Changing black carbon transport to the Arctic from present day to the end of 21st century

Abstract

Here we explore how climate warming under the Representative Concentration Pathway 8.5 (RCP8.5) impacts Arctic aerosol distributions via changes in atmospheric transport and removal processes. We modify the bulk aerosol module in the Community Atmosphere Model to track distributions and fluxes of 200 black carbon-like tracers emitted from different locations, and we conduct idealized experiments with and without active aerosol deposition. Changing wind patterns, studied in isolation, cause the Arctic burdens of tracers emitted from East Asia and West Europe during winter to increase about 20% by the end of the century while decreasing the Arctic burdens of North American emissions by about 30%. These changes are caused by an altered winter polar dome structure that results from Arctic amplification and inhomogeneous sea ice loss and surface warming, both of which are enhanced in the Chukchi Sea region. The resulting geostrophic wind favors Arctic transport of East Asian emissions while inhibiting poleward transport of North American emissions. When active deposition is also considered, however, Arctic burdens of emissions from northern midlatitudes show near-universal decline. This is a consequence of increased precipitation and wet removal, particularly within the Arctic, leading to decreased Arctic residence time. Simulations with present-day emissions of black carbon indicate a 13.6% reduction in the Arctic annual mean burden by the end of the 21st century, due to warming-induced transport and deposition changes, while simulations with changing climate and emissions under RCP8.5 show a 61.0% reduction.