Tropospheric ozone is a greenhouse gas and air pollutant that is frequently depleted to near-zero levels in the polar regions during springtime. These ozone depletion events (ODEs) are caused by reaction with bromine radicals (Br-), produced upon photolysis of Br2, emitted from the snowpack. Reactions of reactive bromine compounds with NOx (NO + NO2) can slow ozone depletion. Due to the few observations made in these polar regions, understanding of the temporal and spatial scales of ODEs, as well as the impacts of NOx, remains limited. In this work, we assess the seasonal ozone variability at Utqiagvik (formerly known as Barrow) and Oliktok Point (within the North Slope of Alaska oil fields), Alaska. Seasonal ozone data was used to define ozone background levels and evaluate ODE timescales. Lower ozone levels were observed at Oliktok Point, compared to Utqiagvik, during the polar night, when nighttime lasts 24 hours, and this may indicate ozone titration by nitrogen oxides (NOx) emitted from Alaskan oil fields in the absence of halogen photochemistry. Dependence of ozone levels on temperature, wind speed, and wind direction were also examined. Comparison of ozone levels across seasons and locations provides insights into the mechanisms driving tropospheric ozone depletion and how increasing combustion emissions in the Arctic impact this chemistry.

Seasonal ozone depletion events and influence of NOx in the arctic troposphere

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