Experiments on the interaction of Large-Scale Oceanic Oirculation with Eddies, Jets and Internal Waves using Optical Altimetry

摘要：这是一项关于海洋环流及其小尺度但能量充沛的组成部分的实验研究。利用一种新发现的实验室遥感技术，我们称之为光学测高，将研究环流与涡流、内波和射流浓度的相互作用。北大西洋次极地环流是特别关注的焦点。在那里，已经确定了几个外部环流源（风、深对流和来自南北的入侵流）。一般环流的内部来源，位涡（PV）场的涡流搅拌，将在详细的动力学实验中进行评估，使用具有显著底部地形特征的理想海洋盆地。平行数值实验将使用分层的流体静力海洋模型进行。具体的实验计划是：(i)，一般环流集中到射流和锋与稳定流动相互作用的底部地形，（ii），由复杂海底脊和海山场上的准地转、时变流动驱动的大尺度环流，（iii），涡流-地形与密度分层的相互作用，包括气压临床不稳定海岸流的生命周期，（iv），内波和对流与分层，gesotrophic流动。光学测高仪利用旋转流体表面的抛物线形状作为牛顿望远镜，使整个表面高程场的成像分辨率优于1微米，并且具有很高的横向分辨率。通过在地表投影彩虹图像，我们恢复了精确的高程、速度和涡度场。分层实验将使用内层厚度传感，也使用光学。第四组实验需要特别说明。这些高纬度海洋的数值模拟很少包含非流体静力学、非地转动力学，在这个领域，三维实验室实验可以具有令人印象深刻的空间分辨率。利用我们新的实验能力，可以探索盆地尺度环流与内波、锋面、对流和三维湍流之间的来回相互作用。所有这些都是在亚极地海洋中很强的。水力“下坡射流”是在水流穿过重要的底部地形时形成的，并将研究它们与中尺度气旋涡产生的相互作用；将探讨内波辐射和孤立涡旋和涡旋组合的捕获，以及边界层湍流和地转流之间的来回能量转换。智力优势：位涡动力学是海洋和大气环流场理论的关键和基础。它表达了涡旋活动和大气环流之间强有力的关系。发展和利用这种“PV思维”对于基础科学和全球气候模式的重要模拟都很重要，因为全球气候模式无法解决控制PV场的所有详细高纬度过程。更广泛的影响：了解海洋气候系统对于解决全球变暖这一更大的问题及其对减缓全球海洋环流的预期影响至关重要。大多数在温室气体增加的情况下运行的气候模型发现，本世纪大西洋经向翻转的速度减慢了40%。如果仔细观察，亚极地大西洋的动力学是这种效应的关键组成部分。横向环流与全球经向翻转环流之间存在相互作用。除了气候研究之外，这项关于基本PV动力学的工作影响了我们对大气环流和其他行星大气的理解。它与全球变暖下地球生态系统的命运有着密切的关系。

ABSTRACTOCE-0648575This is an experimental investigation of the oceanic circulation and its small-scale, yet energetic, components. Using a newly discovered laboratory remote-sensing technique which we call optical altimetry, the interaction of the circulation with eddies, internal waves and jet-like concentrations of flow will be studied. The circulation of the subpolar North Atlantic Ocean is the particular focus. There, several external sources of circulation have been identified (wind, deep convection, and incursion of currents from north and south). An internal source of general circulation, the eddy stirring of the potential vorticity (PV) field, will be evaluated in detailed dynamics experiments using idealized ocean basins with significant bottom topographic features. Parallel numerical experiments will be carried out using a layered, hydrostatic ocean model. The specific experiments planned are (i), the concentration of general circulation into jets and fronts with steady flow interacting bottom topography, (ii), large-scale circulation driven by quasi-geostrophic, time-variable flow over a field of complex seafloor ridges and seamounts, (iii), eddy-topography interaction with density stratification including the life-cycle of a baroclinically unstable coastal current and, (iv), internal waves and convection interacting with stratified, gesotrophic flows. Optical altimetry exploits the parabolic shape of the surface of a rotating fluid as a Newtonian telescope, allowing the entire surface elevation field to be imaged with better than 1 micron resolution, and high lateral resolution. By projecting a rainbow image on the surface, we recover accurate elevation, velocity and vorticity fields. Stratified experiments will use interior layer thickness sensing, also optically. The fourth set of experiments requires special comment. Numerical modeling of these high latitude oceans rarely incorporates non-hydrostatic, non-geostrophic dynamics, and in this area 3-dimensional lab experiments can have impressive spatial resolution. With our new experimental capability the back-and-forth interaction among basin-scale circulation and internal waves, fronts, convection and 3-dimensional turbulence can be explored. All are known to be strong in the subpolar oceans. Hydraulic 'down-slope jets' form as flow crosses significant bottom topography, and their interaction with mesoscale cyclonic eddy generation will be investigated; internal wave radiation and trapping by isolated vortices and vortex assemblages will be explored, as will the back-and-forth conversion of energy between boundary-layer turbulence and geostrophic flow.Intellectual Merit: Potential vorticity dynamics is the key, underlying field theory of thecirculation of oceans and atmosphere. It expresses powerful relationships between eddy activity and general circulation. Developing and exploiting this 'PV thinking' is important both as basic science, and as support for important simulations of global climate models, which cannot resolve all the detailed high-latitude processes which control the PV field.Broader impacts: Understanding the ocean climate system is of key importance to the largerproblem of global warming and its predicted effect in slowing the global ocean circulation. Most climate models run with increasing greenhouse gases find a slowing of the Atlantic meridional overturning, by as much as 40%, during this century. If one looks closely, the dynamics of the subpolar Atlantic is a crucial component of this effect. There is interaction of lateral gyre circulations interact with the global meridional overturning circulation. Beyond climate research, this work on basic PV dynamics impacts our understanding of circulations of the atmosphere, and the atmospheres of other planets. It has strong relationships with the fate of Earth's ecosystems under global warming.