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Accelerating Change in the Arctic? Perspectives from Observations and Global Climate Models

Accelerating Change in the Arctic? Perspectives from Observations and Global Climate Models. David Lawrence NCAR With contributions from Marika Holland, Mark Serreze, Don Perovich. Greenland Ice Sheet Melt 16% increase in melt area between 1979 and 2002

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Accelerating Change in the Arctic? Perspectives from Observations and Global Climate Models

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  1. Accelerating Changein the Arctic?Perspectives from Observationsand 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 • ~1.4o longitude x 1.4o 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. 9 events across 8-member CCSM3 A1B ensemble Abrupt reductions in the September sea ice cover September sea ice extent Ice Extent ( 106 km2 ) SSMI observed CCSM3 CCSM3 – smoothed “Abrupt” transition Holland et al., 2006

  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) Warming is ~2x faster in Arctic compared to global average } Global

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

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

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

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

  19. Arctic terrestrial climate-change feedbacks Arctic warming Arctic runoff increases Thermohaline slows Carbon sequester Global warming CO2 efflux CH4 efflux Permafrost warms and thaws Enhanced [nitrogen] Expanded wetlands

  20. Arctic terrestrial climate-change feedbacks Carbon stocks in permafrost soil ~ 800 – 1300 PgC Atmospheric carbon content ~ 750 PgC + 8-9 PgC yr-1 Arctic warming Global warming CO2 efflux CH4 efflux Permafrost warms and thaws Expanded wetlands

  21. What happens to soil carbon as soil warms and permafrost thaws? If soils get drier  aerobic decomposition  CO2 emissions If more wetlands  anaerobic microbial activity CH4 production (25x GWP) 1978 Bubier et al. 1995 1998

  22. Arctic terrestrial climate-change feedbacks Arctic warming Arctic runoff increases Thermohaline slows Carbon sequester Global warming CO2 efflux CH4 efflux Permafrost warms and thaws Enhanced [nitrogen] Expanded wetlands

  23. 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 Bernhard Edmaier National Geographic

  24. Timeline of Climate Model Development

  25. Timeline of Climate Model Development

  26. Permafrost “Humor”

  27. CCSM Working Groups Chemistry Climate BioGeo Chemistry Atm Model Land Model Polar Climate Ocean Model Climate Change PaleoClimate Climate Variability Development Application Software Engineering 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. CO2 emissions and concentrations increasing faster than expected Fraction of CO2 emissions staying in atmosphere is increasing (0.4 to 0.45) Is the earth system losing its capability to soak up CO2? 2000 1960

  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 IPA Permafrost Distribution Map Continuous Discontinuous Continuous (90 – 100% coverage) Discontinuous (50 – 90%) Sporadic (10 – 50%) Isolated (0 – 10%) Brown et al. 1998

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