Impacts of Future Climate Change on Aerosol Transport to the Arctic

Abstract:

Arctic climate is sensitive to small concentrations of light-absorbing aerosols like black carbon, and hence the impacts of global climate change on aerosol transport to the Arctic are of interest. Here, we explore how climate warming under the RCP 8.5 scenario would impact 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, operating in isolation, cause the Arctic burdens of tracers emitted from East Asia and West Europe during winter to increase about 20-30% by the end of the century, while decreasing the Arctic burdens of North American emissions by 20-40%. 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 mid-latitudes 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 17% reduction in the Arctic annual-mean burden by the end of the 21st century, due to warming-induced transport and deposition changes.