HR: 12:00h
AN: B42C-07    [Abstracts]
TI: Carbon Fluxes over North America during 2001-2005: A Comparison between Land- and Atmosphere-based Approaches
AU: * Wang, W
EM: weile.wang@gmail.com
AF: California State University, Monterey Bay, 100 Compus Center, Seaside, CA 93955,
AU: * Wang, W
EM: weile.wang@gmail.com
AF: NASA Ames Research Center, NASA Ames Research Center, M/S 242-4, Moffett Field, CA 94035,
AU: Dungan, J
EM: jdungan@arc.nasa.gov
AF: NASA Ames Research Center, NASA Ames Research Center, M/S 242-4, Moffett Field, CA 94035,
AU: Nemani, R
EM: rnemani@arc.nasa.gov
AF: NASA Ames Research Center, NASA Ames Research Center, M/S 242-4, Moffett Field, CA 94035,
AB: Carbon fluxes inferred from atmospheric inversion experiments are generally conditioned on prior knowledge of biospheric fluxes, yet the influence of the latter on the inversion results is rarely assessed. As an initial step to address this question, this study compares two independent datasets: CarbonTracker NEE (net ecosystem exchange) and MODIS GPP (gross primary production) over North America between 2001 and 2005. CarbonTracker NEE (Peters et al. 2007) is a newly released product based on inversion of atmospheric measurements and MODIS GPP (Zhao et al. 2005) is based on forward modeling and satellite observations. Annual mean MODIS GPP and CarbonTracker NEE for the continent are about 13.8 (PgC/yr) and -0.65 (PgC/yr, negative sign indicates a carbon sink), respectively, consistent with previous studies; their monthly anomalies are correlated significantly ( r=-0.57, p<0.01), and also appear to be correlated with variations of ENSO (El Nino- Southern Oscillation) indices during the period, suggesting the impact of large-scale climate variability on regional ecosystems. Despite the overall agreement, however, the spatial patterns of the two datasets show remarkable differences. In particular, while MODIS shows the most substantial GPP over forest ecosystems, CarbonTracker suggests that a large proportion (30%) of the estimated carbon sink is located in the agricultural regions of the Midwest, which also contribute importantly to the interannual variability of NEE. Regression analyses suggest that the particular spatial pattern of CarbonTracker is influenced by the biospheric fluxes used in the inversion algorithm. Therefore, ensemble experiments with different prior biosphere fluxes may be necessary to verify the robustness of the spatial distribution of carbon sinks and sources estimated by atmospheric inversions.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0414 Biogeochemical cycles, processes, and modeling (0412, 0793, 1615, 4805, 4912)
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 0428 Carbon cycling (4806)
DE: 4806 Carbon cycling (0428)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting