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Evolution of Mixing and Restrification Segments in N2 and M2 Profiles

Study on the evolution of mean profiles of N2 and M2 during mixing and restratification segments over 10 days, with varying resolution and zonal gradients. Analysis of surface forcing and Langmuir circulation effects on mixing phases.

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Evolution of Mixing and Restrification Segments in N2 and M2 Profiles

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  1. Modeling Focus (2006): Mixing Segment; Restratification

  2. Mixing, day ~214; Restratification, ~217

  3. Mixing SegmentEvolution of mean profiles of N2, M2

  4. Restratification Segment N2, M2

  5. Long integration time: 10 days covering both mixing and restratification segments.Low resolution: 3m X 3m X 2.8m; 1s timestep Smallest domains: 144m X 144m X 57m Largest domains: 1152m X 1152m X 57m Horizontally periodic in departure from background zonal gradients in T & S ; r & pInitial Conditions: 20m mixed layer over stratification ~ 9.0x10-2 C/m & 1.2x10-2 psu/m or N2=2.5x10-4 s-2 & vertical spice stratification 1.2x10-4 s-2Zonal Gradients: dr/dx = + 6.25x10-5 kg/m4 from -1.17x10-4 C/m & 4.75x10-5 C/m or M2=-5.9x10-7s-2 & horizontal spice stratification 1.1x10-7 s-2Surface Forcing‘COAMPS/WW3’ Case: Surface Stress + Stokes drift US from COAMPS & WW3 ‘Obs./WW3’ Case: Surface Stress + Stokes drift US+ Obs. Heat Fluxes, Radiation LES modeling cases

  6. COAMPS/WW3 model case SST, mixing phase ‘Large’ Domain, 576m x 576m U10

  7. COAMPS/WW3 model case SST, mixing phase ‘Largest’ Domain, 1152m x 1152m U10

  8. Near-Surface Langmuir Circulation W(cm/s) ‘Largest’ Domain, 1152m x 1152m U10

  9. Brief Summary of Some Results: • Mean observed & LES modeled mixed layer Vertical TKE levels are consistent with Langmuir Turbulence. ‘Ekman Convection’ does not increase mean VKE. • Mixed layer deepens rapidly by ‘Ekman Adjustment’, not ‘Ekman Convection’, independent of model domain scale & mixed layer TKE variability (i.e. turning Stokes drift off changes TKE but not mixed layer deepening). • Rapid Observed restratification after wind falls is similar to LES with surface heat flux forcing, but differs in some details. • Comparing LES with KPP: Horizontal vorticity (& P.V.) very different.

  10. Horizontal Fluxes Example with No Mean Lateral Gradients: Entraining Mixed Layer, u*=1 cm/s, Mature Seas

  11. COAMPS/WW3 Case (‘Large’ Domain)

  12. Sharp mini-fronts: Local downwelling, increased VKE

  13. Lagrangian float VKE variability: Is it something, or is it just statistical? Potential Model-Data Comparisons Surface signature of ~300m long surface convergence observed at FLIP, later and to South during AESOP’06 by J M Smith.

  14. Summary: Modeled lateral fluxes in upper ocean during wind-driven mixing are significant compared to K~1-10m/s significant compared to along & cross-front dispersion by mean U,VLateral fluxes increase with LES domain size… presumably corresponds to resolution dependence of subgrid flux.Turning off surface wave Stokes drift greatly reduces LES horizontal fluxes.

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