Role of Mesoscale Eddies in Ventilation of the Southern Ocean

南大洋及其与大气的相互作用在海洋和气候动力学中起着重要作用。然而，控制南大洋表面和内部之间交流的过程（“通风”）仍然知之甚少。一个主要的挑战来自中尺度涡旋的重要和复杂的作用。涡旋输运的空间分布是复杂的，涡旋的影响是极其丰富的。这种复杂性的重要性还没有得到系统的评估。该项目的主要目标是分析中尺度涡旋在南大洋上层（2000米以上）水域通风中的作用。研究了涡旋输运的大尺度空间变化、各向异性、输运障碍、相干涡旋平流和非扩散效应等特性的重要性。主要的假设是，上面列出的涡流及其性质在南大洋的通风中起着重要作用。为此，将通过研究涡流在被动示踪剂（理想化和氯氟化碳）分布中的重要性，分析涡流如何直接影响通风。具体目标是：(i)分析涡旋通量散度和涡旋扩散率的分布，并研究它们与其他物理过程的关系；（ii）研究涡旋对南大洋上部主要水团通风的重要性；（iii）识别涡旋输送的特定性质，例如它们的各向异性结构，这对南大洋的通风最为重要。这些目标将通过一套精心设计的数值实验来实现，以隔离涡流的直接影响。特别是，在有和没有涡旋的情况下，用规定的平流速度分析离线模拟的方法将使研究人员能够分离和分析涡旋对南大洋通风的影响。知识价值：该项目正在解决涡旋在南大洋通风中的作用这一根本性的重要问题。提出的研究是基于一种技术，使研究人员能够最准确地分离出涡流对示踪剂分布和通风的直接影响。这是第一次可以定量地检验这些影响的重要性。涡流对理想被动示踪剂和氟氯化碳分布的主要影响可以预期适用于动态主动示踪剂，如密度和位涡量。众所周知，理解后一种影响的进展是具有挑战性的，并将极大地受益于所提出的分析。更广泛的影响：了解和量化涡旋在发展南大洋水域混合历史中的作用，对南大洋与全球其他海洋之间的气体（氯氟烃、二氧化碳、氧气）和营养物质的交换和输出具有重要意义。识别需要在模型中精确表示的最重要的涡流效应将使建模界受益。最后，该项目将有助于观测数据集的解释和未来观测策略的规划。在教育和培训方面，博士后将提高他对控制海洋通风和重新分配瞬态海洋示踪剂的过程的理解，并将学习各种数值模拟的定量分析技术及其与数据的比较。其中一名研究人员参与了一些针对科学界代表性不足的群体——女性——的推广活动。她曾在指导物理海洋学女性提高保留率（MPOWIR）指导委员会任职，参加了两次Pattullo会议，并领导了一个MPOWIR指导小组。她也是迈阿密大学NSF-Advance项目指导委员会成员。

The Southern Ocean and its interactions with the atmosphere play an important role in the ocean and climate dynamics. The processes that govern the communication between the surface and the interior of the Southern Ocean ("ventilation") remain, however, poorly understood. A major challenge comes from the essential and complex role of mesoscale eddies. The spatial distribution of the eddy transports is complicated, and the effects of eddies are incredibly rich. The importance of this complexity has not been systematically evaluated.The main goal of this project is to analyze the role of mesoscale eddies in ventilation of the upper waters (top 2000 meters) of the Southern Ocean. The importance of such properties of the eddy transports as large-scale spatial variations, anisotropy, transport barriers, advection by coherent vortices and non-diffusive effects will be investigated. The main hypothesis is that eddies and their properties listed above play an important role in ventilation of the Southern Ocean. To that effect, an analysis of how ventilation is directly affected by eddies, by studying the importance of eddies in the distribution of passive tracers (idealized and Chlorofluorocarbons) will be undertaken.Specific objectives are to: (i) analyze distributions of the eddy flux divergences and eddy diffusivities, and study their relationship to other physical processes; (ii) examine the importance of eddies for ventilation of the major water masses of the upper Southern Ocean; (iii) identify specific properties of eddy transports, such as their anisotropic structure, that are the most important for the ventilation of the Southern Ocean. These objectives will be achieved using a suite of numerical experiments that are carefully designed to isolate the direct effects of eddies. In particular, the method of analyzing offline simulations with prescribed advective velocities with and without eddies will enable the investigators to isolate and analyze the effects of eddies on ventilation of the Southern Ocean.Intellectual Merit: This project is addressing the fundamentally important problem of the role of eddies in ventilation the Southern Ocean. The proposed research is based on a technique that allows the investigators to most accurately isolate the direct effects of eddies on tracer distributions and ventilation. For the first time, the significance of these effects can be examined quantitatively. Main effects of eddies on distribution of idealized passive tracers and CFCs can be expected to be applicable to dynamically active tracers, such as density and potential vorticity. The progress in understanding the latter effects is notoriously challenging and will greatly benefit from the proposed analysis.Broader Impacts: Understanding and quantifying the role of eddies in developing the mixing history of Southern Ocean waters has important implications for exchange and export of gases (Chlorofluorocarbons, Carbon Dioxide, Oxygen) and nutrients between the Southern Ocean and the rest of the global oceans. The identification of the most important eddy effects that require accurate representation in models will benefit the modeling community. Finally, this project will aid in the interpretation of observational data sets and in the planning of future observational strategies In terms of education and training, a post-doctoral fellow will advance his understanding of processes that govern ventilation of the oceans and redistribute transient oceanic tracers, and will learn various techniques of quantitative analysis of numerical simulations and their comparisons with data. One of the investigators is involved in several outreach activities for an under-represented group in science: women. She has served on the Mentoring Physical Oceanography Women to Increase Retention (MPOWIR) steering committee, participated in two Pattullo Conferences, and leads an MPOWIR mentoring group. She is also on the Steering Committee for the University of Miami's NSF-Advance program.