The Agulhas Current System: A Key Control of the Atlantic System

本文提出了研究控制阿古拉斯海流回折和环形成低频变化的物理过程。这种可变性是由内部过程和外部（ACS）影响引起的。从动力系统理论的方法将被用来研究ACS的内部变化，并制定一个新的动力学理论的回射和环的形成。输出从一个高水平（1/32）分辨率海军分层海洋模式（NLOM）模拟在1979年至2002年将被用来评估的重要性，内部动态的低频变化的ACS（与外部原因）。这项研究的动机是最近的观察显示存在较强的低频（年际到十年）的变化，上层运输在厄古拉斯电流retroflection区域，并建议有一个很强的对应关系之间的最大运输值和环脱落事件。最近的古海洋学代用指标分析表明，在冰川期，阿古拉斯环流入量显着减少，这也是动机。然而，流入量在冰川期结束时急剧增加。有人认为，由于环携带的盐异常，这种流入量的增加有助于大西洋深水形成的重新开始。虽然目前有两个独立的理论都回射和环的形成，有没有令人满意的理论连接这两种现象，以及解释其年际变化。没有这些问题的答案，关于ACS行为的理论将是不完整的。动力系统的研究也适合更广泛的尝试，以确定系统的解决方案的结构，特别是过渡到复杂的行为，这些解决方案，在层次结构的海洋模型的西部边界流的阿古拉斯电流。

It is proposed to investigate the physical processes controlling the low-frequency variations of the Agulhas Current retroflection and ring formation. This variability is caused by internal processes and external (to the ACS) influences. Methods from dynamical systems theory will be used to study the internal variability of the ACS and to develop a new dynamical theory of retroflection and ring formation. Output from a high horizontal (1/32) resolution Navy Layered Ocean Model (NLOM) simulation over the years 1979-2002 will be used to evaluate the importance of internal dynamics on the low-frequency variability of the ACS (versus external causes). This study is motivated by recent observations showing the existence of strong low-frequency (interannual-to-decadal) variability of the upper layer transport in the Agulhas Current retroflection region, and suggesting that there is a strong correspondence between maximum transport values and ring shedding events. It is also motivated by recent paleoceanographic proxy analyses indicating that during a glacial period, the Agulhas rings in- flux was significantly reduced. The influx, however, dramatically increased towards the end of the glacial period. It has been suggested that, due to salt anomalies carried by the rings, this increase of influx contributed to the re-start of deep water formation in the Atlantic. Although there are presently separate theories for both retroflection and ring formation, there is no satisfying theory connecting both phenomena as well as explaining their interannual variability. Without answers to these questions, the theory on the behavior of the ACS will stay incomplete. The dynamical systems study of the Agulhas Current fits also a broader attempt to determine systematically the solution structure, in particular the transitions to complex behavior of those solutions, in a hierarchy of ocean models of western boundary currents.