1. Assessment of the ECCO2 optimized solution in the Arctic An T. Nguyen, R. Kwok, D. Menemenlis JPL/Caltech ECCO-2 Team Meeting, MIT Sep 23-24, 2008

2. Outline:  Optimized solution in the Arctic  Ocean: hydrography fresh water & heat content heat & volume fluxes  Sea ice: Extent  summer 2007 Velocities & fluxes Thickness Volume  Summary Arctic solution total cost reduction Greenland Sea

3. Regional optimized solution:  Data: Sea-ice velocity, sea-ice thickness, CTD profiles, Initial conditions, Forcings  Parameters: salt-plume parameters air / sea-ice drag coefficients sea-ice and ocean albedos sea-ice strength and H0 initial conditions freshwater content GMredi

4. Sea ice velocity

5. Sea ice extent

7. c37 : NCEP c47 : c37, WOCE climatology, without specifying net shortwave radiation, bug fixes in growth.F, including Peter Winsor's new monthly Arctic Ocean runoff c55 : first blend integration (c49), more realistic initial sea-ice conditions from a PSC estimate SEAICEadvSnow=.true., SEAICEuseFlooding=.TRUE. c62 : c55, but with blend forcing and blend wind  NCEP at high lat arc1 : First integration of Arctic domain, open boundary, NCEP wind, c55 param Passive Microwave data: 1991-2002 Sea Ice flux: Fram Strait greenland Annual c37 c47 c55 c62 arc1 Mean(  ) -22 301 503 419 325 Std(  ) 134 147 190 159 141 % 2.5 35 58 48 38  model – data

8. Sea Ice flux: comparison

9. Sea ice extent: Arctic Ocean

10. Sea ice thickness Apr May Aug Apr Sep Aug Oct Arctic sea ice: too thin Mean STD Apr-May: -0.93 0.37 Aug-Sep: -0.74 0.20 Oct: -0.25 0.19 greenland siberia alaska ULS data from submarine: 1991-2002

11. Sea Ice thickness: ULS data at Fram Strait: 1991-2002 greenland

12. Sea ice volume Note: c37: specifying net shortwave radiation c47: remove net shortwave radiation specification and fix growth.F  reduces sea-ice volume c55 & c62: starts with higher initial sea-ice thickness  increases volume c57: increase dry-ice & dry-snow albedos  increases ice-thickness & volume c56: increase wet-ice & wet-snow albedos  higher increase in volume Dropping too fast? Positive trend 96-02

13. Sea ice velocity Expect: ice velocity direction to the right of wind at ~ 25-40 o Model: Turns to the right, but not enough Sometimes: parallel to the wind dir turning angles correlate with |  vel|

14. Sea ice velocity Angle difference between data and model ice vel Velocity residuals (mm/yr) Sensitivity experimen t %cube Oct-Dec Jan-May Mar-May 29 19.0 4.4 1.7 %NCEP? 31 20.0 12.4 10.7 %NCEP 37 19.7 12.4 10.0 %NCEP 47 20.0 10.4 2.0 %NCEP 55 20.3 9.8 1.3 %75%CORE 62 20.7 9.6 1.0 %NCEP -1 20.3 10.6 3.0 %NCEP Consistently high, essentially // to the wind dir

15. Summary-1: Sea Ice 1.Sea Ice flux:  over-estimates net ice export across Fram Strait by 40% to 60% 2.Sea ice thickness/extent/volume:  too much ice extent in winter, too little in summer  ice thickness small relative to ULS data in Arctic ocean  closer to data in Greenland sea  ice volume too small, with positive trend! 3.Sea ice velocity:  parallel to wind direction, consistently to the left of data  turning angles correlate with magnitude of  vel

16. Arctic ocean (5): Fresh water volume: 1 2 3 4 5 Expect: ~7.5x10 4 km 3 Too low

17. Arctic ocean : freshwater input through Bering Strait Expect: ~0.053Sv [Aagaard and Carmack, 1989]

18. Arctic ocean: SST and Dynamic Topography:

19. Summary-2: Arctic ocean 1.Fresh water volume: Between 60,000km 3 to 67,000km 3 2.Fresh water input through Bering Strait: ~ 0.031Sv 3.Arctic domain:  SST does not drift  ETAN drifting  Ice velocity across Bering Strait: significantly larger than both c47 and c55  ice import increases by 8% to 10% (NOT SHOWN HERE)

20. END

21. List of things to do (04/13/07): 1)Fix drifts in Arctic domain 2)Fix vertical mixing  fix ice thickness + ice vol + fresh water vol? 3)Jinlun’s comments: Initial condition for ice thickness: in the wrong season? Ice extent problem in summer: thermodynamics Tear-drop vs. elliptical yield curves: might not solve discrepancies of vel near coast Need to check if stresses lie on the yield curve

22. Arctic ice thickness PDF too thin, lacking modes

23. Sea Ice strength