Spatial and temporal variations in snow chemistry along a traverse from coastal East Antarctica to the ice sheet summit (Dome A)

• Main Authors: Shi, Guitao, Ma, Hongmei, Hu, Zhengyi, Chen, Zhenlou, An, Chunlei, Jiang, Su, Li, Yuansheng, Ma, Tianming, Yu, Jinhai, Wang, Danhe, Lu, Siyu, Sun, Bo, Hastings, Meredith G.
• Format: Text
• Language: English
• Published: 2020
• Subjects: Antarctic; East Antarctica; Indian; Princess Elizabeth Land; The Antarctic; Zhongshan; Zhongshan Station; Antarc*; Antarctica; Ice Sheet; Sea ice
• Online Access: https://doi.org/10.5194/tc-2020-255; https://tc.copernicus.org/preprints/tc-2020-255/

There is a large variability in environmental conditions across the Antarctic ice sheet, and it is of significance to investigate the snow chemistry at as many locations as possible and over time, given that the ice sheet itself, and precipitation and deposition patterns and trends are changing. The China inland Antarctic traverse from coastal Zhongshan Station to the ice sheet summit (Dome A) covers a variety of environments, allowing for a vast collection of snow chemistry conditions across East Antarctica. Surface snow and snow pit samples were collected on this traverse during five campaigns, to comprehensively investigate the spatial and temporal variations in chemical ions (Cl − , NO 3 − , SO 4 2− , Na + , NH 4 + , K + , Mg 2+ , and Ca 2+ ) and the related controlling factors. Results show that spatial patterns of ions in surface snow are consistent among the five campaigns, with Cl − , Na + , K + , and Mg 2+ decreasing rapidly with distance from the coast and NO 3 − showing an opposite pattern. No clear spatial trends in SO 4 2− , NH 4 + and Ca 2+ were found. In the interior areas, an enrichment of Cl − versus Na + with respect to seawater composition is ubiquitous as a result of the deposition of HCl, which can account for up to ~40 % of the total Cl − budget, while enriched K + and Mg 2+ are associated with terrestrial particle mass. Ca 2+ and SO 4 2− in surface snow are significantly enriched relative to Na + , related to terrestrial dust inputs and marine biogenic emissions, respectively. Snow NH 4 + is mainly associated with marine biological activities, with higher concentrations in summer than in winter. On the coast, parts of the winter snow are characterized with a depletion of SO 4 2− versus Na + , and a significant negative correlation between nssSO 4 2− and Na + was found, suggesting that sea salts originated from the sea ice. In the interior areas, the negative nssSO 4 2− signal in winter snow resulted from inputs of sea salts being completely swamped by the contribution of marine biogenic emissions. Ternary plots of Cl − , Na + , and SO 4 2− suggest that sea salt modification is generally negligible on the coast, while the degree of modification processes to sea salts is high in the interior areas, especially during the summertime. Ion flux assessment suggests an efficient transport of nssSO 4 2− to at least as far inland as the ~2800 m contour line. The interannual variations in ion concentrations in surface snow on the traverse are likely linked to the changes in the Southern Indian Ocean low (SIOL) from year to year, and the deepening of the SIOL in summer tends to promote the transport of marine aerosols to Princess Elizabeth Land.