Collaborative Research: Investigating the Asymmetric and Temporally Varying Nature of Gulf Stream Ring Formation

合作研究：调查墨西哥湾流环形成的不对称和随时间变化的性质

• 批准号: 2122726
• 负责人: Glen Gawarkiewicz
• 金额: $ 57.27万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2122726&HistoricalAwards=false
• 关键词: Collaborative; Research; Investigating; Asymmetric; Temporally

As the vigorously meandering Gulf Stream (GS) flows between Cape Hatteras and the Grand Banks, this western boundary current extension sheds anticyclonic warm core rings (WCRs) into the Slope Sea and cyclonic cold core rings (CCRs) into the Sargasso Sea. Long term observations indicate asymmetries in the generation of warm- and cold-core rings as well as a regime shift. This study will investigate several hypotheses for the processes behind this variability by fully exploiting existing observational datasets. Identifying the causes and consequences of seasonal and interannual variability in the GS and rings will help clarify the ocean’s role in climate variability and establish to what extent elements of the system are predictable. Reports from the commercial fishing industry note recent increases off New England in warm water species commonly associated with the GS, and hence likely related to WCR activity. Results from this work will be communicated at semi-annual meetings at the Commercial Fisheries Center of Rhode Island and also to the general public through regional and national media. Andres will continue her ongoing outreach efforts with an elementary school that serves a group traditionally underrepresented in STEM. This project will support a graduate student who will be trained in both advanced data analysis and dynamical aspects of the changes in the North Atlantic. The research will generate observation-based derived products (e.g., CCR census, track census, and a regional Argo-Rings census) which will be made available to others.Analysis of four decades of synoptic data based on Clark Analysis Charts demonstrates three characteristics of ring formation that are not yet understood dynamically: (i) the number of WCRs shed in a given year does not equal the number of CCRs (“spatial asymmetry”); (ii) after a striking WCR Regime Shift in 2000, more WCRs are usually formed each year during 2000-2018 than are CCRs; prior to this shift (during 1980-1999) more CCRs were formed than WCRs (“interannual asymmetry”); and (iii) the formation of CCRs peaks in winter/spring, whereas WCR formations peak in summer/fall (“seasonal asymmetry”). Based on these observed asymmetries, it is hypothesized that three different ring-types (“aneurisms”, “pinched-off rings”, and “large-ring splits”) are shed from the Stream, and that each type has distinct characteristics due to its respective formation processes. An additional hypothesis is that an observed spatial asymmetry of relative vorticity across the GS is dynamically linked to the observed asymmetry in the annual rates of WCR versus CCR formations. Finally, it is hypothesized that seasonal changes in stratification contribute to the difference in the seasonality of WCR versus CCR formations and that seasonal asymmetry in ring formation depends on spatial asymmetry in the stratification across the Stream. To investigate each of these asymmetries, existing datasets will be analyzed to test these three hypotheses. First the researchers will identify the conditions which give rise to formation of the different ring-types. Then they will quantify whether (and how) a set of state-space parameters changes and whether these changes are associated with the observed regime shift, in order to determine whether the GS System exhibits multiple equilibria. In addition to using the Clark Chart-derived WCR and CCR Censuses, ring-types and the system’s asymmetries will be explored with along-track satellite altimetry, Argo floats (trajectories and vertical property profiles) and existing regional datasets from the Line W Program (moored and shipboard measurements of velocity and water properties), the Oleander Project (temperature profiles and velocity sections) and the Pioneer Array (velocity, temperature, and salinity). Maps of satellite-measured sea surface height and sea surface temperature will provide spatial and temporal context. The analysis plan includes (i) examining all available along-track altimeter data from 1993-2020 along the GS path (75-55W); (ii) calculating conditional averages selected, for example, by sector, by ring-type, and by focusing on a specific year or season, (iii) characterizing individual ring events that are well-sampled, and (iv) examining the state-space for evidence of multiple equilibria using available and derived long-duration time-series of variables (including relative vorticity, stratification, transport, basin scale winds, sea surface height) to compare and contrast the regime change period of 1997-2003 with a recent possible shift period spanning 2016-2021.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

当墨西哥湾流 (GS) 在哈特拉斯角和大浅滩之间蜿蜒流动时，这种向西边界流的延伸将反气旋暖核环 (WCR) 抛入斜坡海，将气旋冷核环 (CCR) 抛入马尾藻海。观测结果表明，暖核环和冷核环的生成存在不对称性，并且存在状态转变。本研究将通过充分利用现有的观测数据集来研究这种变化背后的过程的几种假设。 GS 和环的季节性和年际变化的原因和后果将有助于阐明海洋在气候变化中的作用，并确定该系统的要素在多大程度上是可预测的。来自商业捕鱼业的报告指出，最近新英格兰海域的温水增加。通常与 GS 相关的物种，因此可能与 WCR 活动相关，这项工作的结果将在罗德岛商业渔业中心举行的半年度会议上公布，并且还将通过地区和国家媒体继续向公众公布。她持续不断的外展努力一所为 STEM 传统上代表性不足的群体提供服务的小学 该项目将支持一名研究生，他们将接受高级数据分析和北大西洋变化动态方面的培训。 、CCR 普查、轨道普查和区域 Argo-Rings 普查），这些数据将提供给其他人。根据克拉克分析图对四十年的天气数据进行的分析表明，环形成的三个特征尚未被动态理解： (i) 某一年的 WCR 数量与 CCR 数量不相等（“空间不对称”）； (ii) 在 2000 年 WCR 制度发生显着转变之后，2000 年至 2018 年期间每年形成的 WCR 数量通常多于是 CCR；在此转变之前（1980-1999 年）形成的 CCR 多于 WCR（“年际不对称”）； (iii) CCR 的形成在冬季/春季达到高峰，而 WCR 的形成在夏季/秋季达到高峰（“季节不对称环”和“大环分裂”）从溪流中脱落，并且每种类型因其各自的形成过程而具有独特的特征。另一个假设是观察到的相对空间不对称性。穿过 GS 的涡度与观测到的 WCR 与 CCR 形成年率的不对称性动态相关。取决于河流分层的空间不对称性。为了研究每一种不对称性，研究人员将分析现有数据集来检验这三个假设。然后，他们将量化一组状态空间参数是否（以及如何）变化以及这些变化是否与观察到的状态转变相关，以确定 GS 系统是否表现出多重平衡。除了使用克拉克图导出的 WCR 和 CCR 普查外，还将利用沿轨卫星测高、Argo 浮标（轨迹和垂直特性剖面）和现有区域数据集来探索环类型和系统的不对称性。 Line W 计划（系泊和船上速度和水特性测量）、Oleander 项目（温度剖面和速度剖面）和 Pioneer Array（卫星测量的海面高度和海面的速度、温度和盐度图）。温度将提供空间和时间背景。 分析计划包括 (i) 检查 1993 年至 2020 年沿 GS 路径 (75-55W) 的所有可用沿轨高度计数据； (ii) 计算所选择的条件平均值，例如按部门、按环类型，并重点关注特定年份或季节，(iii) 描述经过良好采样的各个环事件的特征，以及 (iv) 检查状态-使用可用的和派生的长期时间序列变量（包括相对涡度、分层、运输、盆地尺度风、海面高度）来比较和对比多个平衡的证据空间1997-2003 年，最近可能的转变期为 2016-2021 年。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

项目成果

A Monthly Index for the Large‐Scale Sea Surface Temperature Gradient Across the Separated Gulf Stream

分离湾流大尺度海面温度梯度月度指数

• DOI: 10.1029/2022gl100914
• 发表时间: 2022-12
• 期刊: Geophysical Research Letters
• 影响因子: 5.2
• 作者: Parfitt, R.;Kwon, Y.;Andres, M.
• 通讯作者: Andres, M.

Wind Stress, Wind Stress Curl, and Upwelling Velocities in the Northwest Atlantic (80-45W, 30-45N) during 1980-2019

1980-2019年西北大西洋（80-45W，30-45N）的风应力、风应力旋度和上升流速度

• DOI: 10.5281/zenodo.8200832
• 发表时间: 2023-01
• 期刊: Zenodo
• 作者: Gifford, Ian;Gangopadhyay, Avijit;Andres, Magdalena;Gawarkiewicz, Glen;Oliver, Hilde;Silver, Adrienne
• 通讯作者: Silver, Adrienne