1. Arctic clouds, circulation, and sea ice during 2007 and beyond Jennifer Kay 1,2, Andrew Gettelman 1, Kevin Reader 1, and Tristan L’Ecuyer 2 1 National Center for Atmospheric Research (NCAR) 1 Colorado State University (CSU) MODIS Image from March 10, 2008 (sea ice maximum extent)

2. MODIS Image from March 26, 2008 1.Lessons and questions from 2007 2.Data assimilation project (CAM-DART) 3.Early observations for 2008

3. “A perfect storm” for ice loss in 2007

4. Cloud and radiative flux differences (2007-2006) Radiative fluxes from 2B-FLXHR produced by Tristan L’Ecuyer (CSU).

5. Were the 2007 clouds really anomalous?

6. In a warmer world with thinner ice, natural summertime circulation and cloud variability is an increasingly important control on sea ice extent. Kay, L’Ecuyer, Gettelman, Stephens, and O’Dell (Geophysical Research Letters, 2008)

7. For clouds, timing is key.

8. Atmospheric forcing on sea ice loss Barrow, Alaska (ARM)July avg 2007 September avg 2007 Total Cloud Cover0.72 0.600.90 0.84 Downwelling Surface LW (Wm -2 )302 305300 Downwelling Surface SW (Wm -2 )209 23853

9. Many remaining questions 1)thermodynamic vs. dynamic loss processes 2)cloud-ice-circulation feedbacks 3) year-to-year variability vs. long-term ice thinning 4) models: reliability?, what can they teach us? 5) tipping point? 2008?

10. MODIS Image from April 13, 2008 1.Lessons and questions from 2007 2.Data assimilation project (CAM-DART) 3.Early observations for 2008

11. Why DART? DART = Data Assimilation Research Testbed Fig. 1 from Rodwell and Palmer (2007) Science Questions - Do climate models capture observed changes in the atmospheric forcing on sea ice loss? - How does the Arctic ocean surface affect the Arctic atmosphere?

12. CAM-DART vs. NCEP

13. DART-CAM Assimilations NameSurface boundary condition July06obsobserved (Hurrell et al., 2008) July07obsobserved (Hurrell et al., 2008) July07climclimatological SST and sea ice Science Questions For Today - How well do CAM/DART reanalyses capture observed changes? (July06 vs. July07) - Does the surface affect the best guess of the atmospheric state? (July07sst vs. July07clim)

14. CAM-DART July06 vs. July07

15. July07 CAM-DART obs vs. climo

16. July07 vs. Sept07 sea ice extent Source: NSIDC

17. MODIS Image from May 19, 2008 1.Lessons and questions from 2007 2.Data assimilation project (CAM-DART) 3.Early observations for 2008

18. NCEP During 08 Ice Melt

19. Clouds During 08 Ice Melt

20. Summary - In a warmer world with thinner ice, the minimum sea ice extent is increasingly sensitive to year-to-year variability in weather and cloud patterns. - The timing of ice loss matters. - CAM-DART can qualitatively reproduce observed changes in the atmospheric forcing on sea ice. - 2008 atmospheric circulation and cloud anomalies are small. But… If the current anti-cyclonic pattern persists/strengthens, there will be significant sea ice loss in 2008.

21. EXTRA SLIDES

22. NCEP During 08 Ice Growth

23. Clouds During 08 Ice Growth

24. Early Fall Cloud Increases (‘07-’06) Near The Dateline

25. 2007 Arctic sea ice extent The sea ice extent at the 2007 minimum was 4.13 million km 2 down 43% from 1979 and down 26% from the last record minimum in 2005. Credit: NSIDC

26. Sea Ice Extent: July vs. Sept, 06 vs. 07

27. DART-CAM noise slide PSL map fc_time=0,3,6 hours

28. Fall/Winter Clouds/LW Rad at ARM Barrow

29. Western Pacific Arctic Variable2007-2006 July CERES FlashFlux, Barrow 2007-2006 JJA CloudSat/CALIOP, Barrow Total Cloud Covern/a, -0.13-0.16, -0.15 TOA Albedo- 0.07, n/an/a, n/a FSDS (Wm -2 )+ 26, + 28+ 32, + 25 FSNS (Wm -2 )+ 19, n/an/a, n/a FLDS (Wm -2 )+ 8, + 2-4, -1

30. Western Pacific Arctic Data 2007-2006 CERES FlashFlux 2007-2006 Barrow, AK JulySeptJulySept Total Cloud Cover---0.13-0.06 TOA Albedo- 0.07 -- TOA Albedo (clear)- 0.11- 0.15-- FSDS (Wm -2 )+ 26+ 4+ 28+ 3 FSNS (Wm -2 )+ 19+ 9-- FLDS (Wm -2 )+ 8+ 20?+ 2- 5? Variable2007-2006 JJA in WPA CloudSat/CALIOP, ARM Barrow Total Cloud Cover-0.16, -0.15 FSDS (Wm -2 )+ 32, +25 FLDS (Wm -2 )-4, -1

31. 2007 Western Arctic cloud reductions CloudSat/CALIOP data revealed reduced cloudiness and enhanced downwelling shortwave radiation (+32 Wm -2 ).