HR: 11:05h
AN: B42B-03    [Abstracts]
TI: Boreal Forest Fire Cools Climate
AU: * Randerson, J T
EM: jranders@uci.edu
AF: Department of Earth System Science, University of California, Croul Hall, Irvine, CA 92697 United States
AU: Liu, H
EM: heping.liu@jsums.edu
AF: Department of Physics, Atmospheric Science, and General Science, Jackson State University, P.O. Box 17660, Jackson, MS 39217 United States
AU: Flanner, M
EM: flanner@uci.edu
AF: Department of Earth System Science, University of California, Croul Hall, Irvine, CA 92697 United States
AU: Chambers, S D
EM: szc@ansto.gov.au
AF: Australian Nuclear Science and Technology Organization, Environmental Division, PMB 1, Menai, NSW 2234 Australia
AU: Harden, J W
EM: jharden@usgs.gov
AF: U.S. Geological Survey, MS 962 345 Middlefield Rd., Menlo Park, CA 94025 United States
AU: Hess, P G
EM: hess@ucar.edu
AF: Atmospheric Chemistry Division, National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder, CO 80305 United States
AU: Jin, Y
EM: yufang@uci.edu
AF: Department of Earth System Science, University of California, Croul Hall, Irvine, CA 92697 United States
AU: Mack, M C
EM: mcmack@ufl.edu
AF: Department of Botany, University of Florida, PO Box 118526, Gainsville, FL 32611 United States
AU: Pfister, G
EM: pfister@ucar.edu
AF: Atmospheric Chemistry Division, National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder, CO 80305 United States
AU: Schuur, E A
EM: tschuur@ufl.edu
AF: Department of Botany, University of Florida, PO Box 118526, Gainsville, FL 32611 United States
AU: Treseder, K K
EM: treseder@uci.edu
AF: Department of Earth System Science, University of California, Croul Hall, Irvine, CA 92697 United States
AU: Welp, L R
EM: welp@caltech.edu
AF: Environmental Science and Engineering, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125 United States
AU: Zender, C S
EM: zender@uci.edu
AF: Department of Earth System Science, University of California, Croul Hall, Irvine, CA 92697 United States
AB: We report measurements, modeling, and analysis of carbon and energy fluxes from a boreal forest fire that occurred in interior Alaska during 1999. In the first year after the fire, ozone production, atmospheric aerosol loading, greenhouse gas emissions, soot deposition, and decreases in summer albedo contributed to a positive annual radiative forcing (RF). These effects were partly offset by an increase in fall, winter, and spring albedo from reduced canopy cover and increased exposure of snow-covered surfaces. The atmospheric lifetime of aerosols and ozone and are relatively short (days to months). The radiative effects of soot on snow are also attenuated rapidly from the deposition of fresh snow. As a result, a year after the fire, only two classes of RF mechanisms remained: greenhouse gas emissions and post-fire changes in surface albedo. Summer albedo increased rapidly in subsequent years and was substantially higher than unburned control areas (by more than 0.03) after 4 years as a result of grass and shrub establishment. Satellite measurements from MODIS of other interior Alaska burn scars provided evidence that elevated levels of spring and summer albedo (relative to unburned control areas) persisted for at least 4 decades after fire. In parallel, our chamber, eddy covariance, and biomass measurements indicated that the post-fire ecosystems switch from a source to a sink within the first decade. Taken together, the extended period of increased spring and summer albedo and carbon uptake of intermediate-aged stands appears to more than offset the initial warming pulse caused by fire emissions, when compared using the RF concept. This result suggests that management of forests in northern countries to suppress fire and preserve carbon sinks may have the opposite effect on climate as that intended.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0360 Radiation: transmission and scattering
DE: 0428 Carbon cycling (4806)
DE: 1615 Biogeochemical cycles, processes, and modeling (0412, 0414, 0793, 4805, 4912)
SC: Biogeosciences [B]
MN: Fall Meeting 2005