Inter-hemispheric Water Exchange in the Indian Ocean: Discovering the Red Sea Overflow Water Pathways and Variability

该项目将分析有关海洋温度和盐度的数据，以及研究红海海水如何进入印度洋并通过印度洋传播的数值模型输出。红海是全球海洋中盐度最高的水域之一。这些水域在500至1500米深的地方进入印度洋；它们沿着人们不太了解的路径扩散，最远可以到达非洲南端，也可以到达澳大利亚西部。我们对红海海水扩散的了解有限，这是因为历史上对印度洋的观测很少。直到最近15年，科学家才能获得该地区的盐度和温度数据。这些数据将被用来识别红海水团，并通过观察它们与周围水域显著不同的温度和盐度特征，在整个海洋中追踪它们。该项目将有助于理解这种水流如何有助于将热量转移到海洋更深的部分，这一过程会影响地球气候。研究结果将推动科学进步，并通过可能改善气候预测的信息间接促进国家健康、繁荣和福利。红海溢流水(ROW)与淡水和较冷的印度尼西亚中流水(IIW)和南极中流水(AAIW)形成鲜明对比，后者出现在类似的中间深度，使其成为中深度环流的示踪物。这种咸水还可能影响中间层的层结和动力学。这项拟议的研究将利用现场观测、数据同化模拟输出和粒子跟踪方法来调查RSOW路径、时间变异性和与其在印度洋传播有关的物理机制。具体目标是：(1)确定印度洋大尺度中间环流的特征，包括与季风有关的变率，并调查其与地面环流的联系；(2)确定印度洋中的热带气旋的路径，以了解它如何到达澳大利亚西部以及是否到达南大西洋；(3)调查与热带气旋扩散有关的物理机制和印度洋三个中间水团之间的锋面带及其与环流的关系。该项目将利用新的数据和现代方法，对印度洋区域海洋和大洋中层环流的时空分布和中间环流进行定量描述。目的是了解这种咸水对环流的作用，以及通过印度-大西洋水交换对全球颠覆环流的潜在影响。印度洋是全球海洋中研究最少的区域之一，甚至其基本动态仍在讨论中。这项工作将填补我们对印度洋环流知识的一些主要空白，印度洋环流与其他大型洋盆明显不同。

This project will be analyzing data on ocean temperature and salinity, and numerical model outputs to examine how Red Sea waters enter and propagate through the Indian Ocean. The Red Sea produces one of the saltiest waters of the global oceans. These waters enter the Indian Ocean at depths 500 to 1,500 m; they spread along pathways that are not well understood and can travel as far as the southern tip of Africa, as well as off western Australia. Our limited understanding of Red Sea water spreading is because of the historical scarcity of observations in the Indian Ocean. It is only the last 15 years that salinity and temperature data from this region have become available to scientists. These data will be used to identify Red Sea water masses and trace them throughout the ocean by looking at their temperature and salinity characteristics that are significantly different than those of the surrounding waters. The project will contribute into understanding how such water flow contributes to the transfer of heat in to deeper parts of the ocean, a process that influences the Earth's climate. The study findings will promote the progress of science and, indirectly, will advance the national health, prosperity and welfare through information that could improve climate prediction. Red Sea Overflow Water (ROW) contrasts sharply with both the fresher and cooler Indonesian Intermediate Water (IIW) and the Antarctic Intermediate Water (AAIW) that occur at similar intermediate depths, making it a tracer for the intermediate- depth circulation. This saline water may also affect the stratification and dynamics of the intermediate layer. The proposed research will investigate the RSOW pathways, temporal variability, and the physical mechanisms associated with its spreading in the Indian Ocean using in situ observations, data-assimilated simulation outputs and a particle tracking method. The specific objectives are to: (i) Characterize the large-scale intermediate circulation of the Indian Ocean, including monsoonal-related variability, and investigate its connection to the surface circulation; (ii) determine the pathways of the RSOW in the Indian Ocean to understand how it reaches western Australia and whether it reaches the south Atlantic; (iii) investigate the physical mechanisms associated with the RSOW spreading and the frontal zones between the three intermediate water masses of the Indian Ocean and their relation to the circulation. The project will lead to the construction of a quantitative description of RSOW space-time distribution and the intermediate circulation of the Indian Ocean using new data and modern approaches. The aim is to understand the role of this saline water to the circulation and potential impacts on the global overturning circulation through the Indo-Atlantic water exchange. The Indian Ocean is one of the most understudied regions of the global oceans, and even its basic dynamics are still under discussion. This work will fill in some of the major gaps in our knowledge of the Indian Ocean circulation, which differs markedly from the other large ocean basins.