کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
4548334 | 1327896 | 2012 | 18 صفحه PDF | دانلود رایگان |
Intensive microstructure sampling over the southern slope of the Cycladic Plateau found very weak mixing in the pycnocline, centered on a thin minimum of diapycnal diffusivity with Kρ=1.5×10−6Kρ=1.5×10−6 m2 s− 1. Below the pycnocline, KρKρ increased exponentially in the bottom 200 m, reaching 1 × 10− 4 m2 s− 1 a few meters above the bottom. Near-bottom mixing was most intense where the bottom slope equaled the characteristic slope of the semi-diurnal internal tide. This suggests internal wave scattering and/or generation at the bottom, a conclusion supported by near-bottom dissipation rates increasing following rising winds and with intensifying internal waves. Several pinnacles on the slope were local mixing hotspots. Signatures included a vertical line of strong mixing in a pinnacle's wake, an hydraulic jump or lee wave over a downstream side of the summit, and a ‘beam’ sloping upward at the near-inertial characteristic slope. Because dissipation rate averages were dominated by strong turbulence, ϵ/νN2 > 100, the effect on KρKρ of alternate mixing efficiencies proposed for this range of turbulent intensity is explored.
► In the ocean, turbulent mixing is usually most intense near topography.
► Topographic mixing processes must be understood and quantified to be represented accurately in numerical models.
► Below the pycnocline on the side of the Cycladic Plateau in the Aegean, diapycnal mixing increased exponentially in the bottom 200 meters.
► Near-bottom mixing was most intense where internal wave scattering and/or generation was most likely.
Journal: Journal of Marine Systems - Volume 89, Issue 1, January 2012, Pages 30–47