Kuroshio Transport: Inter-annual to Decadal Variability and the Underlying Mechanisms

以前的观测研究强调了黑潮输送变率相对于流域尺度大气强迫的延迟，因此强调斜压Rossby波调整是远程强迫到达西部边界的机制。然而，最近的观测研究和初步分析表明，事实上，黑潮及其延伸都表现出延迟和立即响应大气强迫，这表明其他机制在黑潮变率中起着重要作用。该项目将全面审查这两个反应时间表，特别注意快速反应和北太平洋副热带环流各组成部分的连通性。本研究的目的是更好地了解海洋如何响应流域尺度风强迫，特别是在西部边界流及其延伸，重点是在黑潮系统的年际到十年变化。在北太平洋，这种变率表现在太平洋十年涛动（PDO）中，这是一种反映大尺度海表温度变率的气候指数，也与最近几十年风应力旋度变率的主导模式有很好的相关性。结合现有的观测数据、理想化的数值模式实验，并将利用一个涡旋分辨海洋环流模式（OGCM）的输出来实现三个目标：（1）研究东海黑潮的年际和年代际变化特征（2）研究局地和远程大气强迫对东海黑潮正、斜压海洋响应的相对作用，并确定远程强迫到达东海黑潮的波导，（3）把东海黑潮的变率与副热带环流的其它部分，特别是黑潮延伸区的变率联系起来。观测数据的综合使用，一个两层模型，和海洋环流模式的输出将导致更完整的描述黑潮系统和更好地了解动力学引起西部边界流及其延伸的变化。提高目前对海洋环流年际至十年变率与大气强迫之间关系的认识，将有利于更广泛的气候研究界，特别是有利于正在进行的提高年际至十年可预测性的社区努力。该项目的第一年将部分支持首席研究员的博士后培训，一个来自弱势群体的年轻科学家此外，首席研究员将与中学生及其科学教师开展外联工作。这项志愿工作将支持罗得岛的一所学校努力实施美国宇航局2009年科学和数学学者（SAMS）赠款，以提高中学科学和数学教育的质量。

Previous observational studies have highlighted a delay in Kuroshio transport variability relative to basin-scale atmospheric forcing, and thus have emphasized baroclinic Rossby wave adjustment as the mechanism by which remote forcing reaches the western boundary. However, recent observational studies and preliminary analyses suggest that, in fact, the Kuroshio and its extension each exhibit both delayed and immediate responses to the atmospheric forcing, suggesting that additional mechanisms play important roles in Kuroshio variability. The project will take a comprehensive look at these two response time scales, paying particular attention to the rapid response and to the connectivity of the components comprising the North Pacific subtropical gyre. The purpose of this study is to develop a better understanding of how the ocean responds to basin-scale wind forcing, especially in the western boundary currents and their extensions, with a focus on interannual to decadal variability in the Kuroshio system. In the North Pacific, such variability manifests itself in the Pacific Decadal Oscillation (PDO), a climate index reflecting the large-scale sea surface temperature variability, which is also well-correlated with the leading mode of wind stress curl variability over the most recent decades.A combination of existing observational data, idealized numerical model experiments, and output from an eddy-resolving ocean general circulation model (OGCM) will be used to accomplish three goals: (1) characterize the interannual to decadal variability in the Kuroshio in the East China Sea (ECS-Kuroshio), (2) investigate the relative roles of local versus remote atmospheric forcing on the barotropic and baroclinic oceanic responses in the ECS-Kuroshio and identify waveguide(s) by which remote forcing reaches the ECS-Kuroshio, and (3) relate the variability in the ECS-Kuroshio to variability in other parts of the subtropical gyre circulation, especially that in the Kuroshio Extension region.Intellectual Merit: The combined use of observations, a two-layer model, and ocean general circulation models output will lead to a more complete description of the Kuroshio system and a better understanding of the dynamics which give rise to variability in the western boundary current and its extension. Advancing the current understanding of the relationship between the inter-annual to decadal variability of ocean circulation and atmospheric forcing will be beneficial to the broader climate research community, particularly in the on-going community effort to improve inter-annual to decadal predictability.Broader Impacts: The first year of this project will partially support the postdoctoral training of the lead investigator, a junior scientist from an under-represented group. In addition, the lead investigator will perform outreach work with middle school students and their science teachers. This volunteer work will support the efforts of a school in Rhode Island to implement a 2009 Science and Math Scholars (SAMS) grant by NASA to improve the quality of science and math education in middle schools.