A regional hydrodynamic model of upwelling in the Southern Benguela
A regional hydrodynamic model of upwelling in the Southern Benguela
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发表时间：
2001-11
影响因子：
2.4
通讯作者：
P. Penven;C. Roy;G. Brundrit;A. Verdière;P. Fréon;A. Johnson;J. Lutjeharms;F. Shillington
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文献类型：
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作者：
P. Penven;C. Roy;G. Brundrit;A. Verdière;P. Fréon;A. Johnson;J. Lutjeharms;F. Shillington
VIBES（本格拉生态系统中远洋鱼类资源开发与环境和空间方面的可行性）计划的实施过程中，表达了对南本格拉地区高分辨率、涡流解析、沿海模型的需求。 VIBES 的主要重点是对环境和沙丁鱼和凤尾鱼等远洋鱼类种群的空间动态进行建模。该项目旨在更好地了解和量化影响本格拉鱼类补充的环境和生物过程。开普半岛沿海急流将卵和幼虫从厄加勒斯浅滩产卵场输送到西海岸育苗场，以及与上升流相关的近海扩散，被认为是影响鱼类补充成功的重要过程。 4 VIBES 建模的第一步是建立一个数值工具来模拟主要产卵场和育苗场的环流动态。在各种可用的数值模型中，我们选择了区域海洋模型系统 (ROMS)，这是罗格斯大学和加州大学洛杉矶分校开发的数值代码，用于实施南本格拉上升流系统的 3D 水动力模型。 2 ROMS 在本格拉的实施 ROMS 是一个由世界各地的大型用户群共享的社区模型，其应用范围从整个海洋盆地到沿海次区域的研究。 ROMS 结合了先进的功能和高阶数值，可以有效、稳健地解析海洋和沿海领域的中尺度动力学。该模型使用垂直方向上的拉伸地形跟随坐标和水平方向上的正交曲线坐标来求解可变地形上的自由表面、流体静力、流体动力学原始方程。这允许增强感兴趣区域的空间分辨率。连接区域模型与公海的主动开放边界也被纳入其中。 5 南部非洲西南海岸附近的本格拉上升流系统产量丰富，但分散性也很高。沙丁鱼和凤尾鱼已经调整了它们的繁殖策略，在远离上升流区域的厄加勒斯浅滩产卵。从产卵场到育苗区的运输被认为是控制补充的主要环境过程之一。为了更好地了解西南非洲海岸的输送过程，我们建立了区域海洋环流的涡旋解析原始方程模型。模型域涵盖南纬 40° 至 28°、东经 10° 至 24° 的陆架和海洋平原。为了获得统计上有意义的解决方案，进行了长时间的模拟（超过 10 年）。模型方案和网格分辨率的高阶精度允许羽流、细丝和涡流的发展，这是上升流系统的特征。虽然只有大尺度和季节性变化是被迫的，但这种充满活力的中尺度活动会引起重要的变化。这种内在的变异性可能会限制本格拉洋流运输过程和鱼类补充的可预测性。
The need for a high-resolution, eddy resolving, coastal model of the Southern Benguela region was expressed during the implementation of the VIBES (for VIability of exploited pelagic fish resources in the Benguela Ecosystems in relation to the envi- ronment and Spatial aspects) programme. VIBES' main focus is to model the spatial dynamics of the environment and of the pelagic fish populations such as sardine and anchovy. This project aims to provide a better understanding and quantifica- tion of the environmental and biological processes affecting fish recruitment in the Benguela. Transport of eggs and larvae by the Cape Peninsula coastal jet from the Agulhas Bank spawning ground to the west coast nursery grounds, as well as offshore dispersion associated with upwelling, are thought to be impor- tant processes affecting fish recruitment success. 4 The first step in VIBES modelling was to set up a numerical tool that would simulate the dynamics of the circulation over the main spawn- ing and nursery grounds. Within the wide range of numerical models available, we selected the Regional Ocean Model System (ROMS), a numerical code developed at Rutgers University and at the University of California at Los Angeles, to implement a 3-D hydrodynamic model of the Southern Benguela upwelling system. 2 Implementation of ROMS in the Benguela ROMS is a community model shared by a large user group around the world, with applications ranging from the study of entire ocean basins to coastal subregions. ROMS incorporates advanced features and high-order numerics, allowing efficient and robust resolution of mesoscale dynamics in the oceanic and coastal domains. The model solves the free surface, hydrostatic, primitive equations of the fluid dynamics over variable topogra- phy using stretched, terrain-following coordinates in the verti- cal and orthogonal, curvilinear coordinates in the horizontal. This allows enhancement of the spatial resolution in the regions of interest. Active open boundaries, connecting the regional model with the open ocean, are also incorporated. 5 The Benguela upwelling system, off the southwest coast of southern Africa, is productive but also highly dispersive. Sardines and anchovies have adapted their reproductive strategy by spawning on the Agulhas Bank, away from the upwelling region. Transport from the spawning grounds to the nursery area is believed to be one of the main environmental processes that control recruitment. To understand the transport processes along the southwest African coast better, we set up an eddy-resolving, primitive equation model of the regional oceanic circulation. The model domain covers the shelves and oceanic plains from 40°S to 28°S and from 10° E to 24°E. To obtain statistically meaningful solutions, long simulations (more than 10 years) were conducted. The high-order accuracy of the model schemes and grid resolution allow the development of plumes, filaments and eddies, which are characteristic features of upwelling systems. While only large-scale and seasonal variations are forced, this energetic mesoscale activity induces an important variability. This intrinsic variability could limit the predictability of the transport processes and fish recruitment in the Benguela Current.