Collaborative Research: Vortex dynamics and interannual variability in the Labrador Sea

合作研究：拉布拉多海的涡动力学和年际变化

• 批准号: 0751697
• 负责人: Jonathan Lilly
• 金额: $ 19.74万
• 依托单位: Earth and Space Research
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-03-15 至 2010-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0751697&HistoricalAwards=false
• 关键词: Collaborative; Research; Vortex; dynamics; interannual

Accumulating evidence suggests that deep convective ventilation in the Labrador Sea is partly controlled by mechanisms other than local surface forcing and local density gradients. It now appears that there exists an active eddy-driven restratification which is modulated by variations in boundary current dynamics. Large inter-annual variations in both eddy shedding and buoyancy transport from the boundary current have been observed but not explained. This project will investigate the processes controlling eddy generation and associated buoyancy transport by combining realistic and idealized numerical modeling, data analysis, and theory. Ensembles of numerical experiments with a high-resolution regional model will explore the sensitivity of eddy generation and property transport to variations in local and external forcing parameters. Extended analysis of eddy and boundary current properties in data, centrally the now fifteen-year TOPEX/Poseidon and Jason altimeter records, will allow comparison of modeled and actual vortex characteristics over a wide range of oceanic conditions. Theory, supported by idealized experiments, will provide criteria to test candidate hypotheses as to the nature of the instability, and will suggest possibilities for its parameterization. The net result will be an understanding of the links between local and non-local forcing variability, and the eddy-driven buoyancy fluxes which limit deep convection. This process-oriented study should form an important step toward the larger goal of understanding and accurately modeling variability of the Atlantic Meridional Overturning Circulation in general.Intellectual Merit: This work has a direct benefit to the representation of the Labrador Sea branch of the Atlantic Meridional Overturning Circulation (AMOC) in large-scale climate models, in which details of the narrow boundary current instability are not possible to resolve. In the face of dramatically increasing freshwater discharge from the Arctic, it is critical to understand the transport of buoyancy from boundary current to the convection region, and in particular, to identify the factors underlying its variability. Furthermore, this collaborative project will contribute to the broader effort of realistically representing the effects of mesoscale features on the large-scale circulation in coarse-resolution numerical models.Broader Impacts: The primary societal benefit of this work is its relevance to understanding and possibly predicting variations of the AMOC. Results will be presented in graduate classes by two of the investigators, A. Bracco at Georgia Tech and J. Pedlosky at WHOI-MIT. The two graduate students supported by the project will benefit from exposure to modeling, analytical investigation and data analysis techniques. Analysis algorithms developed in this work will be freely distributed to the greater scientific community, by inclusion in JLAB, J. M. Lilly?s open-source software package for Matlab. The proposed research will also be incorporated into teaching material for high school teachers in the Atlanta area, with the support of the Center for Education Integrating Science, Mathematics and Consulting (CEISMC).

越来越多的证据表明，拉布拉多海的深层对流通风部分受到局部表面强迫和局部密度梯度以外的机制控制。现在看来，存在一种活跃的涡流驱动的再分层现象，它受到边界流动力学变化的调节。已经观察到涡流脱落和边界流浮力传输存在较大的年际变化，但尚未得到解释。该项目将通过结合现实和理想化的数值建模、数据分析和理论来研究控制涡流产生和相关浮力传输的过程。具有高分辨率区域模型的数值实验集合将探索涡流产生和属性传输对局部和外部强迫参数变化的敏感性。对数据中涡流和边界流特性的扩展分析，主要是现在十五年的 TOPEX/Poseidon 和 Jason 高度计记录，将允许在广泛的海洋条件下比较模型和实际涡流特征。由理想化实验支持的理论将提供测试关于不稳定性本质的候选假设的标准，并将提出其参数化的可能性。最终结果将是了解局部和非局部强迫变化之间的联系，以及限制深层对流的涡流驱动的浮力通量。这项以过程为导向的研究应该是朝着理解和准确模拟大西洋经向翻转环流变化的更大目标迈出的重要一步。智力价值：这项工作对大西洋经向的拉布拉多海分支的代表性有直接的好处大规模气候模型中的翻转环流（AMOC），其中窄边界流不稳定的细节无法解决。面对北极淡水排放量的急剧增加，了解浮力从边界流到对流区域的传输至关重要，特别是确定其变化背后的因素。此外，这个合作项目将有助于更广泛的努力，在粗分辨率数值模型中真实地表示中尺度特征对大尺度环流的影响。更广泛的影响：这项工作的主要社会效益是它与理解和可能预测的相关性AMOC 的变体。结果将由两名研究人员在研究生班上公布，他们是佐治亚理工学院的 A. Bracco 和 WHOI-MIT 的 J. Pedlosky。该项目支持的两名研究生将受益于建模、分析调查和数据分析技术。这项工作中开发的分析算法将通过包含在 JLAB（J. M. Lilly 的 Matlab 开源软件包）中免费分发给更大的科学界。在科学、数学和咨询教育综合中心（CEISMC）的支持下，拟议的研究还将被纳入亚特兰大地区高中教师的教材中。