Ozone variability and halogen oxidation within the Arctic and sub-Arctic springtime boundary layer

The influence of halogen oxidation on the variabilities of ozone (O-3) and volatile organic compounds (VOCs) within the Arctic and sub-Arctic atmospheric boundary layer was investigated using field measurements from multiple campaigns conducted in March and April 2008 as part of the POLARCAT project. For the ship-based measurements, a high degree of correlation (r = 0.98 for 544 data points collected north of 68 degrees N) was observed between the acetylene to benzene ratio, used as a marker for chlorine and bromine oxidation, and O-3 signifying the vast influence of halogen oxidation throughout the ice-free regions of the North Atlantic. Concurrent airborne and ground-based measurements in the Alaskan Arctic substantiated this correlation and were used to demonstrate that halogen oxidation influenced O-3 variability throughout the Arctic boundary layer during these springtime studies. Measurements aboard the R/V Knorr in the North Atlantic and Arctic Oceans provided a unique view of the transport of O-3-poor air masses from the Arctic Basin to latitudes as far south as 52 degrees N. FLEXPART, a Lagrangian transport model, was used to quantitatively determine the exposure of air masses encountered by the ship to first-year ice (FYI), multi-year ice (MYI), and total ICE (FYI+MYI). O-3 anti-correlated with the modeled total ICE tracer (r = -0.86) indicating that up to 73% of the O-3 variability measured in the Arctic marine boundary layer could be related to sea ice exposure.