Direct measurements reveal instabilities and turbulence within large amplitude internal solitary waves beneath the ocean
Direct measurements reveal instabilities and turbulence within large amplitude internal solitary waves beneath the ocean
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DOI：
10.1038/s43247-020-00083-6
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发表时间：
2021-01-22
影响因子：
7.9
通讯作者：
Tseng, Ruo-Shan
中科院分区：
文献类型：
--
作者：
Chang, Ming-Huei;Cheng, Yu-Hsin;Tseng, Ruo-Shan
内孤立波在世界各大洋的沿岸和边缘海中普遍存在。当波浪向岸边浅滩移动时，它们通过全球显著的湍流混合和耗散失去了从海洋潮汐中获得的能量，从而泵出富含营养的水来滋养沿海生态系统。在这里，我们提出了精细的尺度，直接测量的浅水内孤立波在南中国海，这使得检查的物理过程中引发的强烈的湍流混合在其内部。这些是在波核的对流破裂和开尔文-亥姆霍兹波涛的崩溃波后部和较低的核心周边，往往同时发生。前者发生在粒子速度超过波的传播速度时。后者是由于强烈的速度切变克服层结而引起的不稳定性。这种不稳定性产生的湍流水平比公海大四个数量级。细尺度，浅内孤立波的直接测量显示，对流破裂和Kelvin-Helmholtz巨浪的崩溃往往同时发生，并产生湍流四个数量级大于在开阔的海洋。
Internal solitary waves are ubiquitous in coastal regions and marginal seas of the world's oceans. As the waves shoal shoreward, they lose the energy obtained from ocean tides through globally significant turbulent mixing and dissipation and consequently pump nutrient-rich water to nourish coastal ecosystem. Here we present fine-scale, direct measurements of shoaling internal solitary waves in the South China Sea, which allow for an examination of the physical processes triggering the intensive turbulent mixing in their interior. These are convective breaking in the wave core and the collapse of Kelvin-Helmholtz billows in the wave rear and lower periphery of the core, often occurring simultaneously. The former takes place when the particle velocity exceeds the wave's propagating velocity. The latter is caused by the instability induced by the strong velocity shear overcoming the stratification. The instabilities generate turbulence levels four orders of magnitude larger than that in the open ocean. Fine-scale, direct measurements of shoaling internal solitary waves reveal that convective breaking and collapse of Kelvin-Helmholtz billows often occur simultaneously and generate turbulence four orders of magnitude larger than in the open ocean.