Dynamics of ozone and nitrogen oxides at Summit, Greenland: I. Multi-year observations in the snowpack

Abstract

Abstract A multi-year investigation of ozone (O 3 ) and nitrogen oxides (NO x ) in snowpack interstitial air down to a depth of 2.8 m was conducted at Summit, Greenland, to elucidate mechanisms controlling the production and destruction of these important trace gases within the snow. Snowpack O 3 values ranged from 30 to 40 ppbv during winter months, and dropped below 10 ppbv in summer. Wintertime NO x levels were low at all depths in the snowpack (below 10 pptv for NO and below 25 pptv for NO 2 ). In the summer, NO values up to 120 pptv, and NO 2 mixing ratios up to ∼700 pptv were observed. O 3 loss within the snowpack was observed throughout all seasons. The magnitude of the O 3 loss rate tracked the seasonal and diurnal cycle of incoming short wave solar radiation. Production of NO within a shallow layer of the snowpack was recorded during the spring and summer months. NO 2 production also occurred, and heightened levels were measured down to 2.5 m in the snowpack. The average daily maximum in NO was observed at solar noon, and the minimum was seen during night. The daily peak in NO 2 was on average 7 h shifted from the incoming solar radiation and NO maxima. NO x levels in interstitial air during spring were enhanced relative to summer and fall. The influence of meteorological effects such as wind pumping on snowpack interstitial air levels of O 3 and NO x was investigated using case study periods. Increased snowpack ventilation during high wind events was found to yield enhancement in snowpack NO x , with this effect being enhanced during times when O 3 was elevated in ambient air. This behavior suggests that O 3 is involved in NO x production in the snowpack. This extensive set of observations is used to re-evaluate physical and chemical processes that describe the dynamic O 3 and NO x chemistry occurring within snowpack interstitial air at Summit.