Collaborative Research: Quantifying the Kinetic Energy Pathways to Dissipation in the World Ocean

海洋环流是海盆尺度强迫与毫米尺度耗散平衡的结果。虽然我们有气候学的机械和热能来源的测量，以及一些小尺度耗散的有限覆盖范围，但对能量从强迫到耗散尺度的转移过程知之甚少。该项目的目标是从观测和数值模型中量化全球海洋中消散的主要途径。分析将是全球性的，但将特别关注南大洋，因为大部分大规模的风强迫为这部分海洋提供动力，由此产生的海流在驱动纬向翻转环流方面发挥着关键作用。人们普遍认为，输入到地面地转流的大部分风力驱动了大尺度平均流的大的可用位能库，而这些能量通过斜压不稳定释放，驱动中尺度涡动动能（EKE）。这种能量是如何消散的，这是一个更有争议的问题。待检验的假设是：1）大部分的EKE级联到海洋底部，通过一个反向级联到更大的水平尺度正压运动。2)这种能量通量的一大部分通过二次阻力耗散在底部附面层中。3)一个显着的剩余能量通量在粗糙的地形上产生地形波，它有可能传播，并在打破驱动混合和消散更高的水柱。将使用卫星和现场观测相结合的方法，以及两个现实的高分辨率海洋环流模型。量化众多消散路径的相对重要性是物理海洋学中一个尚未解决的大问题。了解能量耗散的机制是在更现实的OGCM中正确参数化纵摇和沿着等密轴混合过程的必要的第一步。混合是一个关键的海洋过程，必须将其参数化，以便在模拟当前和未来气候的最先进模式中进行适当的反馈。这些结果将对指导未来关于全球海洋及其影响的气候的可变性和可预测性的研究至关重要。

The ocean circulation is the result of a balance between forcing at basin scales and dissipation at millimeter scales. While we have measurements of the climatological mechanical and thermal energy sources, and some limited coverage of small-scale dissipation, much less is known about the processes that transfer energy from the forcing to the dissipation scales. The goal of this project is to quantify from observations and numerical models the major pathways towards dissipation in the global oceans. The analysis will be global, but particular attention will be paid to the Southern Ocean, because most of the large scale wind forcing powers this part of the ocean and the resulting currents play a key role in driving the meridional overturning circulation. It is widely believed that most of the wind power input to the surface geostrophic flow drives the large reservoir of available potential energy of the large-scale mean flow, and that this energy is released by baroclinic instability, driving mesoscale eddy kinetic energy (EKE). How this energy is dissipated is much more controversial. The hypotheses to be tested are: 1) A majority of the EKE cascades to the bottom of the ocean through an inverse cascade into larger horizontal scale barotropic motions. 2) A large fraction of this energy flux is dissipated in the bottom boundary layer by quadratic drag. 3) A significant residual energy flux generates topographic waves over rough topography, which have the potential to propagate and upon breaking to drive mixing and dissipation higher in the water column. A combination of satellite and in situ observations, and two realistic, high-resolution ocean general circulation models (OGCMs) will be used. Quantifying the relative importance of the many pathways to dissipation is a great unsolved problem of physical oceanography. Knowing the mechanisms of energy dissipation is a necessary first step in proper parameterization of diapycnal and along isopycnal mixing processes in more realistic OGCMs. Mixing is a critical oceanic process that must be parameterized in order to have the proper feedbacks operative in state-of-the-art models that simulate present and future climate. Together these results will be crucial for guiding future research on the variability and predictability of the global oceans and the climate that it influences.