Collaborative Research: Tasmanian Tidal Dissipation Experiment (T-TIDE)

深海的潮汐混合并不一定发生在正压潮能量损失的地方，而是发生在低模斜压潮消散的地方，也许在数千公里之外。海洋环流模式对深度混合的强度和地理位置很敏感，但对这一过程的观测很少。了解潮汐耗散的位置和机制对它们的持续改进是必要的。塔斯马尼亚潮汐耗散实验？s （T-TIDE）假说认为，当传播的低模态内潮撞击陡峭的大陆斜坡时，会发生显著的潮汐耗散。斜坡的几何形状影响波的反射、透射、散射和破碎，进而决定混合的空间分布。重要的破坏机制可能包括小尺度测深中的背风效应和临界斜坡附近的非线性钻孔形成。我们提出了一个协调的观测/建模努力，以了解物理几何，以及耗散和混合的大小。目标是1)确定混合发生在大陆斜坡上的位置，2)确定主要的耗散过程，3)评估传输到大陆架并反射回深海并在其他地方耗散的能量量，以及4)将这些结果概括为数值模式中地形散射和耗散的参数化，理想情况下，地形散射和耗散取决于地形、分层、正压和/或低模斜压潮汐。实验计划的三个主要组成部分是：1)在实地考察前后进行密集的二维和三维建模，以规划和情境化测量；2)基于滑翔机的侦察实验，识别动态过程，评估模型，确定系泊地点；3)利用船舶、滑翔机和系泊的时间和空间分辨率进行综合过程实验，以解决T-TIDEs假设并实现其目标。一系列剖面和固定传感器系泊将与充当虚拟系泊的滑翔机相结合。潮汐分辨或更高频率的观测将直接或通过精细尺度参数化测量内部波运动、能量通量、耗散和混合。内潮海面高度的测高分析将与澳大利亚滑翔机一起评估事件内潮的中尺度折射，该滑翔机将监测塔斯曼海的水文和内潮位移。更广泛的影响拟议的工作将提供关于潮汐能耗散的全球见解。具体地说，大陆坡上的潮汐耗散可能是气候模式中下一代混合参数化的一个重要组成部分。作为实验的一部分，研究生将接受培训。除了其科学意义之外，T-TIDE还将赞助并参加两个培训研讨会，参与者是负责在圣地亚哥联合学区提供地球科学课程的高中科学教师。这项工作将与斯克里普斯的桦树水族馆一起进行。最后，该项目的一个基本要素是与澳大利亚和加拿大科学家开展强有力的合作和资源共享。

Intellectual MeritTidal mixing of the deep ocean does not necessarily occur where energy is lost from the barotropic tide, but rather where the low-mode baroclinic tide dissipates, perhaps thousands of kilometers away. Ocean general circulation models are sensitive to the magnitude and geography of deep mixing, but very few observations of this process exist. Understanding the location and mechanisms of tidal dissipation is necessary for their continued improvement. The Tasmanian Tidal Dissipation Experiment?s (T-TIDE) hypothesis is that significant tidal dissipation takes place where propagating low-mode internal tides impinge on steep continental slopes. Slope geometry affects wave reflection, transmission, scattering, and breaking, which in turn determine the spatial distribution of mixing. Important breaking mechanisms may include lee effects at small-scale bathymetry and nonlinear bore formation near critical slopes. We propose a coordinated observational/modeling effort to understand the physics geometry, and magnitude of dissipation and mixing. The goals are to 1) identify where mixing occurs on the continental slope, 2) determine the dominant dissipative processes, 3) assess the amount of energy transmitted onto the shelf and reflected back into the deep sea to be dissipated elsewhere, and 4) generalize these results as a parameterization of topographic scattering and dissipation in numerical models, which ideally depends on the topography, stratification, and the barotropic and/or low-mode baroclinic tides. The three main components to the experimental plan are 1) intensive 2D and 3D modeling before and after the fieldwork to plan and contextualize the measurements; 2) a glider based Scout Experiment to identify dynamic processes, evaluate models, and finalize mooring sites; and 3) a comprehensive Process Experiment using ships, gliders, and moorings with the time and space resolution to address T-TIDEs hypothesis and achieve its goals. An array of profiling and fixed-sensor moorings will be combined with gliders acting as virtual moorings. Tidally-resolving or higher-frequency observations will measure internal wave motions, energy fluxes, and dissipation and mixing either directly or via finescale parameterizations. An altimetric analysis of internal-tide sea surface height will assess mesoscale refraction of the incident internal tide along with Australian gliders, which will monitor hydrography and internal tidal displacements in the Tasman Sea. Broader ImpactsThe proposed work will provide global insights on the dissipation of tidal energy. Specifically, inclusion of tidal dissipation on continental slopes may be an important component of the next generation of mixing parameterizations in climate models. Graduate students will be trained as part of the experiment. In addition to its scientific import, T-TIDE will sponsor and participate in two training seminars with high school science teachers who are charged with delivering the earth science program in San Diego Unified School District. This effort will be performed in conjunction with the Birch Aquarium at Scripps. Finally, an essential element of the project is the development of strong collaboration and resource sharing with Australian and Canadian scientists.