The potential role of thermohaline–shear instability in turbulence production in the Bering Sea and the subarctic North Pacific

A recent linear stability analysis and a numerical simulation suggest that diffusive convection (DC), a regime of the double-diffusive convection, plays a potential role in onset of thermohaline–shear instability, implying that DC could contribute to turbulence production in the oceans. However, an...

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Veröffentlicht in:Journal of oceanography 2021-06, Vol.77 (3), p.431-446
Hauptverfasser: Tanaka, Mamoru, Yoshida, Jiro, Lee, Keunjong, Goto, Yasutaka, Tanaka, Takahiro, Ueno, Hiromichi, Onishi, Hiroji, Yasuda, Ichiro
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Sprache:eng
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Zusammenfassung:A recent linear stability analysis and a numerical simulation suggest that diffusive convection (DC), a regime of the double-diffusive convection, plays a potential role in onset of thermohaline–shear instability, implying that DC could contribute to turbulence production in the oceans. However, an existence of such a thermohaline–shear instability has not been examined in real oceans. We examine if this newly proposed instability mechanism exists in the subarctic North Pacific by analyzing our fine- and micro-scale turbulence measurement data. Vertical inversions were cautiously detected in seawater density profiles and used as a proxy for instability events for gradient Richardson number larger than the critical value of 1/4. We found that a portion of inversions were associated with active DC. Such DC-related inversions exhibited elevated levels of turbulent kinetic energy dissipation rate even for gradient Richardson number largely exceeding 1/4. Our estimate suggested that the thermohaline–shear instability contributes to roughly only 10% of the dissipation of turbulent kinetic energy in the diffusively convective layer in our observation site.
ISSN:0916-8370
1573-868X
DOI:10.1007/s10872-021-00602-9