The Kuroshio flowing over seamounts and associated submesoscale flows drive 100-km-wide 100-1000-fold enhancement of turbulence

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...

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Bibliographic Details
Published in:Communications earth & environment 2021-08, Vol.2 (1), p.1-11, Article 170
Main Authors: Nagai, Takeyoshi, Hasegawa, Daisuke, Tsutsumi, Eisuke, Nakamura, Hirohiko, Nishina, Ayako, Senjyu, Tomoharu, Endoh, Takahiro, Matsuno, Takeshi, Inoue, Ryuichiro, Tandon, Amit
Format: Article
Language:English
Subjects:
Carbon dioxide
Computational fluid dynamics
Energy dissipation
Mathematical models
Microstructure
Mixing processes
Numerical models
Nutrients
Phytoplankton
Primary production
Seamounts
Turbulence
Vorticity
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Summary: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 CO 2 uptake.
ISSN:2662-4435
2662-4435
DOI:10.1038/s43247-021-00230-7