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Strength and Timing of the Permafrost Carbon Feedback (PCF) - PowerPoint PPT Presentation

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CO 2 Concentration (ppm). Date (year). Strength and Timing of the Permafrost Carbon Feedback (PCF) Schaefer, Kevin 1 , Tingjun Zhang 1 , Lori Bruhwiler 2 , and Andrew Barrett 1 1 National Snow and Ice Data Center, University of Colorado

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CO2 Concentration (ppm)

Date (year)

Strength and Timing of the Permafrost Carbon Feedback (PCF)

Schaefer, Kevin1, Tingjun Zhang1, Lori Bruhwiler2, and Andrew Barrett1

1 National Snow and Ice Data Center, University of Colorado

2NOAA Earth System Research Laboratory, Boulder, Colorado

Contact: Kevin Schaefer: 303-492-8869; [email protected]

1) Objective

4) A1B IPCC Scenario

6) PCF Timing

Estimate the strength and timing of the Permafrost Carbon Feedback (PCF)

Ens. mean with PCF


Cumulative NEE (Gt C)

Surface Warming

Increased CO2

Figure 1: The PCF is an amplification of surface warming due to the thaw and decay of carbon currently frozen in permafrost.

Sink to source (2023±4)

Permafrost carbon decays

Figure 4: The A1B IPCC scenario. We ran 18projections to 2200using SiBCASA, randomly selected years from the ERA40 reanalysis, and weather trends from three General Circulation Models (CCSM3, HadCM3, and MIROC3.2) representing low, medium, and high warming rates.

Date (year)

Active Layer

Figure 6: Ensemble mean cumulative Net Ecosystem Exchange (NEE) with permafrost carbon indicates the Arctic changes from a sink to a source in 2023±4 years.

2) Permafrost Carbon


5) Permafrost Degradation

7) PCF Strength

Soil Depth

Active Layer

Permafrost Table


Cumulative Permafrost Carbon Flux (Gt C)

Siberia [Davis, 2000]

Figure 2: 1670 Gt of carbon is frozen in permafrost [Tarnocai et al., 2009]. Sedimentation (e.g., loess deposition) increases soil depth, freezing organic matter at the bottom of the active layer into permafrost.

190±64 Gt

CCSM3 (low)

29% loss

HadCM3 (med)

50% loss

MIROC3.2 (high)

59% loss

Date (year)

Figure 5: Increases in ALT by 2200 (cm). Black indicates where SiBCASA did not simulate permafrost after spinup. Red indicates where permafrost is lost. We project a 29-59% loss of permafrost area by 2200.

Figure 7: The cumulative permafrost carbon flux is 190±64 Gt C by 2200, equivalent to a 52±6 ppm change in atmospheric CO2, 65±23% of the global land sink in 2100, and 14±5% of fossil fuel emissions for the A1B scenario.

3) Permafrost Carbon Pool

Active Layer

Active Layer

8) Conclusions

Soil Carbon Pools


Thawed Carbon

Permafrost Carbon

Permafrost Carbon

1) Emission reductions should include PCF

2) PCF is strong: 190±64 Gt C by 2200

3) Arctic from sink to source in mid 2020s

4) 29-59% permafrost area loss by 2200

Paper in press:

Schaefer, K., T. Zhang, L. Bruhwiler, A. P. Barrett (2011), Amount and Timing of Permafrost Carbon Release in Response to Climate Warming, Tellus Series B, in press.

3 m



ALTmax = maximum Active Layer Thickness

Figure 3: Permafrost carbon is below ALTmax and above 3 m. As the active layer deepens, thawed carbon is transferred to soil carbon pools, essentially reversing the burial process.