Abstract ID: 506

Greenhouse Gas Induced Changes in the Seasonal Cycle of the Amazon Basin in a Coupled Climate-Vegetation Regional Model

Cook and Vizy(2008) used a regional atmospheric model asynchronously coupled with a potential vegetation model and constrained by simulations with the Canadian Climate Center GCM to show that, by the end of this century under the IPCC A2 emissions scenario, changes in seasonality lead to a 70% reduction in the extent of the Amazon rainforest. The primary cause of the dieback of the rainforest is a lengthening of the dry season, and the ultimate cause of the changes is a weakening of the large-scale tropical circulation. Here we more closely examine these changes in the seasonal cycle. Under present day conditions the Amazon climate is mainly characterized by a zonal separation in terms of the dominance of the annual and semi-annual seasonal cycles. This behavior is found to be completely modified under greenhouse warming conditions, with the annual cycle becoming dominant throughout the Amazon basin, increasing differences between the dry and wet seasons. In particular, there are substantial changes in the warmest and coldest months due to the increase in temperature of the warmest month.

Session:  Feedbacks to Climate - Effects of deforestation on regional and global climate.

Presentation Type:  Oral