HR: 0800h
AN: B51E-0447
TI: Comparison of Global Model Results from the Carbon-Land Model Intercomparison Project (C-LAMP) with Free-Air Carbon Dioxide Enrichment (FACE) Manipulation Experiments
AU: * Hoffman, F M
EM: forrest@climatemodeling.org
AF: Oak Ridge National Laboratory, Computer Science & Mathematics Division Building 5600, Room C221, MS 6016 P.O. Box 2008, Oak Ridge, TN 37831-6016, United States
AU: Randerson, J T
EM: jranders@uci.edu
AF: University of California, Irvine, 3212 Croul Hall, Irvine, CA 92697, United States
AU: Fung, I
EM: ifung@berkeley.edu
AF: University of California, Berkeley, 307 McCone, Mail Code 4767, Berkeley, CA 94708, United States
AU: Thornton, P
EM: thorntonpe@ornl.gov
AF: Oak Ridge National Laboratory, Environmental Sciences Division, Oak Ridge, TN 37831, United States
AU: Covey, C
EM: covey1@llnl.gov
AF: Lawrence Livermore National Laboratory, PCMDI, Livermore, CA 94551, United States
AU: Bonan, G
EM: bonan@ucar.edu
AF: National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307, United States
AU: Running, S
EM: swr@ntsg.umt.edu
AF: University of Montana, NTSG, Missoula, MT 59812, United States
AU: Norby, R
EM: norbyrj@ornl.gov
AF: Oak Ridge National Laboratory, Environmental Sciences Division, Oak Ridge, TN 37831, United States
AB: Free-Air CO₂ Enrichment (FACE) manipulation experiments have been carried out at a handful of sites to gauge the response of the biosphere to significant increases in atmospheric [CO₂]. Early synthesis results from four temperate forest sites suggest that the response of net primary productivity (NPP) is conserved across a broad range of productivity with a stimulation at the median of 23±2% when the surrounding air [CO₂] was raised to 550~ppm. As a part of the Carbon-Land Model Intercomparison Project (C-LAMP), a community-based model-data comparison activity, the authors have performed a global FACE modeling experiment using two terrestrial biogeochemistry modules, CLM3-CASA' and CLM3-CN, coupled to the National Center for Atmospheric Research (NCAR) Community Climate System Model (CCSM). The two models were forced with an improved NCEP/NCAR reanalysis data set and reconstructed atmospheric [CO₂] and N deposition data through 1997. At the beginning of 1997 in the transient simulations, global atmospheric [CO₂] was abruptly raised to 550~ppm, the target value used at the FACE sites. In the control runs, [CO₂] continued to rise following observations until 2004, after which it was held constant out to year 2100. In both simulations, the last 25 years of reanalysis forcing and a constant N deposition were applied after year 2004. Across all forest biomes, the NPP responses from both models are weaker than those reported for the four FACE sites. Moreover, model responses vary widely geographically with a decreasing trend of NPP increases from 40°N to 70°N. For CLM3- CASA', the largest responses occur in arid regions of western North America and central Asia, suggesting that responses are most strongly influenced by increased water use efficiency for this model. CLM3-CN exhibits consistently weaker responses than CLM3-CASA' with the strongest responses in central Asia, but significantly constrained by N limitation. C-LAMP is a sub-project of the Computational Climate Science End Station led by Dr. Warren Washington, using computing resources at the U.S. Department of Energy's National Center for Computational Sciences (NCCS).
UR: http://www.climatemodeling.org/c- lamp/
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 0429 Climate dynamics (1620)
DE: 0430 Computational methods and data processing
SC: Biogeosciences [B]
MN: 2008 Fall Meeting