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

海洋环流是海盆尺度上的强迫和毫米尺度上的消散平衡的结果。虽然我们已经测量了气候、机械和热能的来源，并对小尺度耗散进行了有限的覆盖，但对从强迫向耗散尺度转移能量的过程所知甚少。该项目的目标是从观测和数值模式中量化全球海洋耗散的主要途径。该分析将是全球性的，但将特别关注南大洋，因为大部分大规模的风力驱动了这部分海洋，以及由此产生的洋流在推动经向翻转环流方面发挥了关键作用。人们普遍认为，输入地面地转流的大部分风力驱动了大尺度平均流的大量可用势能库，这些能量通过斜压不稳定释放，驱动中尺度涡动能（EKE）。这些能量如何消散则更有争议。需要验证的假设是：1)大部分的EKE通过反向级联进入更大的水平尺度正压运动而到达海底。2)这种能量流的很大一部分通过二次阻力在底层边界层中耗散。3)大量的剩余能量通量在粗糙的地形上产生地形波，这些地形波有可能传播并在破碎后推动水柱中的混合和耗散。将使用卫星和现场观测的结合，以及两个真实的高分辨率海洋环流模型（ogcm）。量化许多耗散途径的相对重要性是物理海洋学尚未解决的一个重大问题。了解能量耗散的机制是在更现实的ogcm中适当地参数化横环流和沿等环流混合过程的必要的第一步。混合是一个关键的海洋过程，为了在模拟当前和未来气候的最先进模式中得到适当的反馈，必须将其参数化。总之，这些结果对于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.