The Changing Terrestrial Arctic Terry Chapin. Polar regions are the cooling system for Planet Earth

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  • The Changing Terrestrial ArcticTerry Chapin

  • Polar regions are the cooling system for Planet Earth

  • Mann et al.Chapman and WalshGlobal to arcticPolaramplification

  • Polar warming is driven by global processesIs mitigation of impacts the only option?Can SEARCH make the case thatWarming 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 arcticRussian arctic

    Total arctic

    American arctic


  • Spring snowmelt is earlierDecreased albedoPositive feedback to warming

  • Sea ice is less extensiveDecreased albedoPositive feedback to warming

    Together these changes in physical environment contribute to polar amplification of global warming

  • Lloyd and FastieForests are expanding

  • Forests are expandingDecreased albedoLess masking of snowDarker, more complex canopyPositive feedback to warming

  • 1949Chandler River, 50 miles S. of Umiat: Sturm, Racine and Tape: Fifty Years of Change in Arctic Alaskan Shrub AbundanceShrub density has increased19492000Sturm

  • Indigenous observations indicate that shrub expansion is widespread

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    ---__Jia et al. GRL, in press

  • Simulated increase in July temperaturedue to shrub expansionChapin , Lynch et al.

  • Hinkel, Brown and NelsonRelationship of air temperature to thaw depthdepends on surface properties

  • Permafrost temperatures are warming warmer air altered thermal insulationOsterkamp and Romanovsky

  • Permafrost is thawingin many places, not just southern margins

  • HinzmanHydrology is changing(confirmed by indigenous observations)

  • Oechel and VourlitisTundra is becoming drier(in places)

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

  • McGuire

  • CO2 efflux is sensitive to warmingIncreased sequestration in wet areasIncreased carbon loss in dry areasNet effect uncertainProbably positive feedback to warming

  • Methane efflux is increasingPositive feedback to warmingSensitive to hydrology

    Overall trace-gas effect is a positive feedback to warming

  • Area burned in W. North America has doubled in last 20 yearsKasischki

  • Fire effects on climateReleases 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

  • (Arcticnations)Global-to-arctic: important, understoodArctic-to-global: poorly understood

    Figure 2, alternative version. Photograph shows treeline at Bear Creek, near Council. Note the dense establishment of spruce in the foreground. The inset graph is the age structure of floodplain forests and non-floodplain forests. The point is that trees have been present on the floodplain since