1. Accelerating Change in the Arctic? Perspectives from Observations and Global Climate Models David Lawrence NCAR With contributions from Marika Holland, Mark Serreze, Don Perovich

2. Greenland Ice Sheet Melt 16% increase in melt area between 1979 and 2002 new record in 2007 (60% increase in area)

3. Arctic sea ice is disappearing Stroeve et al. 2008

4. Permafrost Features Warmer climate leads to soil warming and permafrost degradation

5. http://www.arctic.noaa.gov/reportcard/index.html

6. Peering into the future ….

7. NCAR-based Community Climate System Model (CCSM3) Coupled Ocean-Atmosphere-Land- Sea Ice model ~1.4 o longitude x 1.4 o latitude resolution 30 minute time step 26 atmosphere levels 40 ocean levels 10 soil levels ~1.2 million points Archive data (monthly, daily, hourly) for over 100 geophysical fields: - Surface air temperature - Sea ice thickness - Snow age

8. Abrupt reductions in the September sea ice cover “Abrupt” transition Holland et al., 2006 Ice Extent ( 10 6 km 2 ) September sea ice extent 9 events across 8- member CCSM3 A1B ensemble SSMI observed CCSM3 CCSM3 – smoothed

9. Observed rate of loss is faster than projected Adapted from Stroeve et al., 2007

10. What impact does sea ice loss have on Arctic?

11. Impacts on Polar Bears

12. …and on broader Arctic climate … in the 1970’s D. Perovich, CRREL

13. Not far from today… D. Perovich, CRREL

14. Arctic Land Area: Surface Air Temperature Change (CCSM3) } Global Warming is ~2x faster in Arctic compared to global average

15. September Sea- ice Extent 3.5-fold increase in rate of warming over land during rapid sea ice loss Lawrence et al. 2008

16. ‘Present-day’ permafrost distribution IPA Permafrost Distribution Map Continuous (90 – 100% coverage) Discontinuous (50 – 90%) Sporadic (10 – 50%) Isolated (0 – 10%) Brown et al. 1998

17. Near-Surface Permafrost in CCSM3 IPA Permafrost Distribution Map Continuous Discontinuous Sporadic Isolated CCSM3 (1980 – 1999)

18. CCSM3 Projections of Degradation of Near-Surface Permafrost Lawrence and Slater, 2005

19. Lakes drain, soil dries Arctic terrestrial climate-change feedbacks Enhanced [nitrogen] CO 2 efflux Global warming CH 4 efflux Microbial activity increases Shrub growth Expanded wetlands Carbon sequester Arctic runoff increases Thermohaline slows Permafrost warms and thaws Arcticwarming

20. Lakes drain, soil dries Arctic terrestrial climate-change feedbacks CO 2 efflux Global warming CH 4 efflux Expanded wetlands Permafrost warms and thaws Arcticwarming Carbon stocks in permafrost soil ~ 800 – 1300 PgC Atmospheric carbon content ~ 750 PgC + 8-9 PgC yr -1

21. What happens to soil carbon as soil warms and permafrost thaws? If soils get drier  aerobic decomposition  CO 2 emissions If more wetlands  anaerobic microbial activity  CH 4 production (25x GWP) 1978 1998 Bubier et al. 1995

22. Lakes drain, soil dries Arctic terrestrial climate-change feedbacks Enhanced [nitrogen] CO 2 efflux Global warming CH 4 efflux Microbial activity increases Shrub growth Expanded wetlands Carbon sequester Arctic runoff increases Thermohaline slows Permafrost warms and thaws Arcticwarming

23. Bernhard Edmaier National Geographic Summary Observations and models indicate system-wide change in the Arctic that is consistent with warming In some cases the observed rate of change exceeds modeled rates (e.g. sea ice) “Sea ice melt unnerves experts” – NY Times Complex array of interrelationships and feedbacks across systems continues to challenge our models and motivates further model development

24. Timeline of Climate Model Development

26. Permafrost “Humor”

27. Chemistry Climate Chemistry Climate BioGeo Chemistry BioGeo Chemistry Software Engineering Climate Variability Polar Climate Polar Climate Land Model Land Model PaleoClimate Ocean Model Ocean Model CCSM Working Groups DevelopmentDevelopment Application Atm Model Atm Model Climate Change CCSM is primarily sponsored by the National Science Foundation and the Department of Energy

28. Mountain Glaciers are Melting / Retreating Pasterze Gletscher, Austria 2003 1900

29. CO 2 emissions and concentrations increasing faster than expected Fraction of CO 2 emissions staying in atmosphere is increasing (0.4 to 0.45) Is the earth system losing its capability to soak up CO 2 ? 1960 2000

30. Appearing and Disappearing Lakes in Siberia ( Smith et al. 2005 ) Smith et al., 2005

31. Impacts on Infrastructure

32. Permafrost: Soil or rock that remains below freezing for two or more years Continuous (90 – 100% coverage) Discontinuous (50 – 90%) Sporadic (10 – 50%) Isolated (0 – 10%) IPA Permafrost Distribution Map Continuous Discontinuous Brown et al. 1998