Internal Tide Studies at the Hawaiian Ridge

[04:25347]知识价值：从盆地尺度的地表潮汐运动到最小的湍流混合尺度的能量转移途径还没有被很好地理解。一个重要的中间步骤是海面潮汐在海山、沉脊和岛屿等大洋中部地形上散射成内部潮汐，这是正压潮汐能的汇。模型显示，从这些生成区域发出的内部潮汐既有能量密度沿内部潮汐特征局域化的波束结构，也有低模态结构。内部潮的高模态分量被认为在产生地点附近消散，可能对局部混合很重要，而低模态内部潮在观测和模式中以1000公里量级的衰减尺度从它们的源区传播出去。我们预测这一过程的能力取决于经过实地观测验证的精心设计的模型。最大和最全面的潮汐转换研究是夏威夷海洋混合实验（HOME），重点研究构成夏威夷山脊的山脊、海山和岛屿地形的潮汐散射。这项研究的建模部分已被证明是非常成功的。模型对内部潮汐产生和辐射的模拟与观测到的洋流、位移、能量密度、能量通量和耗散比较有利。HOME潮汐建模工作的继续是基于普林斯顿海洋模型。该项目的目标是：1)确定整个海岭的潮汐能预算；2)检查在海岭顶部观测到的非流体静力学特征；3)评估模型湍流关闭方案与直接微观结构和精细结构测量的对比；4)确定与内部潮梁相关的海岭侧翼发生的深层混合量；5)评估内部潮对背景分层和环流变化的敏感性。HOME提供了一个理想的测试站点，以扩展我们对潮汐散射过程的理解，评估当前的建模方法，并根据现场结果开发新的工具。更广泛的影响：最终，这种活动可以改善潮汐耗散和混合的参数化，用于更大尺度的环流和气候模式，以及海山和海脊环境的区域模式。本项目将有一名本科生和两名研究生参与，目标是完成一篇毕业论文和博士论文。该项目将在夏威夷大学的年度公众开放日上得到强调，这是由海洋地球科学与技术学院赞助的一项外展活动。我们将联系夏威夷檀香山的毕晓普博物馆，根据这项研究的结果讨论可能的展览。

0425347Intellectual merit: The pathways of energy transfer from the basin-scale surface tidal motions to the smallest turbulent mixing scales are not understood well. An important intermediate step is the scattering of the surface tide into internal tides at mid-ocean topography, such as seamounts, submerged ridges, and islands, which is a sink for barotropic tidal energy. Models show internal tides emanating from these generation regions with both beam structure, where energy density is localized along internal tidal characteristics, and low-mode structure. The high-mode components of the internal tide are believed to dissipate near the generation site and may be important for local mixing, while the low-mode internal tides propagate away from their source regions with decay scales on the order of 1000 km in observations and models. Our ability to predict this process depends on well-conceived models that are validated against field observations. The largest and most comprehensive tidal conversion study has been the Hawaii Ocean Mixing Experiment (HOME), focusing on tidal scattering at the ridge, seamount, and island topography making up the Hawaiian Ridge. The modeling component of this study has proven to be highly successful. The model simulations of internal tide generation and radiation compares favorably to observed currents, displacements, energy densities, energy fluxes, and dissipation. The continuation of the HOME tidal modeling effort is based on the Princeton Ocean Model. The goals of this project are to 1) finalize the tidal energy budget for the entire ridge, 2) examine non-hydrostatic features observed over the ridge crest, 3) assess the model turbulent closure scheme versus direct microstructure and finestructure measurements, 4) determine the amount of deep mixing occurring along the ridge flanks associated with internal tide beams, and 5) assess the sensitivity of the internal tide to changes in the background stratification and circulation. HOME provides an ideal test site to expand our understanding of the tidal scattering process, to assess current modeling approaches, and to develop new tools based on the field results. Broader impacts: Ultimately this activity can lead to improved parameterizations of tidal dissipation and mixing to be used in larger scale circulation and climate models, as well as in regional models for seamount and ridge environments. An undergraduate and two graduate student will participate in this project, with the goal of achieving a senior thesis and PhD dissertations. The project will be highlighted during the annual public open house at the University of Hawaii, an outreach activity sponsored by the School of Ocean Earth Science and Technology. The Bishop Museum in Honolulu, Hawaii will be contacted to discuss a possible display based on the results of this study.