Nitrate deposition and preservation in the snowpack along a traverse from coast to the ice sheet summit (Dome A) in East Antarctica

• Published in: The Cryosphere
• Main Authors: Shi, Guitao, Hastings, Meredith G., Yu, Jinhai, Ma, Tianming, Hu, Zhengyi, An, Chunlei, Li, Chuanjin, Ma, Hongmei, Jiang, Su, Li, Yuansheng
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2018
• Subjects: article; Verlagsveröffentlichung; Antarctic; East Antarctica; Antarc*; Antarctica; ice core; Ice Sheet; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-12-1177-2018; https://noa.gwlb.de/receive/cop_mods_00006867; https://noa.gwlb.de/servlets/MCRFileNodeServlet/cop_derivate_00006824/tc-12-1177-2018.pdf; https://tc.copernicus.org/articles/12/1177/2018/tc-12-1177-2018.pdf

Antarctic ice core nitrate (NO 3-) can provide a unique record of the atmospheric reactive nitrogen cycle. However, the factors influencing the deposition and preservation of NO 3- at the ice sheet surface must first be understood. Therefore, an intensive program of snow and atmospheric sampling was made on a traverse from the coast to the ice sheet summit, Dome A, East Antarctica. Snow samples in this observation include 120 surface snow samples (top ∼ 3 cm), 20 snow pits with depths of 150 to 300 cm, and 6 crystal ice samples (the topmost needle-like layer on Dome A plateau). The main purpose of this investigation is to characterize the distribution pattern and preservation of NO 3- concentrations in the snow in different environments. Results show that an increasing trend of NO 3- concentrations with distance inland is present in surface snow, and NO 3- is extremely enriched in the topmost crystal ice (with a maximum of 16.1 µeq L−1). NO 3- concentration profiles for snow pits vary between coastal and inland sites. On the coast, the deposited NO 3- was largely preserved, and the archived NO 3- fluxes are dominated by snow accumulation. The relationship between the archived NO 3- and snow accumulation rate can be depicted well by a linear model, suggesting a homogeneity of atmospheric NO 3- levels. It is estimated that dry deposition contributes 27–44 % of the archived NO 3- fluxes, and the dry deposition velocity and scavenging ratio for NO 3- were relatively constant near the coast. Compared to the coast, the inland snow shows a relatively weak correlation between archived NO 3- and snow accumulation, and the archived NO 3- fluxes were more dependent on concentration. The relationship between NO 3- and coexisting ions (nssSO 42-, Na+ and Cl−) was also investigated, and the results show a correlation between nssSO 42- (fine aerosol particles) and NO 3- in surface snow, while the correlation between NO 3- and Na+ (mainly associated with coarse aerosol particles) is not significant. In inland snow, there were no significant relationships found between NO 3- and the coexisting ions, suggesting a dominant role of NO 3- recycling in determining the concentrations.