Slippery Bottom Boundary Layers: The Loss of Energy From the General Circulation by Bottom Drag
Slippery Bottom Boundary Layers: The Loss of Energy From the General Circulation by Bottom Drag
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DOI：
10.1029/2021gl094434
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发表时间：
2021-09
影响因子：
5.2
通讯作者：
X. Ruan;J. Wenegrat;J. Gula
中科院分区：
文献类型：
--
作者：
X. Ruan;J. Wenegrat;J. Gula
底部阻力被认为是从海洋总体环流中消除动能的关键机制之一。然而，全球底部阻力消散的估计仍然存在很大的不确定性。不确定性的一个重要来源来自底部附近的速度结构，其中倾斜地形和分层的组合可以降低平均流量大小，从而降低底部阻力耗散。使用高分辨率数值模拟，我们证明之前对底部阻力耗散的估计偏差很大，因为它们忽略了底部边界层的速度剪切。与先前使用近海底层外的总速度进行的估计相比，与大陆坡上的地转流相关的估计底部阻力耗散至少小 56%。诊断表明有必要解决粗分辨率海洋模型和观测中的底部边界层结构，以关闭全球动能预算。
Bottom drag is believed to be one of the key mechanisms that remove kinetic energy from the ocean's general circulation. However, large uncertainty still remains in global estimates of bottom drag dissipation. One significant source of uncertainty comes from the velocity structures near the bottom where the combination of sloping topography and stratification can reduce the mean flow magnitude, and thus the bottom drag dissipation. Using high‐resolution numerical simulations, we demonstrate that previous estimates of bottom drag dissipation are biased high because they neglect velocity shear in the bottom boundary layer. The estimated bottom drag dissipation associated with geostrophic flows over the continental slopes is at least 56% smaller compared with prior estimates made using total velocities outside the near‐bottom layer. The diagnostics suggest the necessity of resolving the bottom boundary layer structures in coarse‐resolution ocean models and observations in order to close the global kinetic energy budget.