The Changing Terrestrial Arctic Terry Chapin

Polar regions are the cooling system for Planet Earth

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

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?

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

Spring snowmelt is earlier Decreased albedo Positive feedback to warming

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

Lloyd and Fastie Forests are expanding

Decreased albedo –Less masking of snow –Darker, more complex canopy Positive feedback to warming

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

Indigenous observations indicate that shrub expansion is widespread

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

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

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

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

Permafrost is thawing in many places, not just southern margins

Hinzman Hydrology is changing (confirmed by indigenous observations)

Oechel and Vourlitis Tundra is becoming drier (in places)

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

McGuire

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

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

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

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)

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

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

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

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