Sarah L. Shafer 1 , Patrick J. Bartlein 2 , Mary E. Edwards 3 , and Steven W. Hostetler 1
1 U.S. Geological Survey, Corvallis, OR
2 Dept. of Geography, Univ. of Oregon, Eugene, OR
3 School of Geography, Univ. of Southampton, UK and
Alaska Quaternary Center, Univ. of Alaska-Fairbanks, AK

What can past vegetation responses to warmerthan-present climates tell us about potential vegetation responses to future climate change in
Beringia?
Examples: 6 ka and 11 ka
• greater summer insolation than present
• warmer growing season temperatures
• deciduous forest expansion
Beringia – RegCM2 domain
July insolation anomaly (45°N)
Figure: Millspaugh et al. 2000

(Edwards et al. 2005)

Vegetation Model
BIOME4 (Kaplan 2001)
• equilibrium biogeography model
• simulates biomes based on plant functional types (e.g., needleleaf evergreen trees, grass)
• simulates the physiological response of vegetation to changes in atmospheric CO
2 concentrations
Modern Climate Data
• CRU TS 2.1 1901-2002 (Mitchell and Jones 2005)
• 1961-1990 30-year mean

Modern Vegetation
Boundary Conditions
Simulated Vegetation
1961-1990 30-yr mean
340 ppm CO
2

Paleoclimate Simulations for 6 ka and 11 ka
• Regional Climate Model: RegCM2
--Genesis 2.0, an atmospheric general circulation model with a mixed-layer ocean
-- ~45-km grid cell resolution
• Boundary conditions: pre-11 ka –
• Bering land bridge exposed
• absence of thaw lakes
• tundra vegetation post-11 ka –
• flooding of Bering land bridge
• development of thaw lakes
• replacement of shrub tundra by forest
6 ka – modern conditions

11 ka Anomalies
Jan
11 ka compared to
1961-1990 30-year mean
Mar
Temperature
Pre-11 ka Post-11 ka
Precipitation
Pre-11 ka Post-11 ka
May
Jul
Sep
Nov

Simulated Vegetation
Pre-11 ka
270 ppm CO
2
Simulated Vegetation
Post-11 ka
270 ppm CO
2

Simulated Modern
1961-1990 30-yr mean
340 ppm CO
2
Simulated Vegetation
Post-11 ka
270 ppm CO
2

6 ka Anomalies
Jan
Temperature Precipitation
6 ka compared to
1961-1990 30-year mean
Mar
May
Jul
Sep
Nov

Simulated Modern
1961-1990 30-yr mean
340 ppm CO
2
Simulated 6 ka
280 ppm CO
2

FUTURE VEGETATION CHANGE
Two hypotheses (Edwards et al. 2005):
1. Expansion of current evergreen needleleaf forest
2. Development of deciduous forest in tundra areas similar to the vegetation at 11 ka
FUTURE CLIMATE DATA
AOGCMs (atmosphere-ocean general circulation models):
• HadCM3 (Flato 2005)
• CGCM3.1 (Collins et al. 2006)
• CCSM3.0 (Gordon et al. 2000)
Time period: 2071-2100 30-year mean
Atmospheric CO
2 concentration: 540 ppm
Emissions scenario: IPCC SRES B1

Storylines:
A2—slower economic growth, high population growth
A1B—rapid economic growth, low population growth
B1—slow economic growth, low population growth
(T. Wigley; Taylor 2004)

TEMPERATURE ANOMALIES
Jan
HadCM3 CGCM3.1 CCSM3.0
2071-2100 30-year mean
540 ppm CO
2
Mar
May
Jul
Sep
Nov

PRECIPITATION ANOMALIES
2071-2100 30-year mean
540 ppm CO
2
Jan
Mar
HadCM3 CGCM3.1 CCSM3.0
May
Jul
Sep
Nov

Simulated Future Vegetation
2071-2100 30-yr mean
540 ppm CO
2
HadCM3
CGCM3.1
CCSM3.0

Simulated Modern
1961-1990 30-yr mean
340 ppm CO
2
Simulated Future
2071-2100 30-yr mean
540 ppm CO
2
Expansion of:
• Evergreen forest
• Deciduous forest
(western Beringia)
• Grassland and desert
HadCM3

Summary
• Deciduous forest expansion is simulated at 6 ka and 11 ka, consistent with the paleorecord
Modern
6 ka
• Both evergreen and deciduous forest are simulated to expand under future climates
11 ka
• Tundra is simulated to contract under future climates
2071-2100
HadCM3

IPCC AR4: We acknowledge the international modeling groups for providing their data for analysis, the Program for Climate
Model Diagnosis and Intercomparison (PCMDI) for collecting and archiving the model data, the JSC/CLIVAR Working Group on Coupled Modelling (WGCM) and their Coupled Model
Intercomparison Project (CMIP) and Climate Simulation Panel for organizing the model data analysis activity, and the IPCC
WG1 TSU for technical support. The IPCC Data Archive at
Lawrence Livermore National Laboratory is supported by the
Office of Science, U.S. Department of Energy.

11 ka Experiments

FUTURE CLIMATE DATA
AOGCMs (atmosphere-ocean general circulation models):
HadCM3
CGCM13.1
CCSM3.0
Time period: 2071-2100 30-year mean
Atmospheric CO2 concentration: 540 ppm
Emissions scenario: IPCC SRES B1

Jul
Sep
Nov
Jan
TEMPERATURE ANOMALIES PRECIPITATION ANOMALIES
HadCM3 CGCM3.1 CCSM3.0
HadCM3 CGCM3.1 CCSM3.0
Mar
May

Simulated Vegetation
11 ka, 270 ppm CO
2

CONCLUSIONS
(ADD TEXT—END OF SLIDES)

Simulated Vegetation
Post-11 ka, 270 ppm CO
2

Simulated Vegetation
HadCM3, 2071-2100, 540 ppm CO
2

Simulated Vegetation
1961-1990 30-yr mean, 340 ppm CO
2

Simulated Vegetation
6 ka, 280 ppm CO
2