The Changing Terrestrial Arctic

Terry Chapin

Polar regions are the cooling system for Planet Earth

Mann et al.

Chapman and Walsh

Global to arctic

Polaramplification

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?

-500

-400

-300

-200

-100

0

100

200

300

1960 1970 1980 1990 2000 2010

BaaBeaBraBarctic

Glacie volume change, km^3

YearChange in volume of Arctic ice caps and mountain glaciers

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

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

1949

2000

Sturm

Indigenous observations indicate that shrub expansion

is widespread

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Jia et al. GRL, in press

Simulated increase in July temperature

due to shrub expansion

Chapin , Lynch et al.

15 20 25 30Sqrt ADDT (air, º C day)

35

40

45

50

55

60

Grid

Average Thaw Depth (cm)

97

98

99

00

9596

97

98

99

00

97

98

99

00

97

98

99

00

97

99

00

97

98

99

00

97

98

99

00

Stefan Best Fit (R2)Atqasuk (0.84)

Barrow (0.81)

BettyPingo (0.33)

WestDock (0.17)

HappyValley (0.79)

Toolik (0.75)

Imnavait (0.83)

Hinkel, Brown and Nelson

Relationship of air temperature to thaw depthdepends on surface properties

1983 1986 1989 1992 1995 1998 2001

-10.0

-9.5

-9.0

-8.5

-8.0

-7.5

-7.0

-6.5

-6.0

Temperatures at the 20 m depth on a N-S transect across the coastal plain of Northern Alaska

Franklin Bluffs

Deadhorse

West Dock

Tom Osterkamp 10/01

Temperature (°C)

Year

Permafrost temperatures are warming warmer air altered thermal insulation

Osterkamp and Romanovsky

Permafrost is thawingin 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. Nature August, 2000

Recent Response ofRecent Response ofNet Ecosystem CarbonNet Ecosystem Carbon

Flux to a Secular Change inFlux to a Secular Change inClimateClimate

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

(Arcticnations)

Global-to-arctic: important, understoodArctic-to-global: poorly understood