Efforts to understand long‐term Indian Ocean dynamics and land‐sea linkages in southeast Africa during periods of significant global and regional climate change have been inhibited by a lack of high‐resolution climate records, particularly during the Plio‐Pleistocene. Here we present new biomarker and pollen records from International Ocean Discovery Program (IODP) Site U1478, located at the Upper Agulhas Confluence near the Limpopo River mouth, to establish environmental conditions at the southeast African margin between 4 and 1.8 Ma and address this spatiotemporal gap. Compound‐specific hydrogen isotopes of terrestrial leaf waxes (δD_wax) and TEX₈₆, using marine archaeal lipids, document hydroclimate variability and sea surface temperature (SST), respectively, permitting an onshore‐offshore climate comparison. The U1478 records establish the Limpopo catchment response to the switch in Indonesian Throughflow source waters, the mid‐Pliocene Warm Period, and intensification of Northern Hemisphere glaciations at ∼2.7 Ma. Broad coherence between the δD_wax and SST records supports a linkage between Indian Ocean temperatures and southeast African hydroclimate. We hypothesize that additional mechanisms including Indian Ocean cross‐basin SST gradients (ΔSST) and high latitude glaciation acted as hydroclimate controls during the Plio‐Pleistocene. We use ΔSST to evaluate ocean‐atmosphere patterns similar to the Indian Ocean Dipole (IOD) and establish generally wetter conditions in the region associated with positive IOD‐like phases. Additionally, an obliquity signal evident in the δD_wax record indicates that glacial‐interglacial variability likely influenced the tropical rain belt position and also controlled rainfall. Hydroclimate and environmental conditions across the Plio‐Pleistocene in southeast Africa may have important implications for regional hominin evolution.

中文翻译：

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东南缘的上新世更新世大陆水气候和印度洋海表温度

缺乏高分辨率的气候记录，尤其是在上新世期间，阻碍了人们在了解全球和区域重大气候变化时期，东南非洲长期印度洋动力和陆海联系的努力。在这里，我们介绍了来自国际海洋发现计划（IODP）站点U1478的新生物标志物和花粉记录，该站点位于林波波河河口附近的上阿古拉斯汇合处，以在4至1.8 Ma之间的非洲东南边缘建立环境条件并解决这一时空差距。陆地叶蜡（δD_蜡）和TEX _86的化合物特定的氢同位素，使用海洋古生类脂质，分别记录了水气候变化和海表温度（SST），从而可以进行陆上-近海气候比较。U1478记录确定了林波波河集水区对印度尼西亚通流源水域的转换，上新世中期的暖期以及北半球冰川在2.7 Ma处的强化的响应。δD_蜡之间的广泛相干性SST记录支持印度洋温度与东南非洲水文气候之间的联系。我们假设，在上新世期间，包括印度洋跨流域海表温度梯度（ΔSST）和高纬度冰川作用在内的其他机制可以作为水气候控制。我们使用ΔSST来评估类似于印度洋偶极子（IOD）的海洋-大气模式，并在与IOD类正相相关的区域中建立一般较湿的条件。另外，在δD_蜡中明显有一个倾角信号记录表明，冰川间的变化可能影响热带雨带的位置并控制降雨。东南非洲上新世更新世的水文气候和环境条件可能对区域人源素的进化具有重要意义。