Tracing Tasman Leakage since the middle Miocene

南半球的海洋是强耦合的。南太平洋、印度洋和南大西洋之间的水和热交换是全球温盐环流的基础。然而，在太平洋和印度洋之间的中等水深的洋间交换的相关性直到最近才被确定。不同的当代海洋学模式确定了从太平洋到印度洋在~1000米水深的显著输送，起源于塔斯曼海。然而，所谓的塔斯曼泄漏从未在古海洋学背景下被确定。本提案旨在评估这条海洋间交换途径的开始，并旨在限制塔斯曼泄漏响应气候（气候带的南北迁移）以及构造过程（澳大利亚大陆的北移）的变异性。海洋钻探计划（ODP）在Broken Ridge（东印度洋）的752和754地点提供了非常合适的沉积档案来解决这些问题：这两个地点都位于塔斯曼泄漏流路径内，目前的中间水深约为1070米。晚渐新世至最近的层段由亚水平的远洋碳酸盐岩富层序组成，允许使用不同的同位素和元素代用物。通过与南印度洋和西南太平洋现有的一系列沉积记录相比较，新生成的752和754站点的替代记录将为评价晚渐新世以来塔斯曼泄漏在调节太平洋-印度洋交换中的作用提供一个独特的机会。

The southern hemisphere oceans are strongly coupled. The exchange of water and heat between the South Pacific, Indian and South Atlantic oceans is fundamental to the global thermohaline circulation. However, the relevance of interocean exchange at intermediate water depths between the Pacific and Indian oceans has only recently been established for the present-day. Different contemporary oceanographic models identify significant transport from the Pacific into the Indian Ocean at ~1000 m water depth, originating in the Tasman Sea. The so-called Tasman Leakage has however never been identified in a paleoceanographic context. This proposal aims to evaluate the onset of this pathway of interocean exchange, and is designed to constrain Tasman Leakage variability in response to climatic (north-south migration of climate belts) as well as to tectonic processes (northward movement of the Australian continent). Ocean Drilling Program (ODP) Sites 752 and 754 on Broken Ridge (eastern Indian Ocean) provide well-suited sedimentary archives to address these questions: Both sites are situated within the Tasman Leakage flow path, at a present-day intermediate water depth of ~1070 m. Their late Oligocene to recent intervals consist of sub-horizontal pelagic carbonate-rich sequences that allow for the use of different isotopic and elemental proxies. When compared to a series of existing sedimentary archives in the southern Indian Ocean and southwest Pacific, the newly-generated proxy records for Site 752 and 754 will provide a unique opportunity to evaluate the role of Tasman Leakage in regulating Pacific-Indian Ocean exchange since the late Oligocene.