Cuddy Decay: Observation of Subthermocline Eddy Spindown and Property Exchange

卡迪衰变：亚温跃层涡旋下降和属性交换的观察

• 批准号: 1153980
• 负责人: Charles Eriksen
• 金额: $ 89.74万
• 依托单位: University of Washington
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-03-01 至 2017-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1153980&HistoricalAwards=false
• 关键词: Cuddy; Decay; Observation; Subthermocline; Eddy

This is a project to study the decay of a subthermocline eddy as it travels from near its generation site in the California Undercurrent (CU) over the continental slope into offshore waters. The CU, a prominent element of the California Current System (CCS), transports relatively warm, saline, anoxic Pacific Equatorial Water north along the North American west coast. Temperature and salinity generally decrease both poleward and offshore, while dissolved oxygen increases, as the CU spins off long lived eddies transporting its water properties away from the CCS into the eastern Pacific. These eddies, nicknamed cuddies for their origin, have been tracked by solitary floats for many months and surveyed hydrographically on occasion, but their structural evolution as they decay has yet to be observed. They take the form of submesoscale coherent vorticies and are largely invisible to remote sensing techniques due both to their small size and subsurface intensification. The extent to which cuddies contribute to broad scale property gradients in the CCS and beyond is tied to the evolution of their radial-vertical structure.This study will use a pair of extended-range Seagliders to frequently survey a cuddy over many months as it travels. A cuddy will be identified and located for study by an ongoing Seaglider repeat transect, separately supported by NOAA and maintained by University of Washington colleagues. With improvements to performance efficiency, Seagliders are projected to be capable of operating as long as a year while transmitting slanting profiles of upper-ocean structure ashore in near real time. Simultaneous transects at 4-6 km resolution along nearly perpendicular paths repeated every week or less over the course of ten months appear feasible, with an additional two months of mission time devoted to reaching from and returning to the coastal region for launch and recovery. The sequence of approximately 50 three-dimensional surveys of a cuddy will be used to observe its decay rate, associated frequency and intensity of fine scale stratification features, and changes in vertical-radial structure.The observed structural evolution of a subsurface eddy will be used to infer the exchange rates of physical, chemical, and biological properties with the surrounding waters. While cuddies are widely suspected to be important agents of property exchange in the CCS, the observations proposed will be the first to describe a cuddy in four dimensions over an appreciable portion of its lifetime.This study will contribute to understanding of eddy transport in general and the role of submesoscale coherent vorticies in particular in transmitting eastern boundary region properties to the ocean interior. Implications of eddy transport are important not only to physical distributions in the ocean, but to chemical and biological ones as well. The project will train a graduate student to be expert in an emerging observational technique as well as in the role of eddies in ocean circulation.

该项目旨在研究温跃层下涡流从加利福尼亚暗流 (CU) 生成点附近越过大陆坡进入近海水域时的衰变。 CU 是加州洋流系统 (CCS) 的一个重要组成部分，它沿着北美西海岸向北输送相对温暖、含盐分高、缺氧的太平洋赤道水。 向极地和近海的温度和盐度通常会降低，而溶解氧会增加，因为 CU 会产生长期存在的涡流，将其水特性从 CCS 输送到东太平洋。 这些漩涡因其起源而被昵称为“可爱的漩涡”，已经被单独的浮标追踪了好几个月，并偶尔进行了水文测量，但它们在衰变过程中的结构演变仍有待观察。 它们采取亚中尺度相干涡旋的形式，并且由于其尺寸小和地下强化，遥感技术在很大程度上是不可见的。 小块对 CCS 及其他区域的大尺度属性梯度的贡献程度与其径向垂直结构的演变有关。本研究将使用一对增程海滑翔机在小块旅行的数月内频繁地对其进行调查。 正在进行的 Seaglider 重复横断面将确定并定位一个小窝，以供研究，该横断面由 NOAA 单独支持并由华盛顿大学同事维护。 随着性能效率的提高，Seagliders预计能够运行长达一年，同时近乎实时地将上层海洋结构的倾斜剖面传输到岸上。 在十个月的时间里，沿着几乎垂直的路径每周或更短时间重复一次以 4-6 公里分辨率同时进行横断面似乎是可行的，另外两个月的任务时间专门用于往返于沿海地区进行发射和回收。 对卡迪进行大约 50 次三维勘测的序列将用于观察其衰减率、相关频率和精细尺度分层特征的强度以及垂直径向结构的变化。将使用观测到的地下涡流的结构演化推断与周围水域的物理、化学和生物特性的交换率。 虽然人们普遍怀疑卡迪是 CCS 中财产交换的重要媒介，但所提出的观察结果将是第一个在四个维度上描述卡迪在其生命周期的相当一部分内的观察结果。这项研究将有助于理解涡流输运的一般情况和亚中尺度相干涡旋的作用，特别是在将东部边界区域特性传输到海洋内部方面。涡流输送的影响不仅对海洋中的物理分布很重要，而且对化学和生物分布也很重要。该项目将培训一名研究生，使其成为新兴观测技术以及涡流在海洋环流中的作用的专家。