Submesoscale coherent eddy in Greenland Sea

1. Discovered in GS during ESOP II (Gascard et al. 2002) • A homogeneous water column, cold core • Vertical extension, 2000 m • The horizontal scale of 10 km • Stationary? Long-lived ? Submesoscale coherent eddy in Greenland Sea NoClim II, module D (ProClim) WP1 Kasajima et al. (2006) ’A mode of deep ventilation’

2. SCV observations References Gascard et al. 2002 Wadhams et al. 2002 Wadhams et al. 2004 (the second one) Budeus et al.2004 Second eddy 2003 May 2003 Sep. 2003 May 1997May 2002 Aug. Active migration in 2003 2001 Oct. 2001 March 2003 April

3. ? ? ? SCV Vertical ventilation Measurements of the chemical tracers in the core in 2003 SF6, CFCs, nutrients, (carbon) Direct velocity measurements with LADCP Formation  where does the core water come from? (Migration where is it transported?) Dissolution where is the core water finaly released? (How about the life time ?)

4. outside of the eddy Inside of the Eddy SF6 profiles 1999 May SF6 measurements 2003 Sep.

5. Time evolution of SF6diffusion 1999 2002 75 N 75 N (From Mandags kollokvium by Truls)

6. -0.86 34.883 317 5.1 2.6 3.1 -0.96 34.882 322 5.4 3.0 2.9 - 1.30 34.878 342 7.4 3.8 2.3 -1.06 34.865 347 7.3 3.8 2.3 -0.90 34.879 323 5.5 2.8 2.9 -0.95 34.882 322 5.6 2.8 2.9 Possible core water end-members Surface water  high CFCs, oxygen concentrations  core water is cold, water in winter SF6 water  relatively high SF6 concentration Eddy (Sep. 2003) SW (NoClim cruise April 2001) GSAIW (Sep. 2003) Possible SW* (assumed) Mixture 2 (20% SW* + 80% GSAIW) θ (°C) Salinity Oxygen (µmol kg-1) CFC-11 (pmol kg-1) CFC-12 (pmol kg-1) SF6(fmol kg-1) Mixture 1 (20% SW + 80% GSAIW)

7. 20 % cold surface + 80 % GSAIW 1999 SCV and 2003 SCV are not the same one  Life time is not several years SCV in 1999 Cold surface water in winter (cold core water, high CFCs, oxygen) Returned Atlantic Water (Little SF6)  Not in the central GS SCV 2003 Cold surface water in winter (cold core water, high CFCs, oxygen) Greenland Sea Arctic Intermediate Water The parents waters are found in the central GS High SF6 water is lifted up toward the surface and cooled

8. Black Blue Red Green Unit : m/s N-S section in SCV

9. N S N 176 177 178 179 (b) S (a) 0.3m/s • Direct velocity measurements by LADCP • EW-comp. • NS-comp. -0.2m/s 0.2m/s Budeus et al. 2004 Geostrophic flow (EW-comp.) Max. Speed 0.2m/s at the radius 9km -0.2m/s

10. -f/2 = vorticity observed earlier Azimuthal velocity Radial velocity Angular velocity = vorticity x 1/2 Vorticity is overestimated by including background flow

11. x(t)= xo + Ut + R exp(iωt) radius Mean flow SCV vorticity is assumed to be -f/2 Vel. obsevation = -f/2 + back ground flow Trajectory of SCV Southward migration ?!?

12. N S 176 177 178 179 The rotation axis is tilted • From the study of tropical cyclones ; • The effects of the background vertical shear on the cyclones • Tilts the rotation axis downshear. • Turns the moving direction (to the left from the shear vector) Vel. obsevation – (-f/2) - mean flow = vertical shear flow Average = mean flow

13. Mean flow θ Φ Shear vector Vertical shear vector Shear effect C |Vshear| x(t)= (xo+Ut+R exp(iωt)) ∙C ∙ A A = cosΦ sinΦ -sinΦ cosΦ The background shear turns the migration direction northward.

14. Conclusion SCV is formed in the Greenland Sea by the mixture of 20 % of cold surface water and 80 % of intermediate water. The source of the core water is principally from the upper intermediate layer in the central GS. The direct velocity measurements reveal high shear in the SCV, which plays an important role in the migration direction. The background flow/shear has changed since 2003?