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The Changing Terrestrial Arctic

The Changing Terrestrial Arctic. Terry Chapin. Polar regions are the cooling system for Planet Earth. Global to arctic. Mann et al. Polar amplification. Chapman and Walsh. Polar warming is driven by global processes. Is mitigation of impacts the only option?

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The Changing Terrestrial Arctic

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  1. The Changing Terrestrial Arctic Terry Chapin

  2. Polar regions are the cooling system for Planet Earth

  3. Global to arctic Mann et al. Polar amplification Chapman and Walsh

  4. Polar warming is driven by global processes • Is mitigation of impacts the only option? • Can SEARCH make the case that • Warming has significant ecological impacts? • Warming is affecting human well-being? • Within the Arctic? • Beyond the Arctic?

  5. Aerial extent of glaciers is decreasing (decreasing albedo) (positive feedback to warming) European arctic Russian arctic Total arctic American arctic Hinzman

  6. Spring snowmelt is earlier • Decreased albedo • Positive feedback to warming

  7. Sea ice is less extensive • Decreased albedo • Positive feedback to warming • Together these changes in physical environment contribute to polar amplification of global warming

  8. Forests are expanding Lloyd and Fastie

  9. Forests are expanding • Decreased albedo • Less masking of snow • Darker, more complex canopy • Positive feedback to warming

  10. 1949 1949 Shrub density has increased 2000 Sturm Chandler River, 50 miles S. of Umiat: Sturm, Racine and Tape: Fifty Years of Change in Arctic Alaskan Shrub Abundance

  11. Indigenous observations indicate that shrub expansion is widespread

  12. --- __ --- __ --- __ --- __ Jia et al. GRL, in press

  13. Simulated increase in July temperature due to shrub expansion Chapin , Lynch et al.

  14. Relationship of air temperature to thaw depth depends on surface properties Hinkel, Brown and Nelson

  15. Permafrost temperatures are warming warmer air altered thermal insulation Osterkamp and Romanovsky

  16. Permafrost is thawing in many places, not just southern margins

  17. Hydrology is changing (confirmed by indigenous observations) Hinzman

  18. Tundra is becoming drier (in places) Oechel and Vourlitis

  19. Carbon sequestration is changing (complexity reflects feedbacks) Oechel et al.

  20. McGuire

  21. CO2 efflux is sensitive to warming • Increased sequestration in wet areas • Increased carbon loss in dry areas • Net effect uncertain • Probably positive feedback to warming

  22. Methane efflux is increasing • Positive feedback to warming • Sensitive to hydrology • Overall trace-gas effect is a positive feedback to warming

  23. Area burned in W. North America has doubled in last 20 years Kasischki

  24. Fire effects on climate • Releases carbon to atmosphere • (positive feedback) • Reduces masking of snow • (increased winter albedo, negative feedback) • Increases vegetation albedo • (negative summer feedback)

  25. Warming effects on human well-being Economic impacts are a mixed bag

  26. Warming effects on arctic well-being (cultural effects generally negative)

  27. Warming effects on global well-being Economic effects generally negative Magnitude still uncertain

  28. Global-to-arctic: important, understood Arctic-to-global: poorly understood (Arctic nations)

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