A sea state dependent gas transfer formulation

该项目旨在产生一个比目前使用的经验关系式更准确的海-气通量的机械公式。它将开发和测试一种新的参数化法，充分考虑海况、风和关键物理化学变量(如扩散系数、溶解度和温度)对气泡介导的气体交换的影响。这是新颖的，因为它跨越了与气体传输问题有关的所有尺度，从气泡尺度到海洋表面的波浪统计。通量将在所有气体物种的统一框架内，通过依赖于海况的气体转移速度来模拟。公式中直接考虑了气泡尺寸分布、气泡停留时间、气泡对盐度、粘度和温度的依赖关系以及不同气体的扩散率和溶解度等关键变量对气泡中介气体传递的影响。为了更好地预测二氧化碳、氧气或二甲基硫化物的相关全球生物地球化学循环，有必要更好地理解和改进气体传输的参数。了解波场如何调节这些与气候相关的气体的通量，将导致气候和天气模型和预报的全面改进。由于二氧化碳增加会导致海洋酸化影响贝壳形成的海洋动物，而氧气的限制具有广泛的生态效应，因此改进这些气体交换的参数化可以帮助解释现有的观测结果，并可能提高我们对当地过程及其对生态系统影响的理解。解释海态依赖性的一般框架并不局限于气体转移，也可以推广到其他类型的通量。这个项目将使普林斯顿大学的本科生和研究生接触到这些关键的环境挑战，需要研究基本的多相流，并通过研讨会和教学活动促进开源方法的使用。这项研究促进了一个一般的理论框架，以解释波浪破碎和空气卷吸的复杂性质，一个两相湍流过程，以及在这个过程中涉及的非常广泛的尺度，从Km，O(1公里)的波浪统计尺度，到波浪破碎动力学，O(1-10m)，空气卷吸，气泡产生和溶解O(厘米到m)。利用波浪模拟的最新进展，一个最先进的波浪模型将被用来直接计算破裂统计，这将有助于在高时间和空间分辨率下研究全波复杂性对气体通量的作用。对于二氧化碳和二甲基硫化物等各种气体，将在区域和全球范围内评估气泡对海气交换的贡献，并通过考虑气泡的不对称贡献，将公式扩展到低溶解度气体，如氧气。将确定区域和季节，在这些区域和季节中，捕获波场和相关风暴对于表示现场观测至关重要。这一模拟方法与最近和历史数据集的系统比较将利用海-气相互作用界在产生高质量现场测量方面所作的巨大努力。将产生一个全球和区域气体转移速度的一致数据集，该数据集将用于为任何气体的转移制定统一的参数化法，并将提供给海洋和气候界，用于波-海-气和气候耦合模式。这将大大减少生物地球化学循环中中到高风速时海气交换的不确定性。这一奖项反映了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。

This project aims to produce a mechanistic formulation for air-sea gas fluxes, more accurate than empirical relationships currently used. It will develop and test a novel parameterization that fully accounts for the effects of sea-state, wind, and key physicochemical variables such as diffusivity, solubility and temperature on the bubble mediated gas exchange. This is novel as it spans all the scales relevant to the gas transfer problem, from the bubble scale, to the wave statistics at the ocean surface. The flux will be modelled through a sea-state dependent gas transfer velocity, within a unified framework for all gas species. The impact of key variables which are known to influence bubble mediated gas transfer, such as the bubble size distribution, bubble residence time, its dependence on salinity, viscosity and temperature, as well as the diffusivity and solubility of different gases are directly incorporated in the formulation. Better understanding and improved parameterizations of the gas transfer are necessary to better predict the associated global biogeochemical cycles of carbon dioxide, oxygen or dimethyl sulfide. Understanding how the wave field modulates the fluxes of these climate-relevant gases will lead to general improvements in climate and weather models and forecast. Since increased CO2 causes ocean acidification impacting shell-forming marine animals, and limitations in oxygen have broad ecological effects, improved parameterization of the exchange of these gases can help interpret existing observations, and might improve our understanding of local processes and their impact on ecosystems. The general framework to account for sea-state dependence is not limited to gas transfer but could be generalized to other type of fluxes as well. This project will expose undergraduate and graduate students at Princeton to these critical environmental challenges that require research on fundamental multi-phase flows, and promote the use of open-source methods through workshops and teaching activities.This research promotes a general theoretical framework to account for the complex nature of wave breaking and air entrainment, a two-phase turbulent process, and the very large range of scales involved in the process, from wave statistics scales of order of km, O(1km), to wave breaking dynamics, O(1-10m), air entrainment, bubble generation and dissolution O(cm to m). Leveraging recent progress in wave modeling, a state-of-the-art wave model will be used to directly compute the breaking statistics, which will help investigate the role of the full wave complexity on the gas flux at high temporal and spatial resolution. Bubble contribution to air-sea gas exchange will be evaluated regionally and globally for various gases like carbon dioxide and dimethyl sulfide, and the formulation will be extended to low solubility gases such as oxygen by considering the bubble asymmetric contribution. Regions and seasons will be identified where capturing the wave field and associated storms is critical to represent field observations. Systematical comparisons of this modeling approach to recent and historical data sets will leverage the large effort by the air-sea interaction community in producing high quality field measurements. A consistent data set of global and regional gas transfer velocity will be produced, that will be used to develop a unified parameterization for the transfer of any gas, and which will be made available to the ocean and climate community, to be used in coupled wave-ocean-atmosphere and climate models. This should significantly reduce the uncertainties of air-sea gas exchange at moderate to high wind speeds in biogeochemical cycles.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.