Quantifying the impacts of fire aerosols on global terrestrial ecosystem productivity with the fully-coupled Earth system model CESM

Abstract

Fire is a global phenomenon and a major source of aerosols from the terrestrial biosphere to the atmosphere. Most previous studies quantified the effect of fire aerosols on climate and atmospheric circulation, or on the regional and site-scale terrestrial ecosystem productivity. So far, only one work has quantified their global impacts on terrestrial ecosystem productivity based on offline simulations, which, however, did not consider the impacts of aerosol–cloud interactions and aerosol–climate feedbacks. This study quantitatively assesses the influence of fire aerosols on the global annual gross primary productivity (GPP) of terrestrial ecosystems using simulations with the fully coupled global Earth system model CESM1.2. Results show that fire aerosols generally decrease GPP in vegetated areas, with a global total of −1.6 Pg C yr−1, mainly because fire aerosols cool and dry the land surface and weaken the direct photosynthetically active radiation (PAR). The exception to this is the Amazon region, which is mainly due to a fire-aerosol-induced wetter land surface and increased diffuse PAR. This study emphasizes the importance of the influence of fire aerosols on climate in quantifying global-scale fire aerosols’ impacts on terrestrial ecosystem productivity.