Poleward-propagating near-inertial waves enabled by the western boundary current
Poleward-propagating near-inertial waves enabled by the western boundary current
复制标题
由西边界流引起的向极传播的近惯性波
DOI：
10.1038/s41598-019-46364-9
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发表时间：
2019
影响因子：
4.6
通讯作者：
Hirose Naoki
中科院分区：
文献类型：
--
作者：
Jeon Chanhyung;Park Jae Hun;Nakamura Hirohiko;Nishina Ayako;Zhu Xiao Hua;Kim Dong Guk;Min Hong Sik;Kang Sok Kuh;Na Hanna;Hirose Naoki
在北方（南）半球具有顺时针（逆时针）旋转运动的近惯性波（NIWs）存在于除赤道以外的海洋中的任何地方;它们的频率在很大程度上取决于当地的惯性频率f。据认为，它们通过强烈的海流剪切和破碎产生的湍流为全球海洋混合提供了约25%的能量;这主要有助于上层海洋混合，这与海气相互作用，台风生成，海洋生态系统，碳循环和气候变化有关。观测和数值模拟表明，低模近红外线可以从源区域向赤道传播数百公里，因为低纬度的低惯性频率允许它们自由传播。在这里，利用观测和数值模拟，我们证明了向极地传播的台风引起的NIW的西边界流，黑潮。在黑潮路径的右侧沿着存在着与地球自转方向相反的反气旋性的负相对涡度，它使当地的惯性频率向低值移动，从而捕获了波浪。这个负涡度区域就像NIW传播的波导一样，强大的黑潮以当地海流的85%左右的速度向极地平流输送波浪。这一发现强调，背景流，如黑潮和墨西哥湾流在全球海洋混合的NIW能量的重新分配中发挥了重要作用。
Near-inertial waves (NIWs), which have clockwise (anticlockwise) rotational motion in the Northern (Southern) Hemisphere, exist everywhere in the ocean except at the equator; their frequencies are largely determined by the local inertial frequency,f. It is thought that they supply about 25% of the energy for global ocean mixing through turbulence resulting from their strong current shear and breaking; this contributes mainly to upper-ocean mixing which is related to air-sea interaction, typhoon genesis, marine ecosystem, carbon cycle, and climate change. Observations and numerical simulations have shown that the low-mode NIWs can travel many hundreds of kilometres from a source region toward the equator because the lower inertial frequency at lower latitudes allows their free propagation. Here, using observations and a numerical simulation, we demonstrate poleward propagation of typhoon-induced NIWs by a western boundary current, the Kuroshio. Negative relative vorticity, meaning anticyclonic rotational tendency opposite to the Earth’s spin, existing along the right-hand side of the Kuroshio path, makes the local inertial frequency shift to a lower value, thereby trapping the waves. This negative vorticity region works like a waveguide for NIW propagation, and the strong Kuroshio current advects the waves poleward with a speed ~85% of the local current. This finding emphasizes that background currents such as the Kuroshio and the Gulf Stream play a significant role in redistribution of the NIW energy available for global ocean mixing.