Collaborative Research: RUI: Investigating Gas Exchange Processes using Noble Gases in a Controlled Environment

大气和海洋之间气体交换的精确描述尚未完全发展，但它是理解气候变化和生态系统动态的关键过程。在评估气泡在海-气气体交换中的重要作用时，尤其是在大风和海浪使直接测量极其困难的偏远海洋位置，这一点尤其成问题。该项目旨在通过使用大型的最先进的风浪箱来提供所需的基本的高风浪气体交换测量。 在这里，PI可以应用他们对稀有气体（氖、氩、氪和氙）的新测量来计算精确控制条件下的总气体通量。这种罐设置允许系统的方法来定义物理和化学参数（温度、盐度、pH、风速、湍流、气泡尺寸分布等）。需要构建更精确的模型，而不会在风暴条件下从船上进行类似测量时固有的巨大不确定性。这项研究的一个重要成果，除了提高对海-气气体交换的理解外，还可以大大提高对光合作用和呼吸作用之间关键生态平衡的估计。目前的方法使用溶解在海水中的二氧化碳和氧气作为生物活动的指标，但无法区分生物过程和大气交换，在高风浪和强烈气泡喷射的情况下，估计尤其不准确。这项研究将提高我们的能力，分离生物和物理过程中的溶解气体在海水中的评价。此外，该项目将为韦尔斯利学院的15名女本科生提供一个令人兴奋的现场研究经验，使用迈阿密大学最先进的罐设施，其结果将纳入普通和高级化学课程。还将支持制作学生创作的短格式视频和其他公众宣传活动，以传播有关海洋气体交换重要性的信息。海洋和大气之间气体交换过程的研究一直受到缺乏所需数据的阻碍，这些数据可以定义各种风，波浪和温度条件下气泡过程的定量关系。目前的气体交换模型往往是非常不可靠的参数化气泡过程。在很大程度上，这是由于在明确定义的条件下，特别是在大风和大浪的情况下，难以在偏远地区进行传统的海上测量。通过使用大型SUSTAIN风浪罐（23 m x 6 m x 2 m），该项目的研究人员计划大大提高我们对风，波浪和温度变化对气体传输影响的理解。使用最近开发的，现场便携式平衡质谱仪，允许几乎连续测量惰性气体的比例（氖，氩，氪，和氘）将导致这些SUSTAIN罐实验提供精确表征的气体流量数据在不同的风速从10到40米/秒。此外，水下阴影系统将对气泡进行成像，使研究人员能够量化气泡大小分布，这是气泡模型中缺少的一个关键因素。目前的模型使用一个大大简化的，两个大小级别的气泡表示;这种方法，本研究将重新评估，希望创造更好的参数化气泡大小对气体通量的作用，从而改善海洋和气候应用的海气交换模型。

An exact description of gas exchange between the atmosphere and the ocean is not fully developed, yet it is a critical process for understanding climate change and ecosystem dynamics. This is particularly problematic when evaluating the important role of bubbles in air-sea gas exchange, especially in remote ocean locations where high winds and waves make direct measurements extremely difficult. This project seeks to provide needed fundamental, high wind/wave gas-exchange measurements by using a large, state-of-the-art, wind-wave tank. Here the PIs can apply their novel measurements of noble gases (neon, argon, krypton, and xenon) to calculate overall gas fluxes under precisely controlled conditions. This tank setting allows a systematic approach to define the physical and chemical parameters (temperature, salinity, pH, wind speed, turbulence, bubble size distribution, etc.) required to construct more accurate models without the great uncertainties inherent in making similar measurements from a ship in storm conditions. A significant outcome of this study, beyond improved understanding of air-sea gas exchange, could be greatly improved estimates of the critical ecological balance between photosynthesis and respiration. Current methods use carbon dioxide and oxygen dissolved in seawater as an indication of biological activity, but cannot distinguish between biological processes and atmospheric exchange, and estimates are especially inaccurate under high wind and wave conditions with strong bubble injection. This study will improve our ability to separate biological and physical processes in evaluation of dissolved gasses in seawater. Also, this project will provide 15 female undergraduate students at Wellesley College with an exciting, on-site research experience using a state-of-the-art tank facility at the University of Miami, and results will be incorporated into general and advanced chemistry classes. The production of student-created, short format videos, and other public outreach activities will also be supported to disseminate information on the importance of marine gas exchange.The study of gas exchange processes between the ocean and the atmosphere has been hindered by the lack of data required to define quantitative relationships that account for bubble processes under a variety of wind, wave, and temperature conditions. Current gas exchange models tend to be highly unreliable in their parameterization of bubble processes. In large part, this is due to the difficulty of making traditional measurements at sea in remote locations within well-defined conditions, especially with high winds and waves. By using the large SUSTAIN wind-wave tank (23 m x 6 m x 2 m), the researchers in this project plan to greatly advance our understanding of the effect of wind, wave, and temperature variability on gas transfer. The use of a recently developed, field-portable equilibrator mass spectrometer that allows nearly continuous measurements of noble gas ratios (Ne, Ar, Kr, and Xe) will result in these SUSTAIN tank experiments providing precisely characterized gas flux data under varying wind speeds from 10 to 40 m/s. In addition, an underwater shadowgraph system will image bubbles, allowing the researchers to quantify bubble size distributions, a key factor missing from bubble models. Current models use a greatly simplified, two size-class representation of bubbles; an approach that this research will re-evaluate in hopes of creating better parameterizations of the role of bubble size on gas flux, and consequently improved air-sea gas exchange models for oceanic and climatic applications.