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

该项目是作为探索性研究早期概念基金（EAGER）资助的。2004年，快速气候变化-经向翻转环流和热通量阵列（Rapid - mocha）开始监测北大西洋从北美到非洲的跨大西洋区域的经向质量输送。它通过从大西洋盆地两侧的小群系泊处收集的不同动态高度剖面来估计气候临界经向翻转环流（MOC），用海流计测量边界流，测量佛罗里达海峡的电力输送，并使用卫星风来估计Ekman输送。虽然底部压力表用于估计时变正压贡献，但RAPID-MOCHA依赖于假设的空间均匀的时间恒定的正压流来估计平均输送。这是新开发的全海洋深度（水面至6公里）自主水下滑翔机的首次科学应用，Deepglider将补充RAPID-MOCHA阵列。深水滑翔机将通过收集巴哈马阿巴科延伸的西部边界区域的重复水文剖面，独立于RAPID-MOCHA来估计绝对输送。一对车辆将在RAPID-MOCHA动态高度系泊的末端成员之间重复穿越100和500公里宽的重叠部分。这些部分将分别由Deepgliders每周和每月重复一次，与系泊所提供的相比，提供了大量的空间分辨率，尽管时间分辨率相当粗糙。每个深水滑翔机预计使用超过1年，可能长达18个月。从剖面中解析的水平密度梯度推断出的综合地转剪切将参考从每个滑翔机潜水周期推断出的深度平均电流。滑翔机在水中的位移与GPS在地面上的位移之间的差值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。独立的Deepglider对传输的估计将与RAPIDMOCHA阵列的估计进行比较。此外，Deepgliders将暂时用于“虚拟系泊”模式，以检查系泊在测量动态高度时的充分性。重复剖面和系泊时间序列的互补将共同用于评估扩展西部边界地区经向输运的误差和改进估计。知识价值：这项工作的知识价值在于它与全球气候动力学的基本问题的联系。MOC的变异性没有得到很好的观察，更不用说理解了。深流也是如此。比较监测MOC的技术对于确定其可信度和有效性至关重要。深海滑翔机重复水文测量将提供对气候至关重要的海洋环流输送、西部边界对MOC的贡献的独立测量。西部边界洋流时空结构的解析是理解这部分气候系统如何运作的先决条件。更广泛的影响：该项目将作为全深度滑翔机监测海洋环流的有效性和经济性的示范，不仅沿着RAPID-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，还监测深海区域。目前，Argo浮标在全球范围内监测上层海洋，但对深海的气候变化观测严重不足，而这种情况可能会被Deepgliders改变。深海滑翔机的技术使人们能够负担得起进入深海的费用，从而使观测全球海洋气候变化的全面程度成为可能。

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.