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.

当蜿蜒的墨西哥湾流（GS）在哈特拉斯角和大浅滩之间流动时，这种西部边界流延伸将反气旋暖核环（WCRs）送入坡海，将气旋冷核环（CCRs）送入马尾藻海。长期观测表明，暖核环和冷核环的产生存在不对称性，也存在一种状态转移。这项研究将通过充分利用现有的观测数据集来调查这种变异性背后的过程的几个假设。确定GS和年轮的季节和年际变化的原因和后果将有助于澄清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，最近新英格兰地区暖水物种的增加通常与GS有关，因此可能与WCR活动有关。这项工作的结果将在罗德岛商业渔业中心的半年度会议上公布，并通过区域和国家媒体向公众公布。安德烈斯将继续在一所小学开展她正在进行的外展工作，该小学为传统上在STEM中代表性不足的群体提供服务。该项目将支持一名研究生，他将接受高级数据分析和北大西洋变化动态方面的培训。这项研究将产生基于观测的衍生产品（例如，CCR普查、轨道普查和区域Argo-Rings普查），这些产品将提供给其他人。基于Clark分析图的40年天气数据分析表明，环的形成有三个尚未被动态理解的特征：(i)给定年份的wcr数量与ccr数量不相等（“空间不对称”）；（ii）在2000年显著的WCR制度转变之后，2000-2018年期间每年形成的WCR通常比ccr多；在此转变之前（1980-1999年），ccr的形成多于wcr（“年际不对称”）；(3) ccr的形成高峰在冬/春，而WCR的形成高峰在夏/秋（“季节不对称”）。基于这些观察到的不对称性，我们假设三种不同类型的环（“动脉瘤”、“夹断环”和“大环裂”）从流中脱落，每种类型由于其各自的形成过程而具有不同的特征。另一个假设是，观测到的相对涡度的空间不对称与观测到的WCR与CCR地层年速率的不对称动态相关。最后，我们假设分层的季节变化导致了WCR和CCR地层的季节性差异，而环地层的季节不对称性取决于跨河分层的空间不对称性。为了研究这些不对称，将分析现有的数据集来检验这三个假设。首先，研究人员将确定形成不同类型环的条件。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体制转移有关，以确定GS系统是否表现出多重平衡。除了使用Clark chart衍生的WCR和CCR普查外，还将使用沿轨道卫星测高、Argo浮标（轨迹和垂直特性剖面）以及来自Line W项目（系泊和船载速度和水特性测量）、夹板项目（温度剖面和速度剖面）和先锋阵列（速度、温度和盐度剖面）的现有区域数据集来探索环型和系统的不对称性。卫星测量的海面高度和海面温度地图将提供空间和时间背景。分析计划包括：(i)检查1993-2020年沿GS路径（75-55W）所有可用的沿轨高度计数据；（ii）计算选择的条件平均值，例如，按部门，按环型，并专注于特定的年份或季节，（iii）表征采样良好的单个环事件，以及（iv）使用可用的和衍生的长时间变量序列（包括相对涡度，分层，运输，盆地尺度风）检查多重平衡证据的状态空间，海面高度)将1997-2003年的状态变化期与最近的2016-2021年可能的转变期进行比较和对比。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识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

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
• 期刊: Zenodo
• 作者: Gifford, Ian;Gangopadhyay, Avijit;Andres, Magdalena;Gawarkiewicz, Glen;Oliver, Hilde;Silver, Adrienne
• 通讯作者: Silver, Adrienne

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
• 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.