HR: 11:50h
AN: B22B-07    [Abstracts]
TI: Impacts of Land Cover Change and Increasing CO2 Concentrations on Amazon Basin Hydroclimatology: High-resolution Results From the Ocean-Land-Atmosphere Model (OLAM)
AU: * Medvigy, D
EM: dmm31@duke.edu
AF: Duke University, PO Box 90287, Durham, NC 27708, United States
AU: Avissar, R
EM: avissar@duke.edu
AF: Duke University, PO Box 90287, Durham, NC 27708, United States
AU: Walko, R L
EM: Robert.Walko@duke.edu
AF: Duke University, PO Box 90287, Durham, NC 27708, United States
AU: Nepstad, D C
EM: dnepstad@whrc.org
AF: The Woods Hole Research Center, 149 Woods Hole Rd, Falmouth, MA 02540, United States
AU: Soares-Filho, B S
EM: britaldo@csr.ufmg.br
AF: Universidade Federal de Minas Gerais, Av. Antonio Carlos 6627, Belo Horizonte, MG 31270, Brazil
AB: It has recently been projected that agricultural expansion will eliminate 40 percent of Amazon forests during the next 50 years. Previous studies have suggested that such dramatic land cover change can significantly alter the regional and possibly global hydroclimate. Furthermore, projections of vegetation response to increasing atmospheric carbon dioxide concentrations and the resulting feedbacks to the hydroclimate are sensitive to water use efficiency, which varies among different land cover types. To assess the influence of Amazonian land cover change on hydroclimate, general circulation models (GCMs) and regional meteorological models have been used. However, both approaches have important limitations: the grid resolution of the GCMs is coarser than the scale of actual land cover change and too coarse to resolve mesoscale circulations, while mesoscale models typically obtain their requisite lateral boundary conditions from global simulations not accounting for land cover change. In this study, we present a new model, the Ocean Land Atmosphere Model (OLAM), which alleviates the resolution problem and eliminates the problem of boundary conditions. OLAM is a global Earth System Model employing a state-of-the-art grid structure which enabled us to use an atmospheric resolution typical of a mesoscale model over South America while using a coarser resolution typical of other GCMs throughout the rest of the world. Vegetation is treated either by the LEAF-3 biophysical scheme or by the Ecosystem Demography (ED) model, a dynamic vegetation model. In this configuration, OLAM reasonably matched observed patterns of precipitation and radiation on monthly to decadal time scales, with particularly good agreement in South America. We investigated how regional and global hydrological cycles were altered in OLAM when the model was forced with current projections of land cover change in Amazon basin and with increased CO2 concentrations. We found that, because of mesoscale feedbacks, the impact of land cover change on basin-wide Amazon precipitation was small relative to the previous projections of coarser-resolution modeling studies. However, changes in land cover had important impacts on sub-basin scales with the eastern Amazon experiencing increased precipitation and strongly increased runoff, and the western Amazon experiencing decreased precipitation and only slightly increased runoff. Similarly, we found that the impact of increased CO2 concentrations on precipitation varied regionally, with both negative and positive impacts possible but relatively small on the basin-average.
DE: 0426 Biosphere/atmosphere interactions (0315)
DE: 1632 Land cover change
DE: 1637 Regional climate change
DE: 1813 Eco-hydrology
DE: 1840 Hydrometeorology
SC: Biogeosciences [B]
MN: 2007 Fall Meeting