This study examines the relationship between the ocean circulation dynamics in the eastern Indian Ocean and climate variability in Northwest (NW) Australia over the last 6.1 million years. The vertical water column of the southeastern Indian Ocean was analyzed using planktic foraminifera assemblages, and oxygen and carbon isotope ratios of surface and subsurface dwelling foraminifera from Ocean Drilling Program (ODP) Site 763A. The X-ray fluorescence data of bulk sediment from ODP Site 763A was also used to understand variability in relative humidity and aridity in NW Australia associated with surface ocean warming. The findings suggest a pronounced change in surface oceanography and climate in the region from 5.4 to 5 Ma, indicating a weak Leeuwin Current (LC) and reduction in mixed layer thickness. Subsequently, between 5.0 and 3.6 Ma, a strongly stratified water column with a thick mixed layer and deep thermocline emerged owing to the intensified Indonesian Throughflow (ITF). This led to a strengthened LC and diminished surface productivity, corresponding to a wet phase in NW Australia. The closure of the Indonesian Seaway during the Middle Pliocene (3.6–3.2 Ma) restricted the flow of West Pacific Warm Water into the Indian Ocean, weakened the LC and intensified the dry phase in NW Australia. Significant shifts in planktic foraminifera abundances are observed in the early Pleistocene (2.6–1.2 Ma) perhaps linked to major changes in surface ocean circulation. During the Mid-Pleistocene Transition (1.2–0.6 Ma), the West Australian Current exerted a significant influence over Site 763A.

中文翻译：

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印度洋东南部的卢纹海流动态及其对最新中新世以来区域地表水文学的影响：来自 ODP 站点 763A 的结果


本研究探讨了过去 610 万年来东印度洋海洋环流动态与澳大利亚西北部 (NW) 气候变化之间的关系。使用海洋钻探计划 (ODP) 763A 站点的浮游有孔虫组合以及表层和地下有孔虫的氧和碳同位素比对印度洋东南部的垂直水柱进行了分析。来自 ODP 站点 763A 的大量沉积物的 X 射线荧光数据也被用来了解澳大利亚西北部与表面海洋变暖相关的相对湿度和干燥度的变化。研究结果表明，从 5.4 Ma 到 5 Ma，该地区的表面海洋和气候发生了显着变化，表明卢文洋流 (LC) 较弱，混合层厚度减少。随后，在 5.0 至 3.6 Ma 之间，由于印度尼西亚穿流（ITF）的增强，出现了具有厚混合层和深温跃层的强烈分层水柱。这导致LC增强和表面生产力下降，对应于澳大利亚西北部的湿润阶段。上新世中期（3.6-3.2Ma）印度尼西亚海道的关闭限制了西太平洋暖水流入印度洋，削弱了LC并加剧了澳大利亚西北部的干旱阶段。在早更新世（2.6–1.2 Ma）观察到浮游有孔虫丰度的显着变化，这可能与表面海洋环流的重大变化有关。在中更新世过渡期间（1.2–0.6 Ma），西澳大利亚洋流对 763A 站点产生了重大影响。