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Upwelling variability in the California Current: bridging local dynamics and climate variability

加州洋流的上升流变化：连接当地动态和气候变化

基本信息

批准号：
1635315
负责人：
Jerome Fiechter
金额：
$ 35.46万
依托单位：
University of California-Santa Cruz
依托单位国家：
美国
项目类别：
Standard Grant
财政年份：
2016
资助国家：
美国
起止时间：
2016-09-15 至 2021-08-31
项目状态：
已结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=1635315&HistoricalAwards=false
关键词：
Upwelling variability California Current bridging

项目摘要

Coastal upwelling research has a long and rich history in the California Current System, yet a comprehensive description of the interplay between physical processes at local, regional, and basin scales has remained elusive. Seasonal upwelling, driven by strong equatorward alongshore winds, plays a fundamental role in shaping the circulation and ecosystem structure along the west coast of the United States. The main objective of this study is to use high-resolution numerical simulations to characterize variability in the full three-dimensional, time varying circulation associated with wind-driven coastal upwelling in the California Current System. More specifically, the model results will be used to: (i) produce a regional synthesis that rigorously identifies and describes regions of enhanced upwelling in the vicinity of major coastal headlands, and (ii) quantify the impact of regional- and basin-scale processes on local-scale upwelling dynamics. This research will provide significant new insight into how regions of enhanced upwelling contribute to shaping alongshore gradients of physical and biogeochemical properties. Of particular relevance is the connection to coastal ocean acidification and the occurrence and persistence of low pH conditions over the continental shelf along the U.S. west coast. Enhanced upwelling centers are likely to play a key role in determining the spatiotemporal variability of nearshore pH levels, and, therefore, alongshore heterogeneity in the short- and long-term ecosystem response to coastal ocean acidification. This study will increase understanding of how much biogeochemical variability is attributable to physical forcing associated with local upwelling dynamics (as modulated by regional- and basin-scale processes), thereby advancing current knowledge of which coastal regions along the U.S. west coast are more prone to frequent and severe acidification events. In addition, the project will support a postdoctoral researcher at UC Santa Cruz who will gain valuable training in state-of-the-art regional ocean circulation modeling and diagnostic methods, such as adjoint-based calculations. Project outcomes will also be integrated into the graduate curriculum at UCSC, and enhance educational tools available for the community-based Regional Ocean Modeling System (ROMS). Finally, the PIs will present general audience lectures at the Seymour Marine Discovery Center in Santa Cruz, as part of an ongoing series on how seasonal California upwelling will respond to changing climate conditions, and the potential impacts on ecosystem processes and socio-economic services. Coastal upwelling trends and variability determined on the basis of coast-wide averages (i.e., integrated over stronger and weaker upwelling regions) likely compound different dynamical processes and may misrepresent the true nature of the local physical and biogeochemical fluctuations occurring along the U.S. west coast. Therefore, this research will provide significant new insight into how regions of enhanced upwelling in the vicinity of major coastal headlands contribute to shaping the coastal ocean circulation and physical variability at local scales. Outcomes from the numerical experiments will also help determine how regional- and basin-scale variability modulates vertical transport and water mass properties in the vicinity of enhanced upwelling centers and surrounding shelf regions. The most innovative aspect of the project is that it will describe the impacts of local-, regional-, and basin-scale processes on the full 3-dimensional, time-varying ocean circulation associated with coastal upwelling, as opposed to relying on traditional upwelling proxies (e.g., Bakun index) which are often unreliable in regions of intense upwelling or strong onshore geostrophic flow. Another important contribution from this research is that it will demonstrate the benefits of downscaling regional data-assimilative solutions to the local scales at which alongshore variability in upwelling dynamics occurs along the U.S. west coast. Finally, the results from the numerical simulations will complement and enhance another research project, funded under NSF's Coastal SEES Program, focused on quantifying the magnitude, frequency of occurence, and predictability of low pH events along California, as well as their potential impact on coastal ecosystem processes.

海岸上升流研究在加州海流系统中有着悠久而丰富的历史，但在地方、区域和流域尺度上物理过程之间的相互作用的全面描述仍然是难以捉摸的。季节性上升流，由强烈的赤道沿岸风驱动，在塑造美国西海岸沿着的环流和生态系统结构方面起着重要作用。本研究的主要目的是使用高分辨率的数值模拟来表征变异的全三维，随时间变化的环流与风驱动的海岸上升流在加州电流系统。更具体地说，模型结果将用于：（一）产生一个区域综合，严格识别和描述主要沿海岬附近的上升流增强区域，以及（二）量化区域和流域尺度过程对局部尺度上升流动力学的影响。这项研究将提供重要的新的见解，如何增强上升流的地区有助于塑造沿岸梯度的物理和地球化学性质。特别相关的是与沿海海洋酸化以及美国西海岸沿着大陆架上低pH值条件的发生和持续的联系。增强的上升流中心可能发挥关键作用，在确定近岸pH值的时空变化，因此，沿岸的异质性在短期和长期的生态系统响应沿海海洋酸化。这项研究将增加了解有多少地球化学变化是由于物理强迫与当地的上升流动力学（调制区域和流域尺度的过程），从而推进目前的知识，沿海地区沿着美国西海岸更容易频繁和严重的酸化事件。此外，该项目将支持加州大学圣克鲁斯的博士后研究员，他将获得最先进的区域海洋环流建模和诊断方法的宝贵培训，例如基于伴随的计算。项目成果还将纳入UCSC的研究生课程，并增强基于社区的区域海洋建模系统（ROMS）的教育工具。最后，PI将在圣克鲁斯的西摩海洋发现中心为普通观众举办讲座，作为正在进行的系列讲座的一部分，该系列讲座将介绍季节性加州上升流如何应对气候条件的变化，以及对生态系统过程和社会经济服务的潜在影响。根据沿岸平均值确定的沿岸上升流趋势和变化（即，综合了较强和较弱的上升流区域）可能复合不同的动力学过程，并可能歪曲了沿着美国西海岸发生的当地物理和地球化学波动的真实性质。因此，这项研究将提供重要的新的见解，在主要沿海岬附近的上升流增强的地区如何有助于塑造沿海海洋环流和物理变化在当地尺度。从数值实验的结果也将有助于确定如何区域和流域尺度的变化调制垂直输送和水团特性增强的上升流中心和周围的货架区域附近。该项目最具创新性的方面是，它将描述当地、区域和流域尺度过程对与沿海上升流相关的全三维、时变海洋环流的影响，而不是依赖传统的上升流代理（例如，巴肯指数），这往往是不可靠的地区，强烈的上升流或强烈的陆上地转流。这项研究的另一个重要贡献是，它将展示降尺度的区域数据同化解决方案的好处，在当地尺度上，沿岸变化的上升流动力学发生沿着美国西海岸。最后，数值模拟的结果将补充和加强另一个研究项目，该项目由NSF的沿海SEES计划资助，重点是量化加州低pH值事件的幅度，发生频率和可预测性，以及它们对沿海生态系统过程的潜在影响。