Wave Breaking in High Winds and its Effects on the Air-Sea Exchange of Gases of Varying Solubility

大风中的波浪破碎及其对不同溶解度气体海海交换的影响

• 批准号: 1537890
• 负责人: Christopher Zappa
• 金额: $ 26.45万
• 依托单位: Columbia University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-15 至 2018-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1537890&HistoricalAwards=false
• 关键词: Wave; Breaking; Winds; its; Effects

The ocean is a major player in the storage and transfer of many greenhouse gases. Understanding the amount of these gases going through the interface between ocean and atmosphere, known as the air-sea flux, is of upmost importance to accurate biogeochemical and climate predictions. The mechanisms which move the gases through the interface are too small to be resolved by most coupled ocean atmosphere models, and are therefore parameterized to account for the effect of the small scale processes. Air-sea fluxes are largely dictated by wind speed, but are sensitive to many other environmental factors such as surfaces waves and surfactants. In situ observations have shown large variability between observed and parameterized air-sea fluxes, especially under high wind speed conditions, suggesting wind speed alone cannot capture all of the factors that influence air-sea gas exchange. This project will analyze a dataset collected during a NSF-funded research project near the southern tip Greenland. This dataset is unique and may offer insight into some previously unmeasured mechanisms with control on air-sea gas flux such as breaking waves and bubble formation under high winds. The findings could help to refine gas transfer parameterizations which, in turn, would help to constrain regional and global estimates of climate sensitive gases. The project will support the training of a PhD student and the development of stimulating teaching materials about research into gas exchange, storms, breaking waves and climate change, available to K-12 teachers. Global air-sea gas flux estimates are based on parameterizations of the gas transfer velocity k. To first order, k is dictated by wind speed (U) and is typically parameterized as a non-linear function of U. There is, however, a large spread in k predicted by the traditional parameterizations, especially at high wind speed. This is due to a large variety of environmental forcings and processes that actually influence k, suggesting wind speed alone cannot capture the variability of air-water gas exchange. At high wind speed, breaking waves become a key factor to take into account when estimating gas fluxes. Wave breaking results in additional upper ocean turbulence and generation of bubble clouds. Here, we propose to analyze the diverse data set collected during the High Wind Gas exchange Study experiment in 2013 to understand and quantify the control of breaking waves on gas transfer velocities. This will be a first study linking turbulent kinetic energy dissipation rates resulting from wave breaking to gas transfer velocities. Insights gained from observation will be incorporated into physical gas transfer models. Whitecap coverage and breaking wave statistics will be determined from visible imagery acquired from the port and starboard side of the flying bridge of the Research Vessel Knorr. Both very soluble (Methanol and Acetone) and less soluble (Carbon Dioxide, Dimethyl Sulfide) gases will be considered, allowing to contrast the degree of wave breaking mediated transfer. Sea state conditions will be computed from laser altimeter and wave rider buoy measurements. Eddy covariance fluxes and sea water concentration of Carbon Dioxide, Dimethyl Sulfide, Methanol and Acetone allow for direct calculation of transfer velocities.

海洋是许多温室气体储存和转移的主要参与者。了解这些气体通过海洋和大气之间的界面的量，即所谓的海-气通量，对于准确的生物地球化学和气候预测至关重要。气体通过界面的机制太小，不能被大多数耦合的海洋大气模式所解析，因此被参数化以考虑小尺度过程的影响。海气通量在很大程度上是由风速决定的，但对许多其他环境因素，如表面波和表面活性剂，也很敏感。现场观测显示，观测到的海气通量与参数化的海气通量之间存在很大的差异，特别是在高风速条件下，这表明仅靠风速不能反映影响海气交换的所有因素。这个项目将分析在格陵兰岛南端附近NSF资助的一个研究项目中收集的数据集。这一数据集是独一无二的，可以提供对一些以前未测量的控制海-气通量的机制的洞察，例如大风下的破碎波和气泡形成。这些发现可能有助于完善气体转移参数，这反过来将有助于限制区域和全球对气候敏感气体的估计。该项目将支持对一名博士生的培训，并为K-12教师编写有关气体交换、风暴、破浪和气候变化研究的激励性教材。全球海气通量的估算是基于气体输送速度k的参数化的。一阶而言，k由风速(U)决定，并且通常被参数化为U的非线性函数。然而，传统的参数估计在k中有很大的扩散，特别是在高风速时。这是由于实际影响k的各种环境作用力和过程所致，这表明仅靠风速不能捕捉到空气-水气体交换的可变性。在高风速时，破碎波成为估算气体通量时要考虑的一个关键因素。波浪破碎会导致额外的上层海洋湍流和气泡云的产生。在这里，我们建议分析2013年高风气体交换研究实验期间收集的各种数据集，以了解和量化破碎波对气体传输速度的控制。这将是首次将波浪破碎引起的湍动能耗散率与气体传输速度联系起来的研究。从观测中获得的见解将被纳入气体物理传输模型。白浪复盖率和破碎波统计数据将根据从科诺尔号考察船飞行驾驶台左右侧获取的可见光图像确定。极易溶的(甲醇和丙酮)和难溶的(二氧化碳、二甲基硫化物)气体都将被考虑，允许对比波破裂介导的转移的程度。海况将通过激光高度计和乘波浮标的测量来计算。涡动协方差通量和海水中二氧化碳、二甲基硫化物、甲醇和丙酮的浓度可以直接计算输送速度。