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

对大气和海洋之间气体交换的准确描述还没有完全开发出来，但这是理解气候变化和生态系统动力学的关键过程。在评估气泡在大气-海洋气体交换中的重要作用时，这一点尤其成问题，特别是在大风和巨浪使直接测量极为困难的偏远海洋地区。该项目寻求通过使用大型、最先进的风浪水箱来提供所需的基本的、高风浪气体交换测量。在这里，PI可以应用他们对惰性气体(霓气、氩、氪和氙气)的新测量来计算在精确控制的条件下的总气体流量。这种储罐设置允许系统地定义物理和化学参数(温度、盐度、pH、风速、湍流、气泡大小分布等)。需要构建更准确的模型，而不存在在风暴条件下对船舶进行类似测量所固有的巨大不确定性。这项研究的一个重要成果，除了改进了对海-气交换的理解外，还可能极大地改进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示，但不能区分生物过程和大气交换，在大风和大浪条件下，强烈的气泡注入情况下，估计尤其不准确。这项研究将提高我们在海水中溶解气体的评价中分离生物和物理过程的能力。此外，该项目将为韦尔斯利学院的15名女本科生提供令人兴奋的现场研究体验，使用迈阿密大学最先进的水箱设施，结果将被纳入普通和高级化学课程。还将支持制作学生制作的短片和其他公共宣传活动，以传播有关海洋气体交换重要性的信息。由于缺乏必要的数据来定义各种风、浪和温度条件下的气泡过程，海洋和大气之间的气体交换过程的研究一直受到阻碍。目前的气体交换模型在气泡过程的参数化方面往往是非常不可靠的。这在很大程度上是因为在定义明确的条件下，在偏远地区进行传统的海上测量很困难，特别是在大风和大浪的情况下。通过使用大型持续风浪水箱(23m X 6m X 2m)，该项目的研究人员计划极大地提高我们对风、浪和温度变化对气体传输影响的理解。使用最近开发的野外便携式平衡仪质谱仪，可以几乎连续地测量惰性气体比率(Ne、Ar、Kr和Xe)，这将导致这些持续储罐实验，提供在风速从10到40米/S变化时精确描述的气体流量数据。此外，水下阴影系统将拍摄气泡图像，使研究人员能够量化气泡大小分布，这是气泡模型中缺失的一个关键因素。目前的模型使用大大简化的两种大小类别的气泡表示；这项研究将重新评估这种方法，希望创建更好的气泡大小对气体通量的作用的参数，从而改进海洋和气候应用中的气-海气体交换模型。

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.