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

海洋环流是盆地尺度上的强迫和毫米尺度上的耗散之间平衡的结果。虽然我们有对气候学、机械和热能来源的测量，以及一些小尺度耗散的有限覆盖，但对从强迫到耗散尺度的能量转移过程知之甚少。该项目的目标是从观测和数值模式中量化全球海洋消散的主要途径。分析将是全球性的，但将特别关注南大洋，因为大部分大尺度风强迫为这部分海洋提供动力，由此产生的洋流在推动经向翻转环流方面发挥关键作用。人们普遍认为，输入到地面地转流的大部分风能驱动了大尺度平均流的大量可用势能，这些能量是通过斜压不稳定释放出来的，从而驱动了中尺度涡动动能(EKE)。这种能量是如何消散的，争议要大得多。要检验的假设是：1)大部分EKE通过逆级联进入更大水平尺度的正压运动，到达海底。2)这种能量通量的很大一部分在底部边界层中被二次阻力耗散。3)显著的剩余能流在粗糙的地形上产生地形波，这些波有可能传播并在破裂时驱动水柱中更高的混合和耗散。将使用卫星和现场观测相结合的方法，以及两个现实的、高分辨率的海洋环流模式。量化许多消散途径的相对重要性是物理海洋学的一个重大悬而未决的问题。了解能量耗散的机制是在更真实的OGCM中适当地对双叶和沿等叶混合过程进行适当参数化的必要的第一步。混合是一个关键的海洋过程，必须将其参数化，以使适当的反馈在模拟当前和未来气候的最先进模型中发挥作用。总之，这些结果将对指导未来研究全球海洋及其影响的气候的可变性和可预测性至关重要。

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.