Modulation of Bubble-Mediated Gas Transfer due to Wave-Current Interactions

该项目将在一个全面的模拟框架内研究跨海气界面的气体转移的空间变异性。理论和模型研究在相对较小的尺度上是一致的，在那里，流动变得不那么受地球自转的支配，运动，特别是沿垂直方向的运动变得更有能量，对海洋生物地球化学和海气通量产生显著影响。然而，还没有关于波-流相互作用引起的波破裂变异性和相关的气泡中介气体传输的研究。目前大多数气体传递系数的参数依赖于风速，而不是更详细的波浪动力学表示，导致了很大的不确定性。最近的参数化包括通过有效波高或波龄等积分波参数来描述波的影响，这都不能解释陡锋上的波流相互作用引起的调制。最近开发的一个波浪破碎统计模型提供了一个框架，可以明确地解释破碎对空气卷吸和气泡介导的气体通量的影响。该模型适用于耦合地球系统的模拟，为研究波流相互作用对气泡介导的气体传输和通量变化的影响提供了一个独特的机会。这些结果将直接应用于气候研究。它们可以解释沿海环境中观测到的气体通量的不确定性，有助于减少全球二氧化碳预算的不确定性。其他影响包括培训学生。具体地说，一名本科生将参与这项研究。该项目将通过为西班牙裔早期科学家的职业生涯做出贡献，并通过让指定的拉美裔服务机构UCSB的学生接触研究及其结果，来加强代表不足群体的参与。这项工作的主要目标是研究亚中尺度上波-流相互作用对气泡介导的气体传输的调制。该模拟是基于表面波破裂和相关的海气通量的最新进展，提供了一个基于物理的框架来模拟气泡介导的气体传递系数。将使用真实的数值模拟来研究气泡介导的气体传输的空间变异性及其对气体通量(即，CO2)的影响。初步模式结果表明，由实际风和海流强迫的海浪破碎统计数据证实了先前观测和理论分析的结果，即海流对波浪的调制，在风与海洋锋斜排列的条件下，海浪破碎增强。在亚中尺度上，随着模式分辨率的提高，海流对海浪的破碎调制作用增强。次中尺度锋面辐合和下沉速度与斜风作用下的波浪破碎增强区重叠。假设在这些条件下，海-气通量增强。这将在上升流条件下的东部边界流进行数值模拟来检验。上升流地区表现出二氧化碳浓度的显著差异，这一点还不是很清楚。溶解的二氧化碳将被模拟为忽略生物和化学反应，从背景平衡水平开始，然后强制使用实际的通量，包括气泡中介的转移系数。这一假设将通过将不同分辨率的模型解与使用仅取决于风速的标准传递系数参数的控制运行进行比较来检验。该奖项反映了NSF的法定使命，并已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 is project will study the spatial variability of gas transfer across the air-sea interface within a comprehensive modeling framework. Theoretical and modeling studies agree at relatively small scales, where the flow becomes less dominated by the rotation of the earth, motion, especially along the vertical direction becomes more energetic, with pronounced impacts on ocean biogeochemistry, and air-sea fluxes. However, no study has focused on wave breaking variability and related bubble mediate gas transfer due to wave-current interactions. Most parameterizations of gas transfer coefficients today depend on wind speed rather than more detailed representation of wave dynamics, resulting in large uncertainties. Recent parameterizations include wave effects through integral wave parameters such as significant wave height or wave age, neither which can explain the modulation due to wave-current interactions at sharp fronts. A recently developed model of wave breaking statistics provides a framework to explicitly account for breaking on air entrainment and bubble-mediated gas fluxes. The model is suitable for coupled earth system simulations providing a unique opportunity to study the effect of wave-current interactions on the variability of bubble-mediated gas transfer and fluxes. The results will have direct applications for climate studies. They can explain the uncertainty of the observed gas fluxes in coastal environments, helping to reduce the uncertainty of global CO2 budgets. Other impacts include training students. Specifically, an undergraduate student will participate in the research. The project will enhance the participation of underrepresented groups by contributing to the career of a Hispanic, early-career scientist, and by exposing the students at UCSB, a designated Hispanic-Serving Institution, to the research and its results. The overarching goal of the work is to investigate the modulation of bubble-mediated gas transfer due to wave-current interactions at submesoscales. The modeling is based on recent advances on surface wave breaking and related air-sea fluxes, which provide a physics-based framework to model bubble-mediated gas transfer coefficients. Realistic numerical simulations will be used to investigate the spatial variability of bubble-mediated gas transfer and their impact on gas fluxes (i.e., CO2). Preliminary model results show that wave breaking statistics forced by realistic winds and currents confirm previous findings from observations and theoretical analysis on the modulation of waves by currents, where wave breaking is enhanced in conditions with winds obliquely aligned with ocean fronts. The wave breaking modulation by currents is enhanced with increasing model resolution at submesoscales. Submesoscale frontal surface convergence and downwelling velocities overlap with areas with enhanced wave breaking with oblique wind forcing. It is hypothesized that under these conditions air-sea gas fluxes are enhanced. This will be tested with numerical simulations at an eastern boundary current during upwelling conditions. Upwelling areas have been shown to exhibit significant variability in CO2 concentrations that is not well understood. Dissolved CO2 will be modeled neglecting biological and chemical reactions starting from a background equilibrium level and then forced with realistic fluxes, including bubble-mediated transfer coefficients. The hypothesis will be tested by comparing model solutions at varying resolutions against a control run using standard transfer coefficient parameterizations that depend only on wind speed.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.