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

以往的观测研究强调了黑潮输运变率相对于盆地尺度大气强迫的延迟，因此强调斜压罗斯比波调整是远距离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，黑潮及其扩展对大气强迫既有延迟响应，也有即时响应，这表明其他机制在黑潮变率中起重要作用。该项目将全面考察这两个响应时间尺度，特别关注快速响应和北太平洋副热带环流组成部分的连通性。本研究的目的是更好地了解海洋如何响应盆地尺度的风强迫，特别是在西部边界流及其扩展中，重点关注黑潮系统的年际到年代际变化。在北太平洋，这种变化表现在太平洋年代际涛动（PDO）上，PDO是一个反映大尺度海面温度变化的气候指数，它也与近几十年来风应力旋度变化的主导模态密切相关。现有观测资料、理想数值模式实验和涡旋解析海洋环流模式（OGCM）输出的组合将用于实现三个目标：(1)表征东海黑潮（ECS-Kuroshio）的年际和年代际变化特征；(2)研究局地和远地大气强迫对ECS-Kuroshio的正斜压海洋响应的相对作用，并确定远地强迫到达ECS-Kuroshio的波导；(3)将ECS-Kuroshio的变率与副热带环流其他部分的变率联系起来。特别是在黑潮延伸地区。知识价值：结合使用观测、双层模式和海洋环流模式的输出将导致对黑潮系统更完整的描述，并更好地理解引起西边界流及其扩展变率的动力学。推进目前对海洋环流年际至年代际变率与大气强迫之间关系的理解，将有利于更广泛的气候研究界，特别是目前正在进行的提高年际至年代际可预测性的努力。更广泛的影响：该项目的第一年将部分支持首席研究员的博士后培训，一名来自代表性不足群体的年轻科学家。此外，首席研究员将与中学生和他们的科学老师进行外展工作。这项志愿者工作将支持罗德岛州的一所学校实施NASA 2009年科学和数学学者（SAMS）拨款，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.