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Upstream section (11-13/Feb)

Upstream section (11-13/Feb). All observation points. Downstream section (18-23/Feb). ASIS launch (13/Feb). ASIS (17-Feb). Test (10/Feb). ASIS recover (23/Feb). Upstream section. speed (u 2 +v 2 ) 1/2. Richardson number. 21196. 21184. 21196. 21184.

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Upstream section (11-13/Feb)

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  1. Upstream section (11-13/Feb) All observation points Downstream section (18-23/Feb) ASIS launch (13/Feb) ASIS (17-Feb) Test (10/Feb) ASIS recover (23/Feb)

  2. Upstream section speed (u2+v2)1/2 Richardson number 21196 21184 21196 21184 with sq from AMP; velocities from 75kHz ADCP (vertical resolution 20m). Black dashed line is depth of mixed layer defined by Dq=0.1°C. Mixed layer is shallower toward the GS.

  3. Estimate entrainment flux Deepest mixed layer North South GS turbulent patch every 50-80m Deep enhanced mixing (Kr~10-2m2/s)

  4. Heat and buoyancy flux across the base of mixed layer qent / W m-2 Cw: specific heat Jbent / W kg-1 G: mixing efficiency (0.2)

  5. Mixing patches in south of the GS could be important for mode water formation. Mixing is weak in vertical shear by the GS. log10(Kr) / m2 s-1 log10(e)/ W kg-1 21196 21184 21196 21184 -7 -3 10 10 -8 -4 10 10 -9 10 -5 10 300 250 200 150 100 50 0 300 250 200 150 100 50 0 Average e, p >1.3MPa Average Kr, p >1.3MPa Averaged values increase around the GS

  6. Comparison of Kr below mixed layer with KPP parameterization (estimated from observed Ri) observation KPP KPP parameterization tends to overestimate Kr in high shear due to the GS and underestimate Kr in enhanced mixing patches due to internal waves.

  7. ASIS section (Mixed layer formation) AMP21198 AMP21200 AMP21201 AMP21202-21203 AMP21199 AMP21204 ASIS (AMP 21198-21204)

  8. Simple density budget (assuming time-series and 1D balance) ASIS section (Time series: Mixed layer formation) yday= 47.18 47.26 47.79 47.90 47.91 47.99 47.46 47.18 47.26 47.46 47.79 47.90 47.91 47.99

  9. 0 1 2 3 depth[MPa] 4 5 6 26.2 26.25 26.3 26.35 26.4 26.45 26.5 26.55 26.6 26.65 -3 s / kg m q Simple one-dimension density budget Density change due to surface buoyancy flux first profile last profile It account for density change 0.013 kg m-3 against 0.06 kg m-3. D(t1) density profile estimated above

  10. A detail on mixed layer formation (AMP21203) u:blue line, v:red line 0 Jb0 convection 0.5 1 inversion 1.5 p / MPa convection? 2 entrainment (by convection or shear?) 2.5 3 -0.6 -0.3 0 0.3 0.6 -10 -9 -8 -7 -6 -5 18.5 18.55 18.6 18.65 18.7 18.75 18.8 18.85 18.9 velocity[m/s] -1 log10(e) / W kg q / °C increasing in mixed layer 36.6 36.605 36.61 36.615 36.62 36.625 36.63 1000*s 26.25 26.3 26.35 26.4 sq / kg m-3 Clockwise rotation is observed in the base of mixed layer. Vertical shear is large around the density inversion.

  11. Downstream section downstream section (AMP21205-21209, 21211) AMP21207 AMP21208 AMP21209 AMP21211 AMP21206 AMP21205 ASIS recover (AMP21210)

  12. Downstream section yday= 50.79 South North GS 51.02 51.12 53.95 49.27 48.99 Deep mixed layer Deep enhanced mixing

  13. Deep mixed layer in the Gulf Stream (AMP21209) 0 shear2 Jb0 1 v 2 p / MPa 3 N2 u 4 5 6 q / °C 14 16 -0.3 0 0.3 0.6 0.9 -8 -6 -4 -10 -9 -8 -7 -6 -5 -5 -4 -3 -2 -1 0 -1 2 2 -2 -1 2 -1 1000*s e Velocity / m sec N ,Shear / s / W kg K / m s 36 36.5 r log10 sq / kg m-3 26.6 26.8 Convection and shear-driven entrainment could be mixed-layer deepening processes.

  14. shear squared v-shear u-shear

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