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存储和转移的主要参与者。 了解这些气体通过海洋与大气之间的界面（称为空气通量）的数量对于准确的生物地球化学和气候预测至关重要。 将气体通过界面移动的机制太小，无法通过大多数耦合的海洋大气模型来解决，因此被参数化以说明小规模过程的效果。 空气通量主要由风速决定，但对许多其他环境因素（例如表面波和表面活性剂）敏感。 原位观察结果表明，观察到的空气通量和参数化的空气通量之间的差异很大，尤其是在高风速条件下，这表明仅风速就无法捕获影响空气气体交换的所有因素。 该项目将分析在南端格陵兰岛附近的NSF资助的研究项目中收集的数据集。 该数据集是独一无二的，可能会深入了解一些以前未衡量的机制，并控制了对空气通量通量的控制，例如在大风下发生断断续续的波浪和气泡形成。 这些发现可能有助于完善气体传输参数化，从而有助于限制气候敏感气体的区域和全球估计。 该项目将支持博士生的培训，并开发有关K-12教师可用的有关天然气交换，风暴，破坏浪潮和气候变化研究的教学材料的发展。全球空气通量通量估计基于气体转移速度k的参数化。到一阶，k是由风速（u）决定的，通常被参数化为美国的非线性函数。但是，在传统参数化的k中，k在k中的扩展很大，尤其是在高风速下。这是由于实际影响K的各种环境强迫和过程，这表明仅风速无法捕获空气水气体交换的变异性。在高风速下，断裂波成为估计气通量时要考虑的关键因素。波浪破裂导致额外的上海湍流和气泡云的产生。在这里，我们建议分析2013年的高风气交换研究实验期间收集的各种数据集，以了解和量化对气体传输速度断裂波的控制。这将是第一个研究，将波动破裂与气体转移速度引起的湍流动能耗散速率联系起来。从观察中获得的见解将纳入物理气体转移模型中。 WhiteCap的覆盖范围和破坏波统计将由从研究船Knorr的飞行桥的端口和右舷获得的可见图像确定。都将考虑非常可溶的（甲醇和丙酮）和较少的可溶性（二氧化碳，二甲基硫化物）气体，从而使波浪破裂介导的转移程度对比。海州条件将根据激光高度计和波骑手浮标的测量计算。涡流协方差通量和海水浓度的二氧化碳，二甲基硫化物，甲醇和丙酮可以直接计算转移速度。