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.

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

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

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

Recent Permafrost Temperature Trends (adapted from Romanovsky et al Country Region Permafrost Temp. Trend Reference USA Trans-Alaska pipeline route (20 m), 1983-2003 +0.6 to +1.5°C Romanovsky and Osterkamp, 2001; Osterkamp 2003 Barrow Permafrost Observatory (15 m), 1950-2003 +1°C Brewer 1958; Romanovsky et al., 2002 Russia Northwest Siberia (10 m), 1980-1990 +0.3 to +0.7°C Pavlov, 1994 European North of Russia (6 m), 1973-1992 +1.6 to +2.8°C Canada Alert (15 m), 1995-2000 +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 (1973-2003) +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 (1973-2003) +0.3° to +0.6°C Sharkhuu, 2003

Arctic Land Area: Surface Air Temperature Change (CCSM3)

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

CCSM3 Projections of Degradation of Near-Surface Permafrost

Are the CCSM3 Projections Plausible?

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

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

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

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

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

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

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

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

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

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.

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.

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

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

Arctic Land Area: Surface Air Temperature Change (CCSM3)