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

智慧价值根据理论、实验室实验和实地观察，峡谷长期以来一直被认为是强烈内波的发源地。蒙特利峡谷(MC)的湍流测量和台湾高坪峡谷(台湾)的密度反转证实了非常强烈的混合。然而，产生混合的过程还没有确定，也没有在足够多的峡谷中测量混合来评估其从一个到另一个的变异性。观测和最近的模拟表明，内部潮汐是蒙特利峡谷的主要能量来源，来自近海和当地产生。此外，峡谷沿线的山脊和狭窄使背风浪和水力跳跃很可能也是混合的主要来源，正如对深海峡谷所推断的那样。该项目将对蒙特利峡谷进行建模和密集观测，并探索附近的阿森松峡谷，后者比蒙特利更直，显然缺乏重要的近海内潮来源。目标是：1)了解内潮如何在峡谷中传播，特别是M2能量通量是如何绕过弯道的，以及当转弯如此尖锐以至于能量被耗散时，2)确定是否可以通过峡谷沿线M2能量通量的汇聚来预测混合位置和水平，3)识别和量化由内波散射、背风波和水力跳跃产生的混合，以及4)通过测量混合和内潮在相对较短的时间内对混合和斜压能量的影响来评估峡谷形状、平整度和与近海M2源对混合和斜压能量的影响。笔直的峡谷止于外大陆架。宽阔的影响美国海岸有几十个峡谷，它们几乎占到西部大陆坡度的一半。#9702；北至阿拉斯加。尽管峡谷似乎具有丰富的生物资源，并输出水和沉积物，但人们对峡谷内部的动力过程了解得太少，无法对峡谷的重要性或它们是否需要在大尺度或区域模型中进行特殊表示做出一般评估。一套测量不能解决关于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的基础。如果完全成功，这个项目可能无法实现部分混合的参数化，或者至少能够为参数化指明方向。作为拟议工作的一部分，调查人员还开始与区域建模人员谈判，将强烈的峡谷混合纳入模型，并进行敏感性运行，以确定混合必须知道有多准确，才能预测其对峡谷外流动和结构的影响。将聘用两名博士后，一名在APL/UW，另一名在夏威夷大学。两人都将参加博士后培训工作的所有阶段。与蒙特利湾MBARI定期抽样的协调和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.