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: G. Shi, M. G. Hastings, J. Yu, T. Ma, Z. Hu, C. An, C. Li, H. Ma, S. Jiang, Y. Li
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2018
• Subjects: Environmental sciences; GE1-350; Geology; QE1-996.5; Antarctic; East Antarctica; Antarc*; Antarctica; ice core; Ice Sheet; The Cryosphere
• Online Access: https://doi.org/10.5194/tc-12-1177-2018; https://doaj.org/article/fe9cdd2216e3438295f8d5e8993bc813

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 4 2− , Na + and Cl − ) was also investigated, and the results show a correlation between nssSO 4 2− (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. ...