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CH4 Biogeochemistry in CLM4
W.J. Riley
Collaborators: Z. Subin, M. Torn, L. Meng, N. Mahowald, P. Hess, S. Swenson, D.
Lawrence
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Overview• A component of DOE IMPACTS project
– Global methane emissions model– Thermokarst lake model– High-latitude dynamic vegetation model– Atmospheric coupling and feedbacks
• Collaborating with Cornell group to analyze tropical CH4 emissions
• Feedback analyses in CCSM
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Outline
• CH4 BGC model integrated in CLM4• Inundated fraction• Global spin-up with changes• Aerenchyma effects• Comparison to site observations• Comparison to global inversions
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CH4 Biogeochemistry
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Inundated Fraction
• Comparison to satellite inferred inundation (Prigent et al. 2007)
• Inverted with CLM predicted water table depth and overland flow
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Global Spinup
• Hydraulic changes for frozen soils• C3 arctic grass rooting depth
• Hydraulic and thermal property for high organic matter soil
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7
Ice Hydraulic Impedance, Perched Water Table
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Change in NPP
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Aerenchyma
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(Preliminary) Comparison to Site Data
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Comparison to Global Inversions
• Model broadly matches inversion estimates of zonal CH4 emissions
• Southern Tropics discrepancy– Analysis underway
to better understand discrepancies
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Next Steps
• Finalize sensitivity analysis and model parameters
• Improvements in next phase– Proper treatment of inundated C cycle– Depth and vegetation representation– Permafrost soil C – Inundated fraction– Redox and pH prediction and effects on CH4
emissions
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NPP
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Global CH4 Emission Prediction