Seasonal Variability and Evolution of Glaciochemistry at An Alpine Temperate Glacier on the Southeastern Tibetan Plateau

Temperate glaciers are highly sensitive to climatic and environmental changes. Studying the chemical composition of snow, firn, and ice on temperate glaciers is important for understanding the variations in atmospheric circulation patterns, deposition conditions, and melting processes. To define snowpack chemistry and environmental significance, seven snowpacks (one snowpack in late autumn, two in winter, two in spring, and two in summer) were sampled in 2008/2009 on Baishui Glacier No.1 in Mt. Yulong. Soluble ions in the winter snowpacks showed low values in the middle part but high values in the lower and upper parts, influenced by the atmospheric deposition of snow accumulation. The larger variations of ionic concentrations in the spring snowpacks were associated with the variable atmospheric patterns with high dust content in spring, leading to high ionic concentrations in the upper snowpack. Strong meltwater percolation resulted in quick migration and redistribution of ions for the profiles during the monsoon period. The ion elution sequence was Ca2+ > SO42- > NH4+ > K+ > NO3- > Na+ > Cl > Mg2+. Factor analysis showed that NO3-, SO42-, NH4+ were mainly supplied by wet deposition-plus-anthropogenic input, while Cl- and Na+ originated from marine sources. Ca2+ and Mg2+ had multiple sources and the local terrestrial source was important because of locally exposed carbonate. The results suggest that chemical concentrations reflect mainly impurities supplied by atmospheric circulation and precipitation during periods of snow accumulation, as well as during the melting process.