Collaborative Research: Autonomous sampling of upper ocean mixing in the Southern Ocean due to wind forcing and double-diffusion

合作研究：由于风力强迫和双扩散而对南大洋上层海洋混合进行自主采样

• 批准号: 1558639
• 负责人: Louis St Laurent
• 金额: $ 79.9万
• 依托单位: Woods Hole Oceanographic Institution
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-07-01 至 2018-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1558639&HistoricalAwards=false
• 关键词: Collaborative; Research; Autonomous; sampling; upper

The Southern Ocean is responsible for about half the uptake of anthropogenic carbon and an even larger fraction of the atmosphere's flux of heat into the sea. The Southern Ocean is the only sector of the global ocean that connects all three major ocean basins through the Meridional Overturning Circulation (MOC). Despite its importance, the region is under sampled largely due to its remote location and severe conditions. The dearth of observations in the Southern Ocean is not limited to ocean measurements. Meteorological measurements such as wind speed and heat fluxes are scarce and often from sensors mounted on sparse ship traffic. With the maturing of autonomous platforms, there is now an opportunity to collect high-resolution spatial and temporal measurements in the full range of conditions characteristic of the Southern Ocean. While climate models have advanced substantially, the inadequate representation of unresolved mixing processes is still a significant source of error. This is perhaps the most severe in the near-surface boundary layer of the ocean where Langmuir physics, frontal processes, and double-diffusion are active in the Southern Ocean, yet the lack of observations have slowed progress in developing parameterizations. This novel observational study will allow sampling of the upper-ocean physics of this region on spatial and timescales much shorter than those sampled during previous experiments, allowing the resolution of inertial and diurnal processes forced by winds and radiation, and on spatial scales that give insight into the turbulent cascade influencing the upper ocean. The results from this project will lead to more realistic parameterizations of subgrid-scale processes in numerical models of ocean circulation, of the coupled ocean-atmosphere system and of climate models. The proposed project will recruit two undergraduate summer fellow through the Women in Science At Yale (WISAY) to provide them hands-on experience in using autonomous platforms to sample the ocean.This project is motivated by the need to understand the overturning circulation of the global ocean in a region that is both rich in small-scale physical processes and severely under-sampled. This circulation governs the transport and storage of heat and carbon dioxide within the huge oceanic reservoir, and thus plays a major role in regulating the Earth's climate. The specific goals of this project are to 1) obtain measurements of turbulent dissipation rates, temperature, salinity and fluorescence in the upper 1000 m collocated with surface wave spectral data and meteorological measurements. The use of autonomous platforms will provide a dataset with unprecedented spatial and temporal resolution of mixing in the Southern Ocean and 2) investigate the turbulent response of the upper ocean to the extreme surface forcing (wind stress, radiative fluxes) in the Southern Ocean. The dataset will eliminate the fair-weather bias of shipboard measurements and will provide motivation for theoretical and model studies of submesoscale and boundary layer dynamics in the region. The study will be conducted in the region of the ACC fronts between Drake Passage and the Argentine Basin. A Wave Glider and drifter constellation will measure wind, waves, air temperature and radiation quantities, and sea surface temperature and salinity. Gliders with microstructure sensors will measure temperature and salinity fine structure and turbulence in the upper 1000 m of the water column where the eddy field is active and water masses interact, and in the near-surface boundary layer where the ocean interacts with the atmosphere. At the end of the deployment the glider array will sample around the Ocean Observatory Initiative site in the Argentine basin to validate the meteorological measurements from the wave glider. This dataset will provide an opportunity to study the physics underpinning mixing rates in this region, while simultaneously contributing valuable insights to the modeling community.

南大洋承担了大约一半的人为碳吸收，以及更大比例的大气热流流入海洋。南大洋是全球海洋中唯一通过子午线翻转环流(MOC)连接所有三个主要洋盆的部分。尽管该地区很重要，但由于其偏远的地理位置和恶劣的条件，抽样不足。南大洋观测的匮乏并不局限于海洋测量。气象测量，如风速和热通量很少，通常来自安装在稀疏船舶交通上的传感器。随着自主平台的成熟，现在有机会在南大洋特有的各种条件下收集高分辨率的空间和时间测量数据。虽然气候模型已经有了很大的进步，但对未解决的混合过程的不充分描述仍然是一个重要的误差来源。这可能是海洋近表面边界层中最严重的，在那里朗缪尔物理、锋面过程和双重扩散在南大洋活跃，但缺乏观测减缓了发展参数化的进展。这项新颖的观测研究将允许在比以前实验中采样的空间和时间尺度短得多的空间和时间尺度上对该区域的上层海洋物理进行采样，从而能够分辨由风和辐射强迫的惯性和昼夜过程，并在空间尺度上深入了解影响上层海洋的湍流级联。该项目的结果将导致海洋环流数值模式、海洋-大气耦合系统和气候模式中的次网格尺度过程的更真实的参数化。这个拟议的项目将通过耶鲁大学女性科学研究中心(WISAY)招募两名本科生暑期研究员，为她们提供使用自主平台对海洋进行采样的实践经验。该项目的动机是需要了解一个既有丰富的小规模物理过程又严重采样不足的地区的全球海洋颠覆环流。这种环流控制着巨大的海洋水库内热量和二氧化碳的运输和储存，因此在调节地球气候方面发挥着重要作用。该项目的具体目标是：1)结合表面波谱数据和气象测量，获得1000米以上的湍流耗散率、温度、盐度和荧光的测量结果。使用自主平台将提供一个具有前所未有的空间和时间分辨率的南大洋混合数据集，并2)调查上层海洋对南大洋极端表面强迫(风应力、辐射通量)的湍流反应。该数据集将消除船上测量的晴天偏差，并将为该区域亚中尺度和边界层动力学的理论和模式研究提供动力。这项研究将在德雷克海峡和阿根廷盆地之间的ACC前缘地区进行。波浪滑翔机和漂流星星座将测量风、浪、气温和辐射量，以及海洋表面温度和盐度。带有微结构传感器的滑翔机将测量水柱上部1000米处的温度和盐度精细结构和湍流，在那里涡流场活跃，水团相互作用，以及在海洋与大气相互作用的近表面边界层中。在部署结束时，滑翔机阵列将在阿根廷盆地的海洋观测站周围进行采样，以验证波浪滑翔机的气象测量结果。这一数据集将为研究该地区混合率的物理基础提供机会，同时为模型界提供有价值的见解。