Collaborative Research: Submesoscale Dynamics over the Continental Shelf: Drivers and Implications for Across-Shelf Exchange

该项目研究大陆架上小尺度（2- 10公里）沿海洋流搅动水团并促进海岸和公海之间物质运输的机制。将部署一个独特的高频雷达系统阵列，以高空间分辨率测量表面电流。这些测量将能够解决大小范围从2？新英格兰大陆架（内斯）上方20 km。所要覆盖的大陆架区域离岸30至80公里，水深30至70米。这些表面电流测量将通过使用水下仪器进行同步水下测量来增强，而自主表面车辆和漂移器将用于测量中架速度结构，精细尺度水平梯度和漂移器轨迹。对收集到的数据进行分析，将增进我们对沿海与广阔大陆架上的公海之间物质交换的了解。这种交换对海洋地球化学、大陆架生产力、渔业、污染物的迁移以及确定热量和淡水收支都有影响;这是诊断大陆架生态系统变异性的关键一步，可提高其可预测性，从而有助于更好地区分人为和自然生态系统变化。拟议的高频雷达测量将输入NOAA运营的国家高频雷达网络，数据将用于沿海海洋模型的数据同化以及支持搜索和救援的轨迹参数化以及污染应对。该项目将通过为伍兹霍尔海洋研究所的暑期学生研究员提供研究机会来促进教育，并使来自美国海岸加德学院（一个以本科教学为重点的机构）的本科生能够参与实地工作，并将研究活动纳入其高级项目。通过在整个年度周期内以约2公里分辨率测量新英格兰大陆架1 200平方公里的表面速度场，该项目将确定涡流场的动态变化和季节性特征。这项工作将确定导致次中尺度海流变异和跨大陆架水团和性质交换的过程和参数。该研究假设涡动变率是由斜压不稳定性驱动的，但与风和底应力有着内在的联系，这会产生空间和时间变化的埃克曼电流和剪切诱导的混合，可以对抗或加强锋面环流。观测结果将被用来确定如何涡流动力学调制的横向和垂直浮力梯度的季节性周期内的内斯。将使用示踪剂和粒子来计算观测到的表面速度范围内的弥散和涡流通量，同时将使用漂移器来获得实地的直接测量值，从而评估中尺度动力学在跨大陆架交换中的作用。所有的估计将合成与我们的动态特性的漩涡，以了解在不同的季节和它们的重要性，相对于大规模的交换机制，导致跨大陆架运输的过程。

This project studies the mechanisms by which small scale (2-10km) coastal oceanic flows, over the continental shelf can stir the water masses and contribute to the transport material between the coast and the open ocean. A unique array of high frequency (HF) radar systems will be deployed to measure surface currents at high spatial resolution. These measurements will be able to resolve eddies with sizes ranging from 2 ? 20 km that are present over the New England Shelf (NES). The shelf area to be covered extends 30 to 80 km offshore, with water depths of 30 to 70 m. These surface current measurements will be augmented by simultaneous underwater measurement using a submerged instrumentation, while autonomous surface vehicles and drifters will be used to measure mid-shelf velocity structure, fine-scale horizontal gradients, and drifter trajectories. The analysis of the data collected will increase our understanding of exchange of material between the coast and the open ocean over a broad continental shelf. This exchange has implications for biogeochemistry, shelf productivity, fisheries, transport of pollutants, as well as for determining heat and freshwater budgets; this is a crucial step in diagnosing shelf-wide ecosystem variability, improving its predictability and thus contributing to better discriminating between anthropogenic and natural ecosystem changes. The proposed HF radar measurements will feed into the National High Frequency Radar (HFR) Network operated by NOAA and the data will be available for data assimilation into coastal ocean models as well as trajectory parameterizations that support search and rescue, and pollution responses. The project will contribute to education by providing the research opportunities for summer student fellows at the Woods Hole Oceanographic Institution and enable undergraduate students from the US Coast Gard Academy, an undergraduate teaching-focused institution, to participate in the field work and incorporate research activities into their senior projects. By measuring the surface velocity fields at about 2 km resolution over 1,200 square kilometers of the New England Shelf (NES) through an entire annual cycle the project will characterize the dynamical variability and seasonality of the eddy field. This work would identify processes and parameters that lead to submesoscale current variability and the across-shelf exchange of water masses and properties. The study hypothesizes that eddy variability is driven by baroclinic instability, but is intrinsically linked with wind and bottom stress, which generate spatially and temporally varying Ekman currents and shear-induced mixing that can oppose or reinforce frontal circulations. The observational results will be used to identify how eddy dynamics are modulated by the seasonal cycle of lateral and vertical buoyancy gradients within the NES. The role of submesoscale dynamics in across-shelf exchange will be assessed using tracers and particles to calculate dispersion and eddy fluxes both within the observed surface velocities, while drifters will be used to gain a direct measure in the field. All estimates will be synthesized with our dynamical characterization of the eddies to gain an understanding of the processes leading to across-shelf transport in different seasons and their importance relative to larger-scale exchange mechanisms.