Physical Oceanography Laboratory/CIMST, Ocean University of China and Qingdao National Laboratory for Marine Science and Technology, 238 Songling Road, 266100, Qingdao, Shandong, China.
Department of Oceanography, University of Hawaii at Manoa, 1000 Pope Road, Honolulu, HI, 96822, USA.
Nat Commun. 2018 Oct 5;9(1):4086. doi: 10.1038/s41467-018-06260-8.
Turbulent mixing, which is critically important for the equilibrium of ocean circulation, is controlled by finescale turbulent shear (S) of oceanic flows through shear instability. Although the relationship between S and mixing is well understood, the latitude-dependent generation processes of S remain poorly known due to the lack of geographically extensive, long-term finescale velocity measurements. Here, using one-year ADCP data from 17 moorings along 143°E, we first show that the upper-ocean S and its resultant mixing rate have a W-shaped latitudinal distribution in the tropical-extratropical northwest Pacific with peaks at 0-2°N, 12-14°N, and 20-22°N, respectively. Further analyses reveal that these S peaks are caused by vertically-sheared equatorial currents, parametric subharmonic instability of diurnal tide, and anticyclonic eddy's inertial chimney effect, respectively. As climate model simulations are sensitive to the mixing parameterizations, our findings highlight the need to incorporate the latitude-dependent generation mechanisms of S to improve climate models' prediction capabilities.
紊流混合对于海洋环流的平衡至关重要，它通过切变不稳定来控制海洋流的细尺度紊流切变（S）。尽管 S 与混合之间的关系已得到很好的理解，但由于缺乏地理上广泛的、长期的细尺度速度测量，S 的纬度相关生成过程仍知之甚少。在这里，我们使用沿 143°E 的 17 个浮标一年的 ADCP 数据，首次表明，在热带-亚热带西北太平洋，上层海洋的 S 及其产生的混合率具有 W 形的纬度分布，峰值分别在 0-2°N、12-14°N 和 20-22°N。进一步的分析表明，这些 S 的峰值分别是由垂直剪切的赤道流、全日潮的参数亚谐波不稳定以及反气旋涡的惯性烟囱效应引起的。由于气候模型模拟对混合参数化非常敏感，因此我们的发现强调了需要结合 S 的纬度相关生成机制来提高气候模型的预测能力。
