Analysis of eddies, mixing, and dense overflows at the Iceland-Faroe Ridge in the Northern Atlantic Ocean observed with Seagliders

用海洋滑翔机观测到的北大西洋冰岛-法罗海脊的涡流、混合和稠密溢流分析

• 批准号: 1029344
• 负责人: Peter Rhines
• 金额: $ 50.64万
• 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: 2010
• 资助国家: 美国
• 起止时间: 2010-09-01 至 2014-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1029344&HistoricalAwards=false
• 关键词: Analysis; eddies; mixing; dense; overflows

The northern Atlantic Ocean, near the seafloor ridge between Greenland and Scotland, is a particularly active part of the global climate system. This project will analyze observations from a recently completed 3-year program of Seaglider deployments in this sub-polar region. It is the first time that robotic gliders have been used to observe the dense overflow waters of the global meridional overturning circulation, and with them the warm northward flowing branch of the AMOC (Atlantic Meridional Overturning Circulation). 17,800 profiles of hydrography, dissolved oxygen, bio-optical variables and depth-averaged velocity were retrieved in 23 successful deployments during this NSF-sponsored work from November 2006 to November 2009.The primary foci of the proposed work are (i) an analysis of the water masses involved in the deep branch of the AMOC, the polar front and warm branch of the AMOC at this site, (ii), a study of mixing, dense-water transformation, and internal waves inferred from glider profiles of vertical velocity, optical backscatter, temperature and salinity at 1m vertical resolution, and (iii) an analysis of horizontal velocity using glider depth-averaged velocity, geostrophic shear and satellite altimetry, emphasizing dense overflow plume structure, polar front structure, and vertical structure of the strong eddy field.This new observational dataset will be combined with historical hydrographic sections, gridded climatology and with models of the Atlantic circulation. The statistical strength of the new data lies in the multiple occupations of the southern slopes of the Iceland Faroe Ridge over 3 years. Top-to-bottom profiles of horizontal velocity normal to the sections are recovered from the hydrography and glider-measured depth-averaged horizontal velocity. The new measurements of fine-scale vertical velocity by the gliders are particularly exciting. "Hot-spots" of turbulent mixing are visible throughout the water column, but particularly intense in the dense overflow water plume near the exit of the Faroe Bank Channel. Complementary observations from moorings and lowered turbulence probes have been made by Norwegian colleagues. Fine structure of temperature and salinity and optical backscatter observed at the 1m scale will be related to the vertical-velocity mixing signature. In parallel laboratory experiments have been investigating mixing induced by flow over seafloor topography. Together, these observations will provide a significant coverage of eddies, water masses, circulation and mixing in an important sector of the global climate system.Intellectual Merit: Human-induced global climate change is accelerating, and yet the natural variability of climate is strong and difficult to predict. Multi-decadal variability of the AMOC is being advanced as a contributor to the rapid late 20th Century global warming, which is largely thought to be driven by greenhouse gases. While climate models are centerpieces of the global warming/climate change debate, it is widely acknowledged that these models (and indeed higher resolution ocean circulation models) are deficient in representing dynamics in these key high-latitude regions. It is necessary to make direct observations of mixing, sinking, water-mass transformation, topographic control and boundary layers. These need to be targeted, and dense in space and time, which is the virtue of gliders. The motivations for this work go back through many years of research with theoretical dynamics of the ocean, which guide the analysis of observations.Broader Impacts: The investigators on this project interact with students through detailed research with graduate students to undergraduate teaching about the global environment. A key argument made to undergraduate students is that scientific technology has reached the point where it can contribute more effectively in assessing environmental problems. This project will foster on-going collaborations with oceanographers in Norway and the Faroe Islands interested in climate issues affecting sustainability of fisheries, dislocation of ecosystems and the precarious nature of human communities at the rim of the Arctic. Seagliders can be applied widely to address such issues as biological productivity and ecosystem change. The links between countries at the rim of the Arctic are strengthened by growing collaborations in climate- and environmental sciences.This project is a contribution to the US AMOC (Atlantic Meridional Overturning Circulation) project of the CLIVAR (CLImate VARiability and predictability) program.

北大西洋靠近格陵兰和苏格兰之间的海底山脊，是全球气候系统的特别活跃的部分。该项目将分析最近完成的3年Seaglider部署计划的观察结果。这是第一次使用机器人滑翔机来观察全球子午翻转循环的密集溢流，而它们与AMOC的温暖向北流动的分支（大西洋子午线翻转循环）。从2006年11月至2009年NSF赞助的工作期间，在23个成功的部署中检索了17,800个水文学，溶解的氧，生物光变量和深度平均速度。拟议的工作的主要焦点是（i）对水域进行了研究（i）涉及艾米克（Amoc）的ii群组的分析（i）（i）ii涉及ii的分支（ii）（i II）（ii），ii涉及ii的ii（ii）（i），ii是ii的群组，并且（i）是ii的ii（ii）。密集的水转化以及从1m垂直分辨率下的垂直速度，光降低的温度和盐度的滑翔机曲线以及（iii）分析水平速度的分析，使用滑翔机的水平速度分析，使用滑翔机的深度水平速度，地理剪切和卫星的质量越过质量的结构。观察数据集将与历史水文部分，网格气候学和大西洋循环模型相结合。新数据的统计强度在于冰岛法罗山脊的南部斜坡的多个职业超过3年。从水文学和滑翔机测量的深度平均水平速度中回收了与部分的水平速度的上下到底部曲线。滑翔机对细尺度垂直速度的新测量特别令人兴奋。整个水柱中都可以看到湍流混合的“热点”，但在Faroe Bank通道出口附近的浓密溢流羽流中尤其强烈。挪威同事们已经对系泊和湍流探针降低的互补观察结果进行了观察。在1m尺度上观察到的温度和盐度的精细结构与垂直混合签名有关。在平行实验室实验中，已经研究了由海底地形上流动引起的混合。总之，这些观察结果将在全球气候系统的重要领域提供涡流，水质量，循环和混合的显着覆盖范围。智能优点：人类引起的全球气候变化正在加速，但气候的自然变化却很强，难以预测。 AMOC的多年差异已成为20世纪末期全球变暖的贡献者，这在很大程度上被认为是由温室气体驱动的。尽管气候模型是全球变暖/气候变化辩论的核心，但人们普遍承认，这些模型（确实是更高的分辨率海洋循环模型）在代表这些关键高纬度区域的动态方面不足。有必要直接观察混合，下沉，水质量转化，地形控制和边界层。这些需要被靶向，并在时空上密集，这是滑翔机的优点。这项工作的动机可以追溯到海洋的理论动态多年的研究，这指导了观察分析。Boader的影响：该项目的研究人员通过与研究生的详细研究与研究生进行有关全球环境的本科教学，与学生与学生进行互动。对本科生的一个关键论点是，科学技术已经达到了可以在评估环境问题方面更有效贡献的地步。该项目将促进与挪威的海洋学家以及对影响渔业可持续性，生态系统脱位以及北极边缘人类社区不稳定本质的气候问题感兴趣的法罗群岛的持续合作。可以广泛应用海格流行器来解决生物生产力和生态系统变化等问题。通过在气候和环境科学方面的合作越来越多地加强了北极边缘国家之间的联系。该项目是对Clivar（气候变异性和可预测性）计划的美国AMOC（大西洋子午翻转循环）项目的贡献。