Global polycyclic aromatic hydrocarbons (PAHs) and future climate and emissions, 2000-2050

• Main Author: Friedman, Carey
• Format: Dataset
• Language: English
• Published: NSF Arctic Data Center 2016
• Subjects: Arctic; Climate change
• Online Access: https://dx.doi.org/10.18739/a2d21rk15; https://arcticdata.io/catalog/view/doi:10.18739/A2D21RK15

We investigate effects of 2000-2050 emissions and climate changes on the atmospheric transport of three polycyclic aromatic hydro- carbons (PAHs): phenanthrene (PHE), pyrene (PYR), and benzo[a]pyrene (BaP). We use the GEOS-Chem model coupled to meteorology from a general circulation model and focus on impacts to northern hemisphere midlatitudes and the Arctic. We project declines in anthropogenic emissions (up to 20%) and concentrations (up to 37%), with particle-bound PAHs declining more, and greater declines in midlatitudes versus the Arctic. Climate change causes relatively minor increases in midlatitude concentrations for the more volatile PHE and PYR (up to 4%) and decreases (3%) for particle-bound BaP. In the Arctic, all PAHs decline slightly under future climate (up to 2%). Overall, we observe a small 2050 "climate penalty" for volatile PAHs and "climate benefit" for particle-bound PAHs. The degree of penalty or benefit depends on competition between deposition and surface-to-air fluxes of previously deposited PAHs. Particles and temperature have greater impacts on future transport than oxidants, with particle changes alone accounting for 15% of BaP decline under 2050 emissions. Higher temperatures drive increasing surface-to-air fluxes that cause PHE and PYR climate penalties. Simulations suggest ratios of more-to-less volatile species can be used to diagnose signals of climate versus emissions and that these signals are best observed in the Arctic.