Collaborative Research: Next-generation Global Altimetric Maps of Internal Tide Energy Flux and Dissipation

知识价值：众所周知，内部潮汐的破裂是深海底流混合的主要驱动力。然而，输入它们的大部分能量都在最初的几个模式中，这些模式在破裂之前可以传播数千公里。因此，尽管众所周知全球环流模式对混合的地理位置很敏感，但人们对它们在哪里断裂以及如何断裂知之甚少。因此，本研究将应用最新技术，结合卫星测高、系泊和数值模型，构建低模态内潮能量通量和耗散的全球地图。该方法既捕获了粗糙地形附近的非均匀正斜压潮汐转换，也捕获了由于低模态内潮的不均匀耗散引起的斑块。卫星高度计的全球覆盖使它们成为这项任务唯一可用的实用观测工具。然而，任何一颗卫星的空间分辨率都很差，而且测高无法探测到时间上不相干的信号，这妨碍了对过去对低模态内部潮汐能和能量通量的测高估计的解释。为了解决低分辨率问题，该团队将通过结合来自T/P-Jason、T/P-Jason串联、GFO和ERS的多颗卫星测高数据，扩展他们之前的工作（其中他们使用了T/P-Jason串联任务）。最近在北太平洋演示了多卫星技术，并表明空间分辨率得到了提高，从而使测高估算与高分辨率数值模式相一致。(2)为了了解内部潮汐在不断变化的海洋中传播的相干性的丧失，pi将分析一个新的高分辨率全球模拟，该模拟包括真实的内部潮汐场以及真实的中尺度海洋环流。模型估计的不均匀运动的海洋是如何使内部潮汐不相干的，将通过分析在全球范围内收集的几个长系泊时间序列来验证。有了这些改进，这些技术现在应该能够完成绘制地球上低模态内潮的能量通量和耗散的任务。这样做，这个项目将导致更好地理解影响全球范围内潮汐传播和消散的过程。更广泛的影响：这项工作的主要更广泛的影响将是提高对消散的大小和地理的理解和参数化，这对一般环流模式具有已知的重要性。此外，小组亦会透过网站及/或与各监测站直接联络，向所有研究人员及公众提供经高空观测的内部潮汐量地图。这种地图除了在规划实验方面有很大用处外，还将与各种物理和生物地球化学研究有关。这些地图和模型模拟将用于社区外展项目，如APL的K-12志愿者名单和西雅图太平洋科学中心。这项研究还将教育三名本科生，作为华盛顿太空资助计划的一部分，该计划是华盛顿州和美国宇航局之间的一个联合计划，旨在鼓励华盛顿大学的学生追求科学事业。

Intellectual Merit:Breaking internal tides are known to be a major driver of deep-ocean diapycnal mixing. However, much of the energy input into them is in the first few modes, which can propagate 1000's of kilometers before breaking. As a result, little is known about where and how they break, in spite of the known sensitivity of global circulation models to the geography of mixing. Therefore, this study will construct a global map of low-mode internal tide energy flux and dissipation by application of state-of-the-art techniques to a combination of satellite altimetry, moorings, and a numerical model. The approach captures both the non-uniform barotropic-to-baroclinic tide conversion near rough topography as well as patchiness due to the non-uniform dissipation of low-mode internal tides.The global coverage of satellite altimeters makes them the only practical observational tool available for the task. However the poor spatial resolution of any single satellite, and the inability of altimetry to detect temporally incoherent signals, have hampered the interpretation of past altimetric estimates of low-mode internal tide energy and energy flux. This study addresses these shortcomings in order to produce the needed global maps:(1) To address the low-resolution problem, the team will expand on their previous work (in which they used the T/P-Jason tandem mission) by combining multiple satellite altimetric data from T/P- Jason, T/P-Jason tandem, GFO, and ERS. The multi-satellite technique was recently demonstrated in the North Pacific, and showed that spatial resolution is improved to the point where the altimetric estimates agree with high-resolution numerical models.(2) To understand the loss of coherence of internal tide propagating in an ever-changing ocean, the PIs will analyze a new high-resolution global simulation that includes a realistic internal tide field as well as realistic meso- and large-scale ocean circulations. The model estimate of how the non- uniform moving ocean makes internal tide incoherent will be validated by the analysis of several long moored time series collected around the globe.With these improvements, the techniques should now be up to the task of mapping the low-mode internal tide's energy flux and dissipation on the globe. In doing so, this project will lead to a better understanding of the processes that affect the propagation and dissipation of internal tide on a global scale.Broader Impacts:The primary broader impact of this work will be an improved understanding and a parameterization of the magnitude and geography of dissipation, of known importance to general circulation models. In addition, the team will provide maps of altimetrically-observed internal tide quantities to all researchers as well as the public via a website and/or direct communication with the PI's. In addition to being of great use in planning experiments, such maps will be of relevance for a variety of physical and biogeochemical studies. The maps and the model simulations will be used in community outreach programs such as APL's K-12 volunteer list and Seattle's Pacific Science Center. The study will also educate three undergraduate students as part of the Washington Space Grant program, a joint program between Washington State and NASA seeking to encourage students at the University of Washington to pursue science careers.