EAGER: Deepglider Pilot Observations of Western Boundary Current Structure Offshore Abaco

EAGER：深滑翔机对阿巴科近海西边界水流结构的试点观测

• 批准号: 1031780
• 负责人: Charles Eriksen
• 金额: $ 29.96万
• 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: 2010-07-01 至 2012-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1031780&HistoricalAwards=false
• 关键词: EAGER; Deepglider; Pilot; Observations; Western

This project is funded as an EArly-concept Grant For Exploratory Research (EAGER).The Rapid Climate Change-Meridional Overturning Circulation and Heat Flux Array (RAPID-MOCHA) began monitoring meridional mass transports in the North Atlantic Ocean along a transatlantic section from North America to Africa in 2004. It estimates the climatically critical meridional overturning circulation (MOC) by differencing dynamic height profiles gathered from small clusters of moorings on either side of the Atlantic basin, measuring boundary current flows with current meters, measuring transport in the Florida Strait electrically, and using satellite winds to estimate Ekman transport. While bottom pressure gauges are used to estimate time-varying barotropic contributions, RAPID-MOCHA relies on an assumed spatially uniform temporally constant barotropic flow to estimate mean transport.The first scientific use of the newly developed full-ocean-depth (surface to 6 km) autonomous underwater glider, Deepglider will complement the RAPID-MOCHA array. Deepgliders will be used to estimate absolute transports independently of RAPID-MOCHA by collecting repeat hydrographic sections of the extended western boundary region off Abaco, Bahamas. A pair of vehicles will repeatedly transit across 100 and 500 km wide overlapping sections between end members of the RAPID-MOCHA dynamic height moorings. These sections will be repeated about weekly and monthly, respectively, by Deepgliders, providing substantial spatial resolution compared to that provided by the moorings, although at considerably coarser temporal resolution. Each Deepglider is expected to last well over 1 year, possibly up to about 18 months. Integrated geostrophic shear inferred from horizontal density gradients resolved in the sections will be referenced to depth-averaged current inferred from each glider dive cycle. The difference between dead-reckoned glider displacement through the water and GPS displacement over the ground is used to estimate depth-averaged current. The Deepglider estimates will include the likely possibility of horizontally varying time-mean barotropic contributions to transport. The independent Deepglider estimates of transports will be compared to those from the RAPIDMOCHA array. In addition, Deepgliders temporarily will be used in 'virtual mooring' mode to check the adequacy of the moorings in measuring dynamic height. Together, the complement of repeat section and moored time series will be used to assess errors and improve estimates of meridional transports in the extended western boundary region.Intellectual Merit: The intellectual merit of this work lies in its connections to basic issues of global climate dynamics. The variability of the MOC is not well observed, let alone understood. The same can be said for the deep flow. Comparison of techniques by which the MOC is monitored is essential to establish their credibility and effectiveness. Deepglider repeat hydrography will provide independent measures of climatically critical ocean circulation transports, the western boundary contributions to MOC. Resolution of the temporal/spatial structure of western boundary currents is prerequisite to understanding how this portion of the climate system operates.Broader Impact: This project will serve as a demonstration of efficacy and economy of full-depth gliders in monitoring ocean circulation not only along the RAPID-MOCHA line, but also along other transects. It will pioneer the use of autonomous gliders to monitor not only the upper ocean, but its deep regions as well. Currently Argo floats monitor the upper ocean globally, but the deep ocean is severely under-observed for climate change, a situation Deepgliders could alter. By making deep ocean access affordable, the Deepglider technology opens the possibility that the complete extent of global ocean climate change may be observed.

快速气候变化-经向翻转环流和热通量阵列（RAPID-MOCHA）于2004年开始监测北大西洋沿着从北美到非洲的跨大西洋部分的纬向物质输送。它估计的气候关键的纬向翻转环流（MOC）的差分动态高度剖面收集从小集群的系泊在大西洋盆地的两侧，测量边界电流与电流米，测量在佛罗里达海峡的电输送，并使用卫星风估计埃克曼运输。虽然底部压力计用于估计随时间变化的正压贡献，RAPID-MOCHA依赖于一个假设的空间均匀的时间恒定的正压流来估计平均运输，第一次科学使用新开发的全海洋深度（表面到6公里）自主水下滑翔机，Deepglider将补充RAPID-MOCHA阵列。深度滑翔机将用于独立于RAPID-MOCHA，通过收集巴哈马阿巴科外海西部边界延伸区的重复水文剖面来估计绝对输运。两辆车将反复穿越RAPID-MOCHA动态高度系泊系统端部构件之间100公里和500公里宽的重叠路段。这些部分将分别每周和每月重复一次，由Deepgliders提供与系泊系统相比相当大的空间分辨率，尽管时间分辨率相当粗糙。每架Deepglider预计将持续超过1年，可能长达18个月。综合地转剪切推断水平密度梯度解决部分将参考深度平均电流推断从每个滑翔机潜水周期。航位推算滑翔机通过水的位移和GPS在地面上的位移之间的差异被用来估计深度平均电流。Deepglider的估计将包括水平变化的时间平均正压对运输的贡献的可能性。Deepglider对运输机的独立估计将与RAPIDMOCHA阵列的估计进行比较。此外，Deepglider将暂时用于“虚拟系泊”模式，以检查系泊设备是否足以测量动态高度。重复部分和系泊时间序列的补充将被用来评估误差，并提高在扩展的西部边界regions.Intellectual优点：这项工作的智力价值在于它的连接到全球气候动力学的基本问题的纬向输送的估计。主运行中心的可变性没有得到很好的观察，更不用说理解了。深流也是如此。对主运行中心监测技术进行比较，对于确定其可信度和有效性至关重要。Deepglider重复水文测量将提供气候关键海洋环流运输的独立措施，西部边界对MOC的贡献。西部边界流的时间/空间结构的分辨率是了解这部分气候系统如何运作的先决条件。更广泛的影响：该项目将作为一个示范的有效性和经济的全深度滑翔机监测海洋环流不仅沿着快速发展-MOCHA线，而且沿着其他横断面。它将率先使用自主滑翔机不仅监测上层海洋，还监测其深层区域。目前，Argo浮标监测全球上层海洋，但深海对气候变化的观测严重不足，Deepglider可能会改变这种情况。通过让人们能够负担得起进入深海的费用，Deepglider技术开启了观测全球海洋气候变化完整程度的可能性。