Collaborative Research: Export Pathways from the Subpolar North Atlantic: Phase Two

合作研究：北大西洋副极地的出口途径：第二阶段

• 批准号: 0824652
• 负责人: Amy Bower
• 金额: --
• 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: 2008
• 资助国家: 美国
• 起止时间: 2008-09-01 至 2011-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0824652&HistoricalAwards=false
• 关键词: Collaborative; Research; Export; Pathways; Subpolar

Intellectual Merit: Profiling float observations in the western subpolar North Atlantic made in the 1990s appeared to contradict the current understanding of the Deep Western Boundary Current (DWBC) as the dominant export pathway for Labrador Sea Water (LSW) from subpolar to subtropical latitudes. All of the profiling floats that exited the Labrador Sea in the DWBC left the boundary well north of the Tail of the Grand Banks, turning eastward into the ocean interior along the path of the North Atlantic Current (NAC) at about 50°N. This unexpected observation motivated a long-term observational effort to obtain a better understanding of LSW pathways and their variability with new float observations and historical hydrographic data analyses.The field component of this project, which began in 2003, is nearly complete. For three years, groups of six acoustically tracked RAFOS floats were released nominally every three months in the DWBC near 50ºN at Upper LSW and Classical LSW levels. When the last floats surface in November 2008, two-year high-resolution trajectories from about 62 RAFOS floats will be available for analysis. Two important results have emerged to date from a study of RAFOS floats that have already surfaced and "e-floats" generated from an ocean eddy-resolving general circulation model. First, there is little evidence for a "fast-track" from the subpolar to the subtropical basin along the DWBC. Second, a significant number of RAFOS and e-floats trace an interior pathway for LSW southward from the Newfoundland Basin to the eastern subtropical gyre, a pathway that was not observed at all by the profiling floats. These results raise critical questions about the importance of the DWBC as an export pathway for newly-ventilated waters, and hence its role in the Atlantic Meridional Overturning Circulation (AMOC) which is a near-term priority of the Ocean Research Priorities Plan (ORPP).With the conclusion of the RAFOS field work in sight, and the capability to generate e-float trajectories in hand, the investigators are now poised to make significant advances in the understanding of the export pathways of LSW and their impact on the AMOC. The specific objectives of this analysis are to:1. Complete the statistical analysis of the full RAFOS float data set and compare to a similar study using e-floats generated from an ocean general circulation model.2. Reconcile the apparent contradiction between the rapid loss of floats from the DWBC in the Newfoundland Basin and the concept of the DWBC as a direct LSW export pathway from the subpolar to subtropical region.3. Elucidate the impact of mesoscale, interannual and decadal variability on LSW pathways.4. Assess the importance of the interior pathway of LSW, relative to the DWBC, to the volume and property transport of the AMOC.Broader Impacts: By providing an improved understanding of subpolar-to-subtropical ocean pathways, this proposed research will contribute to an unraveling of the ocean's role in global climate. The Lagrangian perspective will provide valuable information on the continuity of the lower limb of the AMOC and as such will aid in the design of monitoring programs. This project will also have a broader impact in that it will contribute to the training and education of a graduate student at Duke University and a postdoctoral investigator at Woods Hole Oceanographic Institution.

学术价值：20 世纪 90 年代在北大西洋西副极地进行的浮标剖面观测似乎与目前对西深边界流 (DWBC) 作为拉布拉多海水 (LSW) 从副极地到副热带纬度的主要输出路径的理解相矛盾。在 DWBC 中离开拉布拉多海的剖面浮标离开了大浅滩尾部以北的边界井，沿着北大西洋洋流 (NAC) 的路径位于北纬 50° 左右，这一意外观测激发了长期观测工作，以便通过新的浮标观测和历史水文数据分析更好地了解 LSW 路径及其变化。该项目于 2003 年开始，三年来已接近完成，名义上每三个月在北纬 50 度附近的 DWBC 上部 LSW 和经典 LSW 水平释放一组六个声学跟踪 RAFOS 浮标。当最后一个浮标于 2008 年 11 月浮出水面时，大约 62 个 RAFOS 浮标的两年高分辨率轨迹将可供分析。迄今为止，对已浮出水面的 RAFOS 浮标和“电子浮标”的研究已得出两项重要结果。首先，几乎没有证据表明沿 DWBC 存在从副极地到副热带盆地的“快速通道”。一些 RAFOS 和电子浮标追踪了 LSW 从纽芬兰盆地向南到东亚热带环流的内部路径，剖面浮标根本没有观察到这条路径。这些结果提出了关于 DWBC 作为一个重要问题的关键问题。新通风水域的出口路径，及其在大西洋经向翻转环流（AMOC）中的作用，这是海洋研究优先计划（ORPP）的近期优先事项。随着 RAFOS 现场工作的结束，以及生成电子漂浮轨迹的能力，研究人员现在准备在了解 LSW 的输出路径及其对 AMOC 分析的影响方面取得重大进展。目的是：1. 完成完整 RAFOS 浮标数据集的统计分析，并与使用海洋大气环流模型生成的 e-floats 进行的类似研究进行比较。2. 调和浮标快速损失之间的明显矛盾。纽芬兰盆地的DWBC和DWBC作为从副极地到亚热带地区的直接LSW输出路径的概念。3．阐明中尺度、年际和年代际变化对LSW路径的影响。4．评估内部路径的重要性。相对于 DWBC，LSW 对 AMOC 的体积和财产运输的影响。更广泛的影响：通过提供对副极地到副热带海洋的更好的了解路径，这项拟议的研究将有助于揭示海洋在全球气候中的作用，拉格朗日观点将提供有关 AMOC 下肢连续性的宝贵信息，因此将有助于监测计划的设计。它还具有更广泛的影响，因为它将有助于杜克大学研究生和伍兹霍尔海洋研究所博士后研究员的培训和教育。