Variability of the Equatorial undercurrent in the eastern tropical Atlantic: Analysis of the 2007-2011 TACE-EUC Experiment

赤道潜流（EUC）是大西洋和太平洋赤道纬向环流的准永久特征。它在两大洋中的主要作用是向赤道盆地中部和东部的主要上升流区提供来自亚热带浅层俯冲带的温跃层水。在近二十年的船上密集观测和热带海洋大气计划的时间序列观测中，太平洋的EUC得到了很好的描述，而大西洋的EUC直到最近才得到相对较少的采样，而且无论是其横跨盆地的平均结构还是其季节-年际变化都不为人所知。它与北方夏季赤道冷舌的温暖和寒冷阶段的联系也知之甚少。2007-2011年期间，德国、法国和美国的调查人员在赤道大西洋中部和东部收集了一套协调的系泊海流计观测数据。这些观测有助于TACE（热带大西洋气候实验）的目标，TACE是一个2007-2012年国际CLIVAR项目，旨在改善热带大西洋地区的气候预测，特别关注东赤道大西洋。美国的部分工作包括在10W和0E的四个地点进行系泊ADCP电流剖面测量，补充了法国（PIRATA）在10W的ADCP系泊，以及IFM-GEOMAR（德国）在23W的一系列系泊。该项目将完成对该项目收集的数据的分析，遵循最初支持美国测量的NSF拨款。知识价值：将记录整个盆地的EUC的变率，其与风强迫和海温变率的联系，以及赤道沿线季节内变率的性质。这些数据将与模型一起使用，以了解控制几内亚湾东部EUC变化的动力学和EUC水域的命运。这一分析的结果有望大大提高人们对大西洋EUC的认识。更广泛的影响：从TACE计划收集的数据，包括所有系泊时间序列和巡航数据，正在被整合到一个可访问的网络数据库中，由TACE观测工作组维护（http://tace.ifm-geomar.de/index.html），为更广泛的研究界提供随时可用的访问。该项目还提供了研究生培训机会，并促进了国际合作伙伴之间的合作和技术专长的分享。这项研究还将有助于更好地了解影响热带大西洋东部海温变率的过程以及与之相关的热带大西洋地区气候变率。

The Equatorial Undercurrent (EUC) is a quasi-permanent feature of the zonal equatorial circulation in both the Atlantic and Pacific oceans. Its main role in both oceans is to supply thermocline waters from the shallow subduction zones in the subtropics to the main upwelling zones in the central and eastern part of the equatorial basins. While in the Pacific Ocean the EUC is rather well-described from nearly two decades of intensive shipboard and time-series observations in the tropical Ocean Atmosphere programs, the EUC in the Atlantic has until recently been relatively poorly sampled and neither its mean structure across the basin or its seasonal-to-interannual variability is understood. Its linkage to warm and cold phases of the boreal summer equatorial cold tongue is also poorly understood. During 2007-2011, a coordinated set of moored current meter observations has been collected across the central and eastern equatorial Atlantic during 2007-2011 by German, French, and U.S. investigators. These observations contribute to the goals of TACE (the Tropical Atlantic Climate Experiment), a 2007-2012 international CLIVAR program designed to improve climate predictions for the tropical Atlantic region, with a particular focus on the eastern equatorial Atlantic. The U.S. part of this effort consisted of moored ADCP current profile measurements at four sites along 10W and 0E, complementing a French (PIRATA) ADCP mooring at 10W, and an array of moorings along 23W maintained by IFM-GEOMAR (Germany). This project will complete the analysis of the data collected in this program, following the original NSF grant that supported the U.S. measurements. Intellectual Merit:The variability of the EUC across the basin, its linkages to wind forcing and SST variability, and the nature of the intraseasonal variability along the equator will be documented. The data will be used together with models to understand the dynamics controlling the EUC variability and the fate of EUC waters in the eastern Gulf of Guinea. The results of this analysis are expected to lead to a vastly improved understanding of the EUC in the Atlantic.Broader Impacts:The data collected from the TACE program, including all moored time series and cruise data, is being assembled into a web-accessible database maintained by the TACE Observations Working Group (http://tace.ifm-geomar.de/index.html), to provide ready access to the broader research community. The program has also provided graduate student training opportunities and promoted collaboration and sharing of technical expertise among international partners. The study will also contribute to an improved understanding of processes influencing SST variability in the eastern tropical Atlantic and associated climate variability in the tropical Atlantic region.