Reduced Arctic air pollution due to decreasing European and North American emissions

Atmospheric transport of midlatitude pollutant emissions to the Arctic can result in disproportionate impacts on the receptor region. We use carbon monoxide (CO), a tracer of incomplete combustion, to study changes in pollutant transport to the Arctic. Using a wavelet transform, we spectrally decompose CO mole fraction measurements from three Arctic sites (Alert, Barrow, and Zeppelin) collected by NOAA over the past 20–25 years. We show that CO concentrations have decreased by −1.0 to −1.2 ppb/yr. We find that the dampened seasonal cycle (−1.2 to −2.3 ppb/yr) is mostly due to a reduction in peak concentrations (−1.5 to −2.4 ppb/yr), which we attribute to reduced source emissions. We find no evidence to support a persistent increase in hydroxyl radical concentration. Using the GEOS-Chem global 3-D chemistry transport model, we show that observed decreases are consistent with reductions in fossil fuel usage from Europe and North America.