Atmospheric nitric oxide and ozone at the WAIS Divide deep coring site: a discussion of local sources and transport in West Antarctica

• Main Authors: Masclin, S, Frey, MM, Rogge, WF, Bales, RC
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: eScholarship, University of California 2013
• Subjects: Climate Action; Astronomical and Space Sciences; Atmospheric Sciences; Meteorology & Atmospheric Sciences; Antarctic; Greenland; The Antarctic; West Antarctic Ice Sheet; West Antarctica; Antarc*; Antarctica; Ice Sheet
• Online Access: https://escholarship.org/uc/item/60g4b1sg

The first measurements of atmospheric nitric oxide (NO) along with observations of ozone (O3), hydroperoxides (H2O2 and MHP) and snow nitrate (NO3- ) on the West Antarctic Ice Sheet (WAIS) were carried out at the WAIS Divide deep ice-coring site between 10 December 2008 and 11 January 2009. Average ±1σ mixing ratios of NO were 19±31 pptv and confirmed prior model estimates for the summer boundary layer above WAIS. Mean ±1σ mixing ratios of O3 of 14±4 ppbv were in the range of previous measurements from overland traverses across WAIS during summer, while average ±1σ concentrations of H2O2 and MHP revealed higher levels with mixing ratios of 743±362 and 519±238 pptv, respectively. An upper limit for daily average NO2 and NO emission fluxes from snow of 8.6×108 and 33.9×108 moleculecm-2 s-1, respectively, were estimated based on photolysis of measured NO3- and nitrite (NO2-) in the surface snowpack. The resulting high NOx emission flux may explain the little preservation of NO3- in snow (∼30 %) when compared to Summit. Greenland (75-93 %). Assuming rapid and complete mixing into the overlying atmosphere, and steady state of NOx, these snow emissions are equivalent to an average (range) production of atmospheric NOx of 30 (21-566) pptvh-1 for a typical atmospheric boundary-layer depth of 250 (354-13) m. These upper bounds indicate that local emissions from the snowpack are a significant source of short-lived nitrogen oxides above the inner WAIS. The net O3 production of 0.8 ppbvday-1 triggered with NO higher than 2 pptv is too small to explain the observed O3 variability. Thus, the origins of the air masses reaching WAIS Divide during this campaign were investigated with a 4-day back-trajectory analysis every 4 h. The resulting 168 back trajectories revealed that in 75% of all runs air originated from the Antarctic coastal slopes (58 %) and the inner WAIS (17 %). For these air sources O3 levels were on average 13±3 ppbv. The remaining 25% are katabatic outflows from the East Antarctic Plateau above 2500 m. When ...