Evidence of enhanced turbulent dissipation in the frontogenetic Kuroshio Front thermocline

Nagai, Takeyoshi; Tandon, Amit; Yamazaki, Hidekatsu; Doubell, Mark

doi:10.1029/2009gl038832

Cited by 63 publications

(53 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Consequently, the energy flux estimated by Scott and Wang (2005) is predominantly toward larger scales, and a downscale energy flux found by Scott and Wang (2005) at smaller scales might be attributed to an inadequate resolution of the satellite altimeter (Arbic et al 2013). Nagai et al (2009) find enhanced dissipation on the cyclonic side of the Kuroshio Front during a period of frontogenesis that they associate with a downscale energy transfer as found by Capet et al (2008c) and Molemaker et al (2010).…”

Section: Introductionmentioning

confidence: 89%

Routes to Dissipation under Different Dynamical Conditions

Brüggemann

Eden

2015

Journal of Physical Oceanography

View full text Add to dashboard Cite

In this study, it is investigated how ageostrophic dynamics generate an energy flux toward smaller scales. Numerical simulations of baroclinic instability are used with varying dynamical conditions ranging from quasigeostrophic balance to ageostrophic flows. It turns out that dissipation at smaller scales by viscous friction is much more efficient if the flow is dominated by ageostrophic dynamics than in quasigeostrophic conditions. In the presence of ageostrophic dynamics, an energy flux toward smaller scales is observed while energy is transferred toward larger scales for quasigeostrophic dynamics. Decomposing the velocity field into its rotational and divergent components shows that only the divergent velocity component, which becomes stronger for ageostrophic flows, features a downscale flux. Variation of the dynamical conditions from ageostrophic dynamics to quasigeostrophic balanced flows shows that the forward energy flux and therefore the small-scale dissipation decreases as soon as the horizontal divergent velocity component decreases. A functional relationship between the small-scale dissipation and the local Richardson number is estimated. This functional relationship is used to obtain a global estimate of the small-scale dissipation of 0.31 +/- 0.23 TW from a high-resolution realistic global ocean model. This emphasizes that an ageostrophic direct route to dissipation might be of importance in the ocean energy cycle

show abstract

Section: Introductionmentioning

confidence: 89%

Routes to Dissipation under Different Dynamical Conditions

Brüggemann

Eden

2015

Journal of Physical Oceanography

View full text Add to dashboard Cite

show abstract

“…Laurent et al ., ; Naveira Garabato et al ., ]. In contrast, recent in‐situ observations during calm summer conditions show very large turbulent kinetic energy dissipation rates in the thermocline under the main stream of the Kuroshio [ Nagai et al ., ]. Repeated observations revealed dissipation rates in the Kuroshio thermocline on average 10–100 times greater than typical thermocline values, which were accompanied by near‐inertial internal‐wave velocity shear along isopycnals [ Nagai et al ., ].…”

Section: Introductionmentioning

confidence: 98%

Evidence of enhanced double‐diffusive convection below the main stream of the Kuroshio Extension

et al. 2015

Self Cite

View full text Add to dashboard Cite

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 scriptO( >10−7 K2s−1), while turbulent kinetic energy dissipation rates ϵ are relatively low scriptO( 10−10−10−9 Wkg−1), with effective thermal diffusivity Kθ of scriptO( 10−3 m2s−1) consistent with the previous parameterizations for double‐diffusion, and, Kθ is two orders of magnitude larger than the turbulent eddy diffusivity for density Kρ. 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.

show abstract

“…The observations used in these two studies were obtained from only one cruise per study: four microstructure profiles (one at a sharp front) in Nagai et al [2009]and 4 days of near‐surface observations along the front in D'Asaro et al [2011]. Therefore, more data, especially across the jet toward the anticyclonic side (not the side investigated by D'Asaro et al [2011]), are needed to demonstrate the turbulence structure across the Kuroshio front.…”

Section: Introductionmentioning

confidence: 99%

Observations of the structure of turbulent mixing across the Kuroshio

Kaneko¹,

Yasuda²,

Komatsu³

et al. 2012

Geophysical Research Letters

View full text Add to dashboard Cite

[1] The mean structure of turbulence intensity across the Kuroshio in spring is presented by compositing microstructure profiles on a stream coordinate. The composite mean of turbulent energy dissipation rate ɛ was high near fronts on both cyclonic and anticyclonic sides. On the cyclonic side, ɛ > 10 À8 W kg À1 (vertical diffusivity of > 3 Â 10 À5 m 2 s À1 ) was observed in the region of strong vertical shear of geostrophic velocity. Depth-averaged ɛ within the depth range 50-150 m (150-250 m) was significantly higher at 0 to 50 km (À25 to 50 km) compared with >50 km from the axis. Although lower than on the cyclonic side, ɛ at depths of 50-150 m on the anticyclonic side near the front was again enhanced. On this side, the total vertical shear of horizontal velocity was strong, whereas the geostrophic shear was weak. Citation: Kaneko, H., I. Yasuda, K. Komatsu, and S. Itoh (2012), Observations of the structure of turbulent mixing across the

show abstract

Evidence of enhanced turbulent dissipation in the frontogenetic Kuroshio Front thermocline

Cited by 63 publications

References 20 publications

Routes to Dissipation under Different Dynamical Conditions

Routes to Dissipation under Different Dynamical Conditions

Evidence of enhanced double‐diffusive convection below the main stream of the Kuroshio Extension

Observations of the structure of turbulent mixing across the Kuroshio

Contact Info

Product

Resources

About