Collaborative Research: Influence of Surfactants on Air-Sea Gas Exchange: 3He/SF6 Experiments in the Baltic Sea

合作研究：表面活性剂对海气交换的影响：波罗的海的 3He/SF6 实验

• 批准号: 1756807
• 负责人: David Ho
• 金额: $ 43.47万
• 依托单位: University of Hawaii
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2018
• 资助国家: 美国
• 起止时间: 2018-03-01 至 2022-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1756807&HistoricalAwards=false
• 关键词: Collaborative; Research; Influence; Surfactants; Air

Gas exchange, the movement of gases between the atmosphere and the surface ocean (in both directions), is an important process to understand in global biogeochemistry. A particular area of interest is the rate of exchange of gases such as carbon dioxide and dimethyl sulfide, which play important roles in Earth's climate. Understanding and modeling air-sea exchange on a global scale requires understanding of how gas exchange rates vary in response to a number of factors such as temperature, wind speed, and the presence of surface chemical films (known as surfactants) in the ocean. Over the past 25 years, major advances have been made in understanding air-sea gas exchange in the open ocean, mainly due to improvements in methodology and a number of successful process studies. However, some important questions remain, such as what happens near coastal areas (including inland seas), and how surfactants affect gas exchange. The Baltic Sea Gas Exchange Experiment (Baltic GasEx) is a collaboration between scientists from the US and Germany designed to address these questions. Participants in Baltic GasEx will measure the air-sea gas exchange rates with different techniques in the Baltic Sea before and after the spring bloom, when concentrations and compositions of surfactants will be different. The expeditions will be conducted on a German ship (Alkor), with the ultimate goal of quantifying the relationship between wind speed and gas exchange in an inland sea, and understanding the impact of surfactants on air-sea gas exchange. The project will involve significant international collaboration, public education and outreach through both participating U.S. institutions, and substantial student training in partnership with the international collaborators.NSF funding will support helium-3 and sulfur hexafluoride measurements during Baltic GasEx to determine the gas exchange rate. German colleagues are independently funded to quantify surfactants with AC voltammetry, surface tension, and sum frequency generation; to determine chemical characteristics of the micro layer; and to estimate the gas exchange rate using eddy covariance flux measurements of CO2 and DMS. The proposed experiment is designed to address the question of whether open ocean wind speed/gas exchange parameterizations can be applied to inland seas like the Baltic. Also, the effect of surfactants on gas exchange has been studied extensively in the laboratory, but there is little direct field evidence for the effect of surfactants on gas exchange. The proposed experiment, with expeditions at times with both high and low surfactant concentrations, should shed new light on the effect of natural surfactants on gas exchange. Finally, some wind speed/gas exchange parameterizations proposed for the Baltic Sea appear to be higher than typical open ocean parameterizations. These are typically based on eddy covariance flux measurements of CO2. However, in open ocean experiments where both the helium-3/sulfur hexafluoride approach and eddy covariance of CO2 have been deployed, there seems to be a discrepancy between gas transfer velocities measured with the two techniques. This experiment should show whether a similar difference in gas transfer velocities measured via these two techniques also exists in the Baltic Sea.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.

气体交换是大气和地面海洋之间的气体运动（在两个方向上），是在全球生物地球化学中理解的重要过程。感兴趣的特定领域是气体的交换速率，例如二氧化碳和二甲基硫化物，它们在地球气候中起着重要作用。在全球范围内理解和建模空气交换需要了解气体汇率如何响应许多因素，例如温度，风速和海洋中表面化学膜（称为表面活性剂）的存在。在过去的25年中，在理解公海中的空气气体交换方面取得了重大进展，这主要是由于方法论的改善和许多成功的过程研究。但是，仍然存在一些重要的问题，例如沿海地区（包括内陆海）发生的事情，以及外冲洗方式如何影响天然气交换。波罗的海气体交换实验（波罗的海Gasex）是美国和德国旨在解决这些问题的科学家之间的合作。波罗的海Gasex的参与者将在春季开花之前和之后使用波罗的海的不同技术测量空气气体汇率，而生存的浓度和成分将不同。这些探险将在德国船（Alkor）上进行，其最终目标是量化内陆海中风速和气体交换之间的关系，并了解表面活性剂对气海气体交换的影响。该项目将通过参与的美国机构涉及大量的国际合作，公共教育和外展活动，并与国际合作者合作进行大量学生培训。NSF资金将支持波罗的海Gasex期间的Helium-3和硫磺Hexafluoride测量值，以确定气体汇率。德国同事是独立资助的，用于用交流伏安法，表面张力和总和频率产生量化表面优美。确定微层的化学特征；并使用二氧化碳和DMS的涡流协方差测量值估算气体汇率。拟议的实验旨在解决是否可以将开海风速/气体交换参数应用于波罗的海像内陆海洋的问题。同样，表面报委会对气体交换的影响是否在实验室中进行了广泛研究，但是直接证据表明表面活性剂对气体交换的影响。拟议的实验有时具有较高和低表面活性剂浓度的探险，应该对天然表面活性剂对气体交换的影响进行新的启示。最后，提出的一些风速/气体交换参数比典型的开放海洋参数高。这些通常基于二氧化碳的涡流协方差通量测量值。然而，在开放海洋实验中，已经部署了氦3/硫六氟化物方法和涡流的涡流协方差，似乎用两种技术测量的气体传递速度之间存在差异。该实验应显示通过这两种技术测得的气体传输速度的相似差异也存在于波罗的海。该奖项反映了NSF的法定任务，并使用基金会的知识分子优点和更广泛的影响评估标准，被认为是通过评估来获得的支持。