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

该项目将研究周期从30秒到一小时的海洋表面重力波，即“亚重力”波段。现有对海底压力、地磁场、大气压力和海洋重力波的观测将用频谱技术进行分析，以研究能量被用来产生次重力波(IGW)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察到的太阳正常模式的能量。IGW可以是不同现象之间的重要连接点，将源的可变性与地球正常模式的激发、南极洲冰架的弯曲、对深海混合的贡献以及在高度计数据中增加“噪音”联系在一起。如果理解并适当地将其建模为IGW，则可以最大限度地减少此类噪声，以改进此类测高数据。此外，该项目将有助于物理海洋学研究生的教育，培养下一代能够探索我们的星球以实现更环境安全的未来的科学家。随着技术的发展，对地球和地外变量的观测越来越广泛，例如太阳风和海底压力，新的信息已经洞察到不同的现象可以有多么高度的联系。长期以来，人们感兴趣的是所谓的次重力波(IGW；周期为30秒至一小时的海洋表面重力波)，因为它们由海啸和海岸膨胀(重力波周期小于30秒)激发。强迫在沿海的政府间水灾是一个因素，它加剧了海啸的洪灾和侵蚀，并导致海平面上升。在开阔的海洋中，IGW较弱，但已被发现是产生显著现象的能量的意想不到的路径，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。但对于IGW的各种能量来源以及这种能量对亚重力波的贡献机制(即能量路径)，人们的了解有限。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式。该项目将：(1)获取更多关于潮汐和太阳能进入全球海洋观测系统的路径的观测证据；(2)量化这两个来源在频率、时间周期(例如，季节；11年太阳周期)和地点(例如，地磁纬度；边缘海与开阔海洋)之间的贡献。这些来源对政府间水资源的相对贡献，特别是它们的空间分布，是理解政府间水资源的影响及其与上述其他现象的联系的关键特征。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智力优势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.