HR: 17:45h
AN: B12G-08    [PDF]
TI: Integrating Multiple Sources of Terrestrial Observations to Calibrate Carbon Models
AU: * Barrett, D J
EM: Damian.Barrett@csiro.au
AF: CSIRO Plant Industry, GPO Box 1600, Canberra, ACT 2601 Australia
AB: In Australia, ENSO driven climate variation plays a major role in determining inter-annual variability of net C-exchange between the land surface and the atmosphere. Annual to decadal climate variation governs C-pool dynamics and fire regimes which exert a major control on net sources and sinks on these timescales. Furthermore, a major difficulty in calibrating large scale carbon models is poor data availability. In this case, it is advantageous to exploit as many different sources of information as possible to estimate model parameters. In this presentation, we demonstrate a `multiple constraints' approach to parameter estimation that combines net primary production, plant, litter and soil C observations. The method uses a genetic algorithm to solve a multi-objective optimization problem in which we minimize differences between predicted and observed long term averages of plant, litter and soil C pools while estimating parameter values. The estimated parameters were then used in the dynamical C model VAST1.2 to quantify variability in net C-exchange of the Australian continent over a 20 year period (1981 - 2000) arising from climate variability effects on both decomposition and fire. Predicted continental monthly net C exchange varied by up to 77 TgC/month from a source of 28 TgC/month to a sink of 49 TgC/month. The 95% confidence intervals of monthly net C-exchange showed that the continent could be either a source or a sink of C in any month between February and October depending on prevailing ENSO conditions. For the remaining months (November to January), the continent was a source of C to the atmosphere. Annual total net primary production varied more than two-fold between 470 and 1032 TgC/year and annual net C-exchange varied between a sink of 118 TgC/year and a source of 80 TgC/year. We also compared modeled continental net C-exchange with published troposphere CO2 measurements over the western Pacific Ocean and show good qualitative agreement between predicted continental net C flux and atmosphere CO2 concentration growth rate, suggesting that VAST1.2 has accurately reproduced the phase of sources and sinks for Australia.
DE: 0315 Biosphere/atmosphere interactions
DE: 0400 Biogeosciences
DE: 1615 Biogeochemical processes (4805)
DE: 3210 Modeling
SC: Biogeosciences [B]
MN: 2003 Fall Meeting