Agulhas Current Time-series (ACT): Towards a multi-decadal index of Agulhas Current transport

厄加勒斯洋流时间序列 (ACT)：建立阿加勒斯洋流运输的多年代指数

• 批准号: 0850891
• 负责人: Lisa Beal
• 金额: $ 335.93万
• 依托单位: University of Miami
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-05-15 至 2016-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0850891&HistoricalAwards=false
• 关键词: Agulhas; Current; Time; series; ACT

Among the world's western boundary currents the Agulhas Current has a uniquely global significance. Its variability has been linked upstream to tropical Indian Ocean Dipole events which are largely coupled to Pacific winds and ENSO (El Nino- Southern Oscillation). Downstream, it feeds an inter-ocean transport of warm and saline waters into the South Atlantic which directly impacts the strength of the Atlantic meridional overturning circulation. This makes the Agulhas Current an effective link between the Indian and Atlantic tropical arrays of the Global Ocean Observing System. It is of significance not just to Indian Ocean variability, but to global climate.Intellectual Merit: The goal of this project is to build a multi-decadal time series of Agulhas Current Transport (ACT). This will be done in a manner similar to what was started in the mid nineties for monitoring Kuroshio transport via satellite altimeter. The first phase of ACT requires deployment of an array of instruments across the Agulhas Current and along an altimeter (TOPEX/Jason) ground track, to obtain a three-year time series of transports via in situ measurements. The second phase involves calibrating the along- track altimeter data with these measured transports to produce a time series of Agulhas Current transport from 1992 and into the future, for as long as altimeter missions continue to along this track. Jason-2 has just been launched (June 2008) ensuring a continuing time series through 2012. This twenty-year time series will provide an important climate index for the Indian Ocean, which can be compared to other climate indices and to the Florida Current and Kuroshio time series. The importance of understanding climatic variability on decadal time scales has come to the forefront over the last decade with the need to distinguish natural modes of variability of the atmosphere/ocean system from anthropogenic changes. In response, the international oceanographic community, particularly through the CLIVAR (Climate Variability and Predictability) program, have developed a collaborative plan for a global ocean observing system, consisting largely of tropical moored arrays, sub-surface floats, repeat XBT (eXpendable BathyThermograph) sections, and satellite data. The CLIVAR Indian Ocean Panel recognizes that western boundary observations of the Agulhas Current are an important and missing element to this observing system. Both the Kuroshio and Gulf Stream transports are continuously monitored, providing a link from tropical to mid-latitude variability in their basins. However, there is no monitoring capability for the Agulhas Current, which has links not only to the tropical Indian Ocean, but also to Pacific variability through the Indonesian throughflow and Tasman leakage, and to the Atlantic via Agulhas Rings.The broader impact of the project concerns the societal value of monitoring a current that has climate and marine impacts on Africa, a region lacking the capacity to monitor the current themselves. African scientists and students will benefit from active participation in the project, in particular through participation on cruises and via a student exchange between the University of Cape Town and the University of Miami. These collaborations will build local oceanographic experience and knowledge. Finally, the ACT array itself, and subsequent long-term time series of Agulhas transports, will allow a broad assessment of the relationship of the Agulhas to other observed climate indices, making an important contribution to the Global Ocean Observing System by building long-term regional capacity.

在世界的西部边界流中，阿古拉斯海流具有独特的全球意义。它的可变性与上游的热带印度洋偶极子事件有关，这些事件在很大程度上与太平洋风和ENSO（厄尔尼诺-南方涛动）有关。在下游，它将温暖和盐水沃茨的大洋间输送输送到南大西洋，直接影响大西洋纬向翻转环流的强度。这使厄古拉斯海流成为全球海洋观测系统的印度洋和大西洋热带阵列之间的有效联系。这不仅对印度洋的变化，而且对全球气候都具有重要意义。智力上的优点：本项目的目标是建立一个多年代的时间序列的阿古拉斯电流传输（ACT）。这将以类似于90年代中期开始通过卫星高度计监测黑潮运输的方式进行。ACT的第一阶段要求在Agulhas海流和沿着高度计（TOPEX/Jason）地面轨道部署一系列仪器，通过现场测量获得三年时间序列的运输。第二阶段涉及校准的沿着轨道高度计数据与这些测得的运输，以产生一个时间序列的阿古拉斯电流运输从1992年到未来，只要高度计任务继续沿着这条轨道。Jason-2号卫星刚刚发射（2008年6月），确保了2012年的连续时间序列。这一20年时间序列将为印度洋提供一个重要的气候指数，可与其他气候指数以及佛罗里达海流和黑潮时间序列进行比较。在过去十年中，由于需要区分大气/海洋系统的自然变化模式与人为变化，了解十年时间尺度上的气候变化的重要性已成为最重要的问题。作为回应，国际海洋学界，特别是通过气候变率和可预测性（CLIVAR）计划，制定了一项全球海洋观测系统的合作计划，主要包括热带系泊阵列，次表层浮标，重复XBT（可扩展的BathyThermograph）部分和卫星数据。气候多变性研究方案印度洋小组认识到，对阿古拉斯海流西部边界的观测是这一观测系统的一个重要和缺失的要素。黑潮和墨西哥湾流输送都受到持续监测，提供了从热带到中纬度流域变化的联系。然而，没有监测能力监测厄古拉斯海流，该海流不仅与热带印度洋有联系，而且通过印度尼西亚的贯流和塔斯曼泄漏与太平洋的变化有联系，并通过厄古拉斯环与大西洋有联系，该项目的更广泛影响涉及监测对非洲有气候和海洋影响的海流的社会价值，因为非洲缺乏监测海流本身的能力。非洲科学家和学生将从积极参与该项目中受益，特别是通过参加航行和通过开普敦大学与迈阿密大学之间的学生交流。这些合作将积累当地的海洋学经验和知识。最后，ACT阵列本身以及随后的厄古拉斯输送长期时间序列将能够广泛评估厄古拉斯与其他观测到的气候指数的关系，通过建立长期区域能力，为全球海洋观测系统作出重要贡献。