Collaborative Research: The Internal Tide and Mixing in Monterey and Ascension Canyons

智力价值根据理论、实验室实验和实地观察，峡谷长期以来被认为是强烈内波的场所。蒙特利峡谷（MC）的湍流测量和高平峡谷（台湾）的密度翻转（其大小和形状相似）证实了非常强烈的混合。然而，产生混合的过程尚未确定，也没有在足够多的峡谷中测量混合以评估其之间的变化。观测和最近的建模表明，内潮汐是蒙特利峡谷的主要能源来源，来自近海以及本地产生。此外，峡谷沿线的山脊和收缩使得背风波和水跃也是混合的主要来源，正如对深渊峡谷的推断一样。该项目将对蒙特利峡谷进行建模和密集观测，并对附近的阿森松峡谷进行勘探，阿森松峡谷比蒙特利笔直得多，显然缺乏重要的近海内潮汐源。目标是：1) 了解内潮如何在峡谷中传播，特别是 M2 能量通量如何围绕弯道引导，以及何时转弯太急以至于能量耗散，2) 确定是否可以通过沿峡谷 M2 能量通量的收敛来预测混合位置和水平，3) 识别和量化由内波散射、背风波和水跃产生的混合，以及 4) 评估峡谷形状、平滑度和对齐方式的影响近海 M2 源通过测量结束于外陆架的相对较短、笔直的峡谷中的混合和内潮汐来产生混合和斜压能量。海岸有数十个峡谷，它们几乎占据了从北纬 45 度到阿拉斯加的西部大陆坡的一半。尽管它们似乎生物丰富，并且输出水和沉积物，但人们对峡谷内的动力学过程知之甚少，无法对峡谷的重要性或它们是否需要在大规模或区域模型中进行特殊表示进行一般评估。一组测量无法解决有关峡谷动力学的所有问题，但拟议的工作应该为评估其他峡谷的混合提供定性和定量基础。如果完全成功，该项目可能无法对某些混合进行参数化，或者至少能够指出参数化的方法。作为拟议工作的一部分，研究人员还开始与区域建模者进行谈判，将强烈的峡谷混合纳入模型中，并进行敏感性运行，以确定必须了解混合的准确程度，以预测其对峡谷外的水流和结构的影响。将聘用两名博士后，一名在 APL/UW，另一名在夏威夷大学。两人都将参与博士后培训的各个阶段的工作。与蒙特利湾定期 MBARI 采样的协调与合作将使该项目受益，反之亦然。外展活动将结合早期的峡谷测量和未来的测量。

Intellectual MeritBased on theory, laboratory experiments and field observations, canyons have long been identified as sites of intense internal waves. Turbulence measurements in Monterey Canyon (MC) and density overturns in Kaoping Canyon (Taiwan), which has similar size and shape, confirm very strong mixing. The processes generating the mixing, however, have not been determined, nor has mixing been measured in enough canyons to assess its variability from one to another. Observations and recent modeling indicate that the internal tide is a major source of energy in Monterey Canyon, coming from offshore as well as being generated locally. In addition, ridges and constrictions along the canyon make it likely that lee waves and hydraulic jumps are also major sources of mixing, as has been inferred for abyssal canyons.The project will undertake modeling and intensive observations for Monterey Canyon and exploration of nearby Ascension Canyon which is much straighter than Monterey and apparently lacks a significant offshore source for the internal tide. The goals are to: 1) understand how the internal tide propagates in canyons, and in particular how the M2 energy flux is steered around bends and when turns are so sharp that the energy is dissipated, 2) determine whether mixing locations and levels can be predicted by convergences in the along-canyon M2 energy flux, 3) identify and quantify mixing produced by internal wave scattering, lee waves and hydraulic jumps, and 4) assess the effects that canyon shape, smoothness and alignment with offshore M2 sources have on mixing and baroclinic energy by measuring mixing and the internal tide in a relatively short, straight canyon ending on the outer shelf.Broader ImpactsU.S. coasts have dozens of canyons, and they account for almost half of the western continental slope from 45◦N to Alaska. Though they appear to be biologically rich and export both water and sediments, dynamical processes within canyons are too poorly understood to make a general assessment of the importance of canyons or whether they require special representation in large-scale or regional models. One set of measurements cannot resolve all questions about canyon dynamics, but the proposed work should provide qualitative and quantitative bases for assessing mixing in other canyons.. If fully successful, this project may unable the parameterization of some of the mixing or at least be able to point the way to parameterizations. As part of the proposed effort the investigators have also begun talks with regional modelers to incorporate intense canyon mixing into the models and to do sensitivity runs to define how accurately the mixing must be known to predict its effect on flows and structures outside the canyon. Two post-doc will be hired, one at APL/UW and another at the University of Hawaii. Both willparticipate in all phases of the work for their postdoctoral training. Coordination and collaboration with the regular MBARI sampling of Monterey Bay will benefit this project, and vice versa. Outreach activities will combine earlier canyon measurements and the future measurements.