Evidence of enhanced double‐diffusive convection below the main stream of the Kuroshio Extension. Issue 12 (29th December 2015)

• Record Type: Journal Article
• Authors: Nagai, Takeyoshi; Inoue, Ryuichiro; Tandon, Amit; Yamazaki, Hidekatsu
• Is Part Of: Journal of geophysical research. Volume 120:Issue 12(2015:Dec.)
• Page Start: 8402
• Page End: 8421
• Publication Date: 2015-12-29
• Subjects: double‐diffusion -- subduction -- obduction -- Kuroshio -- near‐inertial waves -- mixing; Oceanography -- Periodicals; 551.4605
• DOI: 10.1002/2015JC011288
• Languages: English
• ISSNs: 2169-9275

Abstract

Abstract: In this study, a Navis‐MicroRider microstructure float and an EM‐APEX float were deployed along the Kuroshio Extension Front. The observations deeper than 150 m reveal widespread interleaving thermohaline structures for at least 900 km along the front, presumably generated through mesoscale stirring and near‐inertial oscillations. In these interleaving structures, microscale thermal dissipation rates χ are very high O ( > 10 − 7 K 2 s −1 ), while turbulent kinetic energy dissipation rates ϵ are relatively low O ( 10 − 10 − 10 − 9 Wkg −1 ), with effective thermal diffusivity K θ of O ( 10 − 3 m 2 s −1 ) consistent with the previous parameterizations for double‐diffusion, and, K θ is two orders of magnitude larger than the turbulent eddy diffusivity for density K ρ . The average observed dissipation ratio Γ in salt finger and diffusive convection favorable conditions are 1.2 and 4.0, respectively, and are larger than that for turbulence. Our results suggest that mesoscale subduction/obduction and near‐inertial motions could catalyze double‐diffusive favorable conditions, and thereby enhancing the diapycnal tracer fluxes below the Kuroshio Extension Front.