A multi-model assessment of pollution transport to the Arctic

[摘要] We examine the response of Arctic gas and aerosol concentrations toperturbations in pollutant emissions from Europe, East and South Asia, andNorth America using results from a coordinated model intercomparison. Thesesensitivities to regional emissions (mixing ratio change per unit emission)vary widely across models and species. Intermodel differences aresystematic, however, so that the relative importance of different regions isrobust. North America contributes the most to Arctic ozone pollution. Foraerosols and CO, European emissions dominate at the Arctic surface but EastAsian emissions become progressively more important with altitude, and aredominant in the upper troposphere. Sensitivities show strong seasonality:surface sensitivities typically maximize during boreal winter for Europeanand during spring for East Asian and North American emissions.Mid-tropospheric sensitivities, however, nearly always maximize duringspring or summer for all regions. Deposition of black carbon (BC) ontoGreenland is most sensitive to North American emissions. North America andEurope each contribute ~40% of total BC deposition to Greenland,with ~20% from East Asia. Elsewhere in the Arctic, both sensitivityand total BC deposition are dominated by European emissions. Model diversityfor aerosols is especially large, resulting primarily from differences inaerosol physical and chemical processing (including removal). Comparison ofmodeled aerosol concentrations with observations indicates problems in themodels, and perhaps, interpretation of the measurements. For gas phasepollutants such as CO and O₃, which are relatively well-simulated, theprocesses contributing most to uncertainties depend on the source region andaltitude examined. Uncertainties in the Arctic surface CO response toemissions perturbations are dominated by emissions for East Asian sources,while uncertainties in transport, emissions, and oxidation are comparablefor European and North American sources. At higher levels, model-to-modelvariations in transport and oxidation are most important. Differences inphotochemistry appear to play the largest role in the intermodel variationsin Arctic ozone sensitivity, though transport also contributes substantiallyin the mid-troposphere.

[学科分类] 大气科学