Changes in ionic concentrations and δ18O in the snowpack of Zhadang glacier, Nyainqentanglha mountain, southern Tibetan Plateau

Abstract

To investigate the effects of depositional and post-depositional processes on chemical records in the snowpack, seven monthly snow pits were sampled at the same site on the pass of Zhadang (ZD) glacier (30°28.079′ N, 90°39.032′ E; 5800 m a.s.l.), Nyainqentanglha mountain, southern Tibetan Plateau, between April and October 2006. Meteorological data from an automatic weather station at the sampling site showed that the annual mean air temperature was -5.6°C on the pass and that monthly air temperature was above 0°C from June to August, indicating that snowmelt could occur in this high-elevation region during the summer. An analysis of δ 18O and major-ion variability in snow pits suggests that glaciochemical records were influenced by both meltwater percolation in mid-summer (July and August) and seasonal deposition. Less negative δ18O values and high concentrations of major ions occurred during the spring. The trends of δ 18O variations in the ZD snow pits were consistent with those in precipitation sampled at the nearby Nam Co station for all months except for July and August, suggesting that climate signals are well preserved in the snow-pit δ18O records during the non-summer months. However, these climate signals were destroyed by strong percolation of meltwater during mid-summer.