Groundwater Hydrology and Stable Isotope Analysis of an Open-System Pingo in Northwestern Mongolia

The first record of stable isotopes through a complete sequence of ice within an open-system pingo in northwestern Mongolia indicates a complex history of ice formation and pingo growth. A continuous section of ice 32 m long was cored through the centre of Mongot Pingo, and ice cores were analysed for stable isotopes and chemical composition. Two different stable isotope patterns in separate ice sections are identified: 1 open-system freezing and 2 semi-closed system (or closed system) freezing. Discharge measurements were observed in 2009 after drilling through pingo ice to artesian sub-pingo water and compared with data collected from the same pingo in 1968. Approximately 850-950 m(3) of sub-pingo water discharged within 120 h during drilling in both 1968 and 2009, a volume equivalent to about 10 per cent of the current pingo ice volume. Between 1968 and 2009, permafrost (pingo ice) thickened by about 60 cm (1.46 cm per year), from 32.0 to 32.6 m, due to the decrease in sub-pingo artesian water pressure after water release from the 1968 drilling. The major mechanism for ice formation at this pingo is groundwater artesian pressure, though not continuously. Four major stages of pingo growth after 8790 yr BP are inferred. Copyright (c) 2013 John Wiley & Sons, Ltd.