Collaborative Research: Eddy-Dynamics and Impacts of Low-Frequency Variations in the California Current System

加州洋流系统(CCS)是一个东部边界地区，毗邻美国的主要人口中心之一，具有非常高的生物生产力。这个项目将验证最近的观测调查提出的假设，即该地区的天气海洋涡旋在控制其低频变化方面发挥了主要作用。具体地说，这项工作将(I)研究内部和外部强迫的中尺度涡旋变化对CCS温度、盐度和洋流年际和年代际变化的影响，(Ii)诊断天气海洋对与厄尔尼诺相关的局部大气强迫和与厄尔尼诺有关的远程海洋强迫和北太平洋环流调整的天气海洋响应(涡量场)的动力学，(Iii)确定来自沿海上升流系统的示踪物分布模式，以及(Iv)探索东北太平洋温跃层对CCS变化的响应。这些研究的主要工具是高分辨率嵌套海洋模式(ROMS)，通过它们现有的伴随线性码和切线性码进行扩充。模式域包括整个太平洋，以提供大尺度条件，以及CCS地区非常高分辨率的区域嵌套区。区域模拟将选择性地应用气候或依赖于时间的大气和海洋边界条件，以隔离海洋内在变异性、大气强迫和远程海洋强迫的影响。特别值得注意的是地表淡水通量公式，它不会使用表面松弛的非物理反馈来参考表面盐度。这些实验的比较将使我们能够确定不同强迫的影响和内在海洋过程的作用。对这些运行的分析将包括：(1)动量、盐度和涡度的预算计算，以确定海洋天气变化在CCS低频变化中的作用，(2)EOFS和谱分析，以统计地描述预算项中的动力关系，并分离海洋过程的特征，(Iii)用切线和伴随模式进行稳定度和敏感性分析，以诊断不同环流和强迫制度期间涡旋的产生机制和动力学，以及(Iv)被动示踪剂的概率分布函数，以进一步阐明来自和进入上升流系统的搅拌和混合路径。智力优势：本研究旨在增加对东部边界地区海洋内在变化的作用和动力学的理解，以及它们在激发和影响区域和大尺度低频气候变化中的作用。这对于理解和预测这些高产的沿海上升流系统的物理、化学和生物学是至关重要的。特别是，这项研究将集中在加利福尼亚州当前的海岸上升流系统，这是美国渔业的主要经济资源。广泛的影响：我们对CCS中观测到的长期变化进行建模的能力的改进将直接应用于NSF长期生态研究站点(LTER)在斯克里普斯的加州当前海岸远洋生态系统中的非线性转变项目。LTER的任务之一是使用CCS的物理-生物模型来检验关于生态系统变化的假设。对涡旋变化和混合路径的动力学推断，在NSF-全球生态系统研究(GLOBEC)中有直接的应用。主要研究人员定期与参与GLOBEC的一些科学家交流，并将迅速分享这项研究的结果。佐治亚理工学院的调查员将参加K-12教育外联活动，在由科学、数学和咨询教育中心(CEISMC)组织的夏令营活动中为高中生举办为期一天的“实践经验”海洋学。作为这一外联活动的一部分，还将在佐治亚理工学院为来自亚特兰大富尔顿县的六年级教师举办两次海洋学教育课程。

The California Current System (CCS) is an eastern boundary region with a very high biological productivity adjacent to one of the main population centers of the United States. This project will test the hypothesis, suggested by recent observational investigations, that synoptic ocean eddies in the region play a major role in controlling its low frequency variations.. Specifically, the work will (i) study the impacts of intrinsic and externally forced mesoscale eddy variability on the inter-annual and decadal changes of temperature, salinity and currents in the CCS, (ii) diagnose the dynamics of the synoptic ocean response (the eddy field) to transient local atmospheric forcing and to remote oceanic forcing associated with El Nino and the adjustments of the North Pacific gyre, (iii) identify the patterns of tracer distribution from and to the coastal upwelling system and (iv) explore the response of the North East Pacific thermocline to variations in the CCS.The primary tools for these studies are high resolution, nested, ocean models (ROMS), augmented by their existing Adjoint and Tangent Linear codes. Model domains include the entire Pacific, to supply the large scale conditions, and regional nested areas of very high resolution in the CCS region. The regional simulations will selectively apply climatological or time dependent atmospheric and oceanic boundary conditions to isolate influences of ocean intrinsic variability, of atmospheric forcing and of remote ocean forcing. Of special note are the surface fresh water fluxes formulations, which will not use the unphysical feedback of surface relaxation to reference surface salinity. The comparison of these experiments will allow the identification of the impacts of the different forcing and the role of intrinsic ocean processes. Analysis of these runs will include (i) budget calculations for momentum, salinity and vorticity to determine the role of ocean synoptic variations in the low frequency changes of the CCS, (ii) EOFs and spectral analysis to statistically characterize the dynamical relationships in the budget terms and isolate the signature of oceanic processes, (iii) stability and sensitivity analysis with the tangent linear and adjoint models to diagnose the generating mechanisms and dynamics of the eddies during different circulation and forcing regimes and (iv) probability distribution functions for passive tracers to further clarify the stirring and mixing pathways from and to the upwelling system.Intellectual Merits: This study aims to increase understanding of the role and dynamics of ocean intrinsic variations of the eastern boundary regions, and their role in energizing and affecting the regional and large-scale low-frequency climate variations. This is essential to the understanding and prediction of the physics, chemistry and biology of these highly productive coastal upwelling systems. In particular this study will focus on the California Current coastal upwelling system, a major economical resource for US fisheries.Broader Impacts: The improvements in our ability to model observed long-term variability in the CCS will directly be available to a related NSF Long Term Ecological Research Site (LTER) sponsored program on Nonlinear Transitions in the California Current Coastal Pelagic Ecosystem at Scripps. Among the LTER tasks is the use of physical-biological models of the CCS to test hypothesis on ecosystem changes. The dynamical inferences on the changes eddy variance and mixing pathways, have direct application in the NSF-GLOBal Ecosystems studies (GLOBEC). The principal investigators communicate on a regular basis with some of the scientists involved in GLOBEC and will promptly share the results of this research. The investigator at the Georgia Institute of Technology will participate in K-12 educational outreach, to promote oceanography in a one day "hands on experience' for high school students during the summer camps activity organized by the Center for Education Integrating Science, Mathematics and Consulting (CEISMC). Two oceanography education sessions for 6th grade teacher from Fulton County, Atlanta, will also be held at Georgia Tech as part of this outreach activity.