Antarctic Intermediate Water Formation in the Southeast Pacific

0327544/Talley智力成果：该项目旨在描述东南太平洋南极中层水（AAIW）形成的过程。 计划研究（1）南极绕极流表面沃茨穿过SAF的向北Ekman平流，（2）由当地海气通量驱动的对流，以及（3）AAIW穿过界定深层混合区的北方锋面的向北俯冲。 南极中层水（AAIW）是一种低盐度、高氧和低位涡（厚）的水团，几乎充满了南半球和热带海洋，深度约为800至1000米。 AAIW是环极次季风沃茨（SAMW）的主要来源，它是在次季风锋（SAF）以北的东南太平洋上形成的一个厚的、出露的混合层。 SAMW和AAIW的形成对人为CO2的海洋汇有重大影响，其最大的不确定性是在中间深度。 AAIW在南半球淡水运输中发挥着重要作用，因此可以影响全球规模的海洋翻转过程。 AAIW是唯一的中深度，大规模的水团，还没有在其冬季来源进行研究，尽管一般知识的来源区域的位置几十年。 该项目包括对AAIW出露区域和边界锋进行冬季水文调查，并在冬季调查之后进行夏季调查，以研究前一个冬季沃茨的演变、限制和扩散。 该区域的结果将与其他区域的亚季风沃茨（SAMW）形成有关。 更广泛的影响：在该项目下收集的高质量数据集涵盖冬季和夏季，将填补全球海洋观测影响长期气候变化的物理过程方面的一个重要和巨大空白。 将为一名研究生和一名博士后提供培训。这项拟议中的工作将加强美国和智利科学家之间的合作。研究人员将继续与智利和欧盟的研究生合作，NSF不承担任何费用。

0327544/TalleyIntellectual Merit: This project aims at characterizing the processes responsible for the formation of Antarctic Intermediate water (AAIW) in the southeast Pacific. The plan is to study (1) northward Ekman advection of Antarctic Circumpolar Current surface waters across the SAF, (2) convection driven by local air-sea fluxes, and (3) northward subduction of AAIW across the northern front bounding the deep mixing region. Antarctic Intermediate Water (AAIW) is a low salinity, high oxygen and low potential vorticity (thick) water mass that fills almost all of the southern hemisphere and the tropical oceans at about 800 to 1000 m depth. As the densest of the circumpolar Subantarctic Mode Waters (SAMW), AAIW is formed as a thick, outcropping mixed layer in the southeastern Pacific just north of the Subantarctic Front (SAF). SAMW and AAIW formation have a major impact on the oceanic sink for anthropogenic CO2, whose largest uncertainty is at intermediate depths. AAIW has a major role in southern hemisphere freshwater transport and as such, can impact global-scale ocean overturning processes. AAIW is the only intermediate-depth, large-scale water mass that has not been studied at its winter source, despite general knowledge of the location of the source region for several decades. The project consists of a winter hydrographic survey of the AAIW outcropping region and the fronts that bound and a summer survey following the winter survey to study the evolution, restratification, and dispersal of the previous winter's waters. Results from this region will be relevant to Subantarctic Mode Waters (SAMW) formation in other regions. Broader Impacts: The high-quality data set collected under this project with a comprehensive coverage in winter and summer will fill an important and large gap in global ocean observations for physical processes that impact long-term climate change. Training will be provided for a graduate student and a post-doc. The proposed work will strengthen collaboration between U.S. and Chilean scientists. The investigators will continue working with Chilean and European Union graduate students, at no cost to NSF.