthic foraminiferal assemblages from ODP Sites 752 and 757, combined with relative abundances of selected planktic foraminiferal species and stable isotope ratios (δ¹⁸O and δ¹³C) of surface-dwelling and thermocline planktic foraminifera from Site 757. The influence of southern source Antarctic Intermediate Water (AAIW) since 4.5 Ma is marked by fluctuations in productivity till the intensification of the Northern Hemisphere glaciation (NHG) at ~3 Ma. Our isotopic data provide no evidence for cooling during the 4–3 Ma interval either for upper (Gs. ruber) or lower (M. menardii) mixed-layer waters, at a time when a switch in the source of the Indonesian Throughflow may have occurred. The increased mixed-layer species abundances since 4 Ma suggest oligotrophic conditions at low-latitude Site 757 due to thick mixed-layer coinciding with the constriction of the Indonesian Gateway and intensification of the NHG. The intensification of the NHG and monsoon seasonality caused an enhanced inflow of AAIW in the southeastern Indian Ocean since ~2.5 Ma.

在上新世时期，地球经历了温暖的温度，随后经历了实质性的冷却，最终在更新世初期达到了冰河时期的气候。这种温暖对全球环境和海洋环流产生了重大影响。印度和欧亚板块的碰撞进一步放大了这种气候模式。在上新世期间，印度洋南部受到海洋环流和气候模式变化的严重影响。我们使用来自ODP站点752和757底栖有孔虫组合，与选定的浮游有孔虫物种和稳定同位素比率的相对丰度（δ组合上新世-更新世重建东南部印度洋古海洋学失误¹⁸ O和δ ¹³C）来自站点757的居住在地面和热跃层的有孔虫。从4.5 Ma开始，南源南极中间水（AAIW）的影响以生产力的波动为特征，直到北半球冰川（NHG）在〜3 Ma加剧为止。我们的同位素数据没有提供证据表明在较高温度（Gs。ruber）或较低温度（M. menardii）在4–3 Ma间隔内冷却）混合层水域，此时印尼流量的来源可能发生了变化。自4 Ma以来增加的混合层物种丰度表明低纬度站点757处于贫营养状态，这是由于厚的混合层与印尼通道的收缩和NHG的增强相吻合。自〜2.5 Ma以来，NHG的加强和季风季节导致印度洋东南部AAIW的流入增加。