On the propagation and decay of North Brazil Current rings
On the propagation and decay of North Brazil Current rings
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DOI：
10.1029/2009jc006042
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发表时间：
2010-10
影响因子：
--
通讯作者：
K. Jochumsen;M. Rhein;S. Hüttl-Kabus;C. Böning
中科院分区：
文献类型：
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作者：
K. Jochumsen;M. Rhein;S. Hüttl-Kabus;C. Böning
在热带北大西洋的西部边界附近，北巴西流(NBC)反射成北赤道逆流，大型反气旋环脱落。从反反射区域分离后，所谓的NBC环沿着巴西海岸向西北方向移动，直到它们到达小安的列斯群岛的岛链并解体。这些环带将南大西洋水带入北部副热带环流，对大西洋经向翻转环流的上端回流有很大贡献。它们与南大西洋水向北输送的相关性取决于它们的产生频率以及它们的水平和垂直结构。在链式联结大西洋模式实验(FLAMP)模型中，研究了环的脱落和传播以及环与小安的列斯群岛之间的复杂相互作用。在火焰中模拟的环的性质达到了观测到的环的直径上限，并与最近关于季节变化的观测结果一致，这表明在今年上半年有最大的脱落。当环到达小安的列斯群岛的浅地形时，它们被圣卢西亚、巴巴多斯和多巴哥的岛屿三角所困，并与岛链相互作用。该模型提供了一种能够解决岛屿复杂地形条件的分辨率，并阐明了环中所含水的各种可能的命运。它还复制了实验室实验，这些实验表明，气旋和反气旋都是在环通过地形缝隙后形成的。在模拟的速度场中插入了人造浮标的轨迹，用来研究环核的路径及其在遇到小安的列斯群岛后的命运。大多数漂浮物进入加勒比海，而向北的大西洋航道被发现是次要的。在巴巴多斯以东没有发现明显的路径，在那里一个环可以避开与岛屿的相互作用，不受干扰地向小安的列斯群岛北部迁移。
Near the western boundary of the tropical North Atlantic, where the North Brazil Current (NBC) retroflects into the North Equatorial Countercurrent, large anticyclonic rings are shed. After separating from the retroflection region, the so-called NBC rings travel northwestward along the Brazilian coast, until they reach the island chain of the Lesser Antilles and disintegrate. These rings contribute substantially to the upper limb return flow of the Atlantic Meridional Overturning Circulation by carrying South Atlantic Water into the northern subtropical gyre. Their relevance for the northward transport of South Atlantic Water depends on the frequency of their generation as well as on their horizontal and vertical structure. The ring shedding and propagation and the complex interaction of the rings with the Lesser Antilles are investigated in the inline equation Family of Linked Atlantic Model Experiments (FLAME) model. The ring properties simulated in FLAME reach the upper limit of the observed rings in diameter and agree with recent observations on seasonal variability, which indicates a maximum shedding during the first half of the year. When the rings reach the shallow topography of the Lesser Antilles, they are trapped by the island triangle of St. Lucia, Barbados and Tobago and interact with the island chain. The model provides a resolution that is capable of resolving the complex topographic conditions at the islands and illuminates various possible fates for the water contained in the rings. It also reproduces laboratory experiments that indicate that both cyclones and anticyclones are formed after a ring passes through a topographic gap. Trajectories of artificial floats, which were inserted into the modeled velocity field, are used to investigate the pathways of the ring cores and their fate after they encounter the Lesser Antilles. The majority of the floats entered the Caribbean, while the northward Atlantic pathway was found to be of minor importance. No prominent pathway was found east of Barbados, where a ring could avoid the interaction with the islands and migrate toward the northern Lesser Antilles undisturbed.