Intrinsic versus Forced Decadal Variability in the Extratropical North Pacific

温带北太平洋的内在与受迫年代际变率

• 批准号: 2019312
• 负责人: Bo Qiu
• 金额: $ 48.94万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2020
• 资助国家: 美国
• 起止时间: 2020-08-01 至 2024-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2019312&HistoricalAwards=false
• 关键词: Intrinsic; versus; Forced; Decadal; Variability

Decadal variability of the Kuroshio Current results from both the intrinsic dynamics of oceanic jets and from atmosphere-ocean feedback processes. The Kuroshio’s distinct path configurations south of Japan are associated with differing states of intrinsic stability within the jet, with variations in volume and heat transport by the Kuroshio, and with the N-S position of the Kuroshio Extension (KE) downstream from Japan. This position affects the character and intensity of air-sea interactions, which in turn feed-back upon Kuroshio variability. This study will examine the mechanisms controlling shifts between paths and stability states, and the interplay between intrinsic ocean dynamics and air-sea feedbacks affecting variability. The scientific goals of the proposal are to (1) clarify the processes by which the intrinsic Kuroshio path variability south of Japan alters the KE dynamic state and how it competes with the KE variability controlled by the basin-scale wind forcing, (2) elucidate the dynamics underlying a recent Kuroshio large meander (LM) event, and (3) quantify the relative contributions of sea surface temperature (SST), SST fronts and mesoscale eddies due to the recent KE dynamic state change in modifying the atmospheric circulation. The project will use process-oriented oceanic and atmospheric numerical modeling to address the system variability. The Kuroshio and KE are important components of climate variability, influencing North Pacific ecosystems and basin-scale weather patterns, both of important societal relevance. Student involvement and international collaboration are planned.Accumulation of high-quality satellite/in-situ observations and improvement in state-of-the-art ocean/atmosphere general circulation models over the past decades have significantly improved understanding of the roles played by the KE in the decadal North Pacific climate variability. The specific feedback loop involves the wind-forced interior ocean thermocline adjustment, its subsequent alteration to the KE dynamic state, and the KE’s influence on the stormtracks and the surface wind field. This wind- forced feedback loop, which had been at work in the past three decades, was disrupted in late 2017 when the Kuroshio south of Japan changed to a large meander path, a manifestation of intrinsic western boundary current variability. Three testable hypotheses have been identified: Hypothesis 1: The 2017 KE index reversal caused the LM occurrence; Hypothesis 2: The 2017 LM was triggered by enhanced Subtropical Counter Current eddy activity; and Hypothesis 3: Meander-induced KE dynamic state reversal impacts the atmosphere. The first two hypotheses will be examined with the Hallberg Isopycnal Model, modified to a three-layer configuration, which (a) accommodates the interception of layer interfaces by steep bottom topography, (b) allows sea-surface outcropping of isopycnic layers, and (c) has isopycnal coordinates to avoid unphysical diapycnal mixing. Hypothesis 3 will be addressed using the Japan Meteorological Agency’s non-hydrostatic mesoscale model, through a collaboration with Prof. Shusaku Sugimoto of Tohoku University, Japan.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

黑素io当前的衰老变异性来自海洋喷气机的内在动力学和大气 - 海洋反馈过程。日本南部的黑鲁西奥（Kuroshio）独特的路径构型与射流内的内在稳定性不同，以及黑鲁西奥（Kuroshio）的体积和热传输的变化，以及日本下游的黑素座扩展（KE）位置。该位置会影响空气相互作用的特征和强度，而黑鲁希奥变异性则反过来。这项研究将检查控制路径和稳定状态之间转移的机制，以及影响变异性的内在海洋动力学和空气反馈之间的相互作用。该提案的科学目标是（1）确定日本南部的内在黑鲁道路径可变性改变了KE动态状态，以及它如何与由盆地尺度风力强迫控制的KE变异性竞争，（2）阐明了最近的kuroshio大型曲折（LM）贡献（3）的动态（3），（3）量化的动态（3）在修改大气循环时，由于最近的KE动态状态变化而导致的中尺度涡流。该项目将使用面向过程的海洋和大气数值建模来解决系统变异性。黑鲁西奥和KE是气候变异性的重要组成部分，影响了北太平洋生态系统和盆地规模的天气模式，这都是重要的社会相关性。计划了学生参与和国际合作。在过去几十年中，高质量卫星/现场观察的积累以及最先进的海洋/气氛通用循环模型的改善已经显着改善了对KE在衰老的北太平洋气候变异性中发挥的作用的理解。特定的反馈回路涉及风力的内部海洋热跃层调节，随后对KE动态状态的改变以及KE对暴风雨和表面风场的影响。过去三十年来一直在工作的风反馈循环在2017年底被破坏了，当时日本南部的黑鲁希奥（Kuroshio）变成了一条大的蜿蜒路径，这表现出了内在的西部边界电流变异性的表现。已经确定了三个可检验的假设：假设1：2017 KE索引逆转了LM的出现；假设2：2017年LM是由增强的亚热带计数器当前涡流活动引发的。和假设3：曲折诱导的KE动态状态逆转影响大气。前两个假设将使用Hallberg Isopycnal模型进行检查，并修改为三层配置，（a）可以通过钢底部地形来容纳图层接口的拦截，（b）允许对等异含量层的露面，（c）（c）（c）具有异位均状物，以避免均匀的透明含量杂种。假设3将使用日本气象局的非静态中尺度模型来解决，这将通过与日本东北大学的Shusaku Sugimoto教授的合作。这项奖项反映了NSF的法定任务，并通过使用该基金会的知识分子功能和广泛的影响来评估NSF的法定任务，并被认为是诚实的支持。