Comparison of Deepglider and RAPID-MOCHA Moored Array Observations

大西洋经向翻转环流（AMOC）是全球气候系统的主要组成部分。在北纬26.5度，AMOC负责携带大约60%由海洋携带的净极向热通量，以及大约30%由大气和海洋共同携带的总热通量，以纬向方式在全球范围内整合。通过海面温度调节，AMOC与年际到几十年时间尺度上的气候信号相关联，这些信号可以产生广泛的社会影响。气候模式预测下个世纪AMOC将大幅减弱，这一变化可能会产生广泛的影响。在过去的十年里，美国和英国的科学家们维持了一个横跨大西洋的大型仪器系泊阵列，以观察AMOC及其热通量的波动。10天以上时间尺度上的变率主要是由跨大西洋动力高度差和边界流波动推断的地转流波动。虽然有效，但系泊阵列的维护成本很高。该项目旨在评估远程全海洋深度水下滑翔机在测量系泊阵列的AMOC方面的有效性。这些名为“深海滑翔机”（Deepgliders）的自动驾驶飞行器，沿着倾斜的轨迹在海洋中近乎实时地收集海洋表面到海底的温度、盐度和溶解氧剖面。它们还返回全深度平均电流的估计。Deepgliders在北纬26.5度线的成功应用将激励将该技术应用于其他感兴趣的样带（如北大西洋亚极地环流和南大西洋亚热带环流），以解决全球重复水文的挑战，并降低此类项目的总体成本，以便这些海洋气候项目可以由资助机构作为一个整体提供。这些一起将导致对地球更深入的了解。年代的气候。该项目的总体目标是学习如何在未来几十年协助可持续地继续监测海洋生物多样性。学习使用Deepgliders测量AMOC将有助于维持当前阵列在北纬26.5度的运行数十年，以解决年际和多年代际变化。只有经过几十年的运行，与自然气候变率和人为气候变化有关的信号才会明显并有可能被区分出来。“深海滑翔机”的设计目的是在18个月的时间里进行250次下潜，下潜深度可达6000米，同时在海洋中飞行1万公里，仅靠一组锂电池。它沿着锯齿状路径在海洋中采样温度、盐度和溶解氧，并在每次到达海面时通过卫星遥测将这些数据传达给岸上。双向通信允许命令传输到Deepgliders，这样它的自主行为可以从任何地方的飞行员远程控制，只要有互联网连接。作为一项试点实验，计划在两年的时间里进行四次为期一年的深度滑翔机任务，这些任务重叠在系泊部署中。其中两个将集中在靠近巴哈马阿巴科近海RAPID-MOCHA系泊的位置，以解决动态高度的主要变化，用于估计海洋内部对AMOC变化的贡献。另外两个将重复一个简短的部分，旨在捕捉安的列斯群岛和深西部边界流的时空变化。Deepglider和系泊测量将进行比较，以评估相对效果。

The Atlantic Meridional Overturning Circulation (AMOC) is a principal element of the global climate system. At 26.5 degrees North latitude, the AMOC is responsible for carrying about sixty percent of the net poleward heat flux carried by the oceans and about thirty percent of the total heat flux carried by the atmosphere and ocean together, integrated zonally around the globe. Through sea surface temperature modulation, the AMOC is linked to climate signals on interannual to multi-decadal time scales that can have extensive societal impact. Climate models predict substantial weakening of the AMOC over the next century, a change with potentially wide ramifications. For the past decade, U.S. and U.K. scientists have maintained a transatlantic heavily instrumented moored array to observe fluctuations in the AMOC and its heat flux. Variability on time scales longer than ten days is dominated by geostrophic current fluctuations inferred from transatlantic dynamic height differences and boundary current fluctuations. While effective, the moored array is costly to maintain. This project is an attempt to assess the effectiveness of very long-range full ocean depth underwater gliders in measuring aspects of the AMOC side-by-side the moored array. These autonomous vehicles, named Deepgliders, collect sea-surface to sea-floor profiles of temperature, salinity, and dissolved oxygen along slanting trajectories through the ocean in near-real time. They also return estimates of the full-depth average current. Successful application of Deepgliders to the 26.5 degrees North latitude line will motivate applying the technique to other transects of interest (such as in the North Atlantic subpolar gyre and the South Atlantic subtropical gyre), to address the challenges of repeat hydrography globally, and reduce the overall cost of such programs in order that such ocean climate projects can be afforded as a whole by funding agencies. These together will lead to deeper understanding of earth?s climate.The overall goal of the project is to learn how to assist the sustainable continuation of AMOC monitoring through coming decades. Learning to measure the AMOC using Deepgliders will help sustain operation of the current array at 26.5 degrees North for the many decades required to resolve interannual and multi-decadal variability. Only by operating for several decades will the signals associated with natural climate variability and anthropogenic climate change be evident and potentially distinguishable. A Deepglider is designed to make about 250 dives to as deep as 6000 m in missions lasting as long as 18 months while traveling as much as 10,000 km through the ocean on a single set of lithium batteries. It samples temperature, salinity, and dissolved oxygen along saw tooth paths through the ocean and communicates them to shore each time it reaches the sea surface via satellite telemetry. Two-way communication allows commands to be transmitted to Deepgliders so that its autonomous behavior can be controlled remotely from a pilot anywhere with an internet connection. As a pilot experiment, four one-year Deepglider missions are planned over a 2-year period overlapping moored deployments. Two of these will concentrate on maintaining position close to a RAPID-MOCHA mooring just offshore Abaco, Bahamas to resolve the principal variability in dynamic height for use in estimating the interior ocean contribution to AMOC variability. Two more will repeat a short section intended to capture temporal and spatial variations in Antilles and Deep Western Boundary Current flow. Deepglider and moored measurements will be compared to assess relative efficacy.