Long-range transport into the Arctic: Pathways, chemical impacts, and interannual variability

We present a modeling and data analysis study of the variability and chemical impact of the import of anthropogenic pollution and biomass burning emissions into the Arctic. We apply principal component analysis (PCA) to a set of observed various trace gases and GEOS-5 tagged CO tracers to identify different air masses sampled by DC-8 aircraft during the NASA ARCTAS mission. The △O3/△CO ratio in individual air masses is calculated to understand the contribution of biomass burning and anthropogenic pollution to ozone in the Arctic troposphere. Anthropogenic plumes observed during both spring and summer show weak positive ozone productivity. Biomass burning plumes (mostly Siberian agricultural burning) observed during spring has a △O3/△CO ratio of 0.28 while the summertime boreal forest fires display a △O3/△CO ratio ~ 0, indicating very fresh plumes with little ozone production. We will analyze data from ARCTAS together with that from previous field missions, INTEX-A and INTEX-B, to further examine the interannual variability of the import of air masses into the Arctic. We will use a combination of observed trace gases and model age and source tracers in the NASA GEOS-5 GCM to assess the spatial/altitude variability of the transport pathways. We will correlate tracers of transport with a few well-known climate indices, i.e. the Arctic Oscillation and Pacific Decadal Oscillation, to understand the controlling dynamics of the interannual variability of import into the Arctic troposphere.