Abstract:

Extremely rapid rates of deforestation are occurring across the Indonesian Archipelago (2% per year from 1980-1990, compared to 0.3% per year in Amazonia 1). The influence of tropical deforestation on regional and global climates has been extensively studied with atmospheric models 2-9. However, to date, no study has examined how the fully coupled atmosphere-ocean system might respond to large-scale deforestation, and whether ocean feedbacks may modulate the response of the atmosphere to deforestation. Here, we investigate the climatic effects of large-scale deforestation in the Indonesian Archipelago using a fully coupled atmosphere-ocean model. Our simulations show that the ocean response amplifies the climatic signal of deforestation on land: the initial decrease in evaporation over the deforested land reduces convergence and modifies the wind patterns over the Indian Ocean, increasing equatorial upwelling and cooling the sea-surface temperatures thereby reducing ocean evaporation. Regional convection is reduced and precipitation decreases by 9% over deforested land. Those results indicate that Indonesian deforestation is likely to favor the dipole mode in the Indian Ocean when the eastern part of the basin experiences anomalous cool sea-surface temperatures and drought conditions on land as was the case during winter 1997-98.