Ocean eddies-topographic interactions along the Brazilian Coast

巴西海岸的海洋涡流与地形相互作用

• 批准号: 1434780
• 负责人: William Dewar
• 金额: $ 49.68万
• 依托单位: Florida State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2014
• 资助国家: 美国
• 起止时间: 2014-09-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1434780&HistoricalAwards=false
• 关键词: Ocean; eddies; topographic; interactions; along

Swift currents can create robust, circular structures approximately 100 kilometers in diameter, known as "rings." The ocean is filled with these rings, which propagate according to their own dynamics. Observations and modeling studies have revealed several formation sites and pathways known for the prevalence of ocean rings. One of these sites is the northeast coast of Brazil. Each year, eight or nine rings form and propagate along the Brazilian coast. These rings trap warm water in their cores as well as nutrients and organisms, and are thus important to all aspects of oceanography. North Brazilian Rings, in particular, are thought to be important for climate variability by contributing half of the northward warm water transport of the global ocean circulation in the Atlantic Ocean. As these ocean rings circulate, they interact with the bottom topography but the ring-topographical interaction is still not well understood. Idealized studies have demonstrated that rings can accelerate or slow down when entering in contact with the topography. However it is unclear if these theories apply in realistic cases such as the North Brazilian Rings. This study will address this question in a combined theoretical and numerical study of the region. This research will clarify the ring-topographic interactions for realistic topographies and lead to a better understanding of the ocean dynamics in coastal areas. Each summer, a high school science teacher will be involved in the conduct of the research. The project team will visit the teacher's classes during the regular school year to give presentations on oceanography and update the class on the work done during the summer by their instructor.North Brazil Current (NBC) rings are observed to accelerate suddenly upon departing the South American coast at 12°N (often doubling their propagation speed). This phenomenon has never been explained, but given that these rings are responsible for roughly 50% of the Meridional Overturning Circulation inter-hemispheric exchange, one needs to understand their pathways and evolution. The ring-topographic interaction will be examined in a combined modeling and analytical study. This study will proceed systematically from simple process-oriented work to regionally embedded, fine scale primitive equation modeling of the western tropical Atlantic. New ideas about the nature of mean flow-topography interaction will be explored and studied by solving a reduced equation set along with complementary process ocean circulation models. This combination should allow the project team to assess the validity of the theory and to test its limits of applicability. In addition, the mechanics of cyclonic vorticity generation, which is potentially a powerful effect on the separation of NBC rings from the coast, will be examined. Finally, a series of aggressive embedded, downscaling modeling experiments will be performed to provide detailed numerical statements of the regional dynamics. The possibility that the mean flow topographic interaction can be explicitly calculated, rather than having to rely on poorly known parameterizations and boundary conditions, could be a significant breakthrough.

快速的洋流可以形成直径约100公里的坚固的圆形结构，被称为“环”。“海洋充满了这些环，它们根据自己的动力学传播。观测和模拟研究揭示了几个已知的海洋环普遍存在的形成地点和路径。其中一个地点是巴西的东北海岸。每年，八或九个环形成和传播沿着巴西海岸。这些环将温暖的水以及营养物质和生物体困在其核心，因此对海洋学的各个方面都很重要。特别是北巴西环，被认为对气候变异性很重要，因为它贡献了大西洋全球海洋环流向北的暖水输送的一半。 随着这些海洋环的循环，它们与海底地形相互作用，但环地形相互作用仍然没有得到很好的理解。理想化的研究表明，当环与地形接触时，环可以加速或减速。然而，目前还不清楚这些理论是否适用于现实情况，如北巴西环。本研究将在对该区域的理论和数值研究中探讨这一问题。这项研究将澄清环地形的相互作用，为现实的地形，并导致更好地了解在沿海地区的海洋动力学。每年夏天，一名高中科学教师将参与研究的进行。项目小组将在正常学年期间访问教师的班级，就海洋学问题进行介绍，并向全班介绍教师在夏季所做的最新工作，观察到北巴西海流环在离开北纬12度的南美海岸时突然加速（通常是传播速度的两倍）。这种现象从未被解释过，但考虑到这些环负责大约50%的子午翻转循环半球间交换，人们需要了解它们的路径和演变。环地形的相互作用将在一个综合的建模和分析研究。这项研究将系统地进行从简单的面向过程的工作，区域嵌入式，精细尺度原始方程模拟的热带大西洋西部。将通过解一个简化的方程组沿着补充过程海洋环流模式来探索和研究关于平均流-地形相互作用的性质的新想法。这种结合应使项目小组能够评估理论的有效性，并测试其适用性的限度。此外，气旋性涡度产生的机制，这是一个潜在的强大的影响NBC环从海岸分离，将进行审查。最后，一系列积极的嵌入式，降尺度模拟实验将进行区域动态提供详细的数值报表。平均流地形相互作用可以明确计算的可能性，而不是依赖于已知的参数化和边界条件，可能是一个重大的突破。