Dynamics of near-surface eastward flows in the South Indian Ocean

目标和智力优势：热带和亚热带南印度洋（SIO）上层海洋环流的一个显着方面是存在近地表，东向流穿过海盆，这往往表现为一组不同的电流和射流。这些电流已在观测中检测到，并在数值模型中进行了模拟。与此同时，它们的内在动力仍不清楚。在这方面，它们的流向与Ekman和Sverdrup理论预测的向西方向相反。此外，它们似乎与沿着澳大利亚西海岸的列文海流和较大规模的环流，即印度尼西亚洋流和南大洋有关。因此，向东的流动代表了我们对SIO中大尺度平均流的理解的一个基本空白。该项目将利用对现场观测和数值模型的分析来填补这一空白。观察分析将依赖于三个主要数据集。 每个数据集都将Argo数据与历史数据相结合，不同的绘图技术产生的产品具有适合不同分析方面的特点：CSIRO开发的汽车数据集是一个高质量的T，S和其他水团属性的月平均数据集，可以跟踪水团; IPRC数据集结合了绝对动力地形的附加产品，允许估计绝对地转速度; UTas数据集将Argo和历史数据映射到密度表面上，这将有助于解决更精细的锋面特征和表征下降流/上升流区域。卫星风将用于计算Ekman和Sverdrup流，并迫使模型。为了验证控制表面向东流动的过程的具体假设，将使用海洋环流模型。研究团队结合了IPRC，CSIRO和塔斯马尼亚大学的科学家的才能，后者的科学家将他们在SIO现场观测的广泛知识贡献给项目Broader Impact：了解这些一阶特征的动态对于验证和改进气候模型是必要的。此外，这些电流与LC和ITF的相互作用，并可能是一个盆地规模的翻转环流的一部分，在LC和南极绕极流附近的下降流关闭。因此，地面东向流的动力学应该在SIO年代际变率中发挥重要作用。这些结果可能适用于其他海洋的类似特征。

Objectives and intellectual Merit: A remarkable aspect of the upper-ocean circulation in the tropical and subtropical South Indian Ocean (SIO) is the presence of near-surface, eastward flow across the basin, which often appears as a set of distinct currents and jets. These currents have been detected in observations and simulated in numerical models. At the same time, their underlying dynamics remain unclear. In this regard, they flow counter to the westward direction predicted by both Ekman and Sverdrup theory. Furthermore, they appear to be linked to the Leeuwin Current (LC) along the west coast of Australia and to larger-scale circulations , namely, the Indonesian Throughflow (ITF) and the Southern Ocean. Thus, the eastward flow represents a fundamental gap in our understanding of the large-scale mean flow in the SIO. This project will use analyses of in situ observations and numerical models to fill that gap. The observational analysis will rely on three main datasets. Each dataset combines Argo data with historical data, the different mapping techniques resulting in products with characteristics suited to different aspects of the analysis: the CARS dataset developed at CSIRO is a high-quality monthly-mean dataset of T , S , and other water-mass properties, which allows for tracing watermasses; the IPRC dataset incorporates the additional product of absolute dynamic topography, allowing an estimation of absolute geostrophic velocity; and the UTas dataset maps Argo and historical data on density surfaces, which will be useful in resolving finer frontal features and characterizing downwelling/upwelling regions. Satellite winds will be used to compute Ekman and Sverdrup flows and to force the models. To test specific hypotheses about the processes that control the surface eastward currents, an ocean circulation model will be used.The research team combines the talents of scientists at the IPRC, CSIRO, and the University of Tasmania, with scientists at the latter institutions contributing their extensive knowledge of in situ observations in the SIO to the project Broader Impact: Understanding the dynamics of these first-order features is necessary to validate and improve climate models. Moreover, these currents interact with the LC and the ITF, and are likely part of a basin-scale overturning circulation closed by downwelling within the LC and near the Antarctic Circumpolar Current. The dynamics of the surface eastward currents therefore should play an important role in SIO decadal variability. The results will likely apply to similar features in the other oceans.