Abstract. Mesoscale eddies affect phytoplankton in several ways, including the horizontal dispersal and mixing of populations. Coherent eddies trap and contain fluid masses, whereas other eddies mix more freely with surrounding waters. To evaluate the role of lateral dispersal and trapping on the biogeochemical properties of eddies, we must accurately characterize their coherency. We employed a Lagrangian approach to identify materially coherent structures in remote sensing observations and developed a methodology to track them over their entire individual lifetimes. We provide an atlas of two decades of coherent eddies with an 8 d resolution in an intensely studied region of the North Pacific Subtropical Gyre (Jones-Kellett, 2023a, https://doi.org/10.5281/zenodo.8139149). The atlas was specifically designed to facilitate biogeochemical applications and was synchronized with available ocean color products. We identified coherent features using backward Lagrangian trajectories because the recent history of coherency (rather than the future coherency) will be most valuable for interpreting associated biogeochemical signatures. We compared the atlas of Lagrangian coherent eddies with an atlas of Eulerian eddies identified using the more conventionally used Sea Level Anomaly method. Although 65 % of tracked Sea Level Anomaly eddies are classified as coherent at some point in their lifetime, only 54 % contain a Lagrangian coherent structure at any given time. We found similar variations in the temporal and spatial distributions of coherent and Sea Level Anomaly eddies. However, strictly coherent eddies have a clearer relationship between size and longevity and form distinct regional regimes based on polarity. We illustrate the potential of the coherent eddy atlas for biogeochemical applications by examining the relationship between bloom development and eddy evolution in a case study of a Hawaiian Lee cyclone.

中文翻译：

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用于北太平洋副热带环流生物地球化学应用的拉格朗日相干涡流图集

摘要。中尺度涡流以多种方式影响浮游植物，包括种群的水平扩散和混合。相干涡流捕获并容纳流体团，而其他涡流则更自由地与周围的水域混合。为了评估横向扩散和捕获对涡流生物地球化学特性的作用，我们必须准确地表征它们的相干性。我们采用拉格朗日方法来识别遥感观测中的物质相干结构，并开发了一种方法来跟踪它们的整个生命周期。我们提供了北太平洋副热带环流经过深入研究的区域中二十年分辨率为 8 d 的相干涡流图集（Jones-Kellett，2023a，https://doi.org/10.5281/zenodo.8139149）。该图集专门为促进生物地球化学应用而设计，并与现有的海洋颜色产品同步。我们使用向后拉格朗日轨迹识别了相干特征，因为最近的相干性历史（而不是未来的相干性）对于解释相关的生物地球化学特征将是最有价值的。我们将拉格朗日相干涡流图集与使用更常用的海平面异常方法识别的欧拉涡流图集进行了比较。尽管 65% 的跟踪海平面异常涡旋在其生命周期的某个时刻被归类为相干涡流，但只有 54% 在任何给定时间都包含拉格朗日相干结构。我们发现相干涡流和海平面异常涡流的时间和空间分布存在类似的变化。然而，严格相干的涡流在大小和寿命之间具有更清晰的关系，并根据极性形成不同的区域机制。我们通过在夏威夷李旋风的案例研究中检查水华发展和涡流演化之间的关系，说明了相干涡流图集在生物地球化学应用中的潜力。