Collaborative Research: Observations of Three-dimensional Transport Pathways and Biogeochemical Fluxes in the Southern Ocean using Autonomous Gliders

南大洋通常被称为通向深海的窗口。南极洲周围这片辽阔的海洋是充满深海的水被带到水面的主要位置，在那里它们与大气和海冰相互作用。由于在全球气候系统中的这一独特作用，南大洋发生的物理和生物过程对全球海洋的性质产生了不成比例的巨大影响，包括困在深海数百至数千年的热量和二氧化碳的数量。对南大洋S环流结构和生物特性，如营养物质和生物量浓度的极稀疏观测，为理解近地表水域的变化及其随后与深海的交换提供了重要障碍。近年来，SOCCOM(南大洋碳与气候观测和建模)项目利用创新的机器人技术，即自主剖面浮标，以前所未有的空间和时间覆盖范围提供对南大洋生物地球化学性质的观测。这一进展标志着我们从机械上理解南大洋S在全球碳循环中的作用的能力发生了一步变化，但许多负责产生所观察到的生物地球化学分布的物理和生物过程没有被浮标充分捕获，因为它们的采样间隔相对较短(10天)。在这个项目中，将试行两架海洋滑翔机跟踪单个浮标，以测量影响海洋表面和内部交换的海洋环流特征。滑翔机每4到5小时对海洋上层1000米进行一次采样，能够在大约一天的时间尺度上解析流体运动的变化。在这些尺度上，垂直速度的变异性很大，因此在这些较短的时间和较小的空间尺度上的环流显著地影响着海洋性质的垂直输送。改进对这些尺度上的运动及其对热量和碳传输的影响的表征，将有助于更好地了解南大洋在全球碳循环中所起的作用。将在南极绕极流的印度部分部署两架自主海洋滑翔机，通过SOCCOM项目与一个或多个配备生物地球化学传感器的半拉格朗日ARGO浮标重合。滑翔机将被引导跟踪ARGO浮标至少四个月，解决围绕浮标的中尺度和亚中尺度结构，以及发生在比浮标S 10天采样间隔更短的周期的变化。对上层海洋水文和速度场的测量将有助于分析混合层内的水动力不稳定性及其对混合层底部垂直输送和交换的影响。滑翔机数据还将与浮标观测和遥感产品相结合，以得出垂直示踪剂通量，目的是量化出口在下沉和平流路径之间的分配。最终，该项目将提供对南大洋示踪剂分布高频时空变异性的物理过程的观测，并将在描述影响南大洋物理和生物地球化学分布和运输路径的机制方面迈出重要的一步。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

The Southern Ocean is often referred to as the window to the deep ocean. This vast ocean around Antarctica is the primary location where the waters that fill the deep ocean are brought to the surface where they interact with the atmosphere and with sea ice. Because of this unique role in the global climate system, the physical and biological processes that occur in the Southern Ocean have a disproportionately large impact on the properties of the global ocean, including the amount of heat and carbon dioxide that is trapped in the deep ocean for hundreds to thousands of years. Extremely sparse observations of both the Southern Ocean?s circulation structure and biological properties, such as nutrient and biomass concentrations, have presented a significant barrier to understanding the modification of near surface waters and their subsequent exchange with the deep ocean. In recent years, the SOCCOM (Southern Ocean Carbon and Climate Observations and Modeling) project has used innovative robotic technologies, namely autonomous profiling floats, to provide observations of biogeochemical properties in the Southern Ocean with unprecedented coverage in space and time. This advance marks a step change in our ability to mechanistically understand the Southern Ocean?s role in the global carbon cycle but many of the physical and biological processes responsible for generating the observed biogeochemical distributions are not adequately captured by the floats because of their relatively coarse sampling interval (10 days). In this project, two ocean gliders will be piloted to track individual floats in order to measure the oceanic circulation features that impact exchange between the surface and interior ocean. Gliders sample the upper 1000 meters of the ocean once every 4 to 5 hours and are able to resolve variations in fluid motion on time scales of about a day. On these scales, the variability of vertical velocities are quite large and thus the circulation at these shorter temporal and smaller spatial scales significantly influences the vertical transport of ocean properties. An improved characterization of motions at these scales, and their impact on heat and carbon transport, will lead to a better understanding of the role the Southern Ocean plays in the global carbon cycle.Two autonomous ocean gliders will be deployed in the Indian sector of the Antarctic Circumpolar Current, coincident with one or more semi-Lagrangian Argo floats equipped with biogeochemical sensors through the SOCCOM project. The gliders will be piloted to track the Argo float for a period of at least four months, resolving the mesoscale and submesoscale structure surrounding the float as well as variability occurring at periods shorter than the float?s 10-day sampling interval. Measurements of the upper ocean hydrographic and velocity fields will permit an analysis of hydrodynamical instabilities within the mixed layer and their impact on vertical transport and exchange across the base of the mixed layer. The glider data will also be combined with the float observations and remote sensing products to derive vertical tracer fluxes, with the goal of quantifying the partitioning of export between sinking and advective pathways. Ultimately, this project will provide observations of the physical processes that contribute to high-frequency spatial and temporal variability in Southern Ocean tracer distributions and will provide a significant step towards describing the mechanisms that influence physical and biogeochemical distributions and transport pathways in the Southern Ocean.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.