Collaborative Research: Forcing, Energy Flow and Impacts of Oceanic Infragravity Waves

该项目将检测周期从30秒到一小时的海洋表面重力波，即“亚重力”波段。现有的海底压力、地磁场、大气压力和海洋重力波观测资料将用光谱技术进行分析，以检验利用能量产生次重力波的机制（源）。来源包括海啸和涌浪与海岸线、海洋表面潮汐的相互作用，以及以前在太阳风、地震、地磁、气压和电离层数据中观测到的太阳正常模态的能量。igw可以是不同现象之间的重要连接器，将源变异性与地球正常模态的激发、南极洲冰架的弯曲、深海混合的贡献以及在高度计数据中添加“噪声”联系起来。如果理解并适当地建模为IGW，则可以将此类噪声降至最低，以改善此类测高数据。此外，该项目将有助于培养一名物理海洋学研究生，培养下一代科学家，使他们有能力探索我们的星球，创造一个更环保的未来。随着技术的发展，对地球和地外变量（如太阳风和海底压力）的观测变得越来越容易，新的信息使人们对不同现象之间的高度联系有了更深入的了解。长期以来，人们对所谓的次重力波（igw；周期为30秒至1小时的海洋表面重力波）感兴趣，因为它们是由海岸的海啸和膨胀（周期小于30秒）激发的。在海岸上形成的igw是加剧海啸和涌浪引发的洪水和侵蚀的一个因素。在开阔的海洋中，igw较弱，但已经发现了意想不到的能量途径，产生了显著的现象，例如地球正常模式的持续激发，这些信号现在经常用于探索地球结构和组成的细节。但是，对于igw的各种能量来源，以及这些能量对亚重力波的作用机制（即能量途径）的理解是有限的。主要研究人员最近证明了两种新能源的存在：海洋表面潮汐和太阳正常模态。该项目将：(1)获得更多关于进入igw的潮汐和太阳能路径的观测证据；(2)将这两种源的贡献量化为频率、时间段（如季节、11年太阳活动周期）和位置（如地磁纬度、边缘海与公海）的函数。这些源对igw的相对贡献，特别是它们的空间分布，对于理解igw的影响及其与上述其他现象的联系至关重要。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project will examine oceanic surface gravity waves with periods from 30 seconds to an hour, the ‘infragravity’ waveband. Existing observations of ocean bottom pressure, geomagnetic field, atmospheric pressure, and ocean gravity waves will be analyzed with spectral techniques to examine the mechanisms (sources) by which energy is used to generate infragravity waves (IGW). Sources include the interactions of tsunami and swell with coastlines, ocean surface tides, and energy from the solar normal modes that have previously been observed in solar wind, seismic, geomagnetic, barometric, and ionospheric data. IGWs can be important connectors between disparate phenomena, connecting source variability to the excitation of earth’s normal modes, flexing of ice shelves in Antarctica, contribution to mixing in the abyssal ocean, and adding ‘noise’ in altimeter data. If understood and modeled appropriately as IGW, such noise could be minimized, to improve such altimetry data. In addition, this project will contribute to the education of a graduate student in physical oceanography building the next generation of scientists capable of exploring our planet for a more environmentally secure future.As technology has expanded the availability of observations of terrestrial and extra-terrestrial variables, such as the solar wind and pressure at the bottom of the oceans, new information has yielded insight into how highly connected disparate phenomena can be. Of longstanding interest are so-called infragravity waves (IGWs; oceanic surface gravity waves at periods of 30 seconds to an hour) due to their excitation by tsunamis and swell (gravity wave periods less than 30 seconds) at the coasts. IGWs forced at the coasts are a factor that enhances flooding and erosion by tsunamis and swell. In the open ocean, IGWs are weaker, but have been found to be unexpected pathways for energy that engender remarkable phenomena, such as the continuous excitation of Earth's normal modes, signals that are now regularly used to explore the details of Earth's structure and composition. But understanding is limited regarding the various sources of energy for the IGWs, and the mechanisms this energy contributes to infragravity waves (i.e., the energy pathways). The principal investigators recently demonstrated the existence of two new energy sources: ocean surface tides and solar normal modes. This project will: (1) acquire more observational evidence of the tidal and solar energy pathways into the IGWs; and, (2) quantify the contributions of these two sources as a function of frequency, time period (e.g., season; 11-yr solar cycle) and location (e.g., geomagnetic latitude; marginal seas vs. open ocean). The relative contributions of these sources to IGWs, and especially their spatial distribution, are crucial characteristics for understanding the impacts of IGWs and their connections to the other phenomena noted above.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.