The Kuroshio flowing over seamounts and associated submesoscale flows drive 100-km-wide 100-1000-fold enhancement of turbulence
The Kuroshio flowing over seamounts and associated submesoscale flows drive 100-km-wide 100-1000-fold enhancement of turbulence
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DOI：
10.1038/s43247-021-00230-7
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发表时间：
2021-08
影响因子：
7.9
通讯作者：
T. Nagai;D. Hasegawa;E. Tsutsumi;Hirohiko Nakamura;A. Nishina;T. Senjyu;T. Endoh;T. Matsuno;R. Inoue;A. Tandon
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作者：
T. Nagai;D. Hasegawa;E. Tsutsumi;Hirohiko Nakamura;A. Nishina;T. Senjyu;T. Endoh;T. Matsuno;R. Inoue;A. Tandon
虽然以前的研究报告说，海流越过海山和海脊等地形特征，在很近的地方造成强烈的湍流，但一直难以理解强烈的湍流向下游传播多远。在这里，我们在2017年11月，2018年6月和2019年11月在日本九州以南的Tokara海峡海山上的黑潮流动中使用最先进的tow-yo微观结构剖面仪进行了一系列密集的原位湍流观测，并采用高分辨率数值模型来阐明湍流产生机制。我们发现，黑潮流经海山产生条纹的负位涡和近惯性波。这些长期存在的机制，除了其他近场混合过程，强烈的混合热点形成超过100公里的规模与100至1000倍的能量耗散升高。观测到的湍流可以提供营养物质的阳光层，促进浮游植物初级生产和CO2吸收。
Although previous studies reported that currents over topographic features, such as seamounts and ridges, cause strong turbulence in close proximity, it has been elusive how far intense turbulence spreads toward the downstream. Here, we conducted a series of intensive in-situ turbulence observations using a state-of-the-art tow-yo microstructure profiler in the Kuroshio flowing over the seamounts of the Tokara Strait, south of Kyusyu Japan, in November 2017, June 2018, and November 2019, and employed a high-resolution numerical model to elucidate the turbulence generation mechanisms. We find that the Kuroshio flowing over seamounts generates streaks of negative potential vorticity and near-inertial waves. With these long-persisting mechanisms in addition to other near-field mixing processes, intense mixing hotspots are formed over a 100-km scale with the elevated energy dissipation by 100- to 1000-fold. The observed turbulence could supply nutrients to sunlit layers, promoting phytoplankton primary production and CO2uptake.