1. Atmospheric Circulation Response to Future Arctic Sea Ice Loss Clara Deser, Michael Alexander and Robert Tomas

2. Future Arctic Sea Ice Loss NCAR Coupled Model Simulation Holland et al. (2006) NCAR CCSM3 model simulation Observations Model drop 1.8 million sq km, 2024–2025 Observed drop 1.6 million sq km, 2006–2007 September Sea Ice Extent Ice Extent (10 6 km 2 ) Figure courtesy of Julienne Stroeve

3. Future Arctic Sea Ice Loss NCAR Coupled Model Simulation Holland et al. (2006) NCAR CCSM3 model simulation Observations Model drop 1.8 million sq km, 2024–2025 Observed drop 1.6 million sq km, 2006–2007 September Sea Ice Extent Ice Extent (10 6 km 2 ) 1980-992080-99 Figure courtesy of Julienne Stroeve ~ 2xCO 2

4. CCSM3 Arctic Sea Ice Concentration 1980-992080-99 (A1B) September March (%)

5. Approach Prescribe sea ice cover for 1980-99 and 2080-99 to Community Atmospheric Model Version 3 T85 (1.4° latitude x 1.4° longitude); 26 levels 60 year integrations with repeating seasonal cycle of time-average sea ice concentration and thickness: 1980-99 (CCSM3 historical) 2080-99 (CCSM3 A1B) SSTs fixed at 1980-99 values, and set to -1.8 C where sea ice removed DETAILS

6. p_12months_ice_pres_fut.gif Sea Ice (%) Sea Ice Change: 2080-99 minus 1980-99 Sea Ice (%) Ice loss Ice gain

7. p_12months_ice_pres_fut.gif Sea Ice (%) Sea Ice Change: 2080-99 minus 1980-99 Sea Ice (%) Ice loss Ice gain

8. p_12months_ice_pres_fut.gif Sea Ice Energy Flux Surface Energy Flux Response (Wm -2 ) Positive upward Sea Ice Energy Flux

9. p_12months_ice_pres_fut.gif Air Temperature Response (°C) Sea Ice Air T Sea Ice Air T 15-20°C

10. p_12months_ice_pres_fut.gif Air Temperature Response (°C): Land Only 2-5°C Sea Ice Air T Sea Ice Air T

11. p_12months_ice_pres_fut.gif Snow Depth Response (cm liquid water equivalent) Air T Snow Air T Snow

12. p_12months_ice_pres_fut.gif Sea Level Pressure Response (hPa) ci=1hPa Sea Ice shading = 95% significant Sea Ice SLP

13. p_12months_ice_pres_fut.gif Sea Level Pressure Response (hPa) ci=1hPa Sea Ice SLP shading = significant Sea Ice SLP

14. How does the atmospheric circulation response to Arctic sea ice loss compare with the response to doubled CO 2 in the fully coupled CCSM3?

15. p_12months_slp_ccsm3_cam.gif Sea Level Pressure Response (hPa) ci=1hPa CAM3 CCSM3 CAM3 CCSM3

16. p_12months_slp_ccsm3_cam.gif Sea Level Pressure Response (hPa) ci=1hPa Atm Model Coupled Model Atm Model Coupled Model

17. SUMMARY Atmospheric Circulation Response to Future Arctic Sea Ice Loss Largest sea ice loss in summer-fall (July-Nov), but largest surface energy flux response (which forces the atmosphere) in fall-winter (Oct-Mar) Thermodynamic response: warming (and moistening) of the boundary layer especially in fall-winter (2-5K over land and 15-20K over the Arctic ocean); increased snow cover over Siberia and northern Alaska Dynamic response: SLP response largest in fall-winter when it accounts for some of the response to 2xCO 2 in the coupled model; negligible in summer

18. Allow sea surface temperatures to respond to sea ice loss Similar experiments with a regional high resolution atmospheric model (Cassano et al.) and an AGCM with a resolved stratosphere Similar experiments for snow cover (Tomas et al.) Next Steps Atmospheric Circulation Response to Future Arctic Sea Ice Loss

19. Thank You

20. Extra Slides

21. p_12months_ice_slp_precp.gif Precipitation Response (mm day -1 ) Sea Ice Precip & SLP Sea Ice Precip & SLP

22. p_12months_z500mb_1000mb.gif

23. p_12months_ice_cldtot.gif

24. p_12months_ice_pres_fut.gif 1980-99 2080-99 Sea Ice Concentration (%)

25. September 2007 sea ice (white area) vs. September long term mean (pink line) Summer 2007 Arctic Sea Ice Loss

26. p_12months_ice_pres_fut.gif SLP (hPa) 2080-99 minus 1980-99 SLP (hPa) Ci = 1hPa; Shading sig Surface Energy Flux (Wm -2 ) Surface Energy Flux (Wm -2 )

27. p_t_profile_contour.gif

28. p_12months_ice_pres_fut.gif Radiative (LW) Turbulent (SH+LH) Surface Energy Flux Response (Wm -2 ) Radiative (LW) Turbulent (SH+LH)