Agulhas System Climate Array (ASCA)

厄加勒斯系统气候阵列 (ASCA)

• 批准号: 1459543
• 负责人: Lisa Beal
• 金额: $ 206.44万
• 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: 2015
• 资助国家: 美国
• 起止时间: 2015-03-01 至 2022-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1459543&HistoricalAwards=false
• 关键词: Agulhas; System; Climate; Array; ASCA

The Agulhas Current is the western boundary current of the South Indian Ocean subtropical gyre and, as such, it dominates the heat budget of the Indian Ocean basin. Variability in sea surface temperature and heat content is central to many aspects of climate over the Indian Ocean basin, such as East African rainfall, tropical cyclone activity, and sea level rise. More than 50% of decadal Sea Surface Temperature variability over the Indian Ocean is explained by uniform, basinwide warming or cooling and it is hypothesized that this could be linked to changes in the meridional overturning circulation. Understanding the links between Indian Ocean overturning, meridional heat transport and sea surface temperature is currently hampered by lack of observations. Estimates of the Indian Ocean meridional overturning circulation have been made less than a handful of times over the past 50 years. Yet, one can expect its short-term variability to exceed the span of these few estimates, just as it does in the Atlantic. The poleward heat transport that exits the Indian Ocean via the Agulhas Current feeds both northward into the Atlantic, where it is believed to influence meridional overturning and hence climate in that basin, and southward into the Southern Ocean. Measuring Agulhas variability and investigating its relationship to wind forcing and Agulhas leakage proxies will lead to a better understanding of how these phenomena are linked in the real ocean. An integral component of this project is to provide skills-transfer to South African scientists and technicians so that they can lead and sustain an Agulhas array in the longer term. Resource sharing, capacity building, an open data policy, and collaborative analyses will promote greater productivity and better quality research from the western Indian Ocean oceanographic community in general. The principal investigator will be a visiting Professor at the University of Cape Town in 2015 and 2018 and teach a 2-week Honors module on large-scale dynamical oceanography, as part of this project. A U.S. graduate student, a postdoctoral researcher and an early career scientist will be trained. The Agulhas System Climate Array (ASCA) project is a collaboration between South African, Dutch, and US scientists to implement sustained observations of the Agulhas Current, as part of the Global Ocean Observing System. This five-year phase for ASCA will establish measurements of velocity, temperature, and salinity variability in the Current, including its influence on coastal waters. These measurements will be synthesized with satellite and Argo data to achieve the following major scientific objectives:(1) Characterize the relationship between volume and temperature transport in the Agulhas Current.(2) Quantify the seasonal variability in basin-wide overturning and heat transports of the Indian Ocean, by synthesizing ASCA measurements with Argo and satellite data over the ocean interior.(3) Investigate the annual and interannual variability of the Agulhas Current in the context of wind forcing and changes in retroflection and leakage.Three ASCA research cruises (2016, 2018 and 2019) will take place aboard South African research vessels, during which the international team will deploy and maintain a linear array of seven full-depth current meter moorings with additional temperature and salinity sensors interspersed with four bottom-mounted Current and Pressure-sensing Inverted Echo Sounders. Finally, three coastal moorings will be added to the array at the shelf break and inshore, all in less than 200 m of water. These are led by the South African partners, whose motivation is to study the regional impact of Agulhas Current variability on coastal currents, upwelling, and the annual sardine run. During deployment and recovery of the mooring, hydrographic sections across the Agulhas Current near 34◦S will be collected. The sampling plan is based on moored velocity observations that have been successfully collected before in this location under the Agulhas Current Time-series experiment funded by NSF. This project is a contribution to the U.S. CLIVAR (CLImate VARiability and predictability) program.

厄加勒斯洋流是南印度洋副热带环流的西边界洋流，因此它主导着印度洋盆地的热量收支。海面温度和热含量的变化是印度洋盆地气候许多方面的核心，例如东非降雨、热带气旋活动和海平面上升。印度洋上超过 50% 的海面温度年代际变化可以用均匀的、全盆地变暖或变冷来解释，并且假设这可能与经向翻转环流的变化有关。目前，由于缺乏观测，了解印度洋翻转、经向热传输和海面温度之间的联系受到阻碍。过去 50 年来，对印度洋经向翻转环流的估计次数不超过几次。然而，人们可以预期其短期变化将超过这几个估计的范围，就像大西洋的情况一样。通过厄加勒斯洋流离开印度洋的极地热传输向北流入大西洋，据信影响经向翻转，从而影响该盆地的气候，并向南流入南大洋。测量厄加勒斯的变化并研究其与风力和厄加勒斯泄漏代理的关系将有助于更好地了解这些现象在真实海洋中的联系。该项目的一个组成部分是向南非科学家和技术人员提供技能转让，以便他们能够长期领导和维持阿古拉斯阵列。资源共享、能力建设、开放数据政策和协作分析将促进整个西印度洋海洋学界更高的生产力和更高质量的研究。作为该项目的一部分，首席研究员将在 2015 年和 2018 年担任开普敦大学的客座教授，教授为期 2 周的关于大规模动力海洋学的荣誉模块。一名美国研究生、一名博士后研究员和一名早期职业科学家将接受培训。厄加勒斯系统气候阵列 (ASCA) 项目是南非、荷兰和美国科学家之间的一项合作，旨在对厄加勒斯洋流进行持续观测，作为全球海洋观测系统的一部分。 ASCA 的这个五年阶段将测量海流的速度、温度和盐度变化，包括其对沿海水域的影响。这些测量结果将与卫星和 Argo 数据综合起来，以实现以下主要科学目标：(1) 表征厄加勒斯洋流的体积和温度传输之间的关系。(2) 量化流域范围内的翻转和热传输的季节变化。通过将 ASCA 测量值与 Argo 和海洋内部卫星数据综合起来，研究印度洋。(3) 研究风力强迫和反射变化背景下厄加勒斯洋流的年度和年际变化南非研究船上将进行 3 次 ASCA 研究巡航（2016 年、2018 年和 2019 年），在此期间，国际团队将部署和维护由七个全深度海流计系泊装置组成的线性阵列，并散布额外的温度和盐度传感器带有四个底部安装的电流和压力感应倒置回声测深仪。 最后，三个沿海系泊点将在陆架断裂处和近岸处添加到阵列中，所有这些都位于不到 200 米的水域中。这些项目由南非合作伙伴领导，其动机是研究厄加勒斯洋流变化对沿海水流、上升流和每年沙丁鱼洄游的区域影响。在系泊装置的部署和恢复过程中，将收集南纬 34 度附近厄加勒斯洋流的水文剖面。采样计划基于之前在美国国家科学基金会 (NSF) 资助的厄加勒斯海流时间序列实验中成功收集到的系泊速度观测结果。该项目是对美国 CLIVAR（气候变异性和可预测性）计划的贡献。