1. 2016-06-23 Impact of sea ice dynamics on the Arctic climate variability – a model study H.E. Markus Meier, Sebastian Mårtensson and Per Pemberton Swedish Meteorological and Hydrological Institute (SMHI) and Stockholm University Markus.Meier@smhi.se H.E. Markus Meier, Sebastian Mårtensson and Per Pemberton Swedish Meteorological and Hydrological Institute (SMHI) and Stockholm University Markus.Meier@smhi.se

2. Regional ocean climate modeling at SMHI and Stockholm University

3. Rossby Centre Ocean model (RCO) based on the BRYAN-COX-SEMTNER code reorganised for running on parallel computer architectures (OCCAM, Webb et al., 1997) spherical rotated ARAKAWA B – grid, level model explicit free surface (Killworth et al., 1991) FCT advection scheme (Zalesak, 1979; Gerdes et al., 1991) open boundary conditions (Stevens, 1990) Pacanowski and Philander (1981) mixing or k-ε turbulence model with improved flux boundary conditions and parameterization of internal waves (Meier, 2001)

4. Sea ice model within RCO based upon CICE reference: two-level dynamic sea ice model with elastic-viscous-plastic ice rheology (Hunke and Dukowicz, 1997) new: Helsinki multi-category ice model HELMI (Haapala, 2000; Haapala et al., 2005) 3-layer model for ice thermodynamics (Semtner 1976)

5. RCO-Arctic maximum depth5000 m horizontal resolution0.25 degree vertical resolution59 levels, 3 - 200 m (10 x 3m) freshwater supplyrunoff climatology, 3156 km 3 /yr open boundaryclimatology (PHC) atmospheric forcing ERA40 + ECMWF (6h, 1958- 2001, 2002-2007), ERA - Interim (1990- 2008) surface salinity relaxation240 days Model setup:

6. Mean winter (November-April) sea ice concentration 1978-2005 for the reference sea ice model (left) and NSIDC satellite data (right):

7. First EOF for winter (November-April) sea ice concentration (upper) and first PC (lower) for RCO (blue), satellite data (green), and AO index (red)

8. Ice extent in the reference model

9. Ice concentration for Sep 2007 in the reference model

10. Helsinki multi-category ice model HELMI takes the sea ice thickness distribution into account 5 undeformed ice categories 2 deformed (incompressible) ice categories: rigded and rafted sea ice References: Hibler (1980), Flato and Hibler (1995), Bitz et al. (2001), Haapala (2000), Haapala et al. (2005)

11. Helsinki multi-category ice model HELMI (Rothrock 1975, Flato and Hibler 1995) ω rigding mode C f ratio of total energy losses to the potential energy change

12. Mean sea ice concentration for April (left) and October (right) and the satellite derived ice extent (magenta) 2007

13. Sea Ice Outlook 2009  Seasonal ensemble predictions with RCO-HELMI  Estimate minimum of sea ice extent in September  Ensemble setup, ERA-Interim forcing from 20 different years (1989-2008)  3 forecasts in June, July and August  August results 4.6 (0.4) mio km 2  Probabilities to fall below 3 prev. lowest 2007 21 % 2008 56 % 2005 99 %.

14. Estimates from all contributions  SMHI MISU

15. All forecasts underestimated the sea ice cover 2009 ~5.3

16. Sea ice extent 1980-2003 (HELMI and REF)

17. Sea ice thickness 1980-2003 (HELMI and REF)

18. Sea ice volume 1980-2003 (HELMI and REF)

19. Monthly mean sea ice concentration difference HELMI-REF 1980-2003

20. Monthly mean sea ice thickness difference HELMI-REF 1980-2003

21. Monthly mean ridged sea ice concentration 1980-2003

22. Monthly mean undeformed (class 1) sea ice concentration 1980-2003

23. Sea ice volume transport through Fram Strait

24. Sea ice volume transport through Fram Strait for all ice categories smoothed with a 30-day running mean

25. Sea ice area transport through Fram Strait for all ice categories smoothed with a 30-day running mean

26. Monthly mean sea ice velocity difference for June between HELMI and REF

27. Ice velocity in the Canadian sector: buoy data (green), HELMI (blue) http://iabp.apl.washington.edu/ cm/s

28. Ice velocity in the Greenland sector: buoy data (green), HELMI (blue) cm/s

29. Ice velocity in the Siberian sector: buoy data (green), HELMI (blue) cm/s

30. Development of RCAO-Arctic (Döscher et al. 2009) Identical grids (0.5 degrees)  facilitates flux coupling Consistent coast definitions in both RCO and RCA OASIS 2.4 Ocean sends  state variables  sea ice albedo Atmosphere responds with fluxes OASIS  t mod  t coup ocean atmos rivers landsurf ice RCO RCA

31. Simulated summer sea ice extent in RCAO with the reference sea ice model --- coupled runs --- ERA40 or sat observation Döscher et al., 2009

32. Climate Scenario Experiments - Dynamic Regional Downscaling - The ensemble: Configuration with tick/thin ice SSS restoring vs salinity flux correction Ocean boundary condition climatological vs GCM forced 1960 2080 1980 - 2080 Rapid change events occur together with recovering Strong decadal variability Extent from RCM model more realistic than GCM Königk, Döscher and Nikulin, 2010

33. 2016-06-23 Conclusions the multi-category sea ice model improved our simulations lower sea ice thickness close to the eastern Siberian coast summer sea ice extent is smaller the sea ice is more mobile with larger sea ice velocities and increased Fram Strait ice export larger sea ice volume in the Arctic