1. David Lawrence1 and Andrew Slater2
A Projection of Severe Degradation of Near-Surface Permafrost: Potential Feedbacks on Global Climate
David Lawrence1 and Andrew Slater2
1 NCAR / CGD
Boulder, CO
2 NSIDC / CIRES
Acknowledge co-author. Talk about projection in a premier GCM.

2. Permafrost: Soil or rock that remains below freezing for two or more years
IPA Permafrost Distribution Map
Continuous Discontinuous
Near-surface permafrost. Many factors influence permafrost and its evolution, MAAT, snow cover, insulating organic layer, vegetation cover, ice content. Different features depending on ice content, latitude, etc.
hypothetical
Continuous (90 – 100% coverage)
Discontinuous (50 – 90%)
Sporadic (10 – 50%)
Isolated (0 – 10%)
Brown et al. 1998

3. Observed Arctic Climate Change
Polar amplification of climate change
Arctic air temperatures rising at twice the rate of rest of world
Arctic sea-ice extent decreasing
Arctic glaciers retreating
Shrub coverage expanding
Treeline migrating northward
Arctic tundra may have shifted from a CO2 sink to a CO2 source
Permafrost temperatures rising
30’s warming due to Atlantic Multidecadal Oscillation (AMO) and is localized to very high latitudes
Diverse, but consistent picture of change
ACIA, 2004; Serreze et al. 2000

4. Soil Temperature Trends
Long term measurements are sparse and relatively incomplete
Romanovsky et al. 2002

5. Recent Permafrost Temperature Trends (adapted from Romanovsky et al
Country
Region
Permafrost Temp. Trend
Reference
USA
Trans-Alaska pipeline route (20 m),
+0.6 to +1.5°C
Romanovsky and Osterkamp, 2001; Osterkamp 2003
Barrow Permafrost Observatory (15 m),
+1°C
Brewer 1958; Romanovsky et al., 2002
Russia
Northwest Siberia (10 m),
+0.3 to +0.7°C
Pavlov, 1994
European North of Russia (6 m),
+1.6 to +2.8°C
Canada
Alert (15 m),
+0.15°C yr-1
Smith et al., 2003
Northern Quebec (10 m), late 1980s - mid 1990s
–0.1oC yr-1
Allard et al., 1995
Norway
Janssonhaugen, Svalbard
+1° to +2°C
Isaksen et al., 2001
Kazakhstan
Northern Tien Shan ( )
+0.2° to +0.6°C
Marchenko, 1999 and 2002
Tibet
Qinghai-Tibet Plateau (1970s-90s)
+0.1 to +0.3°C
Huijin et al., 2000
Mongolia
Khentei and Khangai Mountains, Lake Hovsgol ( )
+0.3° to +0.6°C
Sharkhuu, 2003

6. Arctic Land Area: Surface Air Temperature Change (CCSM3)

7. Near-Surface Permafrost in CCSM3
(1980 – 1999)
IPA Permafrost
Distribution Map
Continuous
Discontinuous
Sporadic
Isolated

8. CCSM3 Projections of Degradation of Near-Surface Permafrost

9. Are the CCSM3 Projections Plausible?

10. Model Validation: Annual Mean Surface Air Temperature and Active Layer Thickness
CALM Monitoring Sites
CCSM3
Observed
CCSM3 – Obs
Validation difficult as there is no observed timeseries of permafrost extent, only can tangentially analyze

11. Model Validation and Development Priorities: Permafrost Simulation
Soil temperature data
Russian hydromet / agromet sites (long time series)
Problems: No associated meteorological data Comparison of site data with gridded model data
Soil depth
Increase from 3.5m to 15m
Organic soil layer / mosses
Alter thermal conductivity and heat
capacity for uppermost soil levels
Discontinuous permafrost
High-res land model, topographic, aspect
Solve Arctic low cloud bias
Photo by A. Slater

12. Kudryavtsev, 1974
25m Soil Column
0.05m layers
15 year run

13. Kudryavtsev, 1974
3.43m Soil Column
CLM3 resolution
15 year run

14. 25m Soil Column
0.05m layers
15 year run
3.43m Soil Column
CLM3 resolution
15 year run

15. Model Validation and Development Priorities: Permafrost Simulation
Soil temperature data
Russian hydromet / agromet sites (long time series)
Problems: No associated meteorological data Comparison of site data with gridded model data
Soil depth
Increase from 3.5m to 15m
Organic soil layer / mosses
Alter thermal conductivity and heat
capacity for uppermost soil levels
Discontinuous permafrost
High-res land model, topographic, aspect
Solve Arctic low cloud bias
Photo by A. Slater

16. Are the CCSM3 Projections Plausible?
Uncertainties in timing and amplitude of projected permafrost degradation –
- biases in simulated climate
- imperfect representation of permafrost
- feedbacks that are not fully-represented
What are the impacts / climate feedbacks?
- vegetation - expansion of shrub coverage and northward forest migration
- hydrologic cycle - freshwater discharge to Arctic Ocean, lake and wetland expansion/contraction
- carbon cycle – release of frozen soil carbon

17. Impact on Freshwater Discharge to Arctic Ocean
Runoff to Arctic Ocean
28% increase in freshwater discharge to Arctic Ocean (2000 to 2099)
~15% due to soil ice melting and drainage of excess soil water
Impacts on Arctic sea-ice formation and ocean circulation
Runoff
P – E

18. Appearing and Disappearing Lakes in Siberia (Smith et al. 2005)

19. Release of Soil Carbon Frozen in Permafrost
~ 200 – 800 Pg C frozen in permafrost soil
Increased wetlands, anaerobic microbial activity  CH4 emissions
Dry, well-drained soil, aerobic decomposition  CO2 emissions
At one Swedish mire, permafrost and vegetation changes linked with 22-66% rise in CH4 emissions (1970 to 2000, Christensen et al. 2004).
Photo courtesy Natural Resources Canada
Permafrost and wetlands, large uncertainties, not usually included in carbon models. More than 5 times more carbon in soil than living biomass.
Soil carbon vulnerable (25%) to land use change, moreso than changes in climate.

20. Release of Soil Carbon Frozen in Permafrost
Gruber et al. 2004
Global Carbon Project
Permafrost
Permafrost ?
Permafrost
Permafrost and wetlands, large uncertainties, not usually included in carbon models. More than 5 times more carbon in soil than living biomass.
Soil carbon vulnerable (25%) to land use change, moreso than changes in climate.

21. Climate Feedbacks Associated with Permafrost Degradation: Model Development Issues
Northward expansion of shrubs and forests
Introduce shrubs into DGVM
Update parameters for Arctic vegetation types
Hydrology, freshwater discharge to Arctic Ocean
‘Dynamic’ wetland and lake distributions
Frozen soil hydrology
Emission of soil carbon from thawing permafrost soil
Spin-up (or initialization) of soil carbon store in permafrost (vertical profile of soil carbon, low GPP in Arctic?)
Partition soil decomposition emissions into CH4 or CO2 depending on moisture conditions

22. Summary
Permafrost temperatures are rising and permafrost is degrading in some locations
CCSM3, which reasonably simulates present-day near-surface permafrost conditions, projects severe degradation of near-surface permafrost during the 21st century
The potential feedbacks associated with a loss of near-surface permafrost are diverse (vegetation, hydrologic cycle, carbon cycle) and could contribute to an acceleration of climate change

23. Arctic Land Area: Surface Air Temperature Change (CCSM3)