Churning the deep: ocean mixing by breaking internal waves

通过研究海洋混合背后的物理机制，这项拟议的研究计划将解决数值气候建模和预测领域的一个关键不确定性。海洋混合发生的尺度太小，无法在全球气候模型中明确解决，因此混合的影响必须通过基于物理的模型或参数化来间接表示。气候模型对参数化混合的分布极其敏感，如何表示海洋混合的不确定性限制了我们准确预测和适应未来气候变化的能力。海洋混合的空间和时间分布主要由内波的消散决定，内波是通过海洋内部的密度界面传播并通过破裂而消散的波，很像海滩上的波浪。这项拟议的研究计划的重点是风和潮汐驱动的内波混合，因为这些过程的参数化仍然不完整，仅部分解释了不同的动力机制，如下所述。该计划有三个目标。第一个是利用数值模式探索沿海地区潮汐驱动的内波的生命周期，重点是北美西海岸。这项工作将强调了解内潮在海岸消散和混合的时间和地点，目标是开发一种用于气候模型的参数化。将利用来自大西洋、太平洋和南大洋的多年系泊观测，为第二个目标研究由风引起的内波在开阔海洋消散的深度。理论和数值模型将与观测一起使用，以了解在这些动态不同的区域中从强迫到耗散的能量路径。最后，这项研究计划的第三个目标是了解斯科特大陆架上的风和潮汐对海洋的混合，这是一个交通便利的沿海环境，有大的潮汐和风力。该区域的历史和正在进行的数据收集为探索这些过程提供了一个大型数据集。这一目标还将涉及海洋混合对海洋生物学的作用，有助于了解维持该区域具有重要商业价值的渔业的过程。这项研究的预期结果有助于我们了解全球海洋中海洋混合的方式和地点，并开发新的参数化方法，提高全球气候模型的准确性，使我们能够更有信心地预测加拿大和全球未来的变化。未来五年，该计划将培养三名研究生和四名优等生，培养他们在应用物理、数值和计算分析以及海洋学方面的技能。

By investigating the physics behind ocean mixing, this proposed research program will address a key uncertainty in the field of numerical climate modeling and prediction. Ocean mixing occurs at scales that are too small to be explicitly resolved in global climate models, and as a result the influence of mixing must be represented indirectly, by physically based models, or parametrizations. Climate models are extremely sensitive to the distribution of parametrized mixing, and uncertainties in how to represent ocean mixing limit our ability to accurately predict and adapt to future changes in climate. The spatial and temporal distributions of ocean mixing is mostly determined by the dissipation of internal waves, waves that propagate across density interfaces in the ocean's interior and dissipate by breaking, much like waves at the beach. The focus of this proposed research program is on mixing by wind- and tide-driven internal waves, as parametrizations for these processes remain incomplete, only partially accounting for different dynamical regimes, as described below. The program has three objectives. The first is to explore the lifecycles of tidally-driven internal waves in coastal regions using numerical models, with an emphasis on the west coast of North America. This work will emphasize understanding when and where internal tides are dissipated and mix at the coast, with the goal of developing a parametrization for use in climate models. The depths at which wind-driven internal waves dissipate in the open ocean will be studied for the second objective, using multi-year moored observations from the Atlantic, Pacific and Southern Oceans. Theory and numerical models will be used with the observations to understand energy pathways from forcing to dissipation in these dynamically distinct regions. Finally, the third objective of this research program is to understand ocean mixing by the winds and tides on the Scotian Shelf, a conveniently accessible coastal environment with large tides and wind forcing. Historical and ongoing data collection in this region provides a large dataset for exploring these processes. This objective will additionally address the role of ocean mixing on ocean biology, contributing to an understanding of the processes that sustain the commercially important fisheries in the region. Anticipated outcomes of this research are contributions to our understanding of how and where ocean mixing occurs in the global ocean, and the development of new parametrizations that will increase the accuracy of global climate models, enabling us to forecast future changes both in Canada and globally with greater confidence. Over the next five years, this program will train three graduate students and four honours students, developing their skills in applied physics, numerical and computational analysis and oceanography.